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Author Topic: Early British gas turbine development  (Read 137244 times)

Offline PMN1

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Early British gas turbine development
« on: November 07, 2006, 02:03:57 am »
Got this form Groggy on the TGP site

http://www.tgplanes.com/Public/snitz/topic.asp?TOPIC_ID=1268

“The L.R.1 bomber project was first submitted to the Ministry of Aircraft Production late in 1944” and “In May, 1945 a project was prepared for a transatlantic civil transport powered by four L.R. 1 engines driving ducted fans. The machine was designed to cruise at 470 m.p.h. at 45,000ft. with a still air range of 5,280 miles and a payload of 20,000 lb. The estimated all-up weight was 156,000 lb.”

“The static thrust of the straight jet version of the engine was envisaged as 5,500lb static thrust at S.L.” The L.R.1 turbo fan would have given with a bypass ratio of 2.5, so this would give a thrust of ?? 10,000 lb? any ideas?

This is about the only details I can find for the L.R. 1 bomber but I was told by Ian Whittle, Whittles son that the prototype L.R.1 engine was almost finished being built.

Any additions or comments?


Anybody have any further information on the bomber, the civilain transport or the engines and what would have been the effect on the early post war designs if a turbofan had been available in the late 40's


Offline Spark

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Re: Early British gas turbine development
« Reply #1 on: July 20, 2009, 02:04:35 am »
Frank Whittle's axial jet, turbofan.
After Frank Whittle left Powerjets worked on continued on his axial turbofan and turbo prop.
It was finally tested circa 1947. But worked stopped with the failure of the gearbox. Can any one help with photos, details , drawings?
Has any one anything on his axial turbofan with afterburner, reheat designed for supersonic flight

Offline Apophenia

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Re: Early British gas turbine development
« Reply #2 on: July 20, 2009, 11:22:49 am »
Spark, are you referring to the Power Jets L.R.1 axial-flow engine? If so, this entry in Cambridge's Janus site may be a lead:

http://janus.lib.cam.ac.uk/db/node.xsp?id=EAD%2FGBR%2F0014%2FWHTL%20AS%202

Whittle Associated Papers

Power Jets (Research and Development) Ltd Projects Department Note No. A.137 (a). "Power Jets L.R.1 Engine". With diagrams and designs. 29 January 1945

Offline red admiral

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Re: Early British gas turbine development
« Reply #3 on: July 20, 2009, 11:31:41 am »
Genesis of the Jet, by Golley and Gunston has some details in the appendices of Whittle's work with thrust augmentors, turbofans and reheat. There are diagrams, but no photos.

I've never heard that the engines were ever finished or tested. From reading other accounts it seems that PowerJets didn't do any further work on whole engines after being nationalised in 1944, just research into bits. Engine development was given by MAP to the aircraft companies.

Offline alertken

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Re: Early British gas turbine development
« Reply #4 on: July 25, 2009, 03:32:35 am »
The Royal Aircraft Factory lost its role as designer of complete vehicles in 1918 and became the Basic, or Pure Research resource. Govts. took the view that the State, in academia or Establishments, should create the knowledge that industry should Apply. RAE organised into specialities, inc. Powerplant. So it was; then Whittle came up with gyre-power just as "Hyper" reciprocating engines were being explored. 1938-41 A.M/MAP perceived that ASM, Bristol, Napier and RR had their hands full making mere Cheetah, Hercules, Dagger, Merlin work, while trying to invent Deerhound, Centaurus, Sabre, Griffon. It would be nugatory to put a wholly new technology there, when logic was to find metalworkers familiar with discs, spin. So, superchargers: GE's 25% affiliate AEI (BTH & Metro-Vick). (Parallel in US - NACA; Pratt/Wright overloaded on big pistons, so enter Allis Chalmers, GE, Westinghouse). Fabrication capacity was idle in the auto industry, so enter Rover, Vauxhall (US: Buick, Studebaker). Geo.DH had some of F.Halford's time, and had capacity beyond Gypsies, and Merlin repair, so was given access to Whittle's work, to evolve Goblin.

As 1942 became 1943, big pistons were fixed and in production, even Service. Massive investment was churning out aero-engines from the original Ring of 4, plus shadows. Stafford Cripps had been the Counsel who had extracted damages from Rootes for infringing Ricardo's diesel compression swirl chamber. Appointed MAP Nov.,1942, despite having been in 1938 so Left Wing that Attlee had expelled him from the Labour Party, he chose to reject Whittle's advice that the entire aero-engine industry should be nationalised (A.Nahum,F.W - Invention of the Jet,Icon,2004,P.105). Instead he: introduced Board harmony at Bristol by taking Fedden as his Special Technical Advisor (Nov.1942); fixed Napier's management shortcomings by causing EE to buy them (Dec.1942); took Rover out and put RR in to W.2-fabrication; buying Power Jets (March,1943) and turning it, at Harry Ricardo's suggestion (Nahum,P.100), into RAE's gyre lab (to be the National Gas Turbine Establishment). So, no change then: Basic Research: NGTE; Applied Research, product development and supply: industry. Same as most munitions bar the actual bangs; same as US.

Why people continue to bang on about maltreatment of Whittle is baffling (not talking about £100K for his invention; but about non-expansion of his lab into a factory). Why would any Minister render idle the engineering competence of an industry dating back to 1909, by duplicating it in an incomer? The reason for parking many of Whittle's schemes in 1944 was neither personal jealousy, not any conspiracy, but simple need: we had no need for plenum chamber burning, or long range turbofans. The War would be resolved on products in prototype by 1942. The Days after VJ Day were for converting swords to ploughshares. From 1947-50 we tried to make colder, easier axials work. Korean War money caused us to do Conway (which stemmed from L.R.1, via Napier E.113), Gyron; both, plus PCB work at BSEL from 1960 (to be BS.100) drew upon NGTE Basic Research which derived from Whittle-memory. A key NGTE scientist in BS.100, Ray Holl, had been in Power Jets. Whittle's legacy is no less secure than if his advice had led to one UK Gyre Co with he as President-Emeritus.
« Last Edit: July 25, 2009, 03:39:36 am by alertken »

Offline Spark

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Re: Early British gas turbine development
« Reply #5 on: August 01, 2009, 07:20:02 am »


[/quote]

Hi
will make a proper reply

but,
The other day I was told that some new documents had been recieved showing that  in 1937 Metrovik were told  or had started by themselves looking at an idea for a jet engine? Will check this story again next week:

 This rather early and is against the generally exceptd wisdom?

Offline red admiral

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Re: Early British gas turbine development
« Reply #6 on: August 01, 2009, 11:24:57 am »
A visit was made by the RAE to Metropolitan Vickers on 3rd June 1937 and three designs outlined.

I'll write up a bit more of the information I have later.

Offline red admiral

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Re: Early British gas turbine development
« Reply #7 on: August 15, 2009, 03:53:55 am »
Sorry for the delay;

The Early History of the Aircraft Gas Turbine in Britain by W Hawthorne

Offline tartle

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Re: Early British gas turbine development
« Reply #8 on: October 28, 2011, 06:36:14 am »
If memory serves me right
....the RAE were pioneers of axial compressors... The 'Betty' is a Haynes Constant Research rig building on the axial compressor work of A A Griffith and after several rig designs eventually led to the Metrovick engines such as Beryl... this series of engines led to the Sapphire, production of which was handed to Armstrong Siddeley, plus further development. Metrovick an American owned company set up at the turn of the century had a long relationship with RAE, no doubt due to their rotating machinary expertise (electricity!). They helped with supercharger design for RAFactory in WW1.
See also this post I have written elsewhere on secretprojects.
« Last Edit: November 13, 2011, 06:35:51 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #9 on: November 13, 2011, 01:12:40 pm »
In case people are still interested ...
the Whittle engine looked like this...........

There were various versions proposed based on this layout..
The one in the diagram is a 2.5:1 bypass ratio single-shaft - 8-stage axial plus 1 stage centrifugal driven by a 2-stage turbine; the turbofan is geared off the front of the compressor turning at 2,300 rpm; the engine itself at take-off rotates at 8,000 rpm. This turbofan is based upon the original six-blade contra rotating turboprop version which was projected to supply 4,870 shp plus 3,160 lbt at take-off.
The 'fan version was designed to give 2,800 thp at cruise with a fuel consumption of 1,890 lb/hr at a weight of 2,770lb.
Leaving off everything forward of the compressor gave a jet of 2,600 lb weight and a static sea level t/o thrust of 5,500 lb.
Yet another version had a separate turbine driving a ducted fan; a further variant was to have the turbine drive a propeller proposed for a 300 mph cruise at 20,000ft aeroplane project that eventually became the Britannia.
The LR1 project was serioius enough for the MAP powerplants committee to order one prototype engine plus spares in Aug 1945. The compressor was run at Pyestock and in 1949 a mechanical failure occured and the project was abandoned. So I am not sure if there ever was a complete engine... maybe NGTE, Pyestock archives hold the answer?
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline red admiral

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Re: Early British gas turbine development
« Reply #10 on: November 13, 2011, 01:19:07 pm »
Interesting information tartle. I seem to remember from Gensis of the Jet that Powerjets were constructing a complete engine in 1944/45 -ish with construction proceding to an advanced stage. I've no idea what archives remain at Pyestock; they might have been subsumed into FAST in Farnborough at some stage?

Offline tartle

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Re: Early British gas turbine development
« Reply #11 on: November 13, 2011, 04:51:02 pm »
red admiral,
I'll do some checking. FAST is a good lead.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Jemiba

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Re: Early British gas turbine development
« Reply #12 on: November 13, 2011, 09:46:39 pm »
From The Aeroplane, March 1959, a design for a transatlantic civil transport, powered
by four L.R.1 engines. With an all-up weight of 156.000 lbs (70.760 kg), the aircraft was
expected to cruise at 470 mph (756 km/h) at a height of 45.000 ft (13.700 m)with a range
of 5.280 miles (8.500 km) and a payload of 20.000 lbs (9.070 kg) .
It takes a long time, before all mistakes are made ...

Offline Skyblazer

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Re: Early British gas turbine development
« Reply #13 on: November 13, 2011, 11:42:29 pm »
http://www.tgplanes.com/Public/snitz/topic.asp?TOPIC_ID=1268

Just two concerns:
1°) You need to be logged (therefore a member) of said site to be able to view the page you linked.
2°) You do not specify what aircraft manufacturer originated the L.R.1 bomber project. Was that Gloster, given the Whittle connection?

Offline alertken

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Re: Early British gas turbine development
« Reply #14 on: November 14, 2011, 09:12:50 am »
I think jemiba's #4 is an aero-engine man's concept, not an airframer's scheme.
 
My understanding of UK's evolution of augmented flow:
1944: Power Jets had as rig hardware, W.2/700, which we would now label as a PCB turbofan. As a components exercise PJ had LR.1. Whittle was pressing Minister Cripps to nationalise the entire aero-engine industry, and generally was being "difficult". 28/4/44 Cripps nationalised Power Jets.
 
1/7/46 it subsumed RAE's powerplant resources, becoming NGTE. Basic Research: Establishment, Applied Research: industry, same as airframes. Augmented flow passed to Napier, schemed as E.132.
1946: UK was trying hard to make axial turbojets work, without notable success. English Electric's entry to modern aero design hinged on A1, whose AJ65 was dammed.
 
July,1947: EE's Medium Bomber bid, and Short's enhancement of Sperrin, both based on E.132, both rejected by MoS.
               EE's Geo.Nelson (owner of Napier) sold E.132 to RR. Hives parked it with his Chief Scientist, AA Griffith, while practical folk tried to make Avon as good as ASM's Sapphire, just acquired ex-MetroVick F.9.
 
1949: Avon improves and sells. Griffith is sponsored to start on (E.132, enhanced as) RB80, chosen:
 
1950: as Conway for Valiant B.2, 17 ordered 10/51, cancelled. Conway continued for V.1000, cancelled. RR took a fixed production price punt to displace Olympus 201 from Victor B.2, then found berths in 707-420/DC-8/40.
 
Points: A) what if...augmented flow had flowed smoothly through 1947-54. Well, why would it do so, when Avon et al did not?
          B )  just to keep perspective on the who-though-of-it-first game: GE axial J35/J47 combustor “drew on Whittle” and was  derived from W.2/700, which used GE compressor rotor; this, the first by-pass turbofan, influenced RB80 Conway, which eroded 1960s’ sales of GE first attempt on the civil market - CJ-805-23. Gunston,Engines,Pp61/108.

Offline tartle

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Re: Early British gas turbine development
« Reply #15 on: November 16, 2011, 06:11:06 pm »
The original gas turbine aerodynamic work undertaken by Whittle was, I always understood, based on the use of a centrifugal compressor using Ellor's supercharger aerodynamic work together with an axial turbine based on the 'aerodynamics' of steam turbines. His genius was stitching it all together and developing combustion chambers or cans that could burn the fuel in a contained way to generate the energy to drive the turbine and give exhaust thrust. At RAE Griffith's genius was to recognise that upto 1926 axial compressor design theory meant all practical designs to date were running with stalled blading. Hayne Constant worked alongside Griffith and continued the work after G left for RR. They originally carried out extensive cascade work to prove out their theoretical methods and then in 1937 commissioned the construction of a test compressor ' a' nicknamed Anne. Work had been proceeding on a distributed gas turbine and it was decided to build one to be called B10 or Betty. Whereas Anne had been built by Allis Chalmers, Betty was made by Metropolitan Vickers with the input of their steam turbine engineer David Smith. Betty was run in Manchester at Metrovick's Trafford Park complex. The Museum of Science and Industry has artefacts on display that are relevant so I dashed into the Hall and took some photos... the place relies a great deal on natural light and it was near dusk and I used my 'phone to get shots.. hence quality! The cascade and Anne are not there so I have used copy of pics from my archive...
mpre on RAE work in Flight report of Hayne Constant's Sir Henry Royce Memorial lecture in 1957
Betty is there and there are shots below. Also a layout diagram I traced in the 1960's . You can see the volute and 4 stage turbine on the layout. RAE realised distributed machinary was not the answer and schemed a more conventional layout... F.1 which was passed to David Smith... his team produced the F.2/1 followed by F.2/2. Whittle's turbofan or augmentor concept based on RAE work was also incorporated as the F.3 augmentor.
« Last Edit: December 12, 2011, 02:30:27 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #16 on: November 16, 2011, 06:20:31 pm »
The B10 Betty layout drawing above can be read with the diagram in an earlier post ...
The flight engine F2/1 is shaown.. it went in the tail of a Lancaster.
The F.2/2 engine is also at MOSI, which can, and was combined with the F.3 Augmentor.  Pictures below.
...and a Flight cutaway of the whole rear fan engine. There is another view of this cutaway with the addition of a sectional view and the aerofoil cross-sections on the Flight website.
« Last Edit: November 21, 2011, 01:52:00 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Johnbr

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Re: Early British gas turbine development
« Reply #17 on: November 16, 2011, 07:07:43 pm »
Thanks you made my week.

Offline tartle

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Re: Early British gas turbine development
« Reply #18 on: November 17, 2011, 12:59:08 pm »
.... and a x-section of Anne from my archive: 6 inches in diameter over the blades.
« Last Edit: November 17, 2011, 01:03:22 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #19 on: November 18, 2011, 03:19:15 am »
I have been waiting for this book to be published... it arrived yesterday and I realised even more how much we owe to A. A. Griffiths's early work in rotating machinery.......
David Bloor's new book "The Enigma of the Aerofoil: Rival Theories in Aerodynamics, 1909-1930" tells the story of two theories intended to explain the origin and nature of the lift of a wing. They may be called the Discontinuity Theory and the Circulatory (or vortex) Theory. Eventually the latter (Gottingen) theory became the accepted one and the other (Cambridge) one fell by the wayside.
The book written after researching the Archives of the relevant people and institutions is a fascinating account of how they theories did or did not develop and how difficult it was for the British 'camp' to get on board the Gottingen Theory 'boat'. Bloor's conclusion is quite complex and he emphasises his simple one can be taken too literally i.e. Because the British placed aerodynamics in the hands of mathematical physicists while the Germans place it in the hands of mathematically sophisticated engineers!
Fortunately Griffiths, whilst mathematically accomplished went, not to Cambridge but to Liverpool where he obtained his B.Eng(1914), M.Eng(1917), and D.Eng(1921) from Liverpool University’s School of Mechanical Engineering; he was to make effective use of the theory.
« Last Edit: November 18, 2011, 04:36:40 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #20 on: November 18, 2011, 03:23:11 am »
 In July 1926 A. A. Griffiths wrote a seminal paper (RAE report H.1111- An Aerodynamic Theory of Turbine Design) in which he demonstrated that the axial gas turbine was feasible as a power unit for aircraft propulsion and determined the basis for a complete design. He wrote:
“The comparatively low efficiency of turbines and turbo-compressors is the only serious obstacle to the development of a successful internal combustion turbine suitable for use on aircraft. The causes of this low efficiency have been investigated. 
The circulation theory of aerodynamics has been applied to the problem of the design of turbine blading. It has been deduced that the main reason for the low efficiency of blades of current design is that they normally work under stalled conditions. Formulae for efficiency have been worked out on the basis of the new theory…..
It appeared on consideration that the use of rotary members similar to airscrews would lead to much higher efficiencies than are at present obtainable from turbo-machines. With existing airscrews, propeller efficiencies as high as 0.80 to 0.85 can be readily obtained. By using airscrews as the rotary members of compressors, even higher efficiencies would be possible since most of the translational energy in the slipstream would be recoverable in the stator blades. Moreover the efficiency of the airscrews can be predicted within narrow limits by the application of known aerodynamic principles, so that the conditions for maximum efficiency are comparatively easy to determine.
These considerations at once suggest the new method for designing turbo-machinery. The blades, instead of being regarded as the walls of channels, whose shape determines the velocity and pressure changes taking place in the fluid, are to be regarded as aerofoils and the changes in velocity and pressure are to be calculated from the blade reactions. These, in turn, can be found with the help of the known aerodynamic characteristics of the blade sections……
A point which emerges at once is that, since the angle through which the fluid stream can be efficiently turned by one row of blades is comparatively small, it will usually be necessary to use multi-stage designs in order to secure a high overall efficiency.”
The A. R. C. discussed the paper and recommended experiments on a single-stage compressor and a single-stage turbine; this was constructed in 1927 under Griffith’s supervision.
The small test unit comprised a compressor and turbine mounted on one shaft and having blading of aerofoil section. The diameter of the rotor barrel was 3 in. and the internal diameter of the casing 4 in. giving a blade height of 0.5 in. less blade tip clearance; the blade section had a chord of 0.6 in.
A. C. Clothier’s tests showed that the unit gave efficiencies that tied in well with Griffith’s prediction and reached 91% including blade, casing and rotor friction losses and windage on rotor ends but neglecting bearing friction losses, at speeds around 15,000 rev/min. This was the first time that high efficiency was obtained from an axial type compressor; Griffith may be said to be the true originator of the multi-stage axial engine.
[Most of the above comes from the Royal Society's Biographical Memoir on A. A. Griffith.]
The effect of the new theory on efficiency can be seen in the graph plotting RAE turbomachinery and their derivatives.

« Last Edit: November 18, 2011, 04:46:50 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #21 on: November 18, 2011, 06:02:05 am »
In 2008 the F.2/1 was in a better position for photography.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline red admiral

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Re: Early British gas turbine development
« Reply #22 on: November 18, 2011, 10:44:05 am »
Thanks for the pictures and information there. I think I've got a couple of papers on Griffith's gas turbine work which might be worth summarising here.

Pictures attached are from the complete F3 engine at RRHT Derby, unfortunately not very good quality.


Offline tartle

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Re: Early British gas turbine development
« Reply #23 on: November 18, 2011, 10:55:13 am »
My reaction is RR Derby... could this be the Aft fan Avon? I'll examine pics with a close scrute later and look at my Aftfan Avon stuff
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline red admiral

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Re: Early British gas turbine development
« Reply #24 on: November 18, 2011, 12:35:17 pm »
My reaction is RR Derby... could this be the Aft fan Avon? I'll examine pics with a close scrute later and look at my Aftfan Avon stuff

It's another Metrovick F3 at Rolls-Royce Heritage Trust Derby. Not an Avon due to the lack of can-annular combustors (and I seem to remember a Metrovick plaque/board next to it).

The article I mentioned previously is "Alan Arnold Griffith. 1893-1963" by "AA Rubbra" published in Biographical Memoirs of Fellows of the Royal Society, Vol. 10 (Nov., 1964), pp. 117-136

Offline tartle

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Re: Early British gas turbine development
« Reply #25 on: November 18, 2011, 06:01:54 pm »
I have quoted from Rubbra's article in #20 above.
The Avon started with individual combustion cans but swapped to a can-annular design from the RA.14 onwards. There are RA.1 and RA.28 photos below to illustrate the changes. The RA.14 onwards incorporated lesson learned from the Sapphire compressor data released to RR at the request of the MoS.
The RA29 or 300 series had a zero stage on the compressor and a third turbine stage added... the Aft Fan version was intended to be behind one of these engines.
The Aft fan version of the Avon is listed in the catalogue but I have asked Derby to tell me what it is.
« Last Edit: November 19, 2011, 02:35:43 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #26 on: November 19, 2011, 02:15:04 pm »
Here is a section of the aft fan Avon ... the fan blade has a diameter 50 in. The close integration with the RA.29 can be seen; note the three turbine stages on the Avon itself.    built as a response to the General Electric CJ805-23 aft fan fitted in a Caravelle..neither engine manufacturer attracted an order... the Avon went on to be used for noise research supporting the RB.211 programme. The Convair 990 was fitted with the GE aft fan .. a front and rear view of installed CJ805-23 are below.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #27 on: November 20, 2011, 08:25:41 am »
Having consulted Mike Evans, who set up the Rolls-Royce Heritage Trust I can confirm that there is a Metrovick at Derby. It is an F.2 turbojet. He confirmed the pictures in #22 are in fact of the Avon Aft Fan. I thought the intake was familiar, see #26, from my time at Hucknall in the '60s when it was on noise, etc. test there.
There was another aft fan version built by Metrovick and this was an open prop concept. Flight describes it here
Yet again it shows ideas based on 'science' can come around again as the external constraints to adoption change and the technologies at 'the fingertips' changes the economics... it is well worth revisiting to see if an idea has become one with legs. Rolls-Royce are at present in a research programme being driven by the desire for cleaner engines. They are involved in  Sustainable and Green Engine (SAGE) Integrated Technology Demonstrator Programme described here.
and here.
This is an extract of the RR description:
"
Open rotor technologies offer the potential for significant reductions in fuel burn and CO2 emissions relative to turbofan engines of equivalent thrust.  Higher propulsive efficiencies are achieved for turbofans by increasing the bypass ratio through increases in fan diameter but there is a diminishing return to this improvement as nacelle diameters and consequently weight and drag increase.  Open rotor engines remove this limitation by operating the propeller blades without a surrounding nacelle, thus enabling ultrahigh bypass ratios to be achieved.
Further improvements in propulsive efficiency can be gained for open rotor engines by using a second row of propeller blades rotating in opposition to the front row to remove the spin from the column of air to give a more direct thrust. "
Which feels like a rewrite of AA Griffith's report, #20, above
 
« Last Edit: November 20, 2011, 08:30:15 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #28 on: November 22, 2011, 03:05:43 am »
In #20 above we read that Griffiths was predicting that compressor stage efficiencies of 90+% should be achievable and that tests corroborated it. This left me curious ... I listen to Radio 4 guerilla economist Tim Harford and the More or Less team investigate numbers in the news... "double the risk of" headlines that cause concern but actually mean going from 1 in a million to 2 in a million... we needn't worry after all.
So what is the context of  Griffiths' statement .... does it mean going from 88 to 91 or what?
Not quite as easy to find the answer as I hoped but when I did it is obvious why people sat up and took notice.Charles Parsons who was our great Victorian/Edwardian pioneer of steam turbines for industrial and marine use (e.g. Turbinia) decided to use steam turbine blading in reverse and built an axial compressor.. it had less than 40% efficiency but he perservered because of other advantages over the reciprocating compressors that were used in mines and steelworks at the time. That is lack of pulsation, size, weight, and less maintenance. He managed to get the efficiency up to 55% and in the early years of the 20th century delivered 17 machines mainly for blast furnace use... then Rateau came along with multi stage centrifugal designs of 70% efficiency and the market for axials disappeared. So when in 1926 Griffith realised why the axial had such a low efficiency and had design methods to raise it 20% above the centrifugal people began to take the axials seriously again. At this stage work on industrial and aero applications diverged and did not come together again until Avons and Olympus were used in industrial/marine applications afte WW2.
Picture from 'Galaxies and Machines' book on Parsons.
« Last Edit: November 22, 2011, 05:54:24 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #29 on: November 22, 2011, 04:57:59 pm »
The'Aeronautical Journal'  March 2010 included a paper 'On the Aerodynamics of the Miles M.52 (E.24/43) - a historical perspective.
It included a Power Jets sketch of the M.52 engine: a W2/700 with a No. 4Design Thrust Augmentor and afterburner, a photo of the 2-stage aftfan augmentor wheels and a further photo of the assembled engine to be tested.
Also an excerpt describing installation and the relevant conclusions. Picture titles also include the source reference.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline taildragger

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Re: Early British gas turbine development
« Reply #30 on: November 23, 2011, 12:15:30 am »

This is an extract of the RR description:
"
Open rotor technologies offer the potential for significant reductions in fuel burn and CO2 emissions relative to turbofan engines of equivalent thrust.  Higher propulsive efficiencies are achieved for turbofans by increasing the bypass ratio through increases in fan diameter but there is a diminishing return to this improvement as nacelle diameters and consequently weight and drag increase.  Open rotor engines remove this limitation by operating the propeller blades without a surrounding nacelle, thus enabling ultrahigh bypass ratios to be achieved.
Further improvements in propulsive efficiency can be gained for open rotor engines by using a second row of propeller blades rotating in opposition to the front row to remove the spin from the column of air to give a more direct thrust. "
Which feels like a rewrite of AA Griffith's report, #20, above

From the dumb questions department:
Is there any clear technical distinction between "open rotor/UDF" and "turboprop"?  What I've understood to be the defining characteristics of the UDF/open rotor (blades coaxial with turbine, scimitar shaped blades, pusher configuration) have all been applied to earlier engines that were known as turboprops.  If it's just marketing, maybe a less technical-sounding label is the answer - how about "DreamPusher", or has Boeing already trademarked that? 

Offline JFC Fuller

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Re: Early British gas turbine development
« Reply #31 on: November 23, 2011, 05:33:28 am »
At this stage work on industrial and aero applications diverged and did not come together again until Avons and Olympus were used in industrial/marine applications afte WW2.


On that subject, a range of innovative things were done with Gas Turbines post war for the Royal Navy, including with the Metrovick designs which were actually used on a number of ships. The Metrovick G2 for instance was used in the Bold class fast attack craft whilst Grey Goose was refitted with two RR units going by the designation RM60 which were intercooled and recuperated. The RM60 was first ordered by the Admiralty in 1946 though it did not go to Sea until 1953. Apparently the USN ordered two (also a pair of G2s) though they seem to have never been delivered as only three were made of which two were fitted in Grey Goose.

Offline tartle

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Re: Early British gas turbine development
« Reply #32 on: November 23, 2011, 12:24:27 pm »
I should have mentioned Metrovick's marine work...
On the subject of naming I remember Ric Parker, technology chief at RR (what a job!) telling us at a Judge Institute presentation that

"In recent years, the drive for more efficient and quieter turbofans — the engines that power most civil airliners — has seen the introduction of ever-larger fans in an effort to route a larger mass of air around the turbine than passes though it. These engines are said to have a higher bypass ratio.

However, there are limitations to the gains possible with existing designs. As you come up and up in fan diameter, you get to a point where the weight of the fan and the drag from the casings start to eat into that efficiency.  ’The idea was to go back to propellers, get rid of the fan case, get rid of all this extra weight around it and then you can make your blades 4m in diameter.

Although the open-rotor concept bears a passing resemblance to the traditional propeller, there are considerable differences. Conventional props limit the speed of the aircraft. The big difference between the open rotor and the prop is that there will be two rotors spinning in opposite directions. In a conventional prop, the air itself comes out spinning so only part of the momentum is pushing the aircraft forward; the rest is trying to turn itself around and is wasted. If you put a second rotor spinning in the opposite direction, you can speed up the air, but you also take out the spin, so you finish up with a high-speed propeller that can propel the aircraft at the sort of velocities and altitudes they fly at today but with probably a 15 per cent better fuel efficiency than an enclosed fan."

This is a subtle but crucial difference in the duty of the propulsion device. As a simple engineer I like to think of the design effort needed to design the component .. In a compressor blade the untwisting effect due to centrifugal force on each blade section is small and can usually be ignored. But for a fan blade this cannot be ignored. In the older design of clappered blade the clappers had a clearance and the rattling of the blades as the engine turned over in the wind could be heard as we went up the stairs into the cabin... however when the engine was running in the air the centrifugal twist would lock up the clappers so much that the faces had to be hard coated with stellite to prevent wear.
So with a propeller the aerofoil sections are virtually placed on a radial line through their centres of area (simplistic, I know). With a propfan the revs are higher and the tip sections are running at M0.8 or so ... think aircraft wings at this speed .. they tend to be swept.. so the sections of the propeller are arranged to sweep the leading and trailing edges relative to the incident streamlines... so the forces generated will tend to distort the prop... so we need to design for the running aero-structural condidtions hence the technology is a step or two from how we design conventional propellers.. hence the name change to acknowledge this when talking to non-technical people who hold the purse strings.... at least that is how I interpret it!
Here is a picture of me using the best technology available at the time to design a fan blade.. rumour has it that they scaled down the RB.207 so the blade fitted my drawing board (on the right).
« Last Edit: November 23, 2011, 12:53:43 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Spark

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Re: Early British gas turbine development
« Reply #33 on: November 23, 2011, 04:07:20 pm »
Hi tartle.
There was, is a Metrovik marine turbine at the Science Museum London.
 
 
I should have mentioned Metrovick's marine work...

Offline tartle

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Re: Early British gas turbine development
« Reply #34 on: November 23, 2011, 04:32:05 pm »
You sparked a memory......In 1947 a Metrovick G.1 Gatric gas turbine was fitted to the MGB 2009, making it the world's first gas turbine powered naval vessel. The Gatric was based on the F.2 engine with a free power turbine in the exhaust outlet and was modified to run on diesel fuel.
The shipping? gallery was refurbished a couple of years ago and includes the Metrovick propulsion unit.
The curator took this photo.
There are some details of the Metrovick and the RM60 here.


From Nature 20 September 1947.
50 YEARS AGO
‘Gas-Turbine Propulsion in a Naval
Vessel’ — Messrs. Metropolitan-Vickers
Electrical Co., Ltd., Trafford Park,
Manchester, have installed gas-turbine
propulsion equipment in the
experimental naval craft, M.G.B. 2009,
the trials of which will take place in the
near future. The Company claims that
this is the first naval vessel ever to be
propelled by a gas-turbine. The
characteristics of the simple-cycle gasturbine
include low overall specific
weight and size with rapid starting, and
these qualities make it very suitable for
light vessels where high speeds may
be required for limited periods and at
short notice. In M.G.B. 2009, normal
cruising and astern power is provided by
two 1,250 B.H.P. 2,400 r.p.m. Packard
internal combustion reciprocating
engines, each engine driving its own
propeller through a reduction gear.
Maximum ahead power is obtained by
bringing into operation a completely
independent Metropolitan-Vickers gasturbine
of 2,500 B.H.P., which drives a
third propeller through speed-reduction
gearing to supplement the power of the
reciprocating engines.

2nd picture from Science and Society Picture Library
« Last Edit: November 26, 2011, 02:16:13 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline red admiral

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Re: Early British gas turbine development
« Reply #35 on: November 24, 2011, 11:43:39 am »
Thanks very much for your efforts here tartle. There's a lot of information to digest. I'll have to have a good read through and see what memories it kicks off.

Offline tartle

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Re: Early British gas turbine development
« Reply #36 on: November 26, 2011, 04:13:37 am »
red admiral... glad you like it.... a pleasure to share!
 In the mean economic times we are in it is useful to remember our engineering heritage and the fact it relied on great people... at all levels. I have tis photo in my archives that should be a fitting tribute to what we are discussing here... teamwork that produces major innovative products that 'changes our world'.The two 'leaders' in the photo are David Smith who was key in getting the aero- and structural- dynamics right, and Robert Whyte, superintendent of the Gas Turbine Department, who got the manufacturing quality required to deliver David's vision. I salute them!

Left to right: Bill Node Ralf Cooke – Assistant Superintendent of Barton Works Robert R. Whyte SAAF representative Bill Smith – Foreman Fitter Eric Strong Chief Production Engineer  Dr. David M. Smith FRS – Chief Engineer RCAF engineer Dr. J. S. Shannon – Assistant Chief Engineer SAAF engineer Bert Hall – Foreman RCAF engineer
« Last Edit: November 26, 2011, 04:54:57 am by overscan »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #37 on: November 26, 2011, 10:16:16 am »
A better picture of the MOSI aft fan... courtesy and copyright of Silicon Owl

"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #38 on: November 27, 2011, 08:47:54 am »
Whittle was one of the earliest protaganists for the turbofan engine... however early in the development of the Whittle engine concepts the added complexity outweighed any calculated advantage so it was not picked up again until around WW2. Griffiths certainly thought about turboprop engines early in his axial gas turbine thinking but also reverted to a simple jet concept especially as his quest for aerodynamic efficiency drove him towards contra rotating stages that eliminated the static stator stages. These concepts were worked on well into the second world war after he moved to RR.........
 Design work on Rolls-Royce’s first gas turbine engine started in September 1940. This was the CR.1, shown in the first illustration below. The large blades at the rear are an application of the engine in a ducted fan application. This part of the engine was never made. The front, smaller part is the engine itself and consists of 14 rotors freely rotating on a fixed central shaft. Each disc moves in the opposite direction to its neighbours. The inner section of the blades are compressors. Air travels from the inlet ducts to the rear of the engine and thence forwards through the compressor to the rotating burner where it is expanded very gently as it travels rearwards through the 14 turbines which make up the outer rows of blades. The high pressure ends coincide, reducing leakage from the compressors to turbines to a minimum. Also the compressor air had some cooling effect on the turbine blade roots.
The engine was first tested in 1942 and it did give 350 lbs of thrust. This design was
overtaken by Whittle’s classic work and so the Griffith concept was abandoned. [description above was delivered in a lecture by J. D. Pearson in 1955] 
The combustion chamber (line diagram of the rig to test this below) was of a rotating burner design. The diffuser section leads to a spherical combustion chamber housing a rotating burner dividing the chamber into eight sections. The fuel inlet is at the front of the chamber and feeds fuel into a fuel sprayer which, due to its rotation, flings the fuel into the combustion chamber proper which leads the hot gases rearwards into the "nozzle guide vanes". The rotating burner is connected to the first stage turbine wheel.
The chamber, in fact, never worked and the engine itself was equipped with 4 Welland combustion chambers.
The turbine outlet is a peripheral outlet formed as the gas flow is turned through 90 degrees.
The engine itself was 71.66" long and had a diameter of 37". Max power was 365 lb. at 5,800 rpm. giving an sfc 1.25 lb/lbt/hr.
Compression ratio was 3.05 and air mass flow was 11.1 lb/sec.
The first rotors had 46 blades per stage, later ones were tried with 60 blades.
In the 1960s the engine was one of the exhibits in the Propulsion Department, at the College of Aeronautics, Cranfield.....
Part or all of the engine is now at the Derby RRHT.
« Last Edit: November 27, 2011, 10:12:05 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Johnbr

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Re: Early British gas turbine development
« Reply #39 on: November 27, 2011, 10:44:15 am »
Thanks for the great find ;)

Offline tartle

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Re: Early British gas turbine development
« Reply #40 on: November 27, 2011, 12:44:50 pm »
Thanks Johnbr... had this stuff since 1966! Now there is an easy way to share!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline red admiral

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Re: Early British gas turbine development
« Reply #41 on: November 27, 2011, 12:58:14 pm »
Some good information on Griffith's turbofan engine there. You look at the scheme and you've got to be impressed by it's brilliance from a theoretical point of view, but simply unworkable in practice. Each compressor stage being driven by it's own turbine stage and so it can run at it's own theoretical best speed. This then coupled onto a large fan (bypass ratio of 5) for maximum propulsive efficiency at subsonic speeds. The only problem then being in actually engineering the thing and getting it to work.

The CR1 is (or was a few years back) still at RRHT Derby.

There's some additional detail and simplified cross-section of the CR1 Turbofan engine in Gunston's The Development of Jet and Turbine Engines.

Offline tartle

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Re: Early British gas turbine development
« Reply #42 on: November 27, 2011, 01:44:44 pm »
Donald Eyre was the designer who drew the Griffith perspective above; it was his job to express visually Griffiths's concepts for communication to the rest of the company. As Don once explained over a cup of coffee... one had to remember we were building very complex pieces of machinery anyway... called a V-12 engine.... so the challenges did not seem too great. Some of the engineering RR did at that time was about reorienting thinking of some of the staff away from V12s and to consider the gas turbine and its implications.. RR did, starting with a WR1 built with Whittle's blessing, and 15 years after the CR.1 had built 17,000 RR designed centrifugal engines based on the Whittle concept. I believe Griffith talked to Jakob Ackeret, (famous) Professor of Aerodynamics at ETH in Zurich, at about this time; who persuaded him that matching such a combination of aerofoils was a bit limiting. Further thinking by Griffith led him to think about more conventional and multi spool engines, leading eventually to the Avon and Conway.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Trident

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Re: Early British gas turbine development
« Reply #43 on: November 27, 2011, 03:27:52 pm »
While ingenious in some respects, the concept certainly doesn't seem to take advantage of the fact that it is aerodynamically much easier to extract work from the flow than adding work to it. A smaller number of turbine stages is able to drive a larger number of compressor stages, presumably with handsome weight savings for airborne applications. So one can sort of see why the tip driven configuration did not catch on in retrospect - or maybe it has for stationary machinery, anybody know?

Offline tartle

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Re: Early British gas turbine development
« Reply #44 on: November 27, 2011, 04:49:29 pm »
Matching the characteristics of compressor and turbine for each stage over the operating range is quite a challenge too! Can't think of any real-world applications as the sealing issue is a killer ... and all those bearings!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #45 on: December 06, 2011, 10:16:11 am »
Although not a turbofan I thought it would be appropriate to show Metrovick's swansong in aircraft gas turbines... the 91st gas turbine they manufactured was the first Sapphire. shown here just after its first run at the 7,000lb rated thrust...17th May 1948. They built other Sapphires then kits of parts for Armstrong Siddeley in order to facilitate the smooth handover of the technology. The plant at Manchester was soon turning out steam turbines for various uses, which is where their expertise really lay. It is interesting that in the USA GE steam division made slow progress in gas turbines with the supercharger division exceeding their capability and creating the aero engine division for the company; just the reverse of Metrovick. It shows how company culture and the competences of the leaders makes a difference.
« Last Edit: December 07, 2011, 06:22:32 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #46 on: December 06, 2011, 05:11:19 pm »
US patent 2168726A, submited Feb 27, 1937, has a slightly more detailed diagram of the original ducted fan patent submitted in 1930 in UK(which I cannot locate).
A Canadian patent of 1947, (CA452368A), introduces a front and rear fan concept. The front fan of the engine is like a child's windmill at the outer edge... driven round as work is transferred from the rearward moving air in the intake; the inner row of blades are arranged as a compressor increasing the pressure of the intake air, i. e. work done on outer row is transferred to work done on air in inner row... then the W2/700 type core engine generates an exhaust stream that works on the rear fan in a conventional manner.
« Last Edit: December 07, 2011, 11:18:20 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #47 on: December 07, 2011, 04:23:19 am »
A report R&M 2607 covers the aerodynamic and mechanical testing at the RAE, of the Griffiths contra rotating rig constructed by Armstrong Siddeley.
Here is the report summary:

"Summary.--Several methods of constructing contra-flow turbo-compressor wheels have been investigated by
mechanical tests on single-stage wheels. The results have been incorporated in a complete unit which has been designed
and tested at the Royal Aircraft Establishment for research purposes. It was designed to pass 200 lb/min of air at
25,000 It with a compression ratio of 2-7 : 1 and a temperature at inlet to the turbine of 145 deg C.
In designing, the compressor results from aerofoil cascade tests were extrapolated beyond the limits then covered
(1938). Subsequent cascade experiments showed that the compressor efficiency would be low and that the blading
used would be stalled under design conditions. Tests on the unit confirmed this, indicating that a compressor efficiency
of about 70 per cent was the maximum obtainable, whereas the designed efficiency was 83 per cent, a figure which
with present day knowledge is easily obtainable. A slight modification to the compressor-blade heights improved
the efficiency and enabled the range of operation to be extended.
In the contra-flow unit the leakage between the shrouds separating the compressor and turbine annuli is a special
problem. Owing to the departure from design conditions and the intake air boost the leakage observed on the unit
was at times as much as 50 per cent of the entering air. The leakage likely to be obtained in a unit operating under
designed conditions is estimated at 4 per cent.
Most Of the remainder of the running time was devoted to investigation of mechanical problems. These included
the temperature gradients in the wheels, bearing cooling and lubrication, and constructional features. At a gas temperature
of 400 deg C. the constricting section in the wheel disc caused a drop of temperature of 150 deg C. above
the high pressure bearing housing. By increasing the cooling air mass flow this drop was increased to 250 deg C.
The bearings were found to be satisfactory provided their temperature could be maintained at less than 200 deg C.,
but the oil metering supply was unsatisfactory. Some movement of the blades in the rotors was observed and relative
axial expansion of t.he rotors andcasing led to rubbing at the high-pressure end. Trouble was also experienced with
the large gland leakage areas at the shrouds and around the bearing housings.
It was concluded that, in spite of the poor aerodynamic performance, there was no fundamental reason why similar
units should not operate efficiently and why a good mechanical performance should not be obtained."
Here are a sectional drawing and photos of the rig.. from the report here
« Last Edit: December 11, 2011, 10:08:34 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline alertken

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Re: Early British gas turbine development
« Reply #48 on: December 07, 2011, 04:08:47 pm »
F.9 became ASM Sapphire because in 1947 MoS was trying to convert much residual munitions industry into the vital Export Drive. HSGroup was willing to build up ASM from its dabbling in turbines and to retain it in Aero, despite its modest stature -Cheetah and not much more. EE had salvaged Napier 23/12/42; its design Consultant, Halford, had moved permanently into DH Engines; those 2 plus Bristol and RR would do nicely, and Aero did not need diversion of the electical powerhouse AEI/BTH/MV. AEI's Chairman was ex-Minister of Production Oliver Lyttleton; a major shareholder (24.8% until 5/53) was (US)GE: both were quite content to exit UK Aero, whose future was blurred.
 
It is just too complicated to resurrect what then happened. In 1949 English Electric (Napier's owner) bought in the residual shareholding of US Westinghouse. Mergers and insolvency led to today's position where Finmeccanica (the Italian State), BAE (a Company accepted by US and UK Defence Ministers as having no distinctive patrimony - then-MoD Hoon noted that scarcely 51% was UK owned) and RR (10% owned by BMW), own such of these enterprises as still breathe. I think the last owner of the trade name Hawker was Lufthansa.

Offline tartle

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Re: Early British gas turbine development
« Reply #49 on: December 07, 2011, 05:25:21 pm »
Thanks Alertkin... makes sense ... a look at the Metrovick builds reflects the drive for exports and for supporting vital industry at home... Coal Board, Canary Islands, Shell Petroleum, etc., etc.
Incidentally,  engine No107, a Sapphire, was shipped in pieces to ASM in April 1950, 3 years to the month after the first run of Sapphire No 91 in the photo above; it was the last Sapphire to be made by the Gas Turbine department. Bench testing of the Metrovick engine at ASM commenced in October, 1948, with official acceptance test being achieved in January 1950.
« Last Edit: December 08, 2011, 02:11:44 am by tartle »
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Offline JFC Fuller

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Re: Early British gas turbine development
« Reply #50 on: December 08, 2011, 03:08:39 am »
It is just too complicated to resurrect what then happened. In 1949 English Electric (Napier's owner) bought in the residual shareholding of US Westinghouse. Mergers and insolvency led to today's position where Finmeccanica (the Italian State), BAE (a Company accepted by US and UK Defence Ministers as having no distinctive patrimony - then-MoD Hoon noted that scarcely 51% was UK owned) and RR (10% owned by BMW), own such of these enterprises as still breathe. I think the last owner of the trade name Hawker was Lufthansa.


A former employer of mine used to have a pair of line drawings that tracked this- one did the actual functioning entities and one the trade names- suffice to say it was all very complicated. One thing I have always been perplexed by is the collapse of DeHavilland (relatively speaking), they seem to have made a bad decision pursuing the Gyron. on the airframe side they had one unfortunate problem (Comet) and one self inflicted one (Venom Nightfighter delay/obsolescence resulting in it being substituted by the F-86 for the NATO all-weather requirement- would have been licence, licence provided in 1950) built by Macchi with Fiat and Alfa Romeo responsible for the Ghost- all funded by US$) but the aero-engine side gets strange. After the Goblin and the Ghost they start on the supersonic Gyron, seemingly without any in-house application and detached from the airframe business pursuing civil aircraft and the Avon powered DH110. There was the brief H3 turboprop project (bench run 1948, 500hp and 130lb of thrust) and an evolved but un-built Ghost (H4) but both seem to have been passed over leaving the turbine business to stumble on with the Gyron (Cancelled F155T- government support for the engine cancelled in 1957 after expenditure of £3.4 million, apparently Dassult looked at it as well) and Gyron Junior (Cancelled SR177, thirsty Bristol 188 and grossly underpowered Buccaneer S1) until finally being acquired by Bristol-Siddeley in November 1961.
« Last Edit: December 08, 2011, 04:33:08 am by sealordlawrence »

Offline tartle

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Re: Early British gas turbine development
« Reply #51 on: December 08, 2011, 04:40:08 am »
Sir Denning Pearson wrote a paper about the Aero industry in the West since WW2, published in 1962. The paper was an honest attempt to give a clear picture of what was going on in the industry at that time and obviously gives the view as seen from Rolls-Royce's perspective, but was not intended to be biased. I have copied the relevant sections for our perusal and comment.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline alertken

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Re: Early British gas turbine development
« Reply #52 on: December 11, 2011, 01:47:33 am »
(I have not yet read tartle's Den). My take on the general demise of DH, not confined to Engine Co.
 
Sir Geoffrey was co-opted onto Brabazon Committee, 5/43. Various Sir Freds were not. Within 1944 he had won Type II, Airspeed AS.57, Type V, DH.104, and Type IV, DH.106. Military would be of modest business in Victory, so didn't he do well? He reconstructed the firm in 1944 in Aircraft, Engine and Propellor Cos. and recruited the great and good to manage them. His own span of control stretched, and losing a son did not help. By 1949 he had Sir Ralph Sorley (he of 8x.303 in Hurricane/Spitfire) at Props - who took them into his ex-MoS' mates' Guided Projectiles; he had Frank Halford as Engines MD and ex-MoS Sir Aubrey Burke as its Chairman. Halford in 1944 defined the future as H.1 (Goblin), H.2 (Ghost), H.3 small turboprop, H.4 (big Gyron), H.5, a centrifugal turbojet above Ghost, below Gyron...but unsuitable for Aircraft's super-Venom, to be DH.110). Halford later added H.6 (Gyron Jr) and H.7 gas generator.
 
MoS funded H.4, later H.6; Sir Geoffrey funded nothing PV and sold H.7 to Napier. Halford retired. Props (GW) and Aircraft took up Sir Geoffrey's and everybody's time. (Your choice of cause and effect:) applications for Gyron/Gyron Jr. stumbled. Engine Co. became the poisoned chalice berth, career-wise, just as Special Projects/Weapons Research were to be avoided at Vickers and Avro. Drift, demise, sale to BSEL as Small Engines Division.
« Last Edit: December 11, 2011, 01:51:32 am by alertken »

Offline JFC Fuller

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Re: Early British gas turbine development
« Reply #53 on: December 11, 2011, 02:52:17 am »
Military would be of modest business in Victory, so didn't he do well?... Halford in 1944 defined the future as H.1 (Goblin), H.2 (Ghost), H.3 small turboprop, H.4 (big Gyron), H.5, a centrifugal turbojet above Ghost, below Gyron...but unsuitable for Aircraft's super-Venom, to be DH.110). Halford later added H.6 (Gyron Jr) and H.7 gas generator.


That is my theory, Halford appears to have been allowed to run and develop a range if military jets with little consideration for the fact that they were not suitable for the military aircraft that airframes were building or for the Civilian aircraft that were becoming the focus.


So for aircraft propulsion gas turbine manufacturing I have:


Armstrong Siddeley: ASX
Metrovick: Eventually became Sapphire
RR: Enough said
DeHavilland: Ghost and Goblin
Bristol: Theseus
Napier: Naiad and Mamba


Am I missing any others?


Offline tartle

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Re: Early British gas turbine development
« Reply #54 on: December 11, 2011, 04:08:21 am »
The roots of the way post WW2 industry developed started way back...
The building of the aero engine industry in the UK started in 1919.
In February 1919 Lieut Col L. F. R. Fell took over the duties of Assistant Director of Research and Development (Engines) under Brigadier-General Brooke-Popham who was appointed overall Director of Research at about the same time.

As Fell explained at a November 1965 lunch with Frank Nixon, an old colleague and presently the director of Quality at Derby, and myself (earning my meal by making notes of the conversation), "There was very little money to spend on engine development, only a few hundred thousand pounds a year, and production was on so small a scale that it could only be made commercially attractive if the prices were high. There was no time to create new designs. All we could do was to examine what was available, concentrate on the development of the most promising, and reach a production stage at the earliest moment, not only to save time but also to conserve the small amount of money available for development expenditure. For the same reason the industry was restricted to not more than four engine builders. Direct competition between engines of similar types and power could not be supported. the makers and their engines that were chosen for future development were:
Siddely-Deasy Jaguar: Double row 14 cylinder air cooled rated at 350 hp
Cosmos Jupiter: single row 9 cylinder air cooled 350 hp
Napier Lion Broad Arrow 12 cylinder liquid cooled 450 hp
Rolls-Royce Condor 12 cylinder Vee liquid cooled 650 hp
These engines were selected as representing clearly defined lines of development on which each engine builder could specialise. History has shown that this policy was sound taking into account all the difficulties of the time. Napier was on the verge of bankruptcy, Cosmos was in liquidation, When Fell visited Derby to discuss engine development Rolls-Royce had expressed (unknown to Royce) themselves as having no interest in aviation and wished to concentrate on their backlog of car orders. Only Siddeley was able and keen to cooperate immediately.
By the mid-1920's Fairey tried to upset the situation with the licence for the D-12; Napier were complacent with production engineers running the show; Bristol and A-S were busy with radials. Fell tried to get Napier to do a British answer to the D-12, even scheming an engine based on Napier Lion components... they were not interested as they had other ideas.. go back to the Mercedes WW1 construction to help manufacturing!
In desparation Fell asked Royce to do a D-12 killer even though it was out of the agreements on horsepower. Royce had been testing a monobloc aero engine so all the experience was folded into an F.X scheme from which emerged the Kestrel. Napier dwindled and tried to stay in the race with Halford's help... it was actually Brodie who was the person to turn Halford's concepts into things that might work.
When Whittle got into gas turbines BTH... in case I exceed post-size I'll continue separately.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Trident

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Re: Early British gas turbine development
« Reply #55 on: December 11, 2011, 04:16:26 am »
A Canadian patent of 1947, (CA452368A), introduces a front and rear fan concept. The front fan of the engine is like a child's windmill at the outer edge... driven round as work is transferred from the rearward moving air in the intake; the inner row of blades are arranged as a compressor increasing the pressure of the intake air, i. e. work done on outer row is transferred to work done on air in inner row... then the W2/700 type core engine generates an exhaust stream that works on the rear fan in a conventional manner.
Interesting - probably an attempt to overcome the limitations in LPT work extraction and hence fan bypass ratio in aftfans due to the lack of supercharging of the engine core by a conventional LP compressor/fan. Weird though!

Offline tartle

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Re: Early British gas turbine development
« Reply #56 on: December 11, 2011, 05:36:49 am »
Off the top of my head......
Whittle chose BTH to help with development as they were steam turbine (rotating machinery) experts. When Rover were designated the production partner issues developed about who had design authority and who had change authority. Whittle tried to maintain control over design whilst Rover wanted to address the technology to production challenge by ad hoc changes a Barnoldswick. The friction caused slowed things down!Rolls addressed manufacturing challenges of piston engines by ruthlessly pruning production projects... trying only to support Merlin and the bigger Griffon, other projects took second place. When RR was asked/volunteered to help Rover/Power Jets with development they made haste slowly, building 2 centrifugal engines as learning exercises for Stanley Hooker and the team. Then they arranged to swap the manufacture of a tank engine version of the Merlin (done to help get enough power into tanks with WW1 Liberty engine technology). Griffith kept on with axial thinking and by the end of the war was looking at single, two and three spool engines... which led to the AJ65- Avon.
Tizard wanted to widen the expertise being focused on the gas turbine and so as the RAE realised Metrovick had their hands full with the F.2 they turned to ASM who hd built and supported the Griffith rig at Farnborough. ASM were not developing any high priority engines although they were producing many existing designs.. this meant thay could take on turbine work in the experi area. So the ASX based on RAE rig work was born.
Napier were challenged by the Sabre and remained so till the end of the war. At that stage they were entrusted with a gas generator design that turned into the Naiad, then the Eland and Gazelle. I worked on the latter on its transfer to Derby and found assembly a nightmare as well as discovering no sane manufacturing engineer could specify the manufacture and build steps of the compressor. As an apprentice I was given the jobs of rewriting the Napier instructions onto RR headed paper.. an easy job? No, the instructions did not work.  A friend was courting a lad who went to Liverpool Uni and met a girl whose dad had recently retired as superintendent of the Speke facilty. We found out that the assembly and balancing of the compressor drum was a 'black art' and that was eventually specified on paper! What a way to win orders for your jet engines... no wonder Napier faded away.
Bristol had lost Fedden and his key engineers (such as Nixon mentioned earlier) and the gas turbine engines they came up with were a nightmare. Hooker fell out with Hives and moved to Bristol... it was he who took turbine development by the scruff of the neck and sorted the Proteus out... the configuration was flawed so he went on to design a new turboprop... the Orion
Fortunately Hooker arrived in time to take the design of the BE 10- the Olympus- into a much less tortured area of the design map and saved the engine division from ignominy. So the company map began to look more like pre war days with ASM, Bristol Napier and Rolls taking a leading role, Metrovick reverting to non-aero and de Havilland enduring by sheer effort and maybe also Napier's lack-lustre performance; this was was not improved by their obsession with the Nomad.. perhaps the diesel division saw it as a good technology platform... certainly its axial compressor should have read across to their early aero gas turbine work. As the direction of dominant gas turbine configurations became cleare and cash got tighter the reversion to a prewar 4 was attractive with a further concentration following as cash got even tighter? The growth of civil aviation was also playing a role as the development monies had to be found even if repaid by royalties. Success in terms of numbers of each engine built was now important as the need for launch money became dependant on previous (economic) performance.... a new world.
« Last Edit: December 13, 2011, 12:53:05 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #57 on: December 11, 2011, 06:34:22 am »
Getting back to the thread ...
Here is a Rolls-Royce layout of the Griffith turbofan shown in post #38. Work on this engine continued until 1944.
Also a link to the Armstrong Siddeley designs inspired by their work on the RAE Griffith contra-rotating rig
« Last Edit: December 13, 2011, 06:02:33 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline alertken

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Re: Early British gas turbine development
« Reply #58 on: December 11, 2011, 12:39:08 pm »
T: thank you.
 
I now have read den. Tight summary of this industry's history. Shame that he descends into begging. Because moaning about Treasury Sales Levy on products created at (our) expense, is begging. That attitude directly led to RR's demise, in which Denning Pearson was key. (We had) “promised a bit more than we could perform (we) never got cash-flow into our heads.” Sir D.Huddie,RR MD, in P.Pugh,Name/II,P156/i] RR expected MoS to funnel Aimed Research+Launch Aid in the National Interest, to admit PV R&D in prices (it is disingenous of den to claim (£33Mn) vast PV investment: it went straight back into overhead on MoS prices), and to waive the Levy by which Treasury (=you and I) recovered Launch Aid: L’État, c’est moi; what’s good for RR is good for UK. Not so.
« Last Edit: December 11, 2011, 01:13:47 pm by alertken »

Offline tartle

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Re: Early British gas turbine development
« Reply #59 on: December 11, 2011, 02:13:42 pm »
Alertkin,
They were interesting times...
Post bankruptcy we had to meet a reduced type test on RB211 at an agreed performance increase seemingly each month in order to get paid... we worked like hell to do the reduced Type Test every two weeks so we could have a second go if our DFA drawing driven modifications did not do the job (DFA= Design Fast Action... draw agree run it across road make build test; do it again faster better!).
Yes launch aid is useful and there should be payback; we are all investors in our future, etc..
I also remember den arguing that RR was a better bet for launch aid as it was just about the only engine company to make enough sales to pay it back... so I think the top team actually thought it was a useful source of funds... I suspect the terms of loan were beginning to be too demanding.. even from a taxpayers' point of view! Or maybe looking out gives a distorted view.
« Last Edit: December 13, 2011, 12:51:49 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #60 on: December 14, 2011, 10:33:30 am »
The mathematics of going turbofan were quite persuasive in the mid-1940s. The Germans were actually first to do a turbofan...looking more like a bypass in the RR Conway sense. SNECMA cooperated on a design scheme to put an aft fan on the Rateau turbojet.
These line drawings can be found in Tony Kay's two volume book 'The early History and Development of the Turbojet'.
« Last Edit: December 14, 2011, 05:05:55 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #61 on: December 20, 2011, 04:15:18 am »
...and why did it take so long to adopt axial compressors? One reason was consistent, high quality manufacture. We discussed the low level of a Parsons compressor above. Here is a couple of pictures of a typical turbine they were turning out in 1895; Rolls-Royce assessed the aerodynamics in terms of what we know today as:
100KW Steam turbine
•Pitch/chord a bit too low.
•Tip thinning on suction side.
•Trailing edge FAR too thick.
•Surface roughness poor.

Compare the photos below with that of #9 above.

Anecdotally... Metrovick were accused of dragging their feet on the F.2, but they did work with High Duty Alloys on pressing techniques in order to turn out blading that was consistent, both blade-to-blade, and engine-to-engine. In the long run Metrovick made rapid manufacture more likely but at the expense of seeming slow to the Ministry.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline PMN1

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Re: Early British gas turbine development
« Reply #62 on: December 26, 2011, 04:55:45 pm »
in which Denning Pearson was key. (We had) “promised a bit more than we could perform (we) never got cash-flow into our heads.”


From what i've read, he had some 'interesting' accounting ideas.....

Offline tartle

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Re: Early British gas turbine development
« Reply #63 on: December 28, 2011, 01:11:22 pm »
Donald Eyre, who taught me much about advanced project design, worked with Griffith for 21 years translating his sketches into design schemes that had a chance of being practical..a fascinating challenge. He drew a perspective of Griffith's latest idea for a gas turbine which was shown to the King and Qhenn on a tour of Derby works Aug 8th 1940.
Spurred by comment in next post... I have added a pic of RB211-535 for comparison
« Last Edit: December 29, 2011, 04:37:41 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Johnbr

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Re: Early British gas turbine development
« Reply #64 on: December 28, 2011, 04:27:26 pm »
Very cool does not look like a 1940 design.

Offline tartle

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Re: Early British gas turbine development
« Reply #65 on: December 29, 2011, 06:54:47 am »
Johnbr ... I agree it looks almost like the style of the RR Propfan of today... it is based on thinking rather than actuality so it is only when technology (materials, tools, techniques and skills) catch up that they turn into practical reality...
Of the contraflow Griffith's right hand man and translator to something visually discussable had some thoughts...

Don Eyre wrote in his book:
"Returning to the contraflow engine itself, after thorough rig tests of bearings, combustion chambers and burners, etc, the 14-stage high-pressure unit was built for test; the first run being on 3rd March 1942. Alternative schemes of blade cooling were investigated and a specimen twin-blade was cast in Vitallium with a hollow turbine blade. A small hole through the intermediate shroud permitted cooling air to flow from the compressor annulus into the turbine blade. Various schemes of airborne bearings were also devised by Dr. Griffith. Many features of the engine were optimistic relative to the knowledge of gas turbines in those days and the initial tests showed clearly that considerable development would be necessary. The fact that the turbine and compressor blades were indivisible would add to the cost of testing alternatives of either and methods of blade manufacture were in their early stages. Accurate profiling of aerodynamic shapes had not been developed and the blade form in the test engines had been seriously modified to suit avalable milling cutters, thus jeopardising their performance and inducing premature surging. The compressor had a much lower efficiency than Dr. Griffith predicted on the basis of accurate blade profiling and effective interstage sealing and the ARC recommendedthe discontinuance of research.
During the eries of tests, I drew a revised contraflow scheme, designed to eliminate some of the difficulties and to incorporate improvenents which the tests had shown to be desirable. However, by the time accurate blade shapes were attainable, the simpler forms of gas turbine - valuable as a short-term war expedient - had progressed so satisfactorily that the need to return to the contraflow principle did not arise and further work on the engine was suspended although Dr Griffith continued for some time to study various alternative contraflow arrangements. "

A fascinating insight into the challenges faced in developing a new form of prime mover by the designer who had to transform Griffith's ideas into testable hardware.
His book 50 Years with Rolls-royce: My Reminiscences (Rolls Royce Heritage Trust Historical Series)is worth a read if you are interested in a descriptive account of working for Royce himself and his senior engineers over  the years.
« Last Edit: December 29, 2011, 04:18:23 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #66 on: January 02, 2012, 10:38:37 am »
Stanley Hooker, Adrian Lombard and co, up in Barnoldswick had a good working relationship with Frank Whittle and took notice of his efforts to create  both a fan engine and a turboprop. engines were investigated whilst they put a gearbox on a Derwent and produced the Trent engine. The RB 39 was schemed out by Hooker's team to be used either as a fan or prop engine. It was decided to proceed and the turboprop seemed the first version to be of use.. there were suitable aircraft being investigated. Aimed to deliver 3,000 shp the RB 39, to be known as the Clyde was stared in 1944. Anyone who has studied the wartime developement of the Merlin will know how adept Hooker was at suggesting adding a bit of this and a bit of that to quickly get a prototype (put a Vulture supercharger in front of the Merlin supercharger yields a twin stage supercharger for the Merlin). Having looked at scaling the Merlin 2-stage supercharger as the basis of the turboprop, Hooker opted for a two-spool engine, giving a PR= 6.0, consisting of an lp turbine driving a gearbox that had shaft outputs for the propeller and the 9-stage axial l-p compressor- which was in fact David Smith's seventh design iteration of the Metrovick F.2 engine, being downrated to 6,000 maximum speed (PR=2.65); co-axially was a single-sided hp centrifugal compressor of 2.35 PR, a scaled up Merlin 46 supercharger, driven by a single hp turbine. The engine ran on 1st Aug. 1945 giving 2,000 shp... sorting out the mismatch between the compressors soon yielded its design power and by the time the ninth engine was built horsepower had reached 4,200 shp. (in 1949). It was a great engine in the Wyvern but for various reasons Hives never let it go into production, one reason being his belief in the Avon as the next Merlin. The Clyde behaved well during its development programme but the fan version was never built
The section drawing and a photo of the Clyde on test are below:
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #67 on: January 02, 2012, 02:49:13 pm »
So let me get this straight, The Clyde axial LP compressor was
driven via the propeller reduction gearbox, and not directly via
the LP turbine.......


Quote
the 9-stage axial l-p compressor- which was the Metrovick F.2 ... co-axially was a single-sided hp centrifugal compressor of 2.35 PR, a scaled up Merlin 46 supercharger,
No wonder the Great Gunston said of this engine in 'World Encyclopaedia of Aero Engines' :-
"Though it looked like two engines joined together"


cheers,
         Robin.
Where ARE the Daleks when you need them......

Offline tartle

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Re: Early British gas turbine development
« Reply #68 on: January 03, 2012, 04:13:17 pm »
Robin,
My only comment to Bill Gunston is only 2 ..have you seen the Clyde dressed for installing in the Wyvern?
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Spark

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Re: Early British gas turbine development
« Reply #69 on: January 04, 2012, 10:13:43 am »
 
Happy New Year,
 
Clyde Fan etc, the manufactures all  waited for Frank’s patents to run out?
 
 
Robin,
My only comment to Bill Gunston is only 2 ..have you seen the Clyde dressed for installing in the Wyvern?

Offline tartle

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Re: Early British gas turbine development
« Reply #70 on: January 06, 2012, 02:46:28 pm »
I think there was a better relationship between RR B'wick and Whittle..as a friend of Sir Frank reminded me the other day... it was Rover's top management that he couldn't abide... apparently.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #71 on: January 06, 2012, 03:33:59 pm »
That's only the third image of the Clyde that I've seen............ ;D




cheers,
         Robin.
Where ARE the Daleks when you need them......

Offline tartle

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Re: Early British gas turbine development
« Reply #72 on: January 07, 2012, 02:17:22 am »
Blame it on kleptomania in the 1960's!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline PaulMM (Overscan)

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Re: Early British gas turbine development
« Reply #73 on: January 07, 2012, 03:02:18 am »
Renamed topic as it is increasing wide-ranging.
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Offline tartle

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Re: Early British gas turbine development
« Reply #74 on: January 08, 2012, 02:47:32 pm »
Let's keep it pre-Avon, Olympus, Sapphire on this thread or we will diverge even more..we can do those elswhere but that seems to be a natural break,  if people are happy with that?
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline JFC Fuller

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Re: Early British gas turbine development
« Reply #75 on: January 09, 2012, 02:00:58 am »
Let's keep it pre-Avon, Olympus, Sapphire on this thread or we will diverge even more..we can do those elswhere but that seems to be a natural break,  if people are happy with that?


Sounds like the perfect split to me; nicely takes into account the primary wartime developments.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #76 on: January 09, 2012, 07:42:21 am »
So was the Clyde compressor geared up or down from the LP turbine speed?

Offline tartle

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Re: Early British gas turbine development
« Reply #77 on: January 10, 2012, 02:58:01 pm »
When I have got some spare time I will, unless a gear expert out there wants to, calculate the gear ratios; but assuming the MV turbine ran optimally and as the Clyde is derated to a lower pressure ratio my guess is compressor runs slower.. but my guesses can be hopeless so I'll do more digging! aha! lp turbine is 12720 rpm and lp compressor is 6,000 rpm, hp is 10,800 rpm.. both ends!!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #78 on: February 13, 2012, 03:08:17 am »
We must not forget the impact of Whittle on early gas turbine development in Britain. There is an interesting family tree of Rolls-Royce RB centrifugals that grew as RR took an interest in the activity at Barnoldswick and began to help Whittle to keep development on track.
RR's centrifugal branch starts with the WR.1, a learning engine done at Derby, and then gets into full swing with the W.2/23 soon to be RB.23 Welland; Lombard straightened out the /23 to create the /26 which annoyed Whittle but when inherited by RR became the RB.26 which was the technology demonstrator for the RB.37 Derwent, followed by the RB.41 Nene and RB.44 Tay ... the latter having a better life abroad as Hives switched efforts to axials...
So we'll start with the WR.1............

Rolls-Royce got involved with the Whittle's development team at Power Jets quite early on in the development of a practical flight engine that Rover aimed to put into production. In August 1940  Hooker took Hives to Lutterworth to see the W1 engine running .. at the time it delivered 800 lb thrust (for powering the Gloster E28/39) and Hives thought it must be a very 'small' engine. Hooker calculated that the Merlin in a Spitfire flying at 300 mph delivered 840 lb thrust which changed Hives' view immediately. Whittle meanwhile  was working on a larger a larger engine for the Meteor. It turned out that there were no facilities for running the larger impeller so Whittle was working in the dark as to how good his design was; during a war the more you can find out before you commit designs to manufacture will shorten development cycles and time.
In spite of the difficulties between Rover and Power Jets over what design authority Rover had over PJ designs (maybe benzedrine played a part in all that) Whittle did not feel that way about Rolls-Royce and when Hives offered help to get the W2 moving he took up the offer immediately. In spite of the huge committment to developing and producing the Merlin plus supporting Ford's factory in Manchesterand Packard's in the USA RR were able to supply some of the critical parts that were delaying the testing and improvement of the W2. Realising that Whittle's PJ team were having to estimate compressor performance and modifications and then test them on a real engine as there was no test rig in the country powerful enough to drive the compressor.  RR suggested a better way was to build on their supercharger experience... Stanley Hooker and Geoff Wilde immediately proposed a rig design that could be quickly built at Derby. The rig was a Vulture 2,000 hp engine driving a 6:1 step up gear increasing the Vulture's 3,000 rpm to 18,000 rpm of the W2. The step up gear was simply constructed by taking two Merlin reduction gears, mounting them in series and then driving them backwards! The individual reduction gear ratio was 0.42:1 so backwards it provided about 2.5:1; so two in series easily gave the 6:1 requirement. Using the rig enabled Whittle to cut and try various fixes to the surge problem and eventually the surge characteristic was made tame enough for service operation
All this support work... compressor testing, turbine blade manufacture in the experi machine shop, etc made Rolls-Royce realise that they needed to get some design and testing experience of their own. The WR1 was designed by Stanley Hooker's Derby design team together with J.P.Herriot as the development engineer. The brief was to follow the conservative initial design phase as used in piston engine development allowing for uprating as experience built up.
The Ministry funded the manufacture of six engine sets of parts so the project went ahead.....
« Last Edit: April 25, 2012, 04:48:20 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #79 on: April 08, 2012, 04:06:28 am »
The catalyst for Rolls-Royce to move from making parts for the W2B was the first flight of the Gloster E28/39  15 May 1941.
Given the other (Merlin, Griffon) priorities at Derby, it was December 1942 before the WR1 was first run
The basic data and comparison to other engines of the time shows how cautious Derby was in entering a new field of technology
(all figures from RR data sheets 1945)
Basic data                                        CR1             B23             W2/500           W2/700
design mass flow lb/sec                   46               31              32.2                  40
max thrust lb                                   2,000          1600           1700                 2,000                 
sfc lb/lb/hr                                          1.27          1.12             1.1                     1.08
max temp deg K                               1,000         1,060           1,000                1,000
max rpm                                          10,000        17,100         16,750             16,750
compression ratio                             2.67           3.9               4.0                     4.0
compressor dia in.                            27.5           20.68            20.0                 20.68
No combustion chambers                 10                10                 10                   10
turbine mean blade speed ft/sec      938            1040             n/a                   n/a
weight lb                                          1,200          850               850                  875
length to end exhaust cone in           78              71                61                     61
max dia in                                          51.5           40                40                     42
-----------------------------------------------------------------------------------------------------------

Taking the W2B as the starter, RR designed their own impellor based on Merlin experience. of design AND manufacture. The mechanical design also differed from the W2B series as RR explored ways of overcoming the deficiencies of the PJ design. It was an experimental rig... not designed to fly and so was comparitively big for its given thrust. The first engine ran for some 35 hours during which the combustion equipment gave trouble so an extensive programme of experimental work started on combustion chambers and turbines was initiated.
The advent of impellers giving 4:1 compression ration and other technology advances rendered the engine concept obsolete and the WR2 improved version never got beyond the project idea stage. The engine introduced Stanley Hooker to the challenges of turbine engine design and also J.P.Herriot who was on loan from the AID at MAP since 1940 (to Rover and RR) gained valuable experience as the development engineer on the project.
I have attached a diagrammatic x-section of the WR1 and B23 for comparison (Note fullscap doesn't fit A4 scanner- will get them redone) and a photo of the prototype.
« Last Edit: April 10, 2012, 04:18:20 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #80 on: April 11, 2012, 02:58:40 am »
To move on to the later developments at Derby we need to retrace our steps and understand the trials and tribulations of Power Jets and Rover. The technical side of the story- in detail for the WU and W1 and less so for W2 can be found in the First James Clayton lecture which can be downloaded here. Note you will have to pay if you go via Sage!
We will pick up the story as the W1 needs to be uprated. Jim Boal gave me a copy of his W1 drawing (below) and he will feature in the Tay story later.. he was unique in that he had continuity of working first at PJ, then Rover and transferring to RR. The W1 was basically a flightworthy redesign of the WU based on the same dimensions for rotating machinery.   
The idea for an aircraft (extract from On the aerodynamics of the Gloster E28/39 – a historical perspective by B. J. Brinkworth, the Aeronautical Journal June 2008:
"Gloster Aircraft Company had become part of the Hawker Siddeley Group in 1934. In 1939, the Company was producing the first of its Hawker Hurricanes, of which 2,750 were eventually built at the Gloucester plants. The Hurricane had been in service for barely two years, and so it will be appropriate to weigh features that emerged in the E28 against those already proven in the Hurricane, and, as the design proceeded, with Hawker’s successor, the Typhoon. This aircraft was also produced in quantity at Gloucester in due course.
The definitive version of the Whittle engine, around which the Specification was to be written, was the W2, intended to produce a
sea-level static thrust of 1,200lb. At a high cruising speed, this engine would give a thrust power comparable with that of the Rolls-Royce Merlin II installation of the Hurricane II, which was then going through the factory. However, the weight of the power-plant would be around a third of that of the Merlin and its associated equipment. Thus, a lighter and smaller aircraft could be envisaged, having correspondingly lower drag, with power available that would enable substantially higher performance to be obtained. The improvement would be greatest at higher altitudes, where the thrust of the jet engine was predicted to fall off less with height than that provided by a piston engine...............
........
Even in plan view, the fuselage still seems tubby, perhaps due to its size relative to the wings. The maximum width of the fuselage is around one-sixth of the span, twice the proportion for the Hurricane, for example.
There was discussion on the effects of the flow required by the engine on the internal duct flow and external airflow. The nose intake and the ducting up to the engine bay were initially designed around the air mass flow-rate of 26lb/sec at sea level, then predicted for the W2 engine at maximum rpm. Whittle had assumed in performance calculations that the energy loss in the ducts would be 10% of the energy at inlet, a substantial penalty. Carter had accepted his advice that the mean velocity in the outlet of the duct, at the engine plenum chamber end, should not exceed 100ft/sec (though RAE representatives thought that the loss would not be 10% even if a mean velocity of 200ft/sec were used, as had been initially proposed by Gloster). At the nose, the diameter of the intake in the Intermediate design had been 18in, with an area of 1⋅76ft².
In the Final version, the diameter is 21in (area 2⋅4ft²), corresponding to a nominal mean inlet velocity of around 150ft/sec at the design point. This would have allowed also for the additional flow expected to be required to provide cooling air for the rear turbine bearing of the W1A and W2 engines, which would be used after the first few flights
Two ducts convey the air from the nose intake to the engine plenum chamber. Bifurcating the flow immediately after the intake, these are straight in elevation, passing along the sides of the fuselage, around the nose-wheel bay and the cockpit, to form two smooth curved tubes. Each has a non-circular and varying cross-section, with three full-length streamwise dividers. It would not have been a simple matter to calculate the flow losses in these, but no records of test measurements have been found. Significant further
losses would have been caused by the radiators, that were initially fitted at the engine bay ends of the ducts. These had been provided for cooling the W1 engine intended to be used for the taxying and initial flight trials, which, being based on the test-bed models, had a water-cooled turbine bearing. Fortunately, air-cooling became available for the W1A version, fitted after early trials with W4041, and for the W2 engines for the main series of tests with both aircraft, so the radiators were not then required.
The delivery of the intake air into a plenum chamber ahead of, and surrounding, the engine compressor casing meant that two bulkheads and part of the airframe structure were subjected to an internal pressure difference. It was agreed that this should be based on the full stagnation pressure at sea level maximum speed (410mph), about 3lb/in². Later, a design value of 5lb/in² was adopted, with a reserve factor of 2. This perhaps represents the first time that a substantial part of the primary structure of an aircraft had to support a pressure difference of this magnitude."

I have added drawings and photo of the aircraft to supplement the text.
« Last Edit: April 12, 2012, 03:52:34 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Trident

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Re: Early British gas turbine development
« Reply #81 on: April 11, 2012, 06:46:11 am »
I suppose this as good an opportunity as any to thank you for your efforts, tartle! I've been reading your notes with great interest and the fascinating insights they provide into this pioneering era are much appreciated, do please keep it coming!

Offline tartle

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Re: Early British gas turbine development
« Reply #82 on: April 11, 2012, 10:14:20 am »
Thanks... it is difficult to gauge whether it is useful without feedback.. which also helps steer the material.. more technical/less technical? more people ... etc.
Incidently the gap in transmission was due to a very early rotating engine the Gnome Omega 50 hp rotary no. 377 which belonged to Maurice Egerton, pioneer aviator 1909-14... he lived at Tatton Park and the engine is in the Mansion.. they have an exhibition of his exploits until beginning of May which I helped put together... he inspired Stanley Hooker who mentor Geoff Wilde who mentored me... but that is another story!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #83 on: April 11, 2012, 10:47:25 am »
 Mike Evans who is emeritus president of RR Heritage Trust is a patient man. When he was in RR Public Relations dept at Derby he would patiently reply to a certain schoolboy's stream of questions that arrived quite regularly... later when I joined RR as an apprentice engineer I was assigned to work a period with him. Mike got his own back and helped my knowledge acquisition by handing all the schoolboy and other questioners's letters to me with a quip "off you go then, find the answer to that one!"
Mike wrote an article about Lord Kings Norton (Roxbee Cox) in the April 1999 commemorative edition of the Aeronautical Journal:
"For his [Whittle's] WU engine in its various forms - the W1X and the W! engine that flew in the Gloster E28/39 at RAF Cranwell on 15th May 1941 - Frank Whittle was continually short of money and, therefore, inevitably, of hardware. Initially this had been sourced from BTH with specialist help on  components like combustors from Laidlaw Drew and Shell. To these sources in 1941 was added Rover which, with support from Lucas, was to build complete engines for Power Jets. Additionally, and informally, Rolls-Royce made parts to help Whittle directly and to support Rover on a sub-contractor.  But it got more complicated than that. Whittle's W! was followed by the more powerful yet more compact W2. When testing showed the need for improvements, Whittle designed the W2B and it was this engine which Rover was given to build. Progress did not stop at Lutterworth, however, the W2B was followed by the W2/500 and ultimately the more powerful W2/700."
The MAP by this time is supporting Halford's H1, RR's WR1 designed in Derby (with PJ support)  whilst  at Barnoldswick Rover are going off on their own initiative without consulting Whittle.
Mike continues, "Capt. Spen Wilks [Managing Director] of Rover proposed a joining of forces with Hives in February 1942, long before relationships with Whittle came to a head. When Rover 'straightened out' the W2B/23 to create the B26 -forerunner of what was to become the RR RB37 Derwent I - Whittle was furious. Understandably he saw it as a further diversion and, therefore, delay in getting the jet engine into service against the enemy." ....tbc
« Last Edit: April 11, 2012, 04:27:56 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #84 on: April 12, 2012, 02:35:05 am »
Roxbee Cox arrives...
Mike Evans continues:
"Such was the multiplicity of experimentation when Roxbee Cox first took office at MAP in 1940, and it continued to complicate itself in 1941. A first glimmer of a way forward rests in a letter from Roxbee Cox to Hives dated 21 August 1941: 'I do not expect there will be any obstacle in the constitution of a committee for pooling our gas turbine facilities and experience but it will take me a few days to make sure of everyone's co-operation.' On 3 October 1941, a letter went out over the signature of Air Marshal Linnell of MAP. It began:
'Dear Sirs,
As you are aware gas turbine development is now going forward in various organisations and along several different lines, and it is clearly desirable to ensure economy in our efforts to produce power units of this new kind as quickly and efficiently as possible. that all parties should collaborate.
To encourage and guide collaboration, it has been decided to form a committee under the chairmanship of Dr Roxbee Cox on which all firms engaged on gas turbine projects will be represented....."
Thus was born the Gas Turbine Collaboration Committee (GTCC) and the beginnings of drawing all the efforts to a focus. It  was not an easy or painless process and the losers were the creators of the gas turbine themselves. In the case of the RAE this was inevitable..... its role was recognised as a research and test agency. In the case of Power Jets Ltd - and Frank Whittle in particular - the case was very different.....tbc
« Last Edit: April 12, 2012, 03:49:34 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #85 on: April 12, 2012, 06:27:21 am »
Jim Boal, who we will remember is the continuity man, said that "there was no W2 design". It was a new an unproven design that Rover were trying to get into production. The extensive use of complex sheet metalwork meant that the production job could not be automated or deskilled by the use of machines so the amount of skilled labour determined the slow build up to quantity production. G. P. Bu;man who reported to Linnell and was director of both research and production wrote pithily in his memoir:
We [Bulman and Tedder] had all long since realised that Whittle was his own worst enemy. He was quick to invest any discussion with the venom of suspicion, scavenging throughletters and minutes of meetings looking for odd words and phrases he could pick on to suggest they were deliberately ambiguous and revealing a sinister influence behind the scenes. He saw us as determined to do him down lest his jet became damaging to the piston aero engine, the powerful array of engine firms and my department. I told him one day in a moment of exasperation that he was the most impossible man I'd ever had to deal with! He never forgot it.
Whittle had met with Tedder (Director  General for Research) and for the first time Wilfrid Freeman (head of MAP) on May 9 1940. Whittle protested that orders to Rovers should be by sub-contract through Power Jets; failing that he argued that he should be formally made chief engineer of the whole project. The two officersdid not agree. Tedder later remarked that Whittle was a 'prima donna -  very important but needed careful handling.
Rather than summarise Bulman's view of the W2 development and production 'complication' I have copied the relevant pages from the RRHT Publication Historical Series No 31 below.
« Last Edit: April 12, 2012, 06:29:46 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #86 on: April 12, 2012, 01:18:05 pm »
You may gather from the above that Frank Whittle was desperately trying to keep control of the detail design and development of his 'baby' and reacted furiously to Adrian Lombard's enthusiastic redesign of the B23. Whittle had originally adopted the reverse flow layout  to achieve a short engine to minimize shaft whirling problems. Whittle himself had ideas for a future development of the engine with straight through combustor air flow but felt that the priority was to get Gloster some engines for the Gloster Meteor. He was upset both by Rover's team going behind his back but also the fact that he had lost design control at Barnoldswick.
Returning to Mike Evans... he wrote that:
"As matters progressed, it became logical in the eye that Rolls-Royce should take over Barnoldswick and Clitheroe. The famous 5/- (25p) meal at the Swan and Royal did take place late in December 1942 as Stanley Hooker described but that was a handshake on what was, in reality, a MAP directive inspired, one suspects, by Roxbee Cox. He, in fact, wrote to Hives on 15 December 1942 following a meeting three days earlier at which they, Wing Commander Whittle and A. G. Elliott, Rolls' chief engineer,had been present. Roxbee Cox had undertaken to lay a series of points which had been agreed before his superiors. These included:
(a) Production of Power Jets W2/500 engine to be in the hands of Rolls-Royce.
(b) The facilities to be used to be those at Barnoldswick.
(c) Research on, and development of, centrifugal type units to be in the hands of Power Jets Limited at Whetstone and Lutterworth.
In the event it did not happen that way. Rolls-Royce did take over frrom Rover. Hooker moved to Barnoldswick at the very beginning of 1943 and the official handover day 1 April. Rover, in exchange, took on board the Meteor tank engine over an extended time horizon. But the factory was not cleared of all work to make way for the W2/500. Rolls-Royce continued with the W2B/23, launching it into service as the Welland in the Gloster Meteor fighter with 616 Squadron in little more than a year. 
« Last Edit: April 12, 2012, 01:26:21 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #87 on: April 12, 2012, 02:02:50 pm »
Now here is some good news and some bad... the bad is that I have mislaid my B26 notes; the good news is that while looking for them I found my RB60 notes which will be useful when we progress. In the meantime what we can say is that the spectre of shaft whirling in an engine was overcome by putting a spherical coupling designed by Lombard and a third deep ball bearing in the centre of the shaft. The coupling enabled varying axial loads to be transmitted as well as the torque loading whilst all remained in perfect balance.
The photo below shows STx 9.. the engine built by modifying the B23.. it is what we would now call a proof-of concept demonstrator. Lombard's team, pleased with the results redesigned the B26's inlets for increased air flow, and thus thrust. Eventually this became the RB37- the Derwent
« Last Edit: April 12, 2012, 02:10:59 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #88 on: April 12, 2012, 02:57:06 pm »
For those of us who aren't gas turbine engine specialists, please explain 'shaft whirling'........


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Offline tartle

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Re: Early British gas turbine development
« Reply #89 on: April 13, 2012, 05:53:25 am »
For a rotating shaft there is a speed at which, for any small initial deflection, the centripetal force is equal to the elastic restoring force.  At this point the deflection increases greatly and the shaft is said to "whirl".  Below and above this speed this effect is very much reduced.  This critical (whirling speed) is dependent on the shaft dimensions, the shaft material and the shaft loads .  The critical speed is the same as the frequency of traverse vibrations. 
Like a tuning fork a rotating shaft may go into transverse oscillations at its natural frequency. If it is slightly out of balance (and all real practical shafts are, if only minutely) then the resulting centrifugal force will induce the shaft to vibrate quite noticeably. Think of what happens if a balance weight falls of the rim of your car's front wheel. The vibration can be a little all the team but get worse at certain speeds... that's whirling. When the shaft rotates at a speed equal to its natural frequency then the vibration can build up and cause blades to scrape their casing and sometimes the shaft itself can fatigue and fail... also bearings can overheat.
The formula for a simple shaft between 2 bearings is the formula shown below:

where f is first critical speed; the deflected shape looks like a skipping rope.
I can define in detail if you like; but the main thing it highlights is that I, the moment of inertia is on the topline and the length between bearings is on the bottom. This means increasing diameter (I increased) increases the natural frequency and increasing length L drops it.
So if we look at the W2B/500, which has 2 bearings,we can see that L is 17.125 inches. The straight through flow Derwent V has three bearings but each span is quite large in comparison:
front to middle bearing is 23.7 and mid to rear is 21.94 inches making a total of 45.64; some 28.515 inches longer than Whittle's reverse flow engine... hence the need to rethink the bearing and Lombard coupling arrangement.

Hope this gives a feel for why Whittle and Lombard made their particular choices. The actual calculation of whirling speeds is more complex and takes into account the masses of turbine and compressor wheels etc. It is best to keep the critical speeds of the rotor above the design peak speed; if this is not possible then making sure the engine passes through the critical speed as fast as possible is an acceptable approach.
« Last Edit: April 13, 2012, 12:18:04 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #90 on: April 13, 2012, 03:15:10 pm »
Many thanks for the explanation, so, if i understand correctly, it's basically a resonance problem, made more severe by increasing the engine shaft length:diameter ratio. Therefore, by splitting the shaft in two, by means of a Lombard coupling, you get two short, thick shafts, with high natural frequencies, which should avoid this problem.
Would I be right in thinking that this is a similar problem to that suffered by the TSR.2's engines, and also the (infamous) ABC Dragonfly, though that of course was a piston engine...


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Offline tartle

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Re: Early British gas turbine development
« Reply #91 on: April 13, 2012, 04:40:06 pm »
Little work was done on the B26 until Rolls-Royce took over the Barnoldswick facility and had received four engines, as well as 32 B23s.
The latter engine became the first gas turbine aero engine to go into series production in October 1943. 167 Welland B23s were manufactured at Barnoldswick, before switching to the B37 Derwent, as the developed B26 was known.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #92 on: April 13, 2012, 04:49:55 pm »
Robin,
The ABC Dragonfly had a torsional vibration mode that sat on the operating speed of the engine leading to fatigue failures of the crankshaft after 2 hours running! This was the first time that vibration threatened to ground an airforce if the war had continued and led to a great deal of theoretical work with a Major A D S Carter deriving a way of calculating these resonant frequencies which was still good for Merlin calculations when that was being designed. The Olympus problem was vibration... I have some details that I will dig out.
Incidentally L F R Fell told me that in 1919 he had all the Dragonflies buried as the best way of disposing of them!
« Last Edit: April 13, 2012, 04:51:50 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #93 on: April 14, 2012, 04:02:57 am »
Robin.. your thought on Olympus was correct...
 John Wragg was the TSR2 development engineer at Bristol. He has said that:
“Indeed the worst problem that dogged the engine for the TSR2 in its development programme was the behaviour of the low pressure shaft. A much longer shaft was fitted to the 22R than had been in use on the earlier Olympus engines and that was, in part at least, as a result of trying to keep the engine bearing compartment as cool as possible in the much hotter environment that was going to be encountered in supersonic flying.
But unfortunately that change also resulted in the design of a shaft which was capable of being excited in vibration by a number of stimuli, one of the most significant being the resonance of a shaft mode with over-fuelling of the reheat system; this had been discovered immediately prior to the first flight of the TSR2. It was necessary to revise the fuelling of the reheat system at that stage and subsequently to introduce a completely new schedule to ensure the over-fuelling and consequent excitation was avoided.”
 
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #94 on: April 14, 2012, 05:17:38 am »
This is the University of Propulsion. Marvellous stuff.

How many pioneering aerospace engineers actually lacked the apocalyptic curmudgeonitude of Whittle, Johnson or Wallis, to name but three?

Offline tartle

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Re: Early British gas turbine development
« Reply #95 on: April 14, 2012, 07:40:25 am »
Before we move on to the RB37 Derwent engine it is worth putting Power Jets development efforts into perspective.
The first engine Whittle built was a 'proof of concept' test engine. Starting off with a single volute (rather like the RAE test units of the same era, although unknown to Whittle), Whittle knew this would deliver the air as a free-vortex flow to the combustor and ultimately the turbine blades and vanes. This gives a whirl velocity that varies, across the annulus, inversely as the radius. Whittle had left the detail design of the blade to the BTH engineers who, unfortunately designed blades according to steam turbine practice of the day, i.e. assuming whirl velocity was constant across the annulus. The result was that the turbine blades had only about half the twist they needed to perform well. The first build of the WU ran on 12 April 1937. A large amount of effort had to go into overcoming the turbine problem and other issues resulting in many minor modifications during the period April-August 1937.. without much improvement in performance. Whittle decided a major reconstruction was needed and so, in his words the 'second edition' was made. It had the same rotating assembly except for turbine blades, but in many other ways was a major tear up. The engine did not last long as the turbine disc exploded after about 5 hours running, in May 1938. The third  configuration, i.e. the second rebuild, had a major change to the diffuser and combustor. The combustor was changed from a single chamber to ten smaller chambers and the single volute became ten each feeding a combustion chamber - the engine was beginning to resemble the reverse-flow configuration we are familiar with today. Each combustion chamber discharged the hot gas flow through a ring of nozzle guide vanes into the turbine. The vanes and blades were designed on free vortex principles. The rig with the third configuration ran in October 1938. Problems were immediately apparent in the combustion chambers but the compressor and turbine were also troublesome. With this engine considerable progress was made. On 30th Dr Pye, Director of Scientific Research, witnessed the engine run up to 16,000rpm and was highly impressed. The following month the Ministry agreed to buy and loan back the WU engine. Also an order was placed for a W1 flight engine as well as an order on Gloster for the E28/39 aeroplane and design of both commenced.
Work continued using the WU until February 1941 when a failure of the turbine disc between the blade roots resulted in damage beyond repair.
The W1 flight engine was essentially the WU but with lighter construction. Water-cooled jackets for the turbine disc were similar to the WU but the rear water jacket was eliminated.
In order to gain time a similar engine, the W1X, was constructed from WU spares and W1 components rejected as non-flightworthy. This engine enabled Whittle to carry out a great deal of development work in advance of the W1 and was in fact fitted in the E28/39 for taxiing trials. In fact one of those trials resulted in the aeroplane performing a hop making the W1X the first Whittle engine to leave the ground!
The W1X experience paid off. The time taken from when W1 went to bench test to completing ten hours of flight trials was only 46 days.
British Thompson Houston (BTH) were responsible for the manufacture of both the W1 and W1X on sub-contract to PJ. To increase efficiency the turbine had 72 blades compared with 66 on the WU.
The W2 was now being designed and in order to check out some of the special features another engine was constructed to test out some of its features. This was the W1A, which incorporated an air cooled turbine disc, using vanes mounted on either side of the disc. Tests showed that having vanes on the bearing side only was sufficient to achieve the desired level of cooling.
A design principle, among others, of these engines was to use as high an exhaust velocity as possible, partly to get the highest mass flow for a given turbine size but also to reduce the degree of deflection needed through the blading. The W1 design target was a 1,000 ft/sec; the figure for the W1A was raised to 1250 ft/sec which corresponds to an exhaust mach number of 0.7. At such high speeds the flow is critical to sizing the diameter. The turbine disc cooling air discharging at the rim of the turbine disc formed a thick boundary layer on the inner wall of the jetpipe causing choking in the jetpipe. This in turn, Whittle reasoned was causing the compressor to surge. Removing the vanes at the rear of the disc reduced the outflow of cooling air and this cured the surging of the compressor.


« Last Edit: April 14, 2012, 09:38:53 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #96 on: April 14, 2012, 09:21:45 am »
The problem of thrust.
You may have noted that every new version of the Whittle engine seems to be accompanied by yet another version... this was driven by a desire to achieve the target thrust necessary to get first the E28/39 in the air and ditto the Meteor, with integrity and reliability also being important.
The WU engine was designed for a thrust around 1,300 lb but never achieved more than 1,000lbt.
The W1 was designed for 1,240 lbt but was cleared for flight at 860 lbt. In fact it could achieve 1,000 lbt for short periods.
The W1A was designed for 1,470 lbt but achieved 1240 lbt.
The W2 was designed for 1,000lbt but was really a failure, never achieving anything like enough power.
The W2B was designed for 1,600 lbt and after a considerable development programme achieved a 100 hour development at this rating in April 1943.
The W2/500 was designed for the same thrust and the design figure was actually achieved as soon as testing began on 13 September 1942, 6 months after design commenced.
The W2/700 achieved its design thrust of 1,800 lb very quickly and soon its rating was raised to 2,000lbt; later modifications enabled 2,500lbt to be achieved. It was essentially an improved /500 with more effective blower and longer turbine blades.
« Last Edit: April 14, 2012, 09:25:08 am by tartle »
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Offline PaulMM (Overscan)

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Re: Early British gas turbine development
« Reply #97 on: April 14, 2012, 01:51:22 pm »
Agreed, very interesting topic, I look forward to new posts here :)
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Offline tartle

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Re: Early British gas turbine development
« Reply #98 on: April 14, 2012, 01:59:47 pm »
In case you are wondering why I keep on about the W2/500..... when Stanley Hooker told Adrian Lombard to get on with the straight through engine to replace the Welland he took the best of the B26 (STx9) and the best features of the W2/500. Using as much of the B23 as possible Lombard's team came up with the B37 Derwent 1.
The improvements in performance of the W2 series came about through the interplay of several factors.
Compared with the W2B the W2/500 had a larger hub/tip ratio which permitted an increase in mass flow. Also fewer turbine blades of longer chord were used; the number used on the W2/500 was 54 each with a chord of 1.4 in., compared with 72 blades of 0.8 in chord. The change to fewer, larger blades was made on the recommendation of the RAE after the W2B suffered a number of turbine blade failures. The new blades were more resistant to the gas bending forces (lower stresses) and minor damage from solid particles passing through the annulus.
Metallurgy was key to development of a light, reliable engine. The advent of Whittle's gas turbine created the need for stronger, more durable alloys capable of high-temperature service When the WU was designed the best available material was Firth-Vickers 'Stayblade' and this was used for both disc and turbine blades. By the time the W1 was on the boards, F-V had produced an improved alloy- Rex 78 and this was used for the blades.  But the first to answer the challeng was Leonard Bessemer Pfeil, who is credited with the development of Nimonic alloy 80 in 1941, at Henry Wiggin's research facility in Hereford. This alloy used for the blading was introduced into the later stages of the W2B development programme and in the W2?500 and /700 from the start.
The top two development issues that kept the W2B engineers awake at night were surging of the compressor and turbine blade failures. Some blade failures were a secondary consequence of a failure elsewhere. A piece of combustion chamber that had broken off could pass through the rear of the engine, notching blades on the way and this often led to blade failure. One series of failures was odd. Sometimes blades failed at the root sometimes half way up and occasionally close to the tip. Resonance would be expected to produce failures at the same place. Eventually it was realised failure was caused by a thermocouple mounted in the exhaust duct 3 inches downstream from the turbine. It was adjustable radially across the annulus and Whittle believed that there must be an upstream pressure field ahead of it of sufficient magnitude  to interfere with the flow through the blades as they passed through it. It seems this was a correct diagnosis as the failure rate dropped dramatically after the thermocouple had been removed. [but it foretold of a similar problem that occurred during early development of the RB211 some 30 years later].
Another source of grief was the rubbing of turbine blade tips. The running clearance was intended to be small in order to minimise aerodynamic losses; unfortunately it is start-up and shut-down that determines the clearance. For instance at shutdown there is a sudden draught of cold air through the annulus which rapidly cools components of small mass like shroud rings, vanes, and blades but larger items, such as the disc cool more slowly. This means if the running clearances are too small the shroud ring could contract onto the blade tips on shutdown and at worst pick up the melted tip of the blades which would cause bending forces as blades passed over the material or as serious it could just lock up the rotating assembly causing much damage.
« Last Edit: April 16, 2012, 04:13:34 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #99 on: April 15, 2012, 05:37:44 am »
Upto now all the reverse-flow engines that can loosely be thought of as of the W2 family have kept the improvements within a 42 in diameter and a similar length of 61 inches, although rearranging accessories makes the Welland come out at 71 in. As mass flow increased the original impeller diameter was increased from 19 in. to 20.68 in. also the vane length at the tip increased for the same reason. It is interesting from a political viewpoint to be enraged by Bill Gunston's comments that the arrival of RR at the Barnoldswick factory immediately brought the engineering magic to the project which accounts for the fact that in December 1942 Rover achieved a W2B running time of 24 hours whilst in January 1943 RR had the W2B running for over 400 hours -magic indeed? The truth is more straightforward and is often met today! John Herriot, the AID engineer on loan to Rover's was an expert on manufacturing issues and their resolution. He was appalled by the bickering, not only between Whittle and Rover but also between Maurice Wilkes, responsible for engineering, at Waterloo Mill and Olaf Poppe, responsible for manufaturing at Barnoldswick.
Although Whittle was struggling to achieve the design thrust of 1,600 lb, Herriot knew it would run reasonably between 1,250 and 1,400 lbt which would enable him to get on with mechanical development by continuous running to establish the mechanical integrity of components.  The situation was that Poppe was making a number of engines to slightly different specs that then sat doing nothing in Barnoldswick. Herriot and Denning, his assistant, decided to take matters into their own hands and took over the test beds and began running engines at the thrust the could actually achieve, soon getting 25, 50 and 100hr tests under way. Even though these were at below-design ratings the mechanical problems began to show up and 'fixes' could be worked on. When RR took over Herriot stayed on and soon Hooker made sure Development had priority and Herriot's engines running even harder.. hence the large increase in hours on machines already available for test. The 'magic' RR added was a focus on the project targets, not departmental empire protection.. focus, focus focus!
Hooker was pleased that on takeover, Herriot elected to stay on at Barnoldswick. Hooker got on well with Whittle and suggested it was time for RR to assume control of the W2B. Whittle readily agreed, knowing his 'baby' was in a safe pair of hands; that left him free to concentrate on the W2/500 and 700.. which turned out to be very elegant designs that RR made great use of as the Welland and then Derwent developed.....
I intend, for now, to push on with RR centrifugals; we can pick up on Halford etc. later.
« Last Edit: April 16, 2012, 04:14:01 pm by tartle »
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Offline LowObservable

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Re: Early British gas turbine development
« Reply #100 on: April 15, 2012, 06:49:44 am »
Interesting aside here: GE was aware of the Whittle program from its early days, because chief scientist Sanford Moss had visited BTH (I believe GE was a part-owner) when they were working with PJ and seen components.

There is a quite detailed account of this in a GEAE I-love-me book called Eight Decades of Progress.

Offline tartle

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Re: Early British gas turbine development
« Reply #101 on: April 15, 2012, 12:52:01 pm »
GE was aware of the programme is an understatement! Under the technical collaboration agreement between US and Britain - On 1st October 1941 the W!X from the E28/39 was flown to US with Power Jets personnel, carrying a complete set of drawings. These were handed over to General Electric who rapidly had one of them manufactured and on test. On 3rd  June 1942 Whittle flies out to GE to assist them. He returns on 14th August. On 2nd October 1942, Bell P-59 Airacomet made its first flight powered by two GEI-A engines, the GE version of W1. This was a fruitful cooperation with improvements flowing both ways as we will see... as you have asked about GE I have attached the IA cutaway drawing that was included in the information gathered when the GTCC went over to tour US aero gas turbine companies in Spring 1944.. the rest will have to wait until we have a few of our own units described.
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Offline tartle

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Re: Early British gas turbine development
« Reply #102 on: April 15, 2012, 01:29:19 pm »
So we have Hooker invited to take over as Chief engineer at Barnoldswick and all the key personnel given the choice of returning to Rover, AID or where ever. According to Bill Gunston a miracle took place when RR arrived. He quotes only 25 hours of W2B testing carried out in December 1942 but over 400 hours in Jan 1943 after Rolls assumed command on the 1st. The truth is enlightening and is a useful thing to remember as we survey what goes on today!
 John Herriott had been seconded from the AID to apply his engine quality manufacturing expertise, acquired at both Bristol and Derby,  to this new jet engine as it geared up for production. Herriott was appalled by the bickering that surrounded him, not just between Whittle and Rover but also between departments. Maurice Wilkes was responsible for engineering at Waterloo Mill, Clitheroe and Olaf Poppe was responsible for production at  Barnoldswick. Poppe was always complaining to Wilkes that the spec never settled and he never produced more than one engine before changes were made. Wilkes believed in the power of slide rule and pencil, so was slow to test any of the modifications- if they work on paper they will work on the engine.. full stop.
Herriott knew that the only way to improve the mechanical reliability and integrity of the engine was to test it for many hours. Whittle was struggling to get the W2 to deliver the design thrust of 1,600 lb, meanwhile it would perform well at between 1,250 and 1,400 lbt.
Herriott and his assistant Denning decided to take things into their own hands. Poppe had made a series of engines to various build standards; they were collecting dust at Barnoldswick... which had four test cells. Herriott wrote an official schedule for 25, 50 and 100 hr performance tests and having persuaded Poppe to keep supplying engines took over the test cells and started testing! When Hooker arrived Herriott knew thay had his approval and just carried on. Hooker soon had a conversation with Whittle where he informed him that he would have to let go control of the W2B so that RR could get it into service with the RAF. Because Whittle repected him and the Derby team he readily agreed and devoted PJ's efforts toward the W2/500 and & /700  that turned out to be really good designs, and of course the Miles M.52 powerplant was based on the /700.
Hives decided that Barnoldswick was not the place for a manufacturing plant bu suggested to Hooker that all research and development should be centred on Barnoldswick, not split with Citheroe and serious production should go elsewhere. In the event The W.2B passed its first 100 hour test at full performance of 1,600 lbt on May 7, 1943. The prototype Meteor airframe was already completed, and took to the air on June 12, 1943, with a B23 engine cleared for flight at 1,400 lbt.  The engine was soon cleared for flight at 1,600 lbt production of the Welland as it was now named, started at  at Barnoldswick starting in October. Rolls-Royce found a suitable facility for future manufacture at Milehouse, Newcastle-under-Lyme. RR took over the works from BSA in 1943, for the specific purpose of making the first jet engines- a few Wellands and then the Derwent. Upto 5,000 workers were employed at the Milehouse site and were sworn to secrecy about what they were producing.
The first Gloster Meteor Is, powered by the Welland were delivered to the RAF's CRD flight in May 1944. This unit was put together by Wing Commander H G Wilson under the auspices of the RAE at Farnborough and by June this flight was equipped with six Meteors. Within weeks they were transferred to 616 Squadron at Manston and began operations against the V.1 flying bomb on 27th July.
There is a Meteor wingtip in the IWM inscribed as follows:

: 'On 4th August 1944, over south east Kent, Flying Officer Dean of 616 Squadron in Gloster Meteor I aircraft EE 216 destroyed a Flying Bomb by directing it into the ground with this wing tip.'

The first flying bombs (also known as the 'doodlebugs' or 'buzz bombs' on account of the weapon's distinctive sound) landed in London and the Home Counties during the night of 12/13 June 1944. A sustained two-week bombardment starting in the middle of June led to a mini-evacuation of the capital as citizens sought to escape the V1's disconcertingly random and unpredictable destruction. Defensive measures included the siting of massed batteries of anti-aircraft guns along the North Downs and (in July) nearer the coast and the use of fast RAF fighter aircraft to shoot or 'tip' down the incoming flying bombs before they reached their intended targets.
« Last Edit: April 15, 2012, 02:55:56 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #103 on: April 15, 2012, 02:17:20 pm »
Hooker's experience on Merlin supercharger development  (a fascinating story) enabled him to look at the size of the W2B compressor and realise it should be capable of delivering 25% more mass flow than it actually did. Also  Lombard ST, straight through, design, the B26, was only a straightening out of the B23 to enable the combustion problems to be reduced and also to facilitate easier production. It delivered the same mass flow and thrust as the B23. Hooker asked Geoff Wilde, his supercharger supremo successor at Derby, to have a look at a better design of impeller and diffuser.
Geoff Wild modified the diffuser design and rig tested on the special rig that had been built for PJ compressor testing a few years before. Basically Wilde adapted the Merlin 20 vane diffuser design and tested it out, achieving he hoped for 25% improvement. So the new diffuser combined with the B26 combustion chambers developed by Lucas for Rover (note.. must expand on Lucas's key role in solving PJ combustion issues) with turbine blade length increased in line with the W2/700 design; about 0.3 in increase in blade length to increase annulus area to match mass flow increase. This changes were incorporated into one of the B26 engines which then delivered a thrust of 2,000lb, precisely 25% more than the unmodified B26. Hooker, against Wilde's advice also left out the inlet diffusers. Whittle always believed that they improved the flow into the impeller eye and therefore the efficiency, but they were a sheet metal assembly of relatively flimsy construction and pieces of it were found to go through the engine causing damage. Two photos of the Carlisle restored Welland diffuser shows why he was concerned. The new configuration was designated the B37 and was later named the Derwent I. It went into production at Milehouse and 500 were produced by the end of the war, equipping the Meteor.  Later work determined that, in fact, compressor efficiency dropped by 5 % to 73% and so the engine had to be run hotter to achieve its rated thrust of 2,000 lb. at a turbine gas temperature of 1136° K and an sfc of 1.178. When the vanes were replaced the rated thrust was delivered at 1027° K and an sfc of 1.083.
« Last Edit: April 15, 2012, 03:49:56 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #104 on: April 16, 2012, 01:32:04 am »
When Power Jets personnel went to USA in October 1941 they also took the plans for the W2 with them.
Via the Ministry, Hooker would read GE of America's reports on progress as indeed they would have read Hooker's reports on progress here.
Early 1944 saw  an invitation arrive from Col. Don Klein of the USAAF for a party of Brtish engineers to vist the USA and see first hand what progress had been made in America. The GTCC set up the team, Hayne Constant of RAE headed the party which included David Smith from Metrovick, Leslie Cheshire of PJ, 'Pat' Liindsey of Armstrong Siddeley, Moul, Brodie and Clarkson from DH and Hooker from RR.
Leaving Liverpool in April 1944 the team travelled aboard an almost empty US Coastguard troop carrying ship Wakefield that zig-zagged at 18 kts across the Atlantic to Boston. The first visit was to GE at Lynn near Boston, home of the I series of Whittle centrifugals. Hooker was taken aback when he saw the I-40 straight through turbojet. Unlike Barnoldswick not only had thay straightened out the gas flow they had gone for a greater thrust level. Designed at 4,000 lbt, at the time of the visit it was delivering 3,750 lbt. 103 inches long with a diameter of 48 in it had a double sided impeller of 30 in diameter and 14 combustion chambers delivering hot gases to a turbine of 25.9 in dia and a blade height of 3.95 in. The rpm was 11,500 and AMF was 76 lb/sec; sfc was 1.19. GE had begun designing the I-40, the successor to the-16, in March 1943 and had run its first test on January 8, 1944.
Hooker resolved to do something about this when he returned to Barnoldswick.
The Halford H-1 or de Havilland Goblin was designed to achieve around 3,000 lbt so Hooker resolved to leapfrog that too.Hooker was back in the office at the end of April and discussed his thoughts with Group Captain George Watt of RNZAF who had taken over the GTCC chair fron Roxbee Cox. "George I want to build a 5,000lbt engine," said Hooker, "we must get cracking or the Americans will beat us to it."
"Are you sure it should be as much as 5,000lb?" came the reply.
"Of course not. Le tus say a figure of 4,200 lb and we will design for 5,000."
"OK, I will issue a specification for 4,200 lb. and you can go ahead now. If you get 5,000lb so much the better."
May !st saw Hooker, Lombard, Pearson and Morley set out to design and produce the engine. This was the first time the team had a clean sheet of paper. They felt they had much experience and so should be able to come up with a better turbojet.  Lombard had already looked at a project for a MAP fighter spec. that Hawker had responded to with a version of the Fury, the P.1031 with an RB40 jet in the nose. The RB40  was a √2.6 scale up of the Derwent. The airflow was set at 100 lb/sec and the dia of the engine came out at 55 in dia 100 in long to the end of exhaust cone, with an impeller diameter of 32 in.
Now with Hooker's clean sheet approach and a great deal of Derwent experience  they were able to start at 80 lb/sec flow and with the best impeller design they could achieve came up with a dia of 28.8 in. Using Whittle's W2/500 diffuser design was also the most efficient design to date. The turbine disc and its bearing had never been properly cooled so a small centifugal comprssor was added specifically to address this issue.  The straight-through combustion chambers were designed by Stanley Clarke at Lucas. He managed to reduce the pressure drop and improve efficiency over what he had achieved on the Derwent.
Bt the summer drawings were being released to the shop and the overall diameter was coming out at 49.5, a full 5.5 in behind the target value set by the RB40. The engine weighed in at 1,600 lb way below the 2,200 target weight. Manufacture and assembly proceeded at a fast pace, with the flying bomb attacks on London giving renewed impetus.  The engine was ready to test on 27 October 1944. Last minute adjustments took all day and it was 10 pm before the team were ready to press the button and start the engine.
The light up procedure for a new engine is:
Using a large electric motor the engine rotates pressurising the fuel supply. At a certain pressure the fuel shut-off cock is opened so that fuel sprays into the combustion chamber when two igniter plugs, essentially big spark plugs are fired and the combustion process starts. The positioning of the igniters is a key factor and is a trial and error procedure. The positioning on the RB41 prototype was wrong and the first two attempts were a failure. The team's ignition experts, Dizzy Drew and Ballantyne, knew a quick fix. They removed one of the ignitors and an oxy acetylene welding torch was stuffed down the hole. The engine started with a bang and was soon running smoothly. The pair had invented the torch ignitor! By midnight the engine had been checked out and slowly opened up to deliver 4,000lbt. Hooker stopped the test and all repaired to the canteen to have a celebratory sausages and mash. Although Denning Pearson had pleaded to have the staic IGVs on the first runs Hooker had overruled him as he did not want a risk of damage from pieces falling off. This meant the 4,000lbt was achieved at maximum allowable temperature and so Hooker remarked there was little hope of achieving 5,000lbt without more development and then went home to bed. The next day when he arrived at work he could hear the Nene running. On arrival at the test bed he saw it was running at the same temperature as last night, but delivering 5,000lbt! Pearson had his IGVs fitted overnight and the improved efficiency enabled the target to be reached.
« Last Edit: April 22, 2012, 04:59:20 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #105 on: April 16, 2012, 09:11:34 am »
During April 1944 Fred Morley schemed out the RB40 at a conservative 4,200 lbt or a full bore 5,000 lbt,  but still basing it on the RB37/1. Denning Pearson carried out the performance calculations assuming a lower speed than the original outline, dropping the design thrust to 4,200. This leads to an engine the same size as before (55 in dia) but more conservatively rated, in line with Derwent experience. Investigation of the optimum number and size of combustion chambers showed that nine chambers of 12.80 in dia gave the best compromise. Fewer larger chambers would give a lower pressure drop but the larger blower casing outlets (which increase in area inversely as the number of chambers), would seriously have limited the possible size of impeller if the 55 inch maximum dia was to be maintained.
The effective length of the combustion chamber, i.e. from burner nozzle to nozzle guide vanes, was 29 inches compared with 32 in. on the RB37. This figure represents what the team thought achievable with the latest combustion techniques.
No Inlet guide vanes at entry to impeller are schemed. The turbine is a scaled RB37 with the disc restressed to take into account an improved material, G.18.B which reduces the weight. The nozzle assembly will be based on the RB37 but will be modified to reduce thermal and mechanical distortions discovered in service.
The shaft and bearing arrangement is as that of the RB37. It is assumed the arrangement of roller, ball and plain bearing will continue. If axial loads are too great for the ball bearing then there is enough space for a balancing piston. 
The engine was estimated to weigh 2,100lb.
But that visit to GE in the USA changed the focus of the team.
« Last Edit: April 19, 2012, 06:29:10 am by tartle »
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Offline LowObservable

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Re: Early British gas turbine development
« Reply #106 on: April 20, 2012, 07:21:41 am »
I was talking about the access GE had (via Moss) in 1937-38. There is a fascinating mirror story to this, which is US knowledge of gas turbine jet propulsion.

Oddly, while Eight Decades describes Moss and GE as being aware of gas turbine jet propulsion, I will swear blind that the previous Seven Decades talks of Moss seeing only "large turbocharger" components. (The book is hiding in a box somewhere.) Cover or rewriting history to look smarter?

Also, it's easy to overlook the fact that gas turbines per se were not all secret:

http://en.wikipedia.org/wiki/SBB-CFF-FFS_Am_4/6_1101

There was the National Academy of Sciences June 1940 study that showed gas turbines to be uncompetitive - which goes to show that it is all about the terms of reference and the assumptions. If you decided that you did not want to sacrifice SFC, you'd go with a recuperative cycle like the Swiss locomotive, and drive the weight and complexity through the roof. If you still thought (as many did) that the prop could run to 500 mph+ with ease with the power-to-weight boost provided by the Hyper engine, you raised the bar for the jet to compete.

Offline tartle

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Re: Early British gas turbine development
« Reply #107 on: April 20, 2012, 07:44:18 am »
 2012 is the 70th anniversary year of the first test runs of the Power Jets W2/500 centrifugal reverse-flow turbojet engine. Based on the W2 design, an unsuccessful attempt to specify a turbojet suitable for series production by Rover at Barnoldswick, the W2 developed into the W2B series that Rover attempted and Rolls-Royce succeeded in launching full-scale manufacture for the Gloster Meteor twin-engined fighter, and the W2/500 and &00 series that Power Jets developed to pre-production standards at Lutterworth.
The technology advances, achieved by Rolls-Royce on the one hand and Power Jets on the other, were combined in a highly successful collaboration which lead to the Welland engined Meteor being available for action against the V-1 ‘Doodle Bug’ missile (see #102 above)
In view of the approaching anniversary of the first run of the W2/500 on 13 September I thought it useful to reiterate some of the achievements of the test programme and how they relate to the W2B programme.
The design and construction of the W2 was authorised by the MAP in 1940 and Power Jets immediately started to scheme out the main features of this new engine. The drawings were produced and a set handed over to Rover who also constructed it, with some changes in mechanical design, under direct contract to the MAP.  Roxbee Cox wrote:
“In this engine, the design efficiencies of the compressor and turbine were not achieved and, as a result, it did not equal expectations and was subject to surge.”
Power Jets performed a series of modifications, including complete changes in blower casing and diffuser design, brought their W2 engine, built by BTH, up to a relatively satisfactory condition, known as the W2 Mk IV, which differd on slightly from their latest design, the W2B.
The most important aspect of Power Jets development of this engine is the step-by step increase in throughput by successively lengthening the turbine blades.
The W2B engines had a turbine blade 2.455 in. long adopted for the first designs of the W2/500. Soon this was increased to 2.73 in. long. This was the engine that ran on September 13, 1942 and at a maximum rpm of 16,750 rpm the engine delivered a thrust of 1,755 lb at a jet temperature of 879 deg K and an sfc of 1.13.
The next step was to increase the blade height at the trailing edge to 3.03 in. Once again performance improved, but the next step of raising both leading and trailing edge to 3.03 in. did not result in any further performance improvement. In this condition the engine delivered 1,850 lbt at 17,750 rpm at 893 deg K jet temperature and for a sfc of 1.12.
The front end of the engine now became a limiting factor and so Whittle undertook a complete redesign of the diffuser in order to remove any restrictions to better performance that may be there. Instead of a classic diffuser topology – long, smoothly varying channels connecting the flow from the impeller to the inlet to the combustion chamber the channels picking up the impeller flow were swung out into the plane of the impeller disc and then the flow was directed into fore and aft channels that lead directly into the combustion chambers. This design, known as Type 16, delivered a worthwhile improvement. The engine test results for the two designs on what was then called the W2/700 were:

Rpm                                        Old                     Type 16
                                            Diffuser                  Diffuser
RPM                                      16,750                   16,750
Thrust lb                                1,850                      2,040
Jet temp deg K                           893                        870
Sfc                                            1.12                       1.17
Delivery pressure lb/in**2            43.5                        47

The rotating machinery on these engines suffered a series of impeller failures so the then current design of impeller was replaced by a design modelled on that being used on the I-16 engine in the States. This had turned out to be a safer design on test over there. It is this modification that may also have led to some commentators thinking the Type 16 diffuser was a diffuser from the I-16, especially as GE promptly adopted the design.
The impeller although better from a mechanical integrity standpoint was slightly less aerodynamically effective and the thrust dropped by 150 lb, a small price to pay for eliminating the failures!
Development was able to proceed apace and soon the W2/700 was delivering a thrust of 2,130 lb at a jet temp of 920 deg K and a sfc of 1.077, all at 16,750 rpm. 
All this improvement was adopted by RR and GE for their particular versions.
The W2/700 with original and Type 16 blower casing and diffuser are shown in photographs below... more detail of the Type 16 will be shown later in Derwent V/Nene discussions.
 ….tbc: Photos to illustrate changes will follow.
« Last Edit: April 22, 2012, 04:51:56 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #108 on: April 20, 2012, 07:51:16 am »
Low Observable.....there is indeed a parallel story which we can get onto in a while if we want to! Of course we do! In the meantime if we finish the centrifugals at RR which fed across the pond and the Trent, it makes a good place to pause and look at USA (and Germany).
There is a great deal of wartime US axial work to discuss and then we have levelled the stories ready for the Avon, Sapphire and US equivalents post WW2, roughly. The wartime needs vs competition needs plus future competitiveness issues make the US story very fascinating... dig your book out of its box.. I've not seen that one (amazing what a hobby break of 40 years does to the collection!).
Jim
P.S: I assume the book was written in the 1980/90 period. Moss got interested in Gas Turbines in 1890s, did an MS degree at Stanford University and built a crude demonstrator to demonstrate principle of gas turbine (reciprocating comprssor driven by a piston engine, combustion chamber and a steam turbine wheel) around 1902. GE employed him to research a practicable GT to replace steam in 1903 but by 1905 it was clear that 4 times fuel consumption of such a machine did not make a commercial oppotunity, so GE abandoned the GT. Moss carried on with them and when in WW1 there was a need to up the altitude performance of aero engines he demonstrated a turbocharger on a Liberty engine.... GE carried on R&D on turbocharging from that moment on.
 Although GE kept discussing converting a turbocharger into a gas turbine in never went anywhere. The isolationist policy of US governments in 30s meant there was no need for a GT in an aeroplane... the enemy had to cross the Atlantic or Pacific so plenty of warning of attack!! The high-speed fighter was seen as an attack machine and as US had no country to attack why bother?
In fact in January 1941 the National Academy of Sciences's Committee on Gas Turbines submitted a report 'An investigation of the possibilities of the Gas Turbine for Marine Propulsion' published in June 1941 that stated:
"In its present state, and even considering the improvements possible when adopting the higher temperatures proposed for the immediate future, the gas turbine could hardly be considered a feasible application to airplanes mainly because of the difficulty in complying with the stringent weight requirements imposed by aeronautics."  The Heinkel He178 flew on 27 August 1939!
In UK & Germany the proximity meant that time from enemy plane approaching to scramble and get to intercept altitude was short and was a sum based on radar effectiveness plus rate of climb (crudely). GT a great idea.. both countries get active about the same time as Germany's aerofoil theory and von Ohain's insight , in UK, Griffith's and Whittle's perceptiveness, meant key people realised the GT's time had come.
 
« Last Edit: August 10, 2012, 06:38:07 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline CJGibson

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Re: Early British gas turbine development
« Reply #109 on: April 20, 2012, 08:50:02 am »
hello LO,

Perhaps this is the book you mean?  I found it, "Gas Turbines and Jet Propulsion for Aircraft" by G Geoffrey Smith, in a shop in Keswick and was surprised by the publication date and the content. Three editions in as many years at a time when paper use was restricted to official documents and Enid Blyton suggests that this was a popular, and officially sanctioned, publication. It has some interesting content, including boundary layer control and your Swiss locomtive.

Chris


Offline tartle

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Re: Early British gas turbine development
« Reply #110 on: April 20, 2012, 04:10:32 pm »
There is a fascinating story of supercharging that the BBC gas turbine, and Moss and Ellor are part of... eventually A A Griffith ends up visiting BBC as part of his scientific duties pre-RR; they gave him some unfortunate steers that actually slowed the development of successful axial compressors at RAE. It is interesting to see how the BBC layout is also reflected in the Betty layouts. We can deal with that here but the other railway stuff, fascinating though it is does not impinge on the thread topic so I will return to British gas turbine development.
The tragedy of the Nene was that it had no outlet! There was originally no aeroplane for it. Whilst the team carried on with development and milestones were passed no one was sure what would happen to the engine. Late in 1944 Whittle arrived to see the Nene run and afterwards a celebratory dinner was held (at the Swan and Royal, Clitheroe) During dinner there was much bemoaning of the fact they had no outlet for such a fantastic engine when Whittle had a brilliant idea... why not scale it downto fit in the Meteor and see what thrust could be obtained. Lombard did the calculations on a tablecloth and came up with 3,650 lbt! As this was much more than the 2,000lbt of the current Derwent I  there was much excitement. A week or two later Hooker raised the matter with Hives at a regular Monday afternoon meeting. According to Hooker HS was not amused having just built a factory for the Derwent I. But he didn't forbid work on such an idea.
Hooker authorised work to start on the scaled engine; on 1st January 1945 design commenced to produce an exact 0.855 scale of the Nene. Unfortunately nuts and bolts don't scale so some change is necessary but no major alterations minimised the calculations necessary to define the design. The engine was first tested on 7 June 1945 running for 100 hr non-stop at a thrust of 2,600 lb.Later the thrust was increased to 3,500 lb. and two flightworthy engines were prepared and installed in a Meteor. Mk 4. On 15 August 1945 Eric Greenwood made the first test flight, returning to say "At last we have a real aeroplane."Within weeks Greenwood was flying at 570 mph at 10,000 ft. Calculations showed that 600 mph at sea level could be attained if the thrust was raised to 4,000 lb. It was decided to go for the official World Speed record and the engines were tested and cleared to run at 4,000lbt for 1 hour. Two aeroplanes were prepared for an attempt on the World Speed record. Eric Greenwood was to fly one and Group Captain H.J. Wilson the other. and flown at sea level The attempt on the World Speed Record took place on 7 November 1945, over Herne Bay (finally EE454 flown by Group Captain Willie Wilson was just faster than Greenwood's steed). The record was successfully raised to 606 mph. Just under a year later, Group Captain E M Donaldson added another 10mph to this record, also in a mark 4 (EE 549), but with clipped wings The photo shows the RAF  High Speed Flight engineers at Tangmere preparing the Rolls Royce Derwent 5 of Group Captain E.M. Donaldson's ready for his attempt on the speed record
setting Meteor F4 in 1946
« Last Edit: April 23, 2012, 06:49:29 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #111 on: April 21, 2012, 10:32:04 am »
A turboprop excursion... Rolls-Royce's Alan Griffith and Hayne Constant at RAE were both keen on turboprops for non-fighter applications of the gas turbine.. the first picture shows why. It is a graph from an RAE report that shows that the most efficient engine for an aircraft like the Lancaster cruising at about 280 mph is a turboprop, hence the intense interest. Eventually, as the intense pressure on Welland development eased somewhat, Hooker realised no one had actually measured what horsepower output could be achieved from a gas turbine. Therefore, in 1943, a Welland was modified to have an output to a gearbox so the shaft performance could be investigated.
The numbers obtained were promising so as the Derwent was now doing nicely in development a scheme to modify that engine with a view to actually flying the turbo prop was put forward. This became the RB50 Trent engine.
The Trent is based on a Derwent II engine. The engine had a modified accessory quillshaft at the front of the impeller driving a gearbox consisting of a 3-layshaft train of straight spur gears giving the propeller shaft. The reduction gearbox had a ratio of 0.141:1 to drive a Rotol 5-bladed propeller of 91 in. diameter.
The Trent engine Test Programme was intended to investigate:
1) The effect of an airscrew hub on intake efficiency
2) The suitability of the gearbox design
3) The degree of skill and co-ordination necessary to coordinate the operation of separate throttle and constant speed unit controls.

The affect of the airscrew was not as great as feared but the straight spur gears gave trouble in an unexpected way. The cyclic loads setup as the gear teeth on one of the gears trains meshed with its partner set, at certain operating speeds, at a frequency equivalent to the natural frequency of the tabwashers used to lock the gear wheels in position. The lockwashers fatigued and on failure allowed the gearwheels to 'float', overload and fail. By changing some of the gears to a helical rather than straight design made for a more progressive meshing that eliminated the high cyclic loading. In addition more care was taken to balance each rotating assembly in the gearbox.
The investigation of the degree of coordination needed by the pilot in order to adjust  both the throttles and constant speed units led to some excitement in the air.  Eric Greenwood, Gloster's chief test pilot took the Trent Meteor into the air and when coming in to land throttled back the engines. The engines lost revs and then the propellers went into zero-pitch and the Meteor dropped like a stone...only by applying full throttle did Greenwood avoid an accident. The zero pitch mode at low revs had been set to allow for easy starting of the engines! At this point all parties realised that the workload and skills required to operate the two controls independently but 'together' was beyond a pilot's capabilities and development of an adequate control system was begun. This ultimately led to the interconnected propeller/engine controls and safety locks used on the Dart engine. Whilst a better control system was being implemented the Trent Meteor continued to fly with a 58 1/2 inch prop absorbing only 350 hp and an increased diameter jetpipe giving a thrust of 1,400lbt.
A total of 398 hours on the test bed and 298 hrs in flight enabled Rolls-Royce engineers to understand the challenges of operating a turboprop powered aircraft and the huge levels of skill and attention necessary to cope with a powerplant during manual movements of the two controls that  result in rapid fluctuations of thrust... sometimes even negative and to ensure that a single-lever control system was developed to overcome this.
With the large propeller the Trent delivered 750 hp and 1,000 lbt versus the 2,200 lbt of the Derwent II. 
« Last Edit: August 15, 2012, 07:38:35 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #112 on: April 23, 2012, 06:10:51 am »
In #91 I wrote what is taken to be the story of Rover's efforts at Barnoldswick; since then I have been reading David S Brooks's account of Rover at Barnoldswick 'Vikings at Waterloo' which was published by RRHT. There are monthly running statistics from the test bed logs in an appendix. I have summarised and included information relevant to our story below:

'Little work was done on the B26 until Rolls-Royce took over the Barnoldswick facility and had received four engines, as well as 32 B23s.
The latter engine became the first gas turbine aero engine to go into series production in October 1943. 167 Welland B23s were manufactured at Barnoldswick, before switching to the B37 Derwent, as the developed B26 was known.'
I have also noted the test bed hours did not leap upwards when RR took over as Gunston writes in his World Encyclopedia of Aero Engines.
Having more facts available now....
The STX engine first ran on 7 March 1942, nine months after the design started. It ran for almost seven hours to the end of May. By the end of the year it had run a total of 33 hr 43 min. A second engine (ST1) started testing in Nov 1942; the third (ST2) engine started testing in January 1943 and ST3 in March 1943. By the end of May the ST engines had run a total of 96 hrs 17 min.
Over the same period W2B23 test hours had totalled 1951 hr 12 min. jumping from double figures per month to triple as Herriott took command of development testing ( as we discussed in #99) i.e. in November running times were 85 hr 48 min and December's were 258 hr 17 min - which set the pace for the rest of the B23 development.
ST1 completed a 50 hour endurance test in February 1943 at a:
Take-off rating  of 1,488 lbt at 16,500 rpm
Cruise rating    of  1,295 lbt at 15,800 rpm
sfc was 1.18 at 1,500 lbt and
             1.155 at 1,300 lbt.
Max thrust delivered was during test was 1607 lb.

In May 1943 ST3 carried out test runs as a preliminary to the 100 hr Type Approval Test achieveing the following ratings:

Max Take-off thrust 1,600 lb at 16800 rpm
all out level and combat climbing 1450 lb at 16,400 rpm
Max cruising condition 1250 lb at 15,800rpm.
A mock up of the ST engine had been sent to Gloster in Dec 1942 so that They could assess and make changes to the rear spar of the F9/40 in advance of engine availability.
One of the design decisions taken for the ST layout was to keep to plain bearing on the recommendation of specialist manufacturer.. this was to cause difficulties to the test programme. The ST1 was the first engine to be built to a 'standard', the STX was a concept demonstrator only,  suffered from excessive oil leakage from the middle and rear bearings. Much time was spent trying to understand why and to devises 'fixes' in an attempt to reduce/eliminate the leak. The first acceptance test were run without a full resolution of the problem. Also by September 1942, Rover realised that the thrust level of the ST was too low and Rolls-Royce offered to run one at Derby to see if there was scope to increase the power. This did not infact take place as the political/commercial events turned away from a collaboration to RR taking complete responsibility for the gas turbine.
It seems the truth is that whilst there was personal antipathy between Whittle and Wilkes which soured the atmosphere this did not affect the development team's efforts to produce the B23 and to improve on it. Herrott's intervention and RR leadership really released the creative talents of that team and enabled them to deliver both the Welalnd and then its successor the Derwent in production quantities.
The second picture shows thw aftermath of an undetected flaw in the impeller of a B23. After start up 2 technicians would enter the cell to perform their duties! They survived this 'incident' without injury but procedures were changed. Nobody was to enter the test cell until the engine had been run up to maximum rpm!
« Last Edit: May 12, 2012, 10:32:22 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #113 on: April 27, 2012, 04:46:34 pm »
In #66 we began to discuss the RB39 Clyde. This was the first two spool engine and was the third engine that Lionel Haworth had been in charge of... the other two being the WR1 and Trent. 1944 saw him working on the RCA series of engines that evolved into the Clyde...his RS biographical memoir states:
"Haworth’s work at this time was not limited to mechanical design but included detailed consideration
of the thermodynamics of turbine engines. He evolved design techniques for the
‘Rolls Compound Axial’ types of engine that led to a start being made on the design of the
Clyde engine, whose detailed design was shared between Haworth’s office in Derby and the
Lancashire design office at Clitheroe. In 1943 Haworth foresaw that the axial compressor
would dominate all but the smallest aero-gas turbines and he evolved a series of compound
axial engines cumulating in his patent of the three-shaft engine of 22 June 1943. The expectation
was that the compression ratio achievable in a single axial compressor might have to be
limited to not much more than 3:1 to avoid surging difficulties, in which case a two-shaft engine
with two independent multi-stage rotors each driven by its own turbine would achieve a compression
ratio of 9:1. For a three-shaft arrangement, the compression ratio would rise to 27:1,
which would lead to a very efficient and economical engine, especially when used to drive a
high by-pass ratio fan. These basic engine concepts have been used by Rolls-Royce, Pratt &
Whitney and General Electric in many of their designs including the Avon (single-shaft),
Olympus (two-shaft) and RB211 (three-shaft) engines. It was a source of great disappointment
to him that the three-shaft engine was not exploited earlier, but attention was focused on bringing
the simpler engines into production. However, the three-shaft configuration was adopted for
the RB211 high by-pass engine launched in 1968, leading to today’s Trent engine, which is the
market leader in the large civil engine sector due in large part to its three-shaft architecture.
In March 1944 he was responsible for the design of the compressor and gearbox of the
RB39 Clyde turbo-propeller engine, which first ran in 1945. This was the first two-shaft aircraft
gas-turbine engine, using an axial flow compressor followed by a centrifugal derived
from the Merlin supercharger on the high-pressure (HP) shaft, the propeller reduction gear
being driven from the low-pressure (LP) shaft. The Clyde proved to be a powerful and reliable
engine but despite its potential it was not adopted for production. However, valuable
experience was gained particularly on fuel and propeller control systems."
The RCA engine could be configured as a jet or as a prop. The pic shows the jet version.
Design AMF is 70.3lb/sec.
The 4-stage LP axial compressor is driven by a single stage turbine at 5,500 rpm.
The 5-stage IP axial compressor is driven by a single stage turbine at 9,350 rpm.
The 6-stage HP axial compressor is driven by a 2-stage turbine at 13,850 rpm.
The propeller version was calculated to deliver 7,350 bhp plus 1525 lbt from jet exhaust giving 8,858 ebhp. sfc is .471lb/ebhp/hr
length to end of exhaust cone 123.0 in and overall diameter is 34.0 in. in jet configuration. More research needs to be done to unearth how the prop was to be configured. There is an RCA4 bypass (turbofan) design that has a 10-stage HP compressor (looks like a Beryl design) driven by a single-stage turbine. The LP compressor is 4-stages driven through a gearbox from a single turbine stage. This strikes me as an intermediate step in thinking on the way to the Clyde. We know the Clyde had the F2 compressor design incorporated. Dimensionally the compressor is identical to the F2; the rear drive cone and bearing front cone are modified for the Clyde configuration. If we look at the RCA3 and RCA4 sections and compare with F2 it can be seen that the same design is being used. The RCA4 had a design AMF of 60lb/sec giving a thrust of 5260 lb and sfc of 0.59. The overall pressure ratio was 8, less than the 9.53 0f the RCA3. The RCA4 has a 4 stage LP and 10 stage HP compressors each driven by a single stage turbine. Speeds are 10,000 and 10,500 rpm respectively for LP and HP.
...tbc
« Last Edit: April 28, 2012, 04:27:16 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #114 on: April 29, 2012, 10:28:09 am »
Now back to the Clyde:

Concerns about the length of the RCA engines and their installation led to discussion of how the Metrovick work on axials and the superb progress being made with centrifugals at Barnoldswick led to another step forwrd in current aero engine thinking. Could a reasonably proportioned turboprop engine be designed to fit aircraft being developed to take advantage of the high powered piston engines that may follow the Merlin? Several aircraft were re-schemed to take the RB39... the Vickers Windsor B Mk2; the Vickers High-altitude heavy bomber  scheme C project would have had six Clydes; the Blackburn Firecrest had a Clyde version and their Spearfish was proposed as a test bed for the engine. Rolls-Royce were working on a more powerful incarnation (Eagle II) of the Napier Sabre (in piston layout only) and this was proposed for a Westland fighter for the RAF and RN. The RAF were not interested so it became a sole RN sponsored project. As the Clyde developed it was proposed to first manufacture the Westland Wyvern as an Eagle powered machine and then swap over to the Clyde. Hives put it to MAP that there were only sufficient resources for the Clyde or the Eagle II as both were two years of hard development away from a real production proposition. In the event the first redesign of the Eagle II was accomplished very quickly and a batch of flightworthy engines were available to get the Wyvern into the air. Basically the Clyde-Wyvern was a re-fuselaged version of the piston design. The first layouts of the Clyde (September 1944, signed by Fred Morley) were sufficiently worked up to be sent to Westlands in October of that year. More work followed by the team at Derby and prototype manufacture began in 1945. This enabled the assistant Chief Designer G Ainsworth Davis to send a better version of the installation scheme in January of 1945.
The first engine ran on 1st August 1945 and immediately revealed that the two spools of the compressor were not properly matched so reducing the performance of the engine, delivering only 2,000 shp of its projected 3,020 shp.  However this was the strt of the development of a forward-thinking concept... the first twin-spool turboprop to run. Nine engines later the Clyde was delivering 4,200 shp and with the jet thrust added, 4,543 eshp. The limit to further power growth was the single stage LP turbine. A scheme to replace it with a 2-stage development was drawn up but never implemented as the engine was cancelled even though MAP wanted 100 for the Wyvern. Depending on one's point of view it was fortunate for the navy that as a parallel development a version the Wyvern had also been tested with the Armstrong Siddeley Python turboprop and it was this engine that went into production. Hives had his Merlin hat on and was looking for an engine that would yield significant production orders... in his mind's eye this was the Avon... although in the post war forties some would take issue. The Clyde was probably the first engine to pass the new joint civil-military type approval test; the ARB and MAP granting type approval on 22nd and 24th August 1948 respectively. The engine was a joint effort by Stanley Hooker and Adrian Lombard as the engineers in overall charge of axial and centrifugal spools respectively, with design by Lionel Haworth and Roy Heathcote. Development was in the hands of John Herriott. Apart from Herriott all the others had the job of mentoring me nearly twenty years later!
[continued below]
« Last Edit: May 14, 2012, 01:16:06 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #115 on: April 29, 2012, 11:54:23 am »
Without getting ahead of the narrative - is it the case that two-spool engines at RR and PW started with high-efficiency turboprops that never entered production (Clyde and T45) and only became jets (Conway and J57) later? In that case, the high-performance turboprop becomes a near-perfect example of Hitchcock's Maguffin, in terms of technological history.

Offline tartle

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Re: Early British gas turbine development
« Reply #116 on: April 29, 2012, 04:44:26 pm »
I hadn't thought of it that way but maybe yes.....
We could go German philosophical with an explanation like:
"Vergesellschaftung und der „MacGuffin“.
Interindividuelle Erklärungen der Innovation in der Architektur" in English here.
One of the things I learned is that goal setting can be about telling a story of a goal that seems unattainable but by carrying out 'serious play' as a colleague Michael Schrage put it enables one to assemble, enthuse and move people along the pathway towards that goal... the goal itself may be changing as a result of those conversations and play around prototypes.. when I worked with the advanced projects department we used a considerable amount of components made from Unobtainium or X-alloy 2000 (it was in the 1960-70s)... a description of the former alloy is
"Unobtainium can also refer to any rare but desirable material used to motivate a conflict over its possession, making it a MacGuffin (it appears in the story as something to obtain, not something that is significantly used) ".
The plot device being used  so far plays out successfully on the Tyne engine... so the understanding that is being assembled by the "prototyping" come to fruition many years later... the three shaft concept even longer.... the solutions are being driven by needs, sciences and technologies (materials, tools, techniques) but sometimes the solution seems to have no known need.. often when it is really about acquiring technology in the broad sense I have defined it above.... but personalities count too..... if these types don't move you then ask an iconoclast!
Hobbs and Hives were hard headed engineers that knew they had a challenging job replacing their profitable war production with the new jet engines. Both knew that aircraft always grew in weight.. payload and structure, range, speed, altitude so growth potential was key. Also they both realised that a gas generator (core) gasturbine could then be used in various ways as the aircraft spec demanded........the graph in #112 above shows for a given set of assumptions how the prop can be useful upto 550 mph.. but as relative component efficiencies change and the range requirements vary so will this curve. Hobbs realised that the B52 bomber spec, as it developed would outstrip its favoured powerplants. Over here Hives realised the axial would be the ultimate solution and as fighters and fast bombers were dominant then he must pursue that route. Both H and H were interested in multi spool engines.... for ease of starting and for performance matching hence the ultimate direction of both companies.... I believe.... but its never that simple is it?
« Last Edit: April 30, 2012, 02:37:03 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #117 on: April 30, 2012, 04:29:10 am »
Following on from #115....
Whilst the flow of air through the intakes of piston engine intakes was was important (think Spitfire and Mustang) it was becoming apparent that it was even more so with turbine engines.On the Trent the plenum chamber inlet to the compressor meant that intake losses were relatively small. However the Clyde was a different matter. Although intake duct losses were important on piston engined aircraft they were more important on gas turbines. The Westland Wyvern was seen as a configuration typical of what may be adopted by the industry. Therefore RAE investigated possible effects of intake design typical of those that may be adopted, based on the Wyvern layout. Their work was reported in R&M 2894 'A Wind-tunnel Investigation of Entry Loss on Propeller Turbine Installations'. The report's fig 1 below shows the scope of the report. The Clyde represents a transition in technologies from the centrifugal to the axial and from single to multi-spool engines. As such it was always at the centre of controversy within RR. The Griffith (and Hayne Constant at RAE) faction were convinced the only way ahead was the axial and Hooker (with Whittle's support) were not against axials but thought centrifugals were working well and had more life in them than the axial faction would admit. http://www.secretprojects.co.uk/forum/index.php?action=post;msg=150796;topic=1016.105Griffith was able to convince Hives that most resources should go axial giving the Centrifugal advocates a hard time to stay in the running. One of the reasons that the F2 was not in production was because of the technical problems presented by the axial configuration plus the combustion issues of an annular design...resulting in a version with cans. The Clyde had the ninth iteration of F2 aerodynamic design and this was before the Beryl! The making of axial blades was also an issue... large production quantities would overwhelm the manufacturing facilities of Metrovick(and, arguably RR).
A NACA report written in 1948 includes an introductory paragraph on why axial compressors are important and is a rationale for more research to be able to increase their duty and efficiency. It also gives colour to the uncertainties on which way to go with compressor design.
Jim Boales was one of the engineers on the Clyde development team. He told me that they had taken the F2 compressor aerodynamic and component arrangement and then incorporated structural changes.. firstly to suit the new Clyde layout and secondly to improve structural integrity in the light of Barnoldswick's experience with a production engine. For instance, this meant incorporating a fir tree root fixing design for the compressor blades, which RR thought a better layout- stresswise. Also the hp compressor diffuser was not straight as on the Derwent V/Nene layout but 'wrapped round' in a gentle curve to reduce the overall diameter of the engine. The blueprint shows a more detailed layout of the engine. A major issue with the Clyde was the overloading of the LP turbine, which led Barnoldswick to propose a 'Clyde replacement' - the RB52 which got to the stage of paper layouts and issue to aircraft project groups; mention can be found in Tony Buttler's British Secret Projects: Fighters and Bombers 1935-1950.
The next Clyde phase is discussed below.
« Last Edit: May 14, 2012, 01:30:28 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #118 on: April 30, 2012, 06:56:24 am »
One of my favorite fictional Macguffins is in Forsyth's The Day of the Jackal. On a tip that a man named Charles Calthrop might have been in the assassination-for-hire game, the British police launch an investigation that leads them to the real hit-man's fake IDs. In one of the final scenes, the plods are going through what they think is the deceased gunman's flat when a tall fair-haired guy marches in and says "I'm Charles Calthrop - what the hell are you doing in my house?"



Offline tartle

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Re: Early British gas turbine development
« Reply #119 on: May 14, 2012, 02:00:50 am »
The reason for the (relative) complexity of the RB39 was the need to match two very different compressor characteristics i.e. that of an axial which tends to be peakier than the relatively flat characteristic exhibited by a centrifugal. Hence the need to have a two-shaft engine. The decision to drive the axial through a gearbox is to do with taking an existing F2 design of axial compressor and matching a turbine to it. As we have discussed the matching was a problem at the beginning of the testing of the Clyde and so Hooker's team took the opportunity to investigate alternatives. The RB52 or Clyde II was their offering.
The original report reads:
"The RB52 comprises a 2-stage centrifugal compressor driven directly by a 2-stage axial turbine., which also supplies power to a airscrew which is geared to the compressor. The hot gas from the turbine is exhausted to atmosphere to provide additional thrust to that obtained by the airscrew. The 2 drawings clearly show the difference between the the two engines. The fundemental difference is the replacement of the axial compressor of the Clyde engine by a double-sided centrifugal compressor, identical with the compressor of the Derwent V engine.. Satisfactory matching of the characteristics of both stges of the compressor is is possible without resorting to a free shaft system which is necessary to match the axial and centrifugal compressors of the Clyde engine. A two stage turbine will be required to provide sufficient power to drive both the compressor and airscrew, although the engine will be single-shafted.
Overall Dimensions and Weight:                       Clyde                   RB52

Max dia (in.)                                                      46.75                     44
Overall length to exhaust cone flange (in.)     120.0                     115.5
engine weight inc. aircraft auxiliaries (lb.)     2200                      1900
excluding engine accessories, jet pipe
and propeller.

Performance                                                 
Sea level static:
airscrew horsepower                                    3020                       3370
jet thrust (lb.)                                               1225                       1205
fuel consumption gal/hr                                  277                         304

400 mph, 36,000 feet:
airscrew horsepower                                    1140                       1650   
jet thrust (lb.)                                                 547                         324
fuel consumption gal/hr                                  115                          117.5

The increase in airscrew power of 350 hp on the test bed is due mainly to the airflow through the RB52 being slightly higher than the Clyde..
The 45% increase in shaft horsepower at 400 mph in the RB52 is obtained by the increased ratio of airscrew power to jet power. On the test bed the Clyde LPTurbine is already supplying the maximum shp/lb of gas that can be expected in the light of present knowledge on a single stage engine and as the available gas hp increaes with forward speed and altitude the extra gas hp has to be used in increasing jet thrust.
 With the RB52 engine however, the first stage of the two stage turbine can be designed to supply a high percentage of the total shaft horsepower on the test bed, leaving the second stage relatively lightly loaded. The difference in the turbine loading of the Clyde and RB52 is stressed by the following test bed figures of the shaft horsepower supplied by each turbine for every pound of gas passing.

                                                Clyde                 RB52
High pressure turbine                     88.5                        130   
Low pressure turbine                   135.6                  96
Power absorbed by airscrew            72.7                          75

In flight the shp supplied by the LP turbine of the RB52 can be increased by approximately 125 hp/lb gas as the expansion ratio increases, and the power absorbed by the airscrew per lb gas will be increased from 75 to 104 horsepower, resulting in the airscrew power being 45% above that of the Clyde. ….

Future development
The most attractive feature of the RB52 engine is the possibilities it holds out for quick development to much higher powers. To increase the power of any type of engine , either the combustion temperature or the air consumption must be increased, and in the past, both on piston engines and jet engines the most profitable way has been one whereby more air is crammed through the engine without increasing its overall dimensions. It is with this idea in mind that the future development of the Clyde and RB52 engine must be compared.
The airflow on all airscrew gas turbine engines will be limited by the permissible turbine annulus area. Due to the fact that airscrew engines will always be used for planes designed for moderate speeds and altitudes, economical fuel consumption will always be more important than engine weight and for economical fuel consumption most of the available gas horsepower must be supplied to the airscrew, leaving a relatively low jet velocity. This means much lower axial velocities through the last turbine stage than in jet engines. And so for a given airflow the turbine annulus area must be considerably larger. In the Derwent series I engine the turbine annulus area is 140 sq. in. whilst on the Clyde it is 214 sq. in., although both engines pass approximately the same airflow. The low pressure blades on both Clyde and RB52 have approximately the same length and mean blade speed, so it is reasonable to suppose both the annulus areas of the two engines can be increased equally. Although the stressing has not been investigated in detail a rough estimate of the permissible increase in annulus area is 25%
There will be no difficulty in passing the 25% increase in airflow through the present RB52 compressor, but a certain amount of development work will be required to maintain the high compressor efficiency of 77% for which we have budgeted on the RB52. Compressor efficiencies of 80% have been obtained on the Derwent Series II compressor at compression ratios of 2.5:1, and it is this figure that leads us to expect high efficiencies on a two-stage compressor giving only with airflows that do not exceed those used at present on single stage compressors of the same size at a given impeller tip speed. If the airflow is increased 25%, either the eye area or the axial velocity of air into the impeller will have to be increased 25%, either the eye area or axial velocity will have to be increased, and the diffuser throat area opened up. This has been done previously on the B23 compressor, when it was decided to build the Derwent Series I engine, and although at first the compressor efficiency fell 2 or 3%, it was regained after a considerable period of development.  At first it will be of paramount importance to obtain a 77% efficient compressor, but ultimately there is no reason why 77% efficiency should not be achieved with a compressor passing 25% more air.
On the Clyde engine, the high pressure centrifugal compressor is already passing 20% less airflow than a Merlin 46 type compressor of thee same size, so no difficulty should be encountered in increasing the airflow 25% through this stage. The axial compressor however, puts a very different complexion on the situation, for a complete redesign will be needed,
As the redesign will probably involve a different rotational speed of the axial compressor, the reduction gear will also have to be extensively modified. There should however, be no difficulty in maintaining the compressor efficiency at the present figure of 78%.
To sum up briefly, both engines can be developed to have the same percentage increase in power and the expansion side of each engine will have to be re-designed for the larger turbine annulus area. On the Clyde a completely new design of axial compressor will have to be made, whilst on the RB52 compressor a certain of development work only will be needed.
Fortified by previous experience on jet engines, there is no doubt that the RB52 can be developed to give amount the maximum increase in power in a much shorter time.”
The report was written by Geoff Fawn, later to rise high in the organisation, dated 19.4.45. The RB52 was never built. The reason I have reproduced so much of the report is because the argument is pertinent to the next number in the series... the RB53
« Last Edit: May 14, 2012, 06:38:44 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #120 on: May 14, 2012, 11:24:08 am »
The Rolls-Royce Nene and Tay linked to Pratt and Whitney:
 
Pratt and Whitney were late getting into gas turbines as the US military did not want them distracted from piston engine manufacture during WW2.
In the meantime Rolls-Royce were looking for new post-war markets in order to maintain revenue streams. In January 1946 a Philip Taylor contacted Hives with a request for a licence to manufacture and sell RR turbine engines in the USA. As the potential for sales in the USA was very attractive negotiations ensued and Taylor, who was the ex-chief engineer at Curtiss-Wright. Hives was reluctant to talk to him at first ...but after some negotiation Taylor signed a contract granting him sales rights to the Nene and Derwent and their spares for two years with a one-year getout clause. Taylor began negotiations with Grumman to supply Nenes and also with Pratt and Whitney. In Jan 1947 Taylor contacted RR with the news that P&W wanted to manufacture Nenes for Grummans under a sub-licence deal. C. J McCarthy vice president of United Aircraft Corporation, owners of P&W, had been given open house by Hives when he visited the UK in the summer of 1946 and so Hives contacted him to say Taylor had been in touch re-P&W licencing. In March 1947 Hives thought the deal so important that he sailed on the 'Queen Elizabeth to the USA to finalise a deal with P&W who were being encouraged by the US Navy to licence the Nene engine as it was more powerful and reliable than US engines and with the cold war starting they needed all the engines that they could get. Taylor eventually drops out of the picture after threatening to sue but P&W reached an accommodation. In May 1947 the Navy announced the deal between P&W and RR for the F9F carrier fighter from Grumman.
 
 Hobbs, boss of P&W, was concerned that Hives was too keen on the axial AJ65 to keep developing the Nene series, but in fact the Tay engine was proposed as the next engine for P&W.
 P&W had a team of engineers at Derby to work on the American version of the Nene and then to help design the Tay, essentially an uprated Nene for later versions of the Panther, as the Grumman F9F had been christened. The F9F-2 Nene powered version first flew on 27th November 1947, Gwinn(of P&W) cabled Derby: "Grumman Nene was flown yesterday for one hour, 15 minutes.Everything O.K. Pilot very pleased and snap rolled machine."
 Jim Boales was one of the RR Derby engineers who had responsibility for making the relationship work and he spent time in East Hartford as well as working in Derby on both the Nene and Tay. The Tay he told me came about because the Navy kept hanging more things onto the aeroplane and so extra power was needed, initially by water-methanol injection on the Nene raising the power from 5,000 to 5,750 then 5,950 lbt, but eventually by enlarging the Nene itself. The challenge was to accommodate a 1.14 times linear scale of the Nene within the airframe of the Panther. The Overall diameter of the Nene is 49.5 in, so the scale-up would give a diameter of 56.43 in.- too big to fit in the hole! The largest diameter that could be accommodated was 50 in so the RR/P&W design and engineering team at Derby started to determine what needed to be done to bring the engine into line with that figure!

......continued in#124 below.
« Last Edit: May 16, 2012, 05:24:32 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #121 on: May 15, 2012, 06:54:20 am »
The US back-story here (in part) is that the USN had bet most of the rent on Westinghouse, which believed in small engines used in large numbers, and thought that jet engines could be scaled easily, despite having no aviation experience. The outcome was two engines that were too small to be of much practical use except as boosters (J30 and J32), the unexciting J34 (two engines required for decidedly subsonic fighters) and the catastrophic J40.

Did centrifugals offer better throttle response at the time?

Offline tartle

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Re: Early British gas turbine development
« Reply #122 on: May 15, 2012, 10:39:02 am »
My gut response is that in the 1940s a centrifugal is less sensitive to abuse than an axial both in terms of control and mechanical integrity... most axials of that time seem to have a long development period whilst surge was tamed or vibration related blade failures were tuned out. The flatter performance characteristics of the CF vs. axial compressor helps but does not eliminate surge problems.
The US government originally put all its eggs in the axial basket which is why Whittle's machine was grabbed so quickly when offered by Britain. P&W after the war had ended also realised that Allison/GE were not getting on with development of the centrifugal with enough urgency and so, as RR were activally looking for outlets in the US, they took a licence for the Nene and later the Tay, as we are exploring at present. Westinghouse did well to design two small  but good turbojets. They scaled up in ambition with the J34 which at least did what it was designed to do. The J40 was a disaster that ruined many aircraft programmes. Westinghouse had entered into a licence agreement with Rolls-Royce and managed to screw up the transfer of technolgy to the USA on both the Soar and the late-model Avons. Geoff Wilde got involved in sorting the J-40 engine problems, but it was cancelled before all the changes could be demonstrated to work... Geoff regarded the Westinghouse venture a total waste of RR engineering time but Pearson was able to point out that the royalty payments were very large and very welcome when lean times were upon the UK  market. David Huddie was told in September 1959 that Westinghouse were out of the aero engine business.
« Last Edit: May 15, 2012, 11:08:40 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #123 on: May 16, 2012, 05:23:30 am »
As I intimated  above, Jim Boales made a major contribution to the successful development of the RB44 Tay and later the Hispano Suiza Verdon engines. Below is a retelling of those times from notes I made after conversations with him in the mid-60s!
Encouraged by the growth in demand for more powerful engines for use by yhre military P&W turned to RR for advice on how to uprate the Nene. The Tay was the resulting engine, designed in Derby by a joint team that decided to scale the Nene by 14% linear.
The Overall diameter was limited to 50 inches by installation considerations. The larger impeller was 2 inches greater in diameter than the existing Nene making it 32.8 in.  Tests with a larger impeller on the Nene had shown that the tip clearance could safely be reduced from the 1.025 in. to 0.67 in. which was also the figure for the Clyde. The Clyde also employed wrap around diffuser passages to the combustion chambers. This has the effect of reducing the flow area for the rear entry of the impeller but has been found not to penalise overall performance.  Adopting this enabled the diameter to shrink to the required 50 in. To improve airflow through the impeller it was decided to allocate the 14% extra axial width by changing the relative proportions of the rotating guide vanes and the impeller itself, reducing the latter dimension. This allows smoother entry for the air and achieves greater efficiency
In order to control the weight many large components cast in aluminium were cast in Magnesium which turned out to be very satisfactory. an experiment was tried out: casting the impeller in Magnesium but was a step too far.
The third picture shows a J42 and J48 side view roughly to the same scale! The afterburner was initiated early in the Tay programme...
The photo of the J48 should be compared with the Tay photo posted earlier.
Rolls-Royce and P&W agreed a delivery programme for prototype engines in June 1948 that would result in 4 engines being constructed:
1st engine for RR by Oct '48
1st engine to be despatched to P&W Nov '48
2nd engine for RR Dec '48
2nd engine P&W end Jan '49
3rd engine P&W end  Feb '49
3rd engine for RR end March '49
4th engine P&W end  April '49.

In the end RR built 34 Tay engines to support all the development activity:
8 prototype flight engines for P&W
6 RR development for Ministry of Supply (2 for Lancastrian)
4 for the Viscount
6 for English Electric
6 for the Avro Tudor
all 34 were delivered by end of 1949.

To assist with RRs workload P&W assumed design responsibility for the design of Tay jetpipe and afterburner for the North American P86, but will submit their designs to RR for comment. Initial design of jet pipe was based on reheat sizes but without reheat system or variable nozzle.
P&W will place an order, when RR is ready, for 2-3 afterburners but in the meantime they carried the workload themselves, using drawings of the RR design of clamshell nozzle.
The programme was very successful and a large number of J48s was produced by P&W. Production numbers at P&W were:
Nene: 1,137 and
Tay: 4,021.
Typical specs were:
                                     J42-P-6           J48-P-5
Dia (in.)                            49.5                50
Len (in.)                         103.2              236
Dry weight (lb.)             1729              2000
PR                                     4.3                4
Max thrust (lb) @          5750 (wi)      8,500 to 9,000 (7,000 with wi)
rpm                              12300           11,000
wi= water injection
« Last Edit: August 10, 2012, 06:36:59 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #124 on: May 18, 2012, 02:43:31 am »
Immediately after the war there was a surge of interest in automotive applications for the gas turbine. Rover developed a 100 hp engine suitable for their production car, Centrax looked at the lorry market with a 160 hp designed by ex-employees of Power Jets, and Rolls-Royce looked at the feasibility of a small engine for automotive or small aircraft application.
Jim Boales was involved in this investigation and extracts from an undated report (late 46 or early 47) reads:
"  there are many uses foreseen for a 500 bhp engine, e.g. cars, light aircraft, where about 200 hp is needed or a trainer aircraft.
Advantages: lightness, simplicity, no gear changing or clutches. For traction purposes a free turbine is desirable, then engine power is not directly related to power turbine torque is obtained for starting. Also [the free turbine arrangement has] general uses for investigating different turbine arrangements, control systems, heat exchangers, etc.
For such an engine it was considered desirable to use an existing compressor that does not need development and a reasonably high pressure ratio, about 5:1. The free turbine enables the engine to be run as a pure jet. This greatly helps as the free turbine can be developed separately.
As a turbine power generator it is desirable to keep the leaving velocity from the turbine down to the minimum possible. Thus a low axial velocity turbine will have to be incorporated."

The RB60 engine was configured as:
"A Merlin 46 2-stage blower delivering via its own volute and single delivery pipe into a single reverse flow combustion chamber, from which the hot gas flows into an annular volute at entry to the high pressure turbine. This is a single stage turbine. The gas then flows through an annulus about 6 inches long to the low pressure turbine. This drives a gearbox at the rear.
The engine is fitted with an oil tank and pumps fitted to the h-p section wheelcase, and on the l-p section for the reduction gear and power turbine.
The cooling air for both turbine casings is an external supply. The wheelcase driven by the h-p unit carries the starter motor, fuel pump, oil pumps and tachometer. The fuel control systems apart from pump is mounted separately."

Jim Boales said that the turbojet ran at Barnoldswick but the power turbine was never built as there were other priorities.
The design performance was:
Press ratio 5:1
compressory efficiency 72.5%
Power output/lb/sec 64 bhp at a gearbox efficiency of 98%
so for 7lb/sec flow the output was 450 bhp at an sfc 0.845
Hp rpm 22,800
lp rpm 17,200
performance as a jet:
jet velocity 1025 ft/sec
total thrust 350 lb
sfc   1.08
« Last Edit: May 19, 2012, 05:40:31 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Hobbes

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Re: Early British gas turbine development
« Reply #125 on: May 18, 2012, 05:46:28 am »
Immediately after the war there was a surge of interest in automotive applications for the gas turbine. Rover developed a 100 hp engine suitable for their production car, Centrax looked at the lorry market with a 160 hp designed by ex-employees of Power Jets, and Rolls-Royce looked at the feasibility of a small engine for automotive or small aircraft application.

Is this the work that led to the Leyland Turbine truck of 1968?


Leyland Turbine by aecsouthall, on Flickr


Leyland Gas Turbine by gylesnikki, on Flickr

Offline JFC Fuller

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Re: Early British gas turbine development
« Reply #126 on: May 18, 2012, 06:11:20 am »
Not to mention similar work that was done on cars by Rover: http://www.rover.org.nz/pages/jet/jet5.htm

And trains by Metropolitan Vickers (BR18100) and English Electric with the GT3: http://www.enuii.org/vulcan_foundry/oddities/gt3.htm

Offline tartle

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Re: Early British gas turbine development
« Reply #127 on: May 18, 2012, 06:25:10 am »
Hobbes... the Leyland organisation acquired Rover in 1967  and its gas turbine research work which had continued all through the 50s and 60s was directed at powering a Leyland truck. There is a pic below from a brochure which can be read here
JFC Fuller ..and boats as we have already discussed.
« Last Edit: May 19, 2012, 05:31:38 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #128 on: May 20, 2012, 05:05:27 am »
 I am intrigued by a review of the thesis The Development and Production of Turbojet Aero-engines in Britain, Germany and the United States by Hermione Giffard. Imperial College London, 2011. ... which leads me to think about how Rolls-Royce and Metrovick did not have the (gas turbine aero engine) field to themselves.

 George Bulman who was DEngRD for aero engines up until his retirement in 1943 relates how Tizard, head of R&D at the MAP (until Lindeman got him removed in 1942... an old feud.. was there a war on?) became increasingly concerned with Whittle's erratic responses to concerns about the speed of development.. decided to involve Frank Halford and de Havilland in the jet engine programme. Frank Halford, aided by Moult and Brodie had produced ranges of piston engines for de Havilland and Napier, of varying degrees of success (often constrained by those two organisations) and was asked to think of the sort of jet engine they could design for dH. Given their expertise in superchargers, such as the elegant Gipsy Twelve engine (see Flight article from which the supercharger drawing comes) and the Napier Sabre, it is not surprising this is where Halford started. With some, but limited access, to all the work then being sponsored the team went for an engine of 2,000 lbt and sized a supercharger impeller to suit. This was necessarily of larger diameter than Whittle's twin-sided design and alarmed the RAE who were aware of the failiures on Whittle's jets. However Halford's close relationship with Wallace Devereux at High Duty Alloys meant they were confident they could deliver a reliable impeller. Isaac Lubbock of Shell had been brought in to help Power Jets combustion challenges and this work was of great influence... Halford realised that two 180 degree bends in the Whittle reverse flow scheme increased the risk of uncertain combustion conditions as well as being a source of pressure loss so they opted for a straight through layout from day 1. They were not concerned about the shaft whirling issues as the single sided impeller design meant that no axial space was needed for the rear intake and so it was the diffuser elbow and combustion chamber length alone that determined the dimension from impeller to turbine, which could be linked by a simple shaft of appropriate (large) diameter.  Also the straight through layout enabled the adoption of a larger diameter turbine (not constrained by the reverse-flow combustion chambers). Progress on turbine disc materials also helped in this respect... so all this thinking without constraints imposed on Whittle a few years before resulted in the H.1, later known as the Goblin engine. A basic section highlighting the features is included below.
 As the various claims made by engine designers are not always as clear cut in practice as they are in theory I thought I would make an unfair comparison by putting a section of the 49.5 inch diameter Nene alongside the 49.85 inch diameter Goblin... see below... it is a really unfair comparison as the thrusts and therefore mass flows are not the same but we can see the Nene is a bit longer in shaft dimension than the Goblin... but the Goblin shaft diameter is relatively large... i. e. much stiffer. But the complexity that goes with a three bearing system on the Nene is certainly more complex than that needed on the Goblin two bearing system.
 
 The MAP and the Air Ministry noted the lack of paranoia as the aero firm just got on with the job... just a touch more challenging than a Gipsy Twelve but may be not as bad as a Napier Sabre?
 de Havilland had their challenges but this was to develop the rated power and sufficient longevity to make it a Serviceable engine for the military. The engine design started in April 1941 and as there was a closeness with the aircraft side of the business, the Spider Crab aeroplane design carried on in parallel... resulting in the engine featuring a bifurcated intake so that the ducting from the wing root air inlets was minimised. The first drawings were issued to the experimental shop on 8th August 1941 and a mere 248 days later the H1 made its first test run on 13th April 1942. Two days later the team were confident enough to carry out a half hour acceptance test at half design speed. On the 5th May the engine suddenly stopped- on investigation it was found that the intake had been sucked flat starving the engine of air and stalling the compressor. after stripping the engine little damage was found and soon it was rebuilt. Initial troubles involved difficulties in starting the engine, overcome by fitting two starter motors, and combustion issues leading to continuous improvements as the hours built up, as well as improving welding quality for longevity. The tailpipe was also liable to buckle so it was reinforced. Fuel supply difficulties were also experienced as the pump capacity was inadequate, so was increased. There were one or two impeller failures but the issues were diagnosed and fixed.. to be discussed later.
 After the strip and rebuild after the incident of May 5th the engine was taken up to full speed on 2nd June reaching the design thrust of 3,000 lb. By the end of July the board of de Havilland were investigating how they were to put the engine into production. On 10th September they received an official Ministry request for a detailed manufacturing plan which was submitted on 18th. On 26th September the engine completed a 25 hour flight approval test; a total of around 120 hours had been achieved in the overall test programme. Two years after the engine programme began the Goblin was ready to fly. However its designated Spider Crab or Vampire as it was to become, was not. The Mosquito and Hornet had been the focus  of DH's attention and so the programme slipped. Meanwhile the other British jet fighter was suffering just the opposite problem... the E1/44 (Meteor) was virtually ready but the Power Jets  engine was not. It seemed a good idea to look at the feasibility of 'Goblining' the Meteor.
 George Carter realised that if the Goblin intake was spun through 90 degrees the air inlet to the engine could be above and below the wing spar making the installation fairly straight forward. The Goblins were installed and cleared for flight at 2,300 lbt, 300 lb more than previously cleared by the simple expedient of increasing max rpm to 9,300 an increase of 300 rpm.So the Meteor and Goblin made their maiden flight on 20th Sept 1943.
 The British and Americans had been discussing the Goblin and the US Military decided to go ahead with Lockheed on an aircraft with one of these engines. The Lockheed XP-80 was the first product of Kelly Johnson's Skunkworks. June 23rd 1943 was the official start date and it was intended to fly 150 days later. he contract called for the aircraft to be completed in 180 days so the pressure was on! A crude mockup of the Goblin arrived on July 10th and it was the lack of engine which was the critical item for delivering the contractual timespan. August 24th saw the British Air Commission informing the Americans that a non-flyable engine was about to ship. A month later the engine was still in Britain as 'a part change necessitated by overheating the engine during a test run'. The engine was finslly delivered Nov 2nd 1943 and arrived on the Skunk Works shop floor on the 3rd. Everything was assembled and finally the aircraft headed off on a truck to Muroc arriving 14th Nov 1943.
 
On Nov 17th the Goblin was powered up for the first time. The installed, non-flyable Goblin delivered 2,460 lbt at 9,500 rpm.
....moved XP-80 stuff to #131.
« Last Edit: May 26, 2012, 02:53:13 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline alertken

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Re: Early British gas turbine development
« Reply #129 on: May 22, 2012, 05:58:51 am »
Who invented what, when?
 
In Spring,’41 DH Engines, repairer of Merlin and supplier of Gipsy for ragwings, was funded by Bulman, MAP into reaction; their design consultant F.Halford, onlie begetter of Sabre, designed H.1(Goblin) “from first principles,entirely independently of the Whittle concept” G.P.Bulman,An Account of Partnership,RRHT,2001,P.324 (pace: H.1 “would not have been designed but for the stimulus and information provided by (W.1” 2/10/47,Royal Commission on Awards to Inventors).
 
AA  Griffith had moved, 1/6/39,  from RAE to be newly designated Chief Scientist at RR, where engineers, not impractical boffins, reigned. His work on C.R.1/2 Internal Combustion Turbines did not move at the pace of Power Jets (nor, as we now know, of v.Ohain).
 
None of them "invented" reaction thrust. Each one applied mind to the "what if..:" the basic metals industry could "invent" discs and blades that would stay where they should, while spinning dementedly in a continuous explosion.
 
Quite sensibly Ministries tasked with putting weapons into young men's hands concentrated on reliability, longevity and power in pistons. Contemplate your day, Air Minister Lord Swinton, after Anschluss, when the writing was on the wall: there you are trying to kick reciprocating teams to cause enhanced Merlins to work well, "Hyper" Sabre, Centaurus, Deerhound...to work at all; you have just sequestered the entire auto industry to stop earning and start spending to build interim Mercury, Pegasus, onway to Hercules when/if that works. An eccentric, difficult engineer (oddly a serving RAF officer - how can that be?) claims his gyre will deliver sci-fi dash speed...if only it would stop exploding on the rig.
 
The wonder is not that UK, Germany, US took awhile before throwing vast sums into reaction, but that any of them ever did, at all.
 
Neither Griffith, nor Whittle, nor v.Ohain, nor RAE scientists, nor Gottingen academics "invented" jet propulsion...alone. They all did.. and all needed a Eureka from obscure grafters in metallurgy. Just as $100Bn. for nerds in Silicon Valley derived from some sandy fellow unsung by history.
« Last Edit: May 22, 2012, 06:05:11 am by alertken »

Offline tartle

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Re: Early British gas turbine development
« Reply #130 on: May 26, 2012, 02:50:36 am »
I thought I would split off the XP-80 story as post #129 was getting very long!
The British and Americans had been discussing the Goblin and the US Military decided to go ahead with Lockheed on an aircraft with one of these engines. The Lockheed XP-80 was the first product of Kelly Johnson's Skunkworks. June 23rd 1943 was the official start date and it was intended to fly 150 days later. he contract called for the aircraft to be completed in 180 days so the pressure was on! A crude mockup of the Goblin arrived on July 10th and it was the lack of engine which was the critical item for delivering the contractual timespan. August 24th saw the British Air Commission informing the Americans that a non-flyable engine was about to ship. A month later the engine was still in Britain as 'a part change necessitated by overheating the engine during a test run'. The engine was finally delivered Nov 2nd 1943 and arrived on the Skunk Works shop floor on the 3rd. Everything was assembled and finally the aircraft headed off on a truck to Muroc arriving 14th Nov 1943.
On Nov 17th the Goblin was powered up for the first time. The installed, non-flyable Goblin delivered 2,460 lbt at 9,500 rpm.
The engine ran up on the first attempt and the installed thrust measurements were taken. The non-flight Goblin gave 2,460 lbt at 9,500 rpm. No major problems were uncovered during this first run.
On the 18th they decided to have a second run with the aircraft restrained. A major incident occured when the engine suddenly stopped. On inspection in the intake ducts had collapsed and debris had entered the engine damaging the leading edge of the impeller. First thoughts were that the engine was ok and ducting had collapsed due to incorrect load distribution. It was stressed assuming there would be a 4psi pressure differential which was exceeded in practice... restressed for 12 psi, the duct was replaced with a heavier gauge one. On the 21st the night shift were shaken to discover a 3½  inch crack in the impeller. Close inspection determined that this was not as a result of the duct incident but was a failure due to a material defect.
De Havilland were working on a more robust impeller. The impellers were machined from great 'cheeses' weighing 500lb and at that time were the largest RR50 forgings to be made. The size meant that there were compromises on the material properties in the centre of the forging (shades of RB211 fan disc disintegration many years later) which were still there after the cheese was reduced to a 109 lb impeller. Wallace Devereux, the engineering brains behind High Duty Alloys, advocated controlling the silicon content of the alloy to less than 0.25%. This produced an impeller with acceptable properties throughout and, with the additional benefit of producing the alloy by continuous casting, a better cheese was produced.
Obviously with so few Goblins around there was no spare easily available, nor spare parts as every part being made went to build a new engine, or replace a broken part. But the DH team were keen to help Kelly and by 27th agreed that a new engine could be shipped on Dec 11th to be in the USA by 15th. The damaged engine was shipped back to England. On 9th December disaster struck when the eleventh Goblin engine, which had been allocated to Lockheed, disintegrated on test! It was decided that swapping out an engine intended for the second Vampire was the best course and this could be shipped out by 22nd December 1943. It arrived at Muroc on the 29th Dec and was immediately prepared for installation. The next day it was statically tested and apart from minor adjustments was running well. New Year's Eve saw the engine run up to 9,600 rpm, the max cleared speed for flight. A well deserved day off followed and on 2nd January 1944 the tail was reattached and the aircraft readied for taxi trials on the 3rd. A day for inspection and then first flight on 5th were pencilled in. Kelly also signed off on most of the XP-80A proposal on that day. Kelly also decided that letting Muroc's test field dry out a day or two longer would also enable them to get all Skunk Works personnel up to witness the take-off so on 8th Milo Burcham, Lockheed's chief test pilot took it into the air for 6 minutes and on landing noted the landing gear would not retract... A fix was found and a second flight of 20 minutes followed.
The final picture shows the XP-80 being readied for its first flight with the Skunk Works team on the hill behind.
...tbc
« Last Edit: May 28, 2012, 01:03:17 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #131 on: May 27, 2012, 08:16:47 am »
I have often wondered whether contact with de Havilland - which had built the first Mosquito using an integrated, isolated and secure design-build team - had an influence on the original Skunk Works approach.

Offline tartle

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Re: Early British gas turbine development
« Reply #132 on: May 27, 2012, 04:32:30 pm »
Good question... my gut feeling is that the two aircraft companies independently came up with a similar solution to a similar question... how do I keep a new project secret, away from people who might object to diversion of some of the best brains away from problems of war production?... both projects were not really accepted by the mainstream military decision makers. Although Lockheed had contact with DH engine personnel they [the DH engine people] may not have been aware of Mosquito activity.
In the end the [Lockheed] Skunk Works achieved a 143 day timespan for XP-80 airframe completion; only non-availability of engine prevented them achieving the 150 days to aircraft availability to fly. The beauty of Skunk Works is that they remove queuing, so contingency can be removed from the critical path...in a sense everything is critical! Dr Eli Goldratt in 1997 talked of the theory of constraints and the critical chain which roughly meant if you were an expert at 'x' and were required to give, say ten projects your attention, then you would be spread so thin that many would suffer as they waited for you to arrive. Health Services experience this!
So do aircraft project teams if they are in the main office.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #133 on: May 30, 2012, 06:23:14 am »
Carrying on from #131:
As well as changing the material to low silicon RR50 aluminium alloy de Havilland also decided to test every impeller on an overspeed rig to check for soundness. The impellers were run at 15-20% over max rpm and then inspected for any evidence of faults. Also as the hours built up some impellers showed signs of fatigue cracking on the blades, which the team thought could be vibration-induced. Work started to investigate what excited the vibrations and what was the magnitude of any induced stresses. This involved working out how to attach strain gauges to the impeller, which had not been done before in such a highly loaded environment. It was soon established that the impeller had natural frequencies excited by the inlet arrangement:
The first was excited at 4x the engine speed, induced by the inlet arrangement, and
the second occured at 16times/rev. This was induced by upstream 'bow waves' from the shock of the air entering the 16 diffuser passages.
The first of these two 'exciters' was mitigated by moving the 4th order excitation (induced by the 4 intake radial vanes- see first picture) out of engine operating speed range- achieved by cutting back and chamfering the leading edge along its front entry part of the blade- raising the first flapping mode to higher frequency. A beneficial side effect was improved aerodynamic performance sufficient to allow a higher thrust and lower operating temperatures.
The bifurcated intake arrangement on both the XP-80 and the Vampire meant a circumferential temperature traverse of the jet exhaust exhibited wide temperature variations. By calibrating the fuel nozzles in each of the 16 cans, adjustments to fuel flow to each chamber could be made removing the hot spots around the traverse.By the end of January the flight tests had indicated flight handling mods necessary to improve the flyability of the XP-80. On 27th it was taken out of service and a whole list of mods incorporated. On the engine side the fuel flow modifications were incorporated.
Flight testing began again on 10th Feb 1944 when it made its 6th flight. The only glitch from an engine perspective happened during a ground run after flight 9- Feb 14th.- excessive heat was spotted on rear fuselage. Investigation revealed 2 stator blades had burned away. The burner in front of these blades had loosened, turned sideways and allowed excessive fuel into the can, generating excess heat. A locking device was devised and fitted on all burner nozzles, eliminating the problem.
A revised and improved engine cleared for 9,800 rpm was made available from Britain and fitted at the end of May. Unfortunately high tailpipe temperatures restricted running with the engine. On May 31st a restriction on rpm was placed on these engines, due to an explosion on test at DH. A few days later this was revised to a 9,500 rpm restriction. But the high jet pipe temperatures were still a nuisance as the hot summer approached.
By this time GE were promising production of the I-40 and so the XP-80A was designed around this engine.
Allis Chalmers never got really into licence-production with the Goblin.
« Last Edit: May 31, 2012, 02:32:43 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #134 on: June 07, 2012, 12:34:24 pm »
Napier, Armstrong Siddeley and Bristol also got into the act a little later than RR and Metrovick. RAE had inspired an axial thread to the gas turbine development and being familiar with Metrovick had asked them to continue after the B10 rig. RR came in via a desire, partly altruistic, to get Whittle out of a pickle! Napier had its hands full with Sabre issues that had to be solved by throwing development and production expertise at it... namely Bristol and English Electric. Eventually the combination of taking over a DH project and using the experience from Nomad supercharging got them into the arena if not into the race. Bristol joined in the the 2nd GTCC meeting and realised the technology train was speeding out of the station so asked if they could get involved. Not wishing to duplicate work they decided their civil and bomber background should help in turboprop development so that is what they suggested to the Ministry. They got a contract to develop a turboprop and heat exchanger system. Armstrong Siddeley shook off the Griffith inspired route they were following and went for an axial turbojet, again trailing Metrovick. They could of picked up the F2 work at this stage but that meant collaborating with Metrovick which was culturally difficult so thay went for a trombone of a layout.
Although Griffith and Hayne Constant were axial advocates their scientific understanding had accelerated past their engineering capability to deliver and so even The small team at Power Jets showed a sound aero technology stretched hard could still win over a new one. Aero engines could not afford to let efficiency leak away like industrial applications, hence the hard time steam turbine firms had in the sky. Roxbee Cox and his backers were wiser souls with their technologies tempered in the heat of war so were more inclined to let firms that would regard the gas turbine as just another prime mover with a different set of problems to solve.
We'll follow their fortunes ............in the next few posts.
« Last Edit: June 09, 2012, 04:31:36 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline PMN1

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Re: Early British gas turbine development
« Reply #135 on: June 09, 2012, 10:14:13 am »
According to Bill Gunston,

'An extremely important feature introduced hesitantly with the original (Armstrong Siddeley) ASX was the use of vapourising combustion. There are inherent problems with high-pressure atomising, but with the ASM system the fuel is sprayed at low pressure into a 'walking stick' 180 degree curved tube where it vapourises, not quite as in a blowlamp, to give near-perfect burning at all fuel flows, which can vary 100-fold between sea-level take off and high altitude flight idle'

'When Dr Stanley Hooker became Technical Director of the combined Bristol Siddeley firm in 1959 he found the ASM system superior to the more common scheme, and ordered it used on former Bristol engines.


Were there any other attempts at vapourising combustion?

Offline tartle

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Re: Early British gas turbine development
« Reply #136 on: June 09, 2012, 01:32:10 pm »
Isaak Lubbock of Shell Labs was one of the team that solved the combustion problem on the Whittle turbojet. In Shell's words from their centenary brochure issued to commerate the 100th anniversary of  Frank Whittle:

The Vaporising Problem
 
 Sir Frank Whittle ensured that Britain entered the Jet age when, on 15 May 1941, the Gloster-Whittle E 28/39, propelled by of his jet engines, flew successfully from Cranwell, England.The Vaporising Problem
 
Shell had played an important part in this milestone with its answer to the combustion problems that the original Whittle WU engine had been experiencing.  The solution was the “Shell” combustion chamber.  Sir Frank once said: “The introduction of the Shell system may be said to mark the point where combustion ceased to be an obstacle of development”.
 
 During the engine’s development, Sir Frank had worried about combustion problems because he was aiming for a combustion intensity more than 24 times greater than any other of that time.
 
 Although a design for a vaporiser combustion system had already been developed, it proved temperamental as its coils either blocked with carbon or burnt out.  Such problems were a major obstacle in the further development of the engine.

However, Isaac Lubbock, of the Shell Petroleum Company, was helping engineers from Power Jets – the Lutterworth company Sir Frank had formed to develop the turbojet engine – on combustion and fuel problems.  Isaac invited the engineers to see a combustion chamber, similar to the size and form as the one being used in the engine.  Shell engineers were also experimenting with the chamber in their laboratory in London.

[first pic]

The fuel was being injected into the chamber in a fine mist of liquid droplets through a controllable atomising burner.  A Power Jets team saw it working in the laboratory and were impressed.  They took it to Lutterworth where it was set up for Sir Frank to see.
 
 After that, they concentrated their effort on the “Shell” combustion chamber, which was adapted to the engine.  Another Shell expert, R. Joyce provided further assistance, developing the burner.
[second pic]


..................
The Armstrong Siddeley system built on the Whittle experience and overcame the shortcomings that had come to light on the Shell system as jets operated for longer hours and was of simple walking stick design first introduced on the ASSa3 engine. In fact they started straight away to develop Vaporisation which appeared on the ASX turbojet and was refined into the system used on the Mamba. Experience from that was eventually fed into the Sapphire ASSa3 in 1948, more or less as soon as they had full control of the programme. Seems pretty quick and bold to me. There is a Flight drawing that illustrates the design of the Python vaporiser. The Mamba picks up on the Sapphire design.
Why RR etc went a different way is another 'Arthur H. Lefebvre' story... the man who changed combustion on gas turbines for ever. He invented the air blast atomiser which gave good control of droplet size and hence predictable vaporisation behaviour in the main area of the chamber and allowed better control of the process for instance on the RB211 but that was way into the future... thank goodmness Hooker did not have the luxury of time to put the system on that engine in 1971.
« Last Edit: June 09, 2012, 04:34:20 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #137 on: June 10, 2012, 04:18:00 am »
I mentioned above the failures of early Whittle impellers and the subsequent redesign to GE America design rules.. these cured the vibration induced failures of the impeller. I remembered reading about this in 1965 and finally found the report which contains a before and after picture. Basically the difficult machining challenge meant the first impellers had blades that were thicker at the eye than the tip... with induced vibration from the diffuser the tips flapped and cracked. GE for an entirely different reason adopted a thick tip approach and were better at machinng the impellers so they were thinner at the eye. This reversal of thickness changed the blade natural frequencies and the level of stress experienced so that the problem went away.
The two pics below show the change in design.
The pictures also show the curvature of the inlet rotating guide vanes; designers of this period used to assume that the rgvs were single stage compressor blades with a high camber. such a blade design exhibits flow break away and is therefore not the most efficient design. We have already noted how RR when scaling the Nene to the Tay increased the axial proportion of the rgvs to make the curvature less drastic, improving the aerodynamics of the design. Also on the Goblin changing the shape of the inlet edge of the rgv also improved the aerodynamic effectiveness.
« Last Edit: June 11, 2012, 03:44:32 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #138 on: June 14, 2012, 06:07:07 am »
When Whittle moved from W1A development to the W2B he was keen to make the diffuser a little less bulky by reducing diffuser length from that shown in the first picture. The design team hit upon the idea of reducing the length whilst maintaining the angle of the walls by making 80 small diffusers working in parallel rather than 10 big ones. This lead to the 80 vane diffuser design at the bottom of the next picture. This was a disaster. Difficult to make uniformly, when fitted on the engine the result was surging that made the engine unable to accelerate... as we discussed above. A rapid reversion to the deign above the 80 vane on-known as Type 13 was rapidly developed on the new low-speed diffuser model rig. The rig enabled new shapes to be tried out at design mass flow and with uniform entry velocity (unlike the engine). It soon became clear that with vanes in the ductwhere the flow was turned to the axial direction not only could the flow be kept relatively smooth but some pressure recovery could occur. This led to the idea for a straight diffuser and then multivane passge for turning the flow.... the Type 16. Being easy to machine accurately this was rapidly adopted here and in the USA. The performance gain is shown in the graph - 3rd picture.
The Type 13 was fitted on the W2/500 and Type 16 on the W2/700. For reference I include a view looking on to the W1A vanes and an axial section of the W2B diffuser. the last pic is an isometric of the W2/700 diffuser.
Once Power Jets got a grip on the aerodynamics of the engine and with Hives, at RR, encouraging them they made good progress.
« Last Edit: June 14, 2012, 06:09:11 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #139 on: June 14, 2012, 02:10:44 pm »
The french arm of Hispano-Suiza was drawn into the jetage when, after WWII, the Ministère de l'Air attempted to reinvigorate some of the stalled projects. As it was not clear that small aircraft would benefit from the gas turbine work was carried out under contract to the M. l'Air to develop a 36 litre piston engine based on the 12-Z engine .. a V12. This was the 12-B with a mechanical supercharger as normal and drove a propeller . The exhaust from the engine was lead to the rear and into a turbocharger turbine which drove a centrifugal compressor to supply the engine intake. A little like a Nomad n'est pas? The engine went to type test in 1951, but the engine never flew. 2nd and 3rd picture shows the design layout.
H-S was responsible for the overhaul of Merlin engines in France so had a good relationship with RR. This made them the choice of manufacturer when the French government decided to take a licence for the Nene. This made good sense as SNECMA were going down the route of developing German technology in the form of the ATAR.

H-S signed the agreement in Feb 1946 and began a long period of infrastructure development to support gas turbine production. It was June 1948 before the first Nene was rolled out of the H-S factory. Production finally ceased in 1955 after 1,073 were built. In 1950 a second licence was signed for the Tay. The first of Tay 220 engines which were built was delivered July 24th 1952. The licence fees were met from British-paid licence fees for the H-S cannon.
There were several versions of the Nene built in France starting with the 102; some prototype 103s followed which were lighter-the compressor casing was cast in magnesium, saving 176 lb for an engine weight of 1587 lb. So far the H-S engines were rated at 5,000 lbt. The six 103 development engines indicated some stiffening of the casing was necessary so the next version, the 104, had a thrust of 5,090 lb at a weight of 1609 lb. This version was the main production for the airforce and 771 units were delivered. The next version, the 105 had improvements in the flame tubes coupled with an improved starting capability. These changes gave a slight weight increase of 11 lbs and a thrust of 5103 lb.
The development team meanwhile had looked at how the thrust could be upgraded significantly and started on the development of the R-300 which used 50% Nene components but had H-S parts for the rest. This resulted in an engine weighing 1664 lb and delivering 5952 lbt. After 3 engines were built and tested the project was abandoned and the Tay went into production.  Alongside all this and to help the SNECMA ATAR programme H-S built a reheat system for the Nene 102 first testing it in 1950. This R-400 version gave a 22% thrust increase  The so called R-401 engine, based on the Nene 105, gave a thrust of 6790 lb for a weight of 2260 lb., preceeding the afterburning work at RR. After production ceased a batch of 200 engines to 104 or 5 standard were upgraded to a 106 which gave a thrust of 5,090 lbt for a weght of 1653 lb.
« Last Edit: June 15, 2012, 04:01:57 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #140 on: June 14, 2012, 02:21:15 pm »
Having taken a Nene and developed a new variant the R-401, H-S again looked at doing the same sort of development of the Tay. This became the Verdon 350, with an rpm of 11,100 rpm up 100 from the Tay and a thrust of 7,710lb.for 2061 lb weight. Continuing to compare with the Tay, the massflow is 132 lb/sec vs 115; Pressure Ratio is 4.9 vs 4.0 (Nene was 4.3). The Verdon 450 is the ultimate afterburning version with a thrust of 9,920 lb.
....tbc
« Last Edit: June 15, 2012, 04:29:27 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #141 on: June 17, 2012, 06:34:31 am »
As so many people have looked at the combustion aspects of the early jets in #137 I thought it worth pursuing the subject a little further. The James Clayton lecture delivered by Frank Whittle in 1945 is an excellent overview of the detailed development carried out by his team to travel from the technology demonstrator to a practical power unit i.e. from WU to W2/700.
The early 10 chamber versions of the WU had vaporiser combustion chambers inspired by the Primus stove (sketch of principle : first attachment courtesy of Wikipedia)
 

The key for Sketch of the Primus stove burner head is
A: Connection to petroleum container;
B: ascending pipes carrying cold petroleum to the burner head
C: Burner head; D: Descending pipes carrying hot petroleum from the burner head to the nozzle;
E: nozzle and escaping hot petroleum ready to burn in the air.

So Whittle switched from diesel oil to kerosene and adapted the Primus principle to fit the ten combustion chambers (Type 31). The problem was the initial heating of the coils to start vaporisation and then stopping the engine from accelerating away due to accumulation of fuel during the light up process when the pilot injector was supplying a fuel mist. The robustness of the vaporising tubes was also in doubt so the team switched over to the Lubbock fuel spray nozzle and combustion chamber for the first W1A engines.
Using two sources of picture- RR's first edition of 'The Jet Engine' from the mis-50s and Power Jet's 1944 report CRN 371 we can build a picture of the early understanding of the combustion challenge. (see 3rd picture)
Just to refesh our memories the combustion chamber has 3 zones:
Primary: where the fuel introduction device and the ignition system resides. This zome is where most of the heat release occurs and where the maximum danger of local overheating of the metal parts. At the entry to the combustion chamber the air will be moving at around 80 ft/sec. As the kerosene flame front only moves at about 2 ft/sec we must do something to slow the air right down or the flame goes out (think lighting of flame to light a cigarette outdoors). So we need to swirl the air and create an inner zone of slow moving air (think eye of tornado). All this has to be achieved in a manner that anchors the flame in a stable manner (4th picture).
Secondary: when the main combustion action is nearly complete we need to introduce more air creating turbulence and mixing and supplying further oxygen to keep the reaction going. Bringing air in too soon will chill the flame and allow incomplete combustion and formation of soild products of combustion (e.g. carbon). The ability to achieve secondary mixing without too mach pressure loss has saprked a great deal of experiment on mixing devices.
Tertiary air has one function: to reduce the overall temperature to a level acceptable to the turbine. It is required to achieve a uniform temperature distribution at minimum pressure loss.
The overall airflow ends up looking like diagram 5.

Returning to vaporisation; the idea is that the fuel is preheated by passing the fuel pipe through the flame and enters the combustion chamber as a vapour. The system offers the possibility of easy mixing and intense combustion. In (Whittle) practice it entailed great difficulties as the tubes burned out very easily and partial combustion was common in the tubes leading to soot formation in the tubes. Also the vaporisers need to be warmed up or stated before they will work sutainably which means providing a pilot spray jet to maintainn combustion until the tubes heat up. The pilot jet needs to be present in every one of the ten tubes on the W series engines. A typical chamber is in the next photograph
Given the difficulty of keeping the tubes in one piece the Whittle team looked around for a more robust solution the would keep going for the flight durations required, at the very least.
...tbc
« Last Edit: June 17, 2012, 11:17:52 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #142 on: June 17, 2012, 11:31:16 am »
The square law pressure relationship iapplies to the atomisation of fuels. The Square Law relationship states ' the flow through the burner is proportional to the square of the pressure drop across it'. Bearing in mind that the flow range idle to max power is around 1:12 and if minimum pressure to maintain atomisation is 30 lbs/sq. in. then the pressure needed to give maximum flow can be as high as 5,000 b/sq. in- well above the pump technology of the time.
Shell and Lucas had both been drawn into the jet engine programme. Shell had a great understanding of combustion and Lucas of fuel delivery systems and sheet metal work. Isaac Lubbock and his assistant Geoffrey Gollin worked on the combustion chamber and came up with a possible design using A moving piston or Lubbock burner. (see the first attachment)
The Lubbock burner makes use of a spring-loaded piston to control the area of the inlet ports to the swirl chamber. At low flows the the ports are partly uncovered by the movement of the piston and at high flows and pressure the piston moves to fully uncover the ports. By this method the square law pressure relationship is mainly overcome and good atomisation is achieved over a wide range of fuel flows.
Whittle found that they could get away with a pump maximum pressure of 400 psi covered the operating envelope of the engine in 1944 but even then there was a small deterioration in atomisation at the lowest throughputs, which caused problems as the combustion chamber flows were very sensitive to small alterations in the spray angle. Due to the huge challenges of making the vaporisers reliable Power Jets switched to the Lubbock burner on all its engines; but again as the hours built up considerable trouble was experienced with sticking of the sliding piston due to dirt particles and with matching a set of burners; both inherent problems of the design, they proved impossible to overcome and the Lubbock burner was never put into production.
The Simplex burner has a simple cylindrical chamber with tangential slots to feed in the fuel and to induce a swirl and a fixed area atomising orifice. Used on the Derwent engine, it works well at high fuel flows but was very unsatisfactory at the low pressures required at low rpm and especially at high altitude. Hence the energence of the Lubbock design.
The inherent disadvantages of the Lubbock meant that the Lucas and Rolls-Royce combustion teams worked on other solutions, taking the Simplex as their starting point. This led to the Duple (RR) and Duplex (Lucas) design which had a swirl chamber with two independent metering orifices, one much smaller than the other. The smaller orifice handles thelower flows and the the larger orifice deals with the higher flows as the burner pressure increases. A pressurising valve is employed to apportion fuel through the two manifolds. At idling speed and at altitude, for example, the pressurising valve allows the fuel to pass the primary manifold and primary orifice only. As the pressure and flow increases, the pressurising valve moves to adnit fuel into the main manifold and the main orifices. in this way the ?Duplex and Duple burners are able to give effective atomisation over a wider flow range than the Simplex, and at altitude.
The Spill burner manufactured by Dowty is like a Simplex burner but with a passage from the swirl chamber for spilling fuel away. The pump delivers fuel at a constant, high, pressure and the flow out of the orifice is controlled by the amount of fuel spilled from the chamber e.g. as rpm reduces or altitude increases. The high pressure ensures good atomisation even at low flows. The spill burner system requires a second pump and controller to ensure starting, adjusting and stopping of the spill flow... see later post.
The graph shows the relative performance of various burners.
This leaves Air boost, air blast and upstream pencil nozzles.
« Last Edit: June 18, 2012, 05:48:18 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Jemiba

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Re: Early British gas turbine development
« Reply #143 on: June 17, 2012, 10:06:13 pm »
tartle,
I think it's time to thank you very much for your contribution to keep this topic alive with lots
of material and especially explanations, that really give more understanding and insights into this not
really simple subject !
Keep it up !    ;)
« Last Edit: June 18, 2012, 03:09:13 am by Jemiba »
It takes a long time, before all mistakes are made ...

Offline tartle

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Re: Early British gas turbine development
« Reply #144 on: June 18, 2012, 01:03:41 am »
Thanks for feedback...especially when it is positive.. I wish I had the knowledge I have now when I was an apprentice and talking to these people..Jim Boales was really interesting and happy to let me see his notes and reports... I wish I had known about Hispano Suiza and the Verdon as he would have filled me in on what went on there as he spent much time in France. His notes may have gone to RRHT... another research thread! Incidentally I reminded myself when I looked at my old lab works for the course at Cranfield that I actually did a testbed run on the vaporiser equipped Mamba!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #145 on: June 18, 2012, 05:56:39 am »
Dowty made a good job of describing the spill burner principles in their technical manuals. I attach the relevant pages below.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #146 on: June 18, 2012, 09:33:32 am »
The realisation by Everybody involved in the Whittle jet engine programme that combustion was the achilles heel (as were Metrovick also) meant that Lucas,  Asiatic Petroleum Company (as Shell were known back then), etc. were brought in to help.
A review of Power Jets efforts is summarised here in order to bring out the great amount of work done on the test bench in order to come up with a viable solution in the midst of a war!
Power Jets review of combustion chamber (CC) design and testing states:
"From August 1939 to about the middle of 1940 a large number of vaporiser CCs were tried ...it would appear that combustion was fairly good when everything was working properly but the fuel system was extremely unreliable and the vaporiser tubes were liable to burn out or block up with carbon at any moment. The difficulty of obtainingan even distribution of fuel toall ten CCs, let alone to each of the fuel jets in a single chamber, was also a source of much trouble, the result being that some chambers ran much hotter than the others and the temperature distribution at the outlet of each chamber was also very bad. In addition to all these troubles, the problem of ignition was very great as a pilot jet had to be fitted into each chamber and kept alight until the vaporisers got sufficiently hot to start functioning. Starting, in fact, was an extremely critical matter as it was then that most of the burning out and blocking up occurred."

Fig 2 shows CC 65 which was the first to be fitted to an engine using a spray jet. It was a development of the chamber which was first designed by the Asiatic Petroleum Company to suit their Lubbock burner. It incorporated a multi-vane primary air swirler, a throat and two rows of stub pipes, while tertiary air was admitted through plain holes.
"It gave good combustion but the pressure loss was very high and the walls of the flame tube got extremely hot, so much so that even the air casings used to attain a dull red heat during running. It also gave a lot of trouble with Carbon formation and both the overheating and the carbon was believed to be due to the liquid fuel hitting the walls, the basic problem being a deficiency of primary air."

CC101 (fig 3): This chamber is the last of a family of flame tubes Nos. 75, 89 and 101, all of which incorporate a six-vane swirler, opposing conical throat and two rows of alternate long and short stub pipes. CC No 75 was the one employed on the first flights in May 1941 and is design incorporates a number of interesting features.
"Firstly, it was developed from the results of a large number of primary zone tests, well over 100 different combinations of swirlers and throats having been tested before any attempt was made to construct a complete flame tube. (Fig 11 is a diagram of rigs used)
These primary zone tests provided such valuable information and the result was that only minor modifications were required to the primary zone when the complete flame tube was tested.
Secondly, the chamber provided some extremely interesting information on the subject of carbon formation. When it was first tried on the engine with long and short stub pipes, as shown in Fig 3, no coking trouble was experienced, but subsequent tests made with shorter stub pipes, invariably resulted in large carbon deposits which could only be got rid of by blocking up some of the tertiary air holes so as to increase the proportion of primary air. It eventually become evident that the long stub pipes were feeding air into the reversal zone and thus the effect of shortening the stub pipes was to reduce the amount of primary air, thus giving rise to carbon formation. The carbon was usually built up in the form of two strips, starting at the inter-connecting tubes and thence pursuing spiral paths down to the stub pipes where they merged into a thick ring all round the wall against the roots of the upstream stub pipes- see Fig 12."
"This chamber gave a fairly low pressure loss and high combustion efficiencies (over 95%)
at rich mixtures but the effeciency tended to drop off at mixtures weaker than 90:1 while some trouble was also experienced with the ends of the stub pipes burning off. An additional disadvantage was that the exhaust was slightly smoky with the result that the aircraft used to leave a trail of smoke in the sky. The  smoky exhaust and the low efficiency at weak mixtures were probably both due to the amount of primary air having been excessive at all but the richest mixtures. this chamber, in fact, provides an excellent example of the advantages which would accrue if it were possible to vary the amount of primary air with mixture strength."
« Last Edit: August 10, 2012, 06:35:57 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #147 on: June 20, 2012, 02:34:00 am »
The Power Jets report, published May 1944, states
"CC102:  This chamber is now standard on all PJ engines. Its essential feature (Fig 4) is the admission of primary air through tangential swirlers as opposed to multi-vane axial swirlers of the CC101. It also has the additional very great advantage of having no stub pipes or other projections which would be liable to burn out or form a nucleus for carbon formation.
Other features are:
1. The primary air is preheated by causing it to flow over the back plate, which gets fairly hot during running.
2. Part of the primary air forms a cool layer next to the walls and thus prevents the latter from getting overheated.
3. The air which is admitted through the first row of holes acts as primary air with rich mixtures but secondary at weaker mixtures, thus giving rise to higher efficiencies over a wider range of fuel/air ratios.
4. The admission of some of the secondary-tertiary air through two sets of tagential swirl ports in opposite senses promotes considerable turbulence and is a very effective mixing device."
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #148 on: June 20, 2012, 04:25:53 am »
Another interesting design that did not see the light of day but confirms PJ's interest in straight thru' engine configurations was developed from CC102 with
".... the object of reducing total head loss by using 5 large CCs instead of the ten small ones and obtaining a greater volume of combustion space  without increasing the length of chamber or engine diameter. The straight through design is approximately the same length as the W2/500 but max diameter is increased from 8 inches to 14, and there are two inlets to each chamber, the idea being to fit 5 chambers to an engine with the normal ten outlets from compressor. This design also tends to nullify the effects of non-axial airflow into the combustion chambers."
It is interesting to see that the same approach was adopted for the deH. Ghost engine.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #149 on: June 20, 2012, 04:29:02 am »
Another promising design that went nowhere was the  surface combustion chamber. The idea is to 'throw' the fuel onto a very hot surface and the vaporising and burning to occur actually at this surface. The limitation which eventually led to abandonment was the lack of a material that would stay in one piece as it was subjected to the high thermal stresses caused during light up and shut down.
Silicon Carbide cement bricks were the best materials but still suffered from cracking and the risk of pieces breaking off and going through the turbine was too great to contemplate!
The chamber itself worked well with a very short flame but the tendency for carbon to build up on the surface when operating with rich mixtures was also a drawback.
« Last Edit: June 20, 2012, 05:30:56 am by tartle »
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Offline Trident

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Re: Early British gas turbine development
« Reply #150 on: June 20, 2012, 05:31:55 am »
It is interesting to note that vapourising combustion chambers are very popular today in micro gas turbines for model aircraft. To get around the coking issue such engines generally have to be run on propane during start-up until the vapouriser tubes have heated up sufficiently.

Offline tartle

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Re: Early British gas turbine development
« Reply #151 on: June 20, 2012, 05:40:34 am »
Just listened to a discussion programme that featured Frank 'I remember you' Iffield. His father invented a variable displacement pump that Lucas realised was just what was needed in a jet engine fuel system and employed him to make it happen.

The last significant CC investigated at PJ was the NERAD CC, which was being developed by GEC of America. It is a very simple design and has air ports as simple circular holes - ideal for manufacture. The version tested at PJ gave good results under ideal conditions but was extremely susceptible to the slightest assymetry in airflow.
The most critical portion of the chamber was the first 2 or 3 holes downstream of the spray jet, as the position of these, in conjunction with the angle of the spray jet, controls the stability and, to a large extent, the performance of the chamber.

In the original report there is a comment "presumably much more work has been done in America, but the results are not known."
I thought I'd look at museum stuff to try and find an answer so found two engine pics.
« Last Edit: June 21, 2012, 03:11:48 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #152 on: June 20, 2012, 12:54:32 pm »
Last night I was giving a lecture on Maurice Egerton, friend of Charlie Rolls of RR fame and his pioneering flying effirts in the Edwardian era.. one of his engines was a Gnome rotary.. a meber of the audience remarked how other people had tried rotaries but it was the Seguin brothers who put the right technologies together and 'conquered the world'. The reason I have shared my studies is apart from the fun of it is to help my understanding of why these factors are relevant now and what technologies allow us to make a better job of it than, say PJs did.
RR has stated:
"Engine 3E being developed by RR in Germany has basic project requirements in principle can be separated into two categories: performance and business related requirements.
Traditionally, the performance related requirements such as emissions and combustion efficiency are in the main focus in the beginning of the technology development whereas the business related requirements such as life, weight and cost set in when the initial concept is demonstrated.

The project requirements are broken down into the following sub-system requirements:
• NOx: <35% CAEP2, CO: <60% CAEP2, UHC: <40% CAEP2, invisible smoke
• combustion efficiency comparable to current in-service (rich burn) combustion systems, maximum efficiency at part power conditions
• cold starting down to -40° C SLS, altitude relight > 25 kft, reasonable pull-away time to idle
• combustion stability during transient operation and hail & rain conditions: sufficient margin against lean blowout (LBO) at flight idle
• temperature traverse meeting turbine requirements
• component life: fuel injector thermal management, combustor cooling
• high reliability, robust design
• weight, cost

In a first step, the combustor volume was determined according to conventional design rules. Fuel mixing and staging is accomplished within the fuel injector configuration of concentrically air swirlers . The internally staged fuel injector operates in a pilot and main mode depending on engine power.
As most of the combustor air flow within a lean burn combustor is required for fuel preparation within the fuel injectors the combustor wall cooling air split was reduced by the introduction of a double skin wall arrangement, where heat resistant tiles attached to the combustor liner are taking the thermal load. The liner absorbs thermal stresses and ensures structural integrity. The split of the combustor wall into two components with individual functions enables the optimisation of material selection for both components. The tile cooling is accomplished by an impingement effusion scheme [definition: Effusion cooling uses cool fluid to create a cool fluid region between hot free-stream gasses and the wall. There are currently two types of effusion cooling: film cooling and transpiration cooling.], where air impinges onto the cold side, flows through an array of holes and exits on the hot side as a cooling film.
The specific challenge for a lean burn combustor constitutes the integration into the core environment. Due to the shifted air distribution towards the fuel injector a stronger interaction between the combustor/compressor and combustor/turbine can be expected. The OGV-diffuser design must take into account the downstream pressure distribution resulting from high air flow fuel injectors. The HP turbine design has to cope with a flatter temperature distribution, e.g. lower relative temperatures at blade mid height and higher temperatures at root and tip. In addition, the residual swirl also needs to be considered during the HP NGV design. The major objective of an internally staged lean burn fuel injector is to generate a homogeneous fuel-air mixture in a
given combustor volume allowing for combustion at reduced peak temperatures at medium to high power operating conditions. This is accomplished by a fuel injector with concentrically arranged main fuel stage surrounded by swirling air streams carrying the main portion of air and a nested pilot fuel injector located in its centre.
As the available mixing length in a combustor is limited, the initial fuel preparation process is critical. The main fuel injection is realised with a pre-filming air-blast concept. Within the prefilmer fuel is distributed over a surface area resulting in a thin fuel layer exposed to air with high velocity. As a result the fuel sheet disintegrates into fine droplets being dispersed and evaporated downstream. This concept becomes more challenging for larger fuel nozzles due to the unfavourable fuel to surface ratio (loading). The fuel rich pilot stage is required for low power operation and stabilization of the main stage maintaining full combustor turn-down ratios for operability. This is important especially for transient manoeuvres during adverse weather conditions such as hail and rain. Two basic fuel injection techniques were investigated for pilot injection: pressure and air blast atomization. The first one features a relative simple design and hence lowers costs. The latter is more complex allowing for a better specific control of fuel air
mixing. Thermal management schemes are implemented into the fuel injectors to control fuel wetted wall temperatures.

The specific fuel scheduling requirements are realised with individual fuel manifolds and a splitting unit delivering fuel to the individual fuel injector groups as a function of the engine thrust. Adequate control laws are implemented into the EEC software taking into account emissions and operability requirements."
« Last Edit: June 21, 2012, 01:58:39 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #153 on: June 21, 2012, 03:23:41 am »
And just when you thought Griffith's ideas were long gone:
Volvo's contribution to concepts for the European funded NEWAC programme:
Description
The benefit of a variable core cycle comes from the raised thermal efficiency of the core at cruise phase. One idea to achieve this benefit is to utilize a stator-less high pressure turbine (HPT) and high pressure compressor (HPC) variable guide vanes (VGV). The corrected mass flowing into a stator-less HPT is dependent on the rota-tional speed. By controlling the angle of the VGVs, shaft speed and core mass flow can be varied. This affects the pressure ratio and thus also the thermal efficiency.
Stator-less HPT alone has limited power output. Meanwhile, it creates undesired large amount of outlet swirl. To overcome these problems, a stator-less, counter-rotating turbine is utilized. This turbine drives a compressor whose front part is con-ventional while the rear part is counter-rotating. Such a compressor distributes the power consumption more to the second turbine. Also, more variable guide vanes can be used at the front stages of the compressor to improve the part-load efficiency.
Benefits
• Increased thermal efficiency at cruise phase
Technology Readiness Level: System 3 (theoretical evaluation); Components 2+
Risks
• Design of a working cooling system
• Amount of fuel saving
• Requirement on profile for mission thrust/speed/altitude
Application: Commercial aero engines

-------------
The ngvaneless idea was incorporated in the XJ99 liftjet.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #154 on: June 23, 2012, 05:59:13 am »
Armstrong Siddeley were involved fairly early in the gas turbine story, having been asked to build the rig to test out Griffith's contra rotating turbomachinery concept. #47 gave details of the testing of this rig. Fritz Heppner at A-S went on to design the A S H contra rotating engines....
Once the firm realised the challenges of the contra route they decided to get into the mainstream activity of the GTCC. At the time of their interest the main activity apart from Metrovick's was aimed a single and double sided centrifugal compressor designs. To stand a chance of competing and to build on their relationship with RAE they decided to look at an axial design. The best design at RAE, so far, was the Freda design. A-S thought a higher pressure ratio might now be obtainable and went for such a target. RAE calculated and schemed a fourteen stage compressor consisting of the existing Freda spool (9 stages) with a new design 5-stage spool bolted on the front. The new spool had blading designed on similar principles to Freda but with the assumption of constant reaction rather than free-vortex (reaction increasing with radius). Explanation of the theory we'll do outside of this post!

The design conditions of Freda and Sarah are tabled below:-

                                                              Freda                       Sarah

Mass flow lb/sec                                        50                            50
Pressure Ratio                                          4:1                           6:1
Rpm                                                         7,390                      8,000
Number of stages                                       9                            14
Max tip speed ft/sec                                   718                         714
Mean axial velocity ft/sec                           500                         490
Tip diameter, in                                          22.2                        20.5
pich/chord ratio
mean                                                                                         1.24
root                                                            0.68
tip                                                               0.9

The blade profile was RAF 27 setout on a circular arc backbone with a mean t/c ratio of 13% on Freda. On Sarah a consequence of the design vortex distribution is that  for a given tip Mach Number the root Mach Number will be greater so a smaller root t/c ratio is used , for a given blade thickness this is achieved by increasing chord length, which increases stage weight; it is a balancing act weather the extra work input done at the root and subsequent greater pressure rise allows a shortening of overall compressor (less stages) to offset the weight gain. Another option is to increase the aspect ratio which will put up blade numbers per stage as the space/chord ratio will have to be maintained for aerodynamic reasons. Bear in mind that, for manufacturing reasons, the Metrovick F2 had the same number of blades and vanes throughout the compressor. In a free vortex design the staor vanes have little or no twist. The same vanes were used throughout and the tips were trimmed for each stage, Similarly the blades were the same throughout and again the tip was trimmed to fit.  We mentioned elsewhere in this thread that HDA and MV had come up with a new pressing process to make the aerodynamic form which was very consistent blade to blade, vane to vane. This also helped make Freda so efficient as a compressor.
The pictures of the ASX rotor and stator casing clearly show the constant Overall diameter of the new LP stages and constant hub diameter of the existing Freda HP stages as they were referred to at the time.
Experience with the annular combustion chamber had by this time highlighted how difficult that section of the engine was; feedback on the tribulations of the early Whittle work was also available. Two other factors- keeping the overall diameter down and minimising engine length also played out in the configuration chosen. Minimising length led to the adoption of the reverse-flow axial equivalent of the Whittle engines... and the long slim combustion chambers are really a consequence of this and diameter minimisation.
Having been awarded a development contract in Nov 1942 A-S managed to have the first engine on the test bed by April 1943.. a sign of how much they 'borrowed' from the RAE and the fact they were not as heavily committed to war work as RR, Bristol and Napier were. Those first runs yielded a thrust of 800 lb, well below the design performance of 2,550 lb which was soon achieved in September wit h an sfc of 1.0.
Flight testing followed in the Lancaster Universal Test Bed and by 1944 2,800 lbt was acieved but at a weight of 1,900 lb... not very inspiring. One good development came out of it. The Vapourising CC. Originally equipped with a Lucas CC with spray nozzles the idea of Whittle's vapourisng system seemed very attractive and so they decided to pursue that route. By 1945 they had combustion test rigs running and had fitted the system to one of the ASX engines. Flying it in the Lancaster enabled them to test the engine up to 35,000 ft altitude with good slow running and reignition performance. As we saw on the PJ engines the system eliminated the need for high pressure pumps and was reliable over the whole flight envelope.
It was decided that possibly a way out of the low performing turbojet issue was to go for a turboprop conversion.. and so the ASP was born.
« Last Edit: June 28, 2012, 10:06:21 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline Nik

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OT: Modern British gas turbine development
« Reply #155 on: June 23, 2012, 08:28:43 am »

Contra-rotating turbine technology[/size] has advantages in pre-cooled engines both for advanced launchers and for hypersonic civil transport when an air compressor is driven by a helium or hydrogen turbine (giving a large speed of sound mismatch between the turbine and compressor).

http://www.reactionengines.co.uk/contraturbines.html


Offline tartle

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Re: Early British gas turbine development
« Reply #156 on: June 23, 2012, 12:07:30 pm »
It is all about the velocity triangles. The RB189/XJ99 had contra rotating blades for the turbines... worked well with ordinary kerosene/air charges too. The turbine designed at VKI uses the different qualities of working fluid to do proof of concept with cheap materials operating at appropriate stresses.. very interesting.. thanks for pointing it out. The reaction engines stuff is about an engine for a 2 hour flight London-Sidney or Paris-Sidney (european project) .. another thread I think?
« Last Edit: June 24, 2012, 06:04:44 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #157 on: June 27, 2012, 05:01:27 pm »
This evening as I was passing the MOSI building that houses the aviation collection, I thought it might be possible to photograph the F2 compressor blades to show the free vortex design. DSC01584g.jp shows the whole set of blading for the nine stages. We can also see the straight stator vanes in the lower casing. DSC01585-87.jpg show close ups of the blading.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #158 on: June 28, 2012, 06:15:53 am »
I also did a quick session on the W2/700 at MOSI....

the first picture is a general view of the engine focussing on the parts we have been discussing.
The second photo shows the impeller as discussed in #128
The third shows the diffuser; as we discussed in #139 it is easy to machine accurately and the turning vanes can be slotted in very easily.
The fourth and fifth pictures show CC102 that we discussed in #148.
I hope the visuals help flesh out the descriptions.
« Last Edit: June 28, 2012, 06:27:07 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #159 on: June 30, 2012, 02:06:04 am »
Fortunately Armstrong Siddeley had on its books an excellent Gear Design Engineer called Norman Barcham, who designed a gearbox to transmit the power to an airscrew; the extra power required to drive the airscrew being provided by redesigning the existing two-stage turbine for increased work.... one reason the jet was heavy was because the components were conservatively or underdesigned in the first place...this is the ASP
The ASP engine, eventually named Python, first ran in April 1945 and eventually delivered 3,600 shp and 1,100 lbt for a weight of 3,450 lb. The Clyde delivered around 4,000 shp and weighed 2,800 lb and had scope to deliver even more power with an additional turbine stage. The Python after a protracted development period gave around 4,000 shp at 3,505 lb weight. It was really only put into production because Hives would not sanction Clyde production.
The NAewis Altitude Wind Tunnel was a unique facility and their archive states:
"In response to a NACA request, the British supplied a Armstrong-Siddeley contra-rotating turboprop engine to study in the Altitude Wind Tunnel These tests from July 1949 through January 1950 were the first time the tunnel was used to study an engine with the sole purpose of learning about, not improving, the engine."
The first photograph taken 25/8//1945 is captioned:
"An engine mechanic checks instrumentation prior to an investigation of engine operating characteristics and thrust control of a large turboprop engine with counter-rotating propellers under high-altitude flight conditions in the 20-foot-diameter test section of the Altitude Wind Tunnel at the Lewis Flight Propulsion Laboratory of the National Advisory Committee for Aeronautics, Cleveland, Ohio, now known as the John H. Glenn Research Center at Lewis Field."
The second photo is captioned:
"The dynamic response of the British Armstrong-Siddeley Python contra-rotating turboprop engine was studied in the Altitude Wind Tunnel using a frequency-response method at altitudes of 10,000 to 30,000 feet. Using four different tailpipe arrangements the Python's static and dynamic performance characteristics were also studied at 10,000 to 40,000 feet and engine speeds of 6800 to 8000rpm."
« Last Edit: June 30, 2012, 02:54:14 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #160 on: July 04, 2012, 05:57:12 am »
 The Python has two claims to fame:
 1) it influenced the layout of the engine that became the Proteus, and
 2) it powered the Westland Wyvern:
 Originally intended to have the Clyde engine but with Rolls-Royce committed to other engine projects, the Armstrong-Siddeley Python was the only turboprop of the necessary size that could be used for the Wyvern.  This decision added at least two years to the development cycle as the engineers struggled to create a throttle control that would allow the engine to be rapidly throttled back for a carrier landing, or rapidly throttled up to make a go-around, the solution being an inertia control unit that was unfortunately mechanically complex.

After carrier trials which started on the 21st June 1950 the Wyvern finally appeared as the S.Mk.4, which began to be delivered to RNAS Ford in May 1953 for use by 813 Squadron.  and were withdrawn from service by 1958. 

     These aircraft did not have the definitive engine control unit and thus were not carrier-compatible until these units were installed in the summer of 1954.  The first operational Wyverns went aboard HMS Albion in September 1954. The problems were not over, as there were a series of flameouts during catapult launch as a result of fuel starvation under high-g loading while the aircraft were with Albion during a Mediterranean cruise. In fact, Lt. B. D. Macfarlane made history when he successfully ejected under water after his Wyvern had ditched on launch and been cut in two by the carrier.  The Wyverns were offloaded at Hal Far, Malta, and remained there until March 1955 when they returned to England.  The problem was not fixed until March 1955. 813 and 827 Squadrons then embarked aboard HMS Eagle in May 1955 for a second Mediterranean cruise, which gave the Wyverns some 1,500 operating hours and 1,000 landings, after which the aircraft was considered proven.
[size=0pt]While in service Wyverns equipped 813 Naval Air Squadron, 827 Squadron, 830 Squadron, and 831 Squadron of the Fleet Air Arm.  Squadron 813 was the last Wyvern squadron to disband on the 22nd April 1958.
We will discuss the first claim to fame elsewhere.[/size]
« Last Edit: July 06, 2012, 01:27:50 pm by tartle »
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Re: Early British gas turbine development
« Reply #161 on: July 04, 2012, 06:01:19 am »
In 1945 it was becoming apparent to the A-S team that there was an opportunity to design a 1,000hp turboprop for one of the Brabazon Committee aircraft requirements so the engine that became the Mamba was proposed. A government contract followed and in towards the autumn of 1945 detail design began. As the understanding of combustion had increased after work on the Python and sharing the results of the wider work undertaken by Lucas, Rolls-Royce, etc. The first engine ran in April 1946 and delivered 800 hp. It was configured as a single-shaft engine with a gearbox drive on the front of the shaft. There was a 10-stage axial compressor driven by a two-stage turbine and six straight through combustion chambers. The Mamba prototype had spray burners supplied by a high-pressure fuel system and the single spool ran on two bearings. Issues with the combustion chambers and with differential thermal expansion of blades and casings that made close clearances impossible to maintain, possibly exaggerated by vibration of the main shaft meant a redesign was called for.
The layout was redesigned to incorporate a 3rd bearing and after the success of the Python vaporising combustion system this was incorporated too.
The Mamba 1 emerged from this redesign and successfully delivered the design rating of 1,010 shp for a weight of 760 lb. As the engine found possible airframes- Apollo, Athena, Balliol- it was realised that additional horsepower and development potential was needed and so the team decided to increase the AMF from 13.5 lb/sec to 17 lb/sec enabling an increase in power to 1,270 shp, which took until 1950 to achieve as a rated power. This power increase was delivered by removing two stages from the rear of the Mamba 1's compressor and adding two more at the front resulting in the Mamba 2, which as the ASM.3 went into limited small scale production.

....tbc
« Last Edit: July 06, 2012, 01:26:30 pm by tartle »
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Re: Early British gas turbine development
« Reply #162 on: July 06, 2012, 04:44:07 pm »
The modifications to the Mamba compressor meant that the A-S engineers suddenly found that the front stages of the compressor, now much larger than before suffered from a condition known as flutter.
Flutter is an aeromechanical phenomenon that usually occurs at a blade natural frequency and involves sustained blade vibration resulting from the changing pressure field around an aerofoil as the blade oscillates.
Flutter is dependent on both the aerodynamic and structural characteristics of a compressor or turbine blade. A straight stator or twisted compressor blade can vibrate in such a way as to increase the local angle of attack, generating lift which feeds into the vibration, increasing the angle of attack- feeding on itself until high stresses are reached. The amplitude will then reverse as, the blade stalls and so the cycle begins again.... high frequency fatigue soon results and cracks begin to propagate...
This form of failure was found on testing the increased mass flow version of the Mamba. The original design of the compressor had aluminium alloy blading throughout and the 'A-frame' configuration of disc was in steel. The first change was to replace the first three rows of alumiium blades with much stiffer steel ones. These generated higher centifugal forces due to higher density, so the discs were redesigned in aluminium and changed to more conventional looking configuration. This enabled the new blades to be accommodated with no increase in weight. At the same time the last two stages were also changed to steel blading as the air temperatures were getting close to the limit for aluminium to work well. The increased mass flow also meant that the turbine was called on to do more work... the blade length was increased to allow this to happen.
The compressor changes can be seen in the cutaways of 1948 and 1951 below.
Another change that happened during development of what became the ASM.2 was improvements in the vaporising combustion chamber. It had been noticed that hotspots were appearing on the outer walls opposite the 4 tertiary holes, also the small tongue across the hole was breaking off as it overheated. The turbine end cutaways show some combustion chamber mods but this was not fixed until greater changes were made in the early '50s- even then the new welded walking sticks needed modification to finally get the reliability required. Incidentally it was the flinging out of unvaporised fuel round the curved walking stick that promoted relative overheating of the inner bend and so set up differential themals that led to failures.
....tbc
« Last Edit: July 07, 2012, 02:58:19 am by tartle »
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Re: Early British gas turbine development
« Reply #163 on: July 08, 2012, 03:06:20 am »
Mamba and variations on a theme... a jet, a turbofan and a gas generator....all wip.
The British and Australian governments made an agreement in 1945 that meant the UK would develop guided missile and Australia would develop the test facilities. This resulted in the creation of the Woomera Test Range and the  development of the target drone by General Aircraft Factory ... the first proof of concept vehicle being the manned Pika and the drone proper was known as the Jindivick. The Pika and initial versions of the Jindivick were powered by a short life engine known as the A-S Adder and later versions that followed the first batch were Viper-engined; the last production batch was in 1997 still with the Viper.
The Adder was used on the Mk1 Jindivick. The prototype Adder first ran in Nov 1948, and was flight tested in a Lancaster flying test bed before powering the Pika into the air in 1950 and the Jindivick Mk1 in Aug 1952. The Adder incorporated some changes to its layout such as air cooling of the centre bearing eliminating the need for scavenge lines used on the Mamba. The second cutaway (first 'Aeroplane'; second 'Flight') shows the bearing layout in more detail. As the simplification worked it was soon incorporated into the Mamba engines.

The cost of neutrality was, for Switzerland, technological isolation. The end of WW2 left the federation rich but woefully ill-equipped to defend its political status in the new world order that was rapidly taking shape. It embarked on two aircraft programmes, under the leadership of Jürg Branger Technical Director of F+W Emmen, Swiss Federal Aircraft Factory, designed to move their expertise forward, with the aid of several world class scientists that were leading edge.
One, the Aigullion N-20 had four engines derived from the Mamba. These were buried in the wing, Comet-style and were configured as plenum chamber burning turbofans with air bleed for flap blowing, etc. Not much has been published but we know the engines were developed by Sulzer Brothers and several versions were planned. The SM-01 engine instruction to proceed was issued in 1947 as the engine would be the critical item, in terms of development timescale.
In an article translated in the late 60s, 'Aviation History in the Swiss Transport Museum it refers to the N-20:
"Potentially the most interesting types at Lucerne are the N-20 Aiguillon STOL fighter and the Arbalète research aircraft, both evolved after the war by the Federal Aircraft Factory at Emmen, near Lucerne.
Of modified delta-wing planform, the N-20 embodied many features that were entirelly new at the time. Its powerplant consisted of four Swiss-designed turbofan engines buried in the wing. In each of these engines, the cold air from the fan was ducted through additional combustion chambers located on each side of the axial 'core', providing a reheat device that doubled the normal thrust and was intended for use during take-off and combat. For short take-off and landing, the secondary airflow could be diverted through large slots on the upper and lower wing surfaces. When only the lower slots were open the deflected air acted as an aerodynamic flap; with upper and lower surface slots open the deflected air acted as a thrust reverser.. As a substantial proportion of the airflow passed through the wing aerodynamic drag of the relatively thick section was kept low.
....
Ground tests of the Aiguillon prototype began at Emmen in 1952 but, to the great disappointment of the designers, no flight tests were authorised due to lack of funds."

So if we read the above whilst looking at the Aiguillon 3-view drawing, the wing sections (both similar to post #22 here) and the photo we can begin to visualise the propulsion set up. The aircraft photo also has the engine under its wing, with the afterburners next to the engine.. there are other photos of the aircraft and engine here.


...and the gas generator? Well originally Fairey were going to use a RR Dart with auxiliary compressor on what became the Rotodyne... Hives pleaded too much work so Fairey decided to go with a Mamba plus auxiliary compressor, known as the Cobra. Like Rolls, A-S pleaded that they were too stretched (Python, Mamba- single and Double and F9 takeover) and so Fairey had to go elsewhere.
....tbcike Rolls
« Last Edit: July 09, 2012, 03:34:09 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

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Re: Early British gas turbine development
« Reply #164 on: July 09, 2012, 10:35:16 am »
Although the aircraft powered by the Mamba were not the main drivers of development of the engine the Double Mamba's steeds certainly were. The beauty of the configuration is that a large amount of development can be done on a single engine and only the twinned systems and components have to be tested in concert. The Mamba therefore grew in power up to the ASM 8 which delivered 1,950 shp.
There is a picture of a Gannet just after catapulting off Victorious here.
The development issues affecting the Double Mamba centred around its gearbox and also surge problems made apparent by the control system and the complexity of mechanical solutions to the Navy's requirement that either engine could be shutdown without loss of 'services'. Treating the engine as one powerplant enabled A-S to provide one accesory gearbox but it had to be possible to drive it from either engine; this meant a system of freewheels had to be introduced. Each engine drove one of the contra-rotating propellers, which means one engine has an idler in the train whilst the other (port) engine has different diameter wheels to absorb the radius of the idler but giving the same output speed but in the reverse direction.
Developing the second (ASMD 3) version was driven by the exclusive needs of the Gannet. The control system became one that enabled the engine to operate at constant 15,000 rpm and the stagger of the compressor blading was altered to move the operating and surge lines apart during accelaeration to operational speed. The Gannet had been grounded due to the surge problem that kicked in at 14,500 rpm and as the original control system allowed rpm to drop during demands for more power at the prop and consequent pitch increases happened... there was a huge problem. This led to a grounding of the aircraft until the solution could be found and incorporated. (The Python was having a torrid time too with Westland losing Wyvern pilots at a high rate). Gearboxes were also suffering from bearing problems brought on by metal pickup leading to worn cages and races. Changing materials and improving manufacture helped eliminate this but it all took time.
A major simplification of the gearbox design improved reliability and also dropped the vertical offset  of the propshaft axis to engine axis by 5 inches to 6 inches.
Flight published two good technical summaries of Double Mamba progress 14th March 1955 p.272 onward and 22 Nov 1957 p. 815 onward; it is unfortunate that 0n p 816-7 the section of the new gearbox has been cutoff on the electronic version so the full impact of the new gearbox design is missing. If anyone can scan their edition of this it would be useful.. if not I'll chase a few institutions for help. The ASM 7 and ASMD 7 projects are interesting in that they are total redesigns of the concept to bring in a free power turbine to reduce the inertial energy in the rotating mass attached to the propellers. This concept was adopted for A-S's next project in the mid-50's.
I've scanned a couple of my Double Mamba photos that give a good idea of the size of the powerplant for the Gannet.
.......tbc
« Last Edit: July 11, 2012, 03:32:18 am by tartle »
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Re: Early British gas turbine development
« Reply #165 on: July 11, 2012, 03:55:38 am »
In 1956 there was agreat deal of interest in helicopters that need upto 1000 shp engines. This resulted in De Havilland taking a licence for the GE T-58 which it named Gnome, Blackburn continuing to work with Turbomeca to uprate the Turmo engine that eventually became the B-S Nimbus and Napier looking at a scaled down Gazelle- the Gazelle Junior (not built). Armstrong Siddeley began to look at concepts for their answer to the challenge and this developed over the last part of '56 and into 57. Flight did a good write-up of the progress in their 21 Feb 1958 edition.
The sketches contained in the article I've captured below as they illustrate the designers' thinking very clearly:
sketch A is essentially a scaled down Dart configuration
sketch B is similar to A but like the contemporary thinking on the Mamba reflects a free turbine layout where the turbine is flipped to be near to the propeller without a long shaft through the rest of the rotating components, keeping the first stage impeller diameter as low as possible.
sketch C shows the result of looking at Turbomeca/Blackburn and incorporating a transonic axial compressor as the first stage of compression; this allows the designers to go for a more conventional shaft arrangement; the challenge of rapidly/cheaply developing the engine meant that the actual demonstrator built was  based on...
sketch D where a conventional compressor is substituted. Only one engine was built and run before the project was abandoned.
I have a copy of the SBAC brochure mentioned in Flight which outlines the current state of A-S thinking... i e sketch B. which was discussed with the airframe people at the Show.
The inner pages are attached

...tbc
« Last Edit: July 11, 2012, 06:41:17 am by tartle »
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Re: Early British gas turbine development
« Reply #166 on: July 11, 2012, 07:06:36 am »
Meanwhile over at Bristol and Napier the wartime efforts to get into the gas turbine business got underway. Napiers were the last to join the race but as soon as Bristol realised what was going on when they were invited to attend the second GTCC meeting in Nov 1941 they got going on a strategy to enter the business. Before Fedden left (pcl for thrown out) the business he and Frank Owner looked at what sort of engine they could develop that did not compete head on with those already in the business. The first go was to put W2/700 engines in the rear of the Buckingham nacelles to give more power than the Centaurus at mission critical events.... this soon died a death!
Owner suggested a 4,000 hp turboprop with similar fuel consumption at 20,000 ft and 300 mph. and at a weight not exceeding the equivalent piston engine. By May 1942 the team - F G Evans and P Fortescue- came back with an answer: An axial plus centrifugal compressor, heat exchanger and free propeller turbine layout. Exploring alternatives took them into a three shaft layout... LP and HP spools plus a free turbine driven propeller. This was soon dropped as they did not think three shafts for a first effort was sane!; RAE suggested driving the prop off the LP spool but they were nervous about the control problem (this would be like or a variation on the 'Clyde' theme... did RAE influence RR?).
The two approaches investigated were a high pressure ratio layout... a prerequisite being to increase component efficiencies by a considerable amount or to live with existing efficiencies but recover power through the use of a heat exchanger. The second route seemed more likely to succeed as only one 'module' was a challenge... they thought. but to keep the size of components and modules within existing testing facilities they decided to halve the target power output.
An intense study of likely heat exchanger configurations took place juggling the thermal ratio, pressure drops, bulk, weight and manufacturing challenges until a scheme was proposed that consisted of a circular outside profile tubular configuration. Daily visits to the Drawing Office would find the 'design of the day' as various detailed attempts to produce a 'lightweight' heat exchanger configuration that  could deliver maximum number of tubes in the available space but with passage ways that were uniform between each tube-way. Eventually a designer at Tockington Manor , Henstridge,  ingenious configuration that used flattened oval tubes with a wall thickness of .012 in. enabling a design wighing 500 lb and transferring the heat equivalent of 2,000 hp to be contemplated. Coventry Radiator and Presswork had the dubious pleasure of translating the design into hardware.
Overall size of the exchanger was 45 in overall diameter tapering to 36 in dia at the rear and 31 in. long.
The heat exchager was designed to receive 1,000 cu. ft. gas per second from the turbine exhaust, at 500 deg C., and delivered 180 cu.ft per sec. of air to the combustion chambers at 300 deg. C.  An exchanger’s effectiveness is the ratio of the actual heat transferred to the heat that could be transferred by an exchanger of infinite size. Theseus effectiveness was a thermal ratio of 0.4. which was calculated to save 150 lb of fuel per hour at cruise conditions.
The turbine exhaust passed through 1,700 (yes one thousand seven hundred) straight tubes of stainless steel, 0.012 in. thick and 0.625 in. at the tube endplates. By arranging the tubes along involute curves and flattening them, air passages of uniform width were formed between adjacent involute curves. Air was taken from the eight inlet chambers, through groups of involute passages to the central space. This space formed an inlet header from which air returned to the peripheral space through other groups of involute passages alternating with the first groups previously mentioned.
The thinness of the tubes and their close pitching made any form of mechanical or expanded (flared or swaged) joint impracticable, and were, therefore, brazed in place. The joints suffered during hot starts that often happened on the test bed. An alternative welded construction withstood the starts, but cracked through excessive contraction stresses on shutdown.
As the first gas turbine to be built at Bristol the engine suffered from similar problems to other first-time developers. The compressor had been designed to deliver a PR of 5:1, any more would have been technically challenging and anyway the temperature differential across the heat exchanger would have been too low to deliver the performance required. It turned out that the predicted efficiency of the combined 8-stage axial, single-stage centrifugal compressor was about right  but the mass flow was 7 % high. In May 1945 attempts were made to start testing the engine, without heat exchanger as CRP were still making this module; the engine refused to accelerate to self-sustaining speed without exceeding a safe turbine entry temperature. It was guessed that the nozzle guide vane area was too low and the turbine was choking. As a quick fix the NGVs were cutback to increase the flow area, but this still did not work so blow off valves were devised, and the engine finally ran on 18th July, 1945... this week, 67 years ago. The engine testing then went ahead in an uneventful manner. The high mass flow meant there was plenty of power but the 'modifications to the NGVs meant turbine efficiency suffered so sfc was below exoectation. The first year of testing clocked up 117 hours including a 25 hour development test. Component research on newly completed experimental rigs ensured there was a steady improvement on sfc but the biggest snag was the high Air Mass Flow.
The first complete heat exchanger (HE) was delivered in July 1945. An engine fitted with the HE ran in December and it was immediately obvious things were not right. The pressure drops at the higher flow rate were excessive, so that the fuel saving at full throttle was only 8% rather than the designed for 20%, while power loss was correspondingly greater. The part load economy was improved by upto 25% but this was not a condition that at the time people thought was a good idea for a propeller turbine.
Rig testing of the compressor made it very clear that great strides were going to be made in a relatively short time and so the slower pace of HE development meant it was better to put resources into the former rather than live with the bulk and weight of the HE. The practical difficulties of attaching the tubes was a bugbear but the expected tube fouling did not take place.
The mechanical integrity of the Theseus was excellent. The Heat Exchanger was abandoned and efforts continued to improve the power/weight ratio and achieve a reliability that would enable meaningful flight testing. In Dec 1946 the engine passed the Ministry 100 hour Type Test at 1950 ehp; the world's first successful TT for a turboprop. In February the Theseus made its first Flight in a Lincoln.
By July 1948 the engine was robust enough to become the first prop turbine to pass the MoS 500 hr endurance test. In 1949 the engine carried out its last TT at a maximum power of 2450ehp.
In order to be able to have an idea of the power being generated by the free turbine drive to the propeller a torque dynamometer was built into the reduction gear. the oil cushion that resulted from the design meant there was a damping mechanism in the drive train which probably accounted for there being no high frequency induced problems in the drive train.
Interestingly the split drum type construction adopted for the axial compressor resulted in three identical sections that constrained the numbers of blades on each row, i.e. identical as the blade roots sat in milled slots in the drum.
Incidentally, there were two Theseus Lincolns and they accumulated 1,000 hours of flying time. A Theseus was also installed in a Hermes V civil airliner, making its first flight in Aug 1948. Flight has 2 pages of pictures starting here.
« Last Edit: July 31, 2012, 05:19:54 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #167 on: July 17, 2012, 03:23:11 am »
So on to the Proteus.... started before the Theseus was built! and so was not necessarily as great a leap forward as it should have been.
The Parliamentary Select Committee system has operated for a great many years and the Public Accounts Committee Report for 1952-53
makes interesting reading. In the section that covers the MoS it uses the Proteus engine as an example of what goes on at the Ministry.
In 1944 the MoS started to develop a special type of gas turbine for long-range transport aircraft; by 1952 they had placed contracts to an estimated value of £13m of which they had spent nearly £10m for this work.
The Proteus ! was abandoned after £3.6m had been spent. The development of the Proteus 2, and finally, the emergence of the Proteus 3 as an engine suitable for the Britannia and likely to earn some return on the cost of public funds.
In reply the MoS, having noted that development costs had been somewhat inflated by the changing views on the ultimate use of the Brabazon and Princess aircraft, proceeded to point out that the uncertainties involved in forecasting the development costs of an entirely new form of propulsion were high; the design of aircraft are dependant on the availability of the engine and the development of the final configuration can involve the engine developer in further modification. before the needed capabilities are finally delivered.
So let us look at these three Proteus engines:
Work carried out under the leadership of Frank Owner indicated that the lower limits of speed and altitude below which Bristol felt the prop-turbine would not compete was 300 mph and 20,000ft. Balancing the engine's propulsive efficiency, weight and cost puts the upper limit at 500 mph and 40,000ft. The increased cruising speed puts a premium on weight and bulk so it was realised that the HE engine they had designed and were building had limitations in both these respects. As soon as design of the Theseus was sufficiently advanced Owner pulled Charles Marchant out of the team and gave him a new task. His assignment was to design a high pressure ratio propeller turbine of around 3,500 bhp with a diameter not exceeding 1 metre (Fran
k thought a yard was a bit too restrictive). Marchant started making layouts in September 1944 and was fortunate that the Theseus work load on the Technical Office was reducing and so attention could be switched to the new scheme. By December there was a fairly complete design scheme backed up by aerodynamic and performance calculations at a similar stage of completion. Air Commodore 'Rod' Banks arrived on Dec 8th 1944 and as head of DERD at MAP asked to see the latest Bristol project. The Bristol team were convinced the free-turbine layout was right in principle and, so, the turbines and reduction gear were based on the Theseus but the compressor had to be designed afresh... They decided to go for a 9:1 pressure ratio which was extremely adventurous considering their experience. As Bristol were still anxious about potential surge problems and so went for an axial section PR of below 5:1 and put on a two-stage centrifugal at the high pressure end to deliver the required overall PR.
By this time it was becoming clear that the Brabazon and Princess powerplants would be buried in the wing and so the location of engine inlets became a challenge. Because Bristol did not want an engine of excessive length they had opted to copy the Python layout and put the intake at the rear- something that the team would come to regret, although it did mean on the Princess they could have a long diffusing pitot entry to a plenum chamber from which the compressor took its air.
Until Bristol built their own compressor testing facility they were dependant on a shared facility. The requirement for separate compressor testing had surfaced early in the development of gas turbines. Rolls-Royce had built one, initially for Power Jets, using a Vulture engine, but this had to operate with a throttled inlet as the W2 impellers absorbed 4,500 hp -well above the Vulture's capabilities. Metrovick used a staem turbine as a temporary measure. Fortunately the RAE knew of a source of power sufficient for the engines then being planned. The Northampton Electric Supply Company had a power station of about 6,000hp and agreed to aloow use as a drive for the various compressord then being developed. The H.1, F.2 and ASX were successfully tested on the plant and Bristol followed with the Theseus and Proteus designs.
Whilst getting ready to test the Proteus's 12 axial plus 2 centrifugal stage compressor, someone had the idea of using the core as a turbojet and this was quickly schemed out and constructed. It was ready to run just as test results were coming out of Northampton in May 1946. The compressor was calibrated upto 7,000 rpm and was delivering 10% above design mass flow but at a lower than desired pressure ratio.
The Phoebus acted as an early warning system on potential troubles on the Proteus. Having designed the Proteus using the same rules as the Theseus, which had not run by the time Proteus design was finished, it suffered from NGV choking making the whole spool extremely sluggish on acceleration, even after trimming the guide vanes and putting in blow-off valves. Also it was realised the first centrifugal compressor stage was causing a pressure drop and so as a short term palliative it was removed and replaced with a diffusing duct.... there never was time to investigate the loss of pressure and so the stage was never replaced. Another shortcoming that experience in running Phoebus enabled them to tackle was was the excesively high axial velocity through the power turbine. This led to a redesign of the turbine stage with wider and longer blades and a thicker turbine disc to support the extra centrifugal rim loading.
All these changes resulted in a much modified engine which became the Proteus 2.
The original Proteus had not met its weight, fuel consumption or power targets, delivering well below 2,000 hp and the Proteus 2 was an attempt to correct this as well as providing a slightly higher rating!
Incidentally the 'early warning Phoebus' was intended to deliver 2,540 lbt sea level static thrust with an sfc of 0.79 and a weight of 1525 lb. In fact the compressor problems described above meant it did not achieve its thrust target, neither did the first and only batch of engines meet the weight target as they weighed in at 1900 lb!
When Hooker arrived at Bristol in Dec 1949 he began to familiarise himself with the Proteus... the first thing he discovered, early in 1950, was far from meeting its target weight and power of 3,050 lb and 3,200 shp plus 800 lb thrust, the Proteus 2 weighed 3,800 lb and gave 2,500 shp plus a host of reliability problems as compressors, turbines and bearings failed.
Hooker decided there was no way the engine was going to close the power and weight gap and also achieve the reliability needed for the Princess, Brabazon and soon the Britannia aircraft... all civil. Now the costs of the first 2 versions of Proteus mentioned in the Public Accounts Committee Report make sense!
Also note the twin Proteus installation that doubled the challenge!
« Last Edit: July 18, 2012, 11:08:14 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline JFC Fuller

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Re: Early British gas turbine development
« Reply #168 on: July 17, 2012, 04:04:03 am »
Tartle,

Excellent thread, thanks for all the detail.

Napier Gazelle Junior: http://www.flightglobal.com/pdfarchive/view/1958/1958%20-%200160.html?search=napier%20gazelle%20junior

Offline tartle

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Re: Early British gas turbine development
« Reply #169 on: July 17, 2012, 05:49:38 am »
JFC.. thanks for Gaz. jnr link..... the text highlights what a crowded market it was for an engine of that size... and for your comments. It has amazed me that outside of an industry like aviation generations of innovators/developers seem to be doomed to make exactly the same mistakes as previous generations. The fact we can find detailed records and comments from the people involved makes it so much more interesting, and useful!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #170 on: July 18, 2012, 11:09:36 am »
So Hooker, on arrival at Bristol, was plunged headlong into a crisis. He soon realised he had a crisis of organisation as well as a hardware problem. He tried to be a good co-operator with no job title with Owner but the team below him was problematic ... the Mansell brothers were both shy and retiring; Swinchatt did not believe in turbines and felt the future was Centaurus, his view being supported by Norman Rowbotham, the engineM/D. There was no collaboration between Design and Development with Design often acting unilaterally.
By mid-1950 the Proteus was at crisis level... Hooker and Owner were summoned to Rowbotham's office; also present was an old friend of Hooker's -Reginald Verdon Smith director and grandson of the founder. Owner was moved sideways and Hooker put in charge.
Hooker soon kicked piston engines out to production area and came up with a stronger more focussed management team.
Time was against them and it was agreed the first Princess (Brabazon had been cancelled) would fly with underpowered Proteus 2; meanwhile Bristol would go ahead with the Proteus 3 to deliver the right power at the right weight. So the third redesign began which we will cover in another post.
In order to have an engine available for the first Princess it was agreed to install ten of the Proteus 2s which would be cleared for flight at 2,500hp. The Twin-Proteus had been tested for 1600 hrs in a specially built hangar and the gearbox seemed to be one more part that gave heartache.
The first and only Princess to fly achieved a total of 100 hrs flying time.
In Saunders-Roe's opinion Development problems were of many kinds but the most challenging are included in the list attached.

Hooker's view was that both the big aircraft were doomed and the Britannia was the best bet. As they considered the redesign they thought of straightening out the flow but the Princess was still on the books so they stuck with the existing flow path.
« Last Edit: July 19, 2012, 09:14:45 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #171 on: July 19, 2012, 11:33:40 am »
The Princess - an amazing machine.

Meanwhile, some really early British gas turbine technology, from The Hospital of St Cross (medieval almshouse) in Winchester. This is looking up at a fan located in the kitchen flue, which is spun by the rising hot air and turns the roasting spit through the cross-shaft (visible), a gearbox and chains (now missing).

The hardware looks like late 18c or later to me. Supposedly it is called a "chimney jack" and Intertubez sources say that it was invented by Leonardo da Vinci (but then, what wasn't?).





Offline tartle

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Re: Early British gas turbine development
« Reply #172 on: July 19, 2012, 01:31:51 pm »
LowObservable... that is a good picture!
I recollect a book on 'Mechanical Devizes' of around the mid 1820s, I think, publicised a device that the Islamic innovators had come up with in about 100 AD... ideas recycle...hopefully the technology gets better on each cycle. Maybe that is why the lunchtime food at Bristol was so good...wrong, or right, sort of turbine!
« Last Edit: July 19, 2012, 01:33:37 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #173 on: July 19, 2012, 01:42:30 pm »
Quote
Excellent thread, thanks for all the detail.


Just to echo the above...you're writing a book here, you know.... ;)
A question. Was the Pheobus ever intended as a production engine, or purely as an aid to Proteus development?
A thought, whoever named the Proteus was prescient indeed, for   like the engine, the Proteus of mythology was shape-shifter...


cheers,
          Robin.
« Last Edit: July 19, 2012, 02:39:39 pm by robunos »
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Offline tartle

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Re: Early British gas turbine development
« Reply #174 on: July 19, 2012, 02:32:52 pm »
Robunos...
The bright idea was to develop it as a turbojet, but the thrust requirements were greater than the thrust delivered by the Phoebus, so it continued as a research vehicle for Proteus, which was slow to be made and tested.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #175 on: July 19, 2012, 02:40:26 pm »
Thanks for the clarification...


cheers,
         Robin.
Where ARE the Daleks when you need them......

Offline tartle

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Re: Early British gas turbine development
« Reply #176 on: July 19, 2012, 04:47:31 pm »
The Twin Proteus 2 looks like the first attachment. Its intake on Princess is also shown.
Stanley Hooker gave the instruction to proceed with the third attempt to get the Proteus right in mid-1950. He had already called Clarke at Lucas and handed them the job of designing and supplying the combustion chambers, freeing up resources to concentrate on getting the rest of the engine right. Lucas's team (who we have already met) of Clarke, Watson and Morley were delighted to take on the work, especially as Hives had decided to bring combustion design in-house at Derby with Arthur Lefebvre recruited to run research (which he did before going to Cranfield as Head of the Propulsion Dept, researching combustion which became World-Class; where he had me as a student!). Hooker had recruited three 'musketeers' from Derby-  Basil Blackwell and Gordon Lewis and from Armstrong Siddeley- Pierrre Young. They were unleashed on the Proteus with Lewis in charge of compressor design and performance, Young i/c overall engine performance and Blackwell i/c turbine testing and analysis. All were in the same office so that they could work together on Hooker's challenge to deliver 3,200 hp (Hooker said to aim for 4,000 hp. Charles Marchant's job was to design an engine of 3,000 lb weight. This engine, the Proteus 3, first ran in May 1952 and coincided with Britannia's first flight on Proteus 2s.  On its first test the engine delivered its design spec figures. At 1,000lb lighter than the 2 it was soon delivering 3,475 shp and 1,000 lbt.
By improving the turbine efficiency the Proteus 705 that went into the first 15 Britannias was replaced by the 755 at 3,780 shp and 1,180 lbt. The colour cutaway is a low res scan of my 705 picture and is representative of the Britannia engines.
« Last Edit: July 30, 2012, 05:07:14 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #177 on: July 25, 2012, 10:26:18 am »
The saga that really did for the Britannia as a huge seller and therefore its Proteus engine and the follow on Orion engine (what the Proteus 3 might have been without the Brab/Princess committment) was icing in the intake that could cause temporary flame out. By the time this had been discovered, on BOAC Britannia route proving the airline in its arrogant way (what happens if you think you are part of the government estabishment) had decided that Boeing 707s might be what it really wanted; the UK government would not sanction cancellation of the former and ordering the second. BOAC may have decided to make an ice-mountain out of an excresence and took Bristol to the cleaners. The new Airworthiness regs being introduced at this time required the demonstration of the effectiveness of prevention of ice build up on the wings, tail etc and extended this to the intakes as well. Consequently the thought of flying around the globe in search of the 'right' extreme weather conditions meant that Bristol utilised flying test bed techniques Napier and Rolls-Royce were using to enable the required icing conditions to be simulated by water sprays into the intake. The rates of impact and the size of ice particles could be controlled to represent any extreme weather condition. Hooker's leadership meant that a solution to the flameout was found fairly swiftly. Basically as a chamber went out due to the ice extinguishing the flame there was a period before relight that was noticeable in the cabin. By putting a glowplug in the chmber a relight happened almost immediately with a drop of only 60-300 rpm in 11,000 before the engine was running again. This was not detectable by anyone who was not listeneing out for it and was a good solution. BOAC decided that only a 'perfect' solution would do and that was to eliminate the flame out altogether... and until that was achieved no introduction to service. As Jacques Fontaine put it:

"Issues are emotional
  Solutions are technical, but
  Decisions are political"

Bristol assumed that their solution, a hollow platinum rhodium alloy tube some 1.5 inches long and 1.375 in. diameter poking into the combustion zone on every other flame tube, was sufficient for BOAC to carry on turned out to be a miscalculation. There are those who were around at the time who thought a reasonable palliative whilst the optimal solution was found would normally be good enough but the desire of BOAC to move on to yet another aircraft (707), incidentally making 5 different aircraft in their fleet meant that they were willing to delay and delay and so BOAC took the opportunity. delaying the introduction for another two years, did not help Bristol's case for the Brittania. As Alertkin points out in the next post the lack of urgency at board level meant that the whole programme was wallowing along and it may be that BOAC had just about lost all confidence in Bristol delivering an airframe and engine that wasn't going to surprise yet again.
The search for a technical solution to eliminate  the icing problem tokk a long time as the data on weather conditions had to be improved as well as just looking at the engines. The problem was one of dry ice crystals... the sort that makes lousy snowballs unless you take your gloves off and warm up the ice slightly so it begines to stick together. The use of test rigs, ground-based and flight, determined that the Proteus installed in the Britannia could swallow 2 gm/cu metre of severely supercooled water for 20 secs before a flame out occured; this is equivalent to fling into normal cu-nim (cumulonimbus) cloud for 1.5 miles. (Thick industrial fog has about 0.1 gm/cu m. and heavy snow about 10 gm/cu m). Unfortunately the typical cu-nim around and on the way to Nairobi was typically 6 gm/ cu m. for distance way beyond 1.5 miles, and surprisingly not always visible to the naked eye. The cold Britannia airfame and skin did not cause a problem but the warm stagnation points within the engine intake did., with slush forming at them. In particular it was eventually found that slush was accumulating on the Combustion chambers and when eventually it broke away it was of suffucient size to partial block a zone of the inlet guide vanes; Eventually detection instruments sensed pieces as large as 5in by 2.5 in when flying through these tropical clouds. Two chambers in particular were the sites for these large pieces and elimination of the warmspots was achieved by fitting mufflers. This gave a satisfactory solution and the problem was eliminated enabling BOAC to continue the service introduction.
« Last Edit: July 30, 2012, 05:06:47 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline alertken

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Re: Early British gas turbine development
« Reply #178 on: July 26, 2012, 06:17:32 am »
That's not how it was. Cathay Pacific, QF, Ansett, TAA, TEAL did not take Electra over Britannia just because BOAC was, ah, lukewarm; nor did QF take 707-138B just because Boeing had the wit to invent a bespoke model for a batch of 7. Though that did show awareness that customers buy utility, not product. Bristol, indeed UK Aero, indeed UK all-and-any-industry did not understand that.
 
(3-volume history of QF) J.Gunn,High Corridors,QUP,88,P69: Britannia: “much too late to be competitive. (negative impression in QF’s 7/55 visit) to assess Bristol(’s ability to meet schedule or to demonstrate an) organisation adequate to service the aircraft”. QF at the same time rejected Comet 4: “unable to consider (it) an economic proposition.” (Very long sectors.) You don't disagree, do you?
 
Not until 2000 could Airbus Industrie overcome that legacy of Brit-uncare for customer support, and pursuade QF to take their products: stringent Guarantees were needed to purge their British past: AOG response times, material burn per flight hour. Bristol...que?
 
Britannia's failure at market was not the fault of Proteus' sensitivity to ice. It was abysmal drift from date of opening the sluice of our money (Tender Design Conference, 14/7/47, which admitted design (we now say) software effort into MoS-recoverable overhead; BOAC order  for 25 (! incredible),(Centaurus-Power) 29/7/49. Srs.102 inaugural, 1/2/57, 312, 19/12/57. Pathetic, and due to the “abysmal lethargy of the (owner-family) Board of Bristol Aeroplane” Sir Peter Masefield,(Bristol A/c’s last MD, whose contact with the firm began in 1943), Flight Path,Airlife,2002,P.209.
 

Offline tartle

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Re: Early British gas turbine development
« Reply #179 on: July 27, 2012, 04:51:46 am »
Alertkin.. you assume too much... I agree entirely with your valuable comments that you make in response to my half finished post.. the board at Bristol was amazingly awful.  How Hooker managed to get a flyable Proteus 2 and a Proteus 3 out of the doors with the board he had was amazing if not heroic. Of course some of the credit must be given to the team he built up at Bristol. Some were Bristol-grown but pre-Hooker lacked responsibility and some migrated to Hooker from his old team at Derby. One of the Derby people was a lubrication (what we now call tribology) expert by the name of Robert Plumb, who had worked on the Merlin and then the early Derby turbine engines. He soon joined Hooker at Bristol and was appointed chief development engineer - Olympus and Proteus. When Bob Plumb realised they were redesigning the Proteus yet again he asked whether the lessons of Derby's gearboxes should be taken into account. He meant, of course, the redesign of the Trent, Clyde and Dart gearboxes to adopt helical gears in preference to straight spur ones, so eliminating the vibratory force input as each tooth engaged- a source of excitation on all three engines(helical gears engage gradually along the teeth thus reducing the shock loading of the straight spur) Hooker pointed out that the Proteus gearbox seemed to have performed well throughout the Proteus's life, unlike the rest of the engine and so they stuck with spurs. As would have happened at Derby, Plumb carried on and developed a helical gear set anyway....thank goodness!
In January 1954 the second prototype, with Proteus 705 engines, G-ALRX commenced her series of flight trials for a certificate of airworthiness from Filton.  Disaster struck on the morning of 4th February 1954, when Bill Pegg, the company chief test pilot, was demonstrating the Britannia's capabilities to KLM officials. The aircraft suffered an oil fed engine fire, the result of a failure in the input pinion of the reduction gear of number three engine which caused the compressor turbine to overspeed and disintegrate. The fire raged for 19 minutes as Pegg headed back towards Filton. A few miles from his destination he decided that the wingspars might burn through and elected to belly land on the mudflats. As he touched down the mud covered the aircraft and extinguished the flames. Unfortunately the aeroplane was damaged beyond repair as the salvage crews spent 2 days trying to pull her out of the tidal estuary.
Once it was determined the gear was the culprit, Hooker ordered the switch to double helical which was done without delay due to Bob Plumb's anticipation.
The photo below is from the RRHT archive.
« Last Edit: July 31, 2012, 06:15:38 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #180 on: July 31, 2012, 07:30:11 am »
After the mudflat incident on 4 th Feb 1954, Bristol were under pressure to get the Proteus powered Britannia in a serviceable state so that BOAC, and hopefully other customers could get started as well. But as we have seen the icing problems were very long-winded in solving.
The first conventional icing trials were carried out in Canada on the Ambassador and showed the normal anti-icing features provided could cope with the ingress of water droplets that froze on contact with the inlet guide vanes.
The second icing challenge was the tropical cloud dry ice injestion which we have already discussed. This was a phenomenon that was little known and according to your point of view BOAC made a meal of for their own ends, or BOAC were nervous about a new type of aircraft having a perceived shortcoming that might make it more difficult to achieve success in service.
If that was not enough, it was found in 1957 that water plus ice crystals could be a difficult combination leading to a build up of ice on the outer surfaces of the intake bend. This sort of weather occured in the monsoons over India. Fortunately by this time the development team had a better understanding of the intake and were able to rapidly devise a set of fixes in the hope that one or two would prove to be effective.
The most effective fix was found to be the provision of a series of air jets mounted in the outer wall of the intake duct and fed with pressurised air tapped from the compressor of the engine. The air was injected along the wall of the intake just ahead of the position on the bend at which the ice tended to accumulate, accelerating the boundary layer to a sufficient extent to prevent ice accumulations and to remove any deposits which might have built up before the air jets were turned on. To be really sure they had fixed it the team also schemed out some 8 ducts between the combustion chamber outlets so that the  areas of warmth were protected like the muffs which were no longer needed. The resulting fix was christened the 'Rabbit Warren'.
All this attention to detail in the air ducts ensured icing was no longer a service problem.
The development of the Proteus 3 took a great deal of test hours as can be seen from the graph.
It is unfortunate that 4 years were taken off the service life of Britannia which had in been developed with aggression, could have been produced in numbers greater than the 77 production versions... even double would have meant that Bristol made something from their effort.
I have clarified the last graph.... and added part of my Aeroplane Britannia cutaway for intake detail.
« Last Edit: August 03, 2012, 12:25:54 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #181 on: August 01, 2012, 03:35:38 am »
In 1952, as Hooker wrestled with the Proteus 2 and all its faults, the designers looked at alternative design schemes that would simplify the engine layout and make it more straightforward to develop. Unfortunately the commitment to the Princess programme meant that the next design scheme had to be suitable for that aircraft; hence Proteus 3. However the ideas that came out of the design office were not wasted as it was decided that rig work should start so that an alternative engine could be built for the Britannia if the opportunity arose. The compressor rig work was also useful when an opportunity for an engine for NATO arose. The LP compressor designed for the B.E. 25 became the compressor for the single-spool B.E. 26 - later Orpheus.
 Hooker delivered a paper to the SAE in New York on the 18th April, 1955. He stated that when the concept of the supercharged turboprop was conceived, late in 1952, the underlying principles were:
 
 (a) To produce a turboprop with a specific fuel consumption equal to that of the best compound piston engine. This implied a pressure ratio greater than 10:1, and hence necessitated the "two-spool" arrangement of compressors.
 (b) To produce a turboprop having a cruising power of the order of 3,500 h.p. at 30,000ft, with the lowest possible specific weight. Such an engine would give more than 8,000 h.p. at full throttle at sea-level and it was desired to restrict this power to between 4,000 and 5,000 h.p. in order to reduce the weight of the reduction gear and airscrew and thus achieve an appreciable improvement in the specific weight under cruising conditions.
 (c) To produce a turboprop the take-off power of which was independent of the altitude and air temperature of every aerodrome in the world. Naturally aspirated turbine engines (i.e., those now in use) suffered badly at the higher and hotter airfields, although the adverse effect of high temperature could be partially mitigated by water/ methanol injection.
 (d) To exploit to the full the known ability of the gas turbine to produce (relative to piston engines) large power for a small bulk and weight.

Three basic layouts were considered:
1. A single spool comressor driving the propeller gearbox. This was rejected for several reasons. The use of a single spool for such a high pressure ratio would result in an inflexible aerodynamic design needing blow-off valves and variable guide vanes. High starter  power would be necessary and operationally a high idling rpm was necessary in order to improve acceleration time and to allow increased propeller drag on approach.
2. A free turbine layout building on Proteus knowledge. Again the high pressure ratio design means that the compressor will have almost as many disadvantages as 1. above. Rejected.
3. 2-spool with LP compressor or 'supercharger'. The LP spool drives the propeller gearbox. This was considered the best compromise between 1. and 2., with the introduction of a moderate inertia problem from the propeller plus LP compressor, whilst preventing the perfect aerodynamic matching that happens on 2-spool turbojet engines such as the Olympus.

As the Britannia was nowhere near its Mach limit in cruise (as had been originally feared) the increased cruise power from the Orion would be easily utilised. Hooker set the target for cruise power at 3,500 eshp at a speed of 350 kts and 30,000 ft altitude; this was double the power of the Proteus 755. The target sfc was 0.4 or less and the engine was to weigh no more than the Proteus.
The Orion ()as it was known after being named on 16th May, 1956) first ran Dec 10th, 1955. It was designed as a 'power egg' and was intended to be supplied as a replacement unit for the Britannia. The target was to swap the Proteus for an Orion in the same time as swapping out a Proteus during normal maintenance, making the upgrade very straight forward.
The Orion's LP spool  has a 7-stage LP compressor driven by a 3-stage turbine. The LP spool also drives the compound epicyclic gearbox with a ratio of 0.1006:1.
The HP spool consists of a 5-stage compressor driven by a single-stage turbine. The combustion chamber is of cannular design with 10 flame tubes fed by simplex fuel nozzles.
LP spool rpm is 10,000 rpm at Take-off.

By December 7th 1956 there had been six engines built; 4 were for test bed work and 2 for flight tests. A seventh was under construction. The six engines had amassed 1,00 hours running, including 50 hrs installed in a Britannia. The Britannia, G-ALBO, first flew on Aug 31st.
The MoS withdrew support for Orion development at the end of January 1958, citing financial constraints. About £4.75 m of government funding had been invested. Convair/Canadair were specifying the Orion in the CL-44 Britannia derivative but as work ceased at Bristol they had to go elsewhere (Tyne).

 ...tbc
« Last Edit: August 02, 2012, 04:23:59 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #182 on: August 02, 2012, 06:31:49 am »
The only other early engine that Bristol designed but never built was the Janus. In 1945 The MoS was asking for design studies for a 1,000hp turboprop. Frank Owner thought that such a small engine would be a challenge for an axial design so went for a centrifugal. The aerodynamic design was for a 2-stage centrifugal compressor driven by a single stage turbine, a second free turbine drove the propeller gearbox. So far it sounds like a Rolls-Royce RB 60; but here the similarity ends. The compressor impellers were arranged back-to-back, hence the name, and the outlet from the first stage was connected to the second-stage inlet by 4 curved pipes between which four highly skewed combustion chambers were located.
During the design of the engine the Ministry asked Bristol to scale the engine to 500 hp. to avoid multiplication of effort. Owner believed the design was very practical being compact and light.
This is the only picture of the projected design I have ever found... a project illustration.
« Last Edit: September 25, 2012, 04:42:13 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #183 on: August 03, 2012, 02:23:09 pm »
Here's the full Flight profile of the Orion, presumably by the Great One himself...

http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%201521.html

Would I be right in guessing that an Orion-Hercules would have been something quite impressive?

Mind you, reading that also caused me to wonder at the polysyllabic style of Flight in those days. I suspect that the sub-editor was closely related to Kipling's Bi-Coloured Python Rock-Snake.

Then the Bi-Coloured-Python-Rock-Snake came down from the bank, and knotted himself in a double-clove-hitch round the Elephant's Child's hind legs, and said, 'Rash and inexperienced traveller, we will now seriously devote ourselves to a little high tension, because if we do not, it is my impression that yonder self-propelling man-of-war with the armour-plated upper deck' (and by this, O Best Beloved, he meant the Crocodile), 'will permanently vitiate your future career.'
« Last Edit: August 03, 2012, 02:38:52 pm by LowObservable »

Offline tartle

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Re: Early British gas turbine development
« Reply #184 on: August 03, 2012, 04:58:28 pm »
LowObservable... yes, a useful technical description... as to an Orion-Hercules.. that would have been interesting.. think of being able to override the throttling of the engine and have a guess looking at Short Belfast with Tynes  or for extra payload, or a bit of both. I suppose the basic Hercules plus Orion might be analogous to Short Tyne-Belfast?
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #185 on: August 03, 2012, 06:02:29 pm »
Was the Tyne similar in philosophy to the Orion? How would they have compared to the constant-speed, single-shaft (and rather primitive) Allison?

Offline tartle

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Re: Early British gas turbine development
« Reply #186 on: August 05, 2012, 10:49:11 am »
LowObservable... you ask an interesting question. My best answer is to look at the parameters that drove the development paths of these engines and how they ended up in the 'marketplace'.
The T56 and Proteus are more or less contemporary engines; the T56 evolving from the T38, which first ran in 1947 following on from private venture studies in 1944 that the US Navy then took on board and financed. A Double-T38 known as the T40 also was developed in the 40s.
Like the Proteus the development period was a long one as Allison wrestled with mechanisms to cope with drag on engine failure and the unreliability of the propeller gearbox caused by lubrication problems. I also reckon the remote gearbox may have allowed more misalignment than a British close-coupled layout as stiffness will be less in the US configuration.
Like the Proteus by the fifties the engine had evolved into a better design which became known as the T56 and was built, run and flown in 1954 as the engine for Lockheed's C-130.
In a NACA RM  'AN INVESTIGATION 1N THE AMES 40- BY 80-FOOT WIND TUNNEL OF A YT-56A TURBOPROP ENGINE INCORPORATING A DECOUPLER AND A CONTROLLED-FEATHERING DEVICE'
By Vernon L. Rogallo, Paul F. Yaggy, and
John L, McCloud III
The summary reads:
"An. investigation of a decoupler and a control:ied-feathering device incorporated with the YT-56A turboprop engine has been made to determine the effectiveness of these devices in reducing the high negative thrust (drag) which accompanies power failure of this type of engine. Power failures were simulated by fuel cut-off, both without either device free to operate, and with each device free to operate singly. The investigation was made through an airspeed range from 50 to 230 mph. It was found that with neither device free to operate, the drag levels realized after power failures at airspeeds above 170 mph would impose vertical tail loads higher than those allowable for the YC-130, the airplane for which the test power package was designed. These levels were reached in approximately one second, The maximum drag realized after power failure was not appreciably
altered by the use of the decoupler although the decoupler did put a limit on the duration of the peak drag.
The controlled-feathering device maintained a level of essentially zero drag after power failure. The use of the decoupler in the YT-56A engine complicates windmilling air-starting procedures and makes it necessary to place operating restrictions on the engine to assure safe flight at lowpower conditions."

So although the T56 is a single shaft engine, there are unique operational challenges that have to be solved in order to safely use the single-shaft design in practice. The A-S Python in the Wyvern was another engine that had severe control challenges.

The Orion for the Britannia was designed to allow the use of higher cruise speeds on the long routes operate by the likes of BOAC where the economic benefits of greater speed are quite clear. The Orion was therefore designed to deliver the correct cruise thrust and then throttled to prevent huge take-off powers beyond the capability of the Britannia to structurally absorb those (Take-Off) thrusts. Also it was a retrofit to an aircraft that had evolved from a 1944 Brabazon concept and had evolved into the Britannia over the years. Had the Brabazon 2 been a straightened-airflow engine the Orion may not have been necessary.

The Tyne evolved from Rolls-Royce's anticipation of the way the Viscount market would evolve and the lack of upgrade to the power  needed from the Dart configuration. Rolls had looked at high-power turboprops in the 1940's first with the Clyde and then with the Tweed, which was the original choice for the Princess. As Rolls-Royce had their hands full with Dart, Avon, Nenes they decided to abandon both Clyde and Tweed in the short-term.
By 1952/3 BEA realised that the Viscount turboprop airliner was opening up the marketplace but by 1959 would be to small to economically service it. So they began to think what a replacement would look like. In 1953 Peter Masefield, chief exec at BEA wrote to Vickers with an outline of their thinking of a Viscount replacement with a targeted in service date sometime in 1959.
Vickers working on various studies with props (RB109 and similar) and jets ('baby Conways") concluding that a turboprop delivered better economics on BEA's routes.
On longer routes serviced by BOAC the economics favour a higher cruising speed and so building an engine that is oversize for take-off but optimised for cruise, then limiting the take-off power means that the pilot will have power to take-off with a normal payload even on hot and high airfields. This is the rationale for the Orion.
On the shorter higher frequency routes the higher cruising speed does not have the same payback overall, (also helps to explain why even today turboprops are still favoured for smaller capacity, shorter range routes), so it is more difficult to justify turbojets (back in 50s) but advanced turbofans can and do slowly replace them.
Therefore the Vickers aircraft for BEA, christened Vanguard had an engine developed for it that was optimised for take-off and delivered sufficient thrust at the required cruising speeds and altitudes.
I have put together some numbers for the 3 engines and put them in a table for easy comparison (see below).
The conclusion I have come to is that the T56, although a simple design, has very good thrust/weight ratios. The Orion has a built-in disadvantage in being too big for the T/O job and therefore carries a weight penalty. One wonders what would happen in a non-Britannia derived aircraft application. Or what would happen if you used a Tyne and ran it it a higher cruise thrust (not optimum sfc power).. would the overall weight reduction make up for extra fuel. An interesting situation that makes me realise why performance departments back then had were so big and had so many bright people in them...3 ft sliderule anyone?

....tbc
« Last Edit: August 09, 2012, 11:33:00 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #187 on: August 06, 2012, 06:59:09 am »
Whilst Bristol had their icing challenges to delay them and so miss the market window, Vickers and RR had a different challenge to lose sleep over. Fortunately the problem that emerged on the Tyne did not take as long to solve but was still a challenge to the intellect!
Opening the Flight magazine for 3rd June 1960 would have come across an article on page 744
"Tyne Investigation
ON May 27 Rolls-Royce Ltd announced that the Tyne turboprop
(described in Flight for April 22) has suffered mechanical failure
of a nature which may not be immediately rectifiable. The trouble
arose during bench testing of a Tyne at Derby and at one point
during the run a compressor disc failed. Although an isolated
occurrence, the company found "confirmatory evidence" on
another engine. A full technical investigation is in hand, which
naturally extends to the many engines already delivered, and
Rolls-Royce have recommended that flying of Vanguards and
CL-44s be suspended until the fault can be rectified. A note on
the effect which this has had on BEA is given in our Air Commerce
section."[below]
STOPPING THE VANGUARD GAP
HOPES that BEA will be able to inaugurate Vanguard services
- on the London - Paris route on July 1 [1960]are now diminishing.
The setback to the Rolls-Royce Tyne programme (see page 744 [above])
is such that BEA are planning on a possible three-month delay
before they will be able to introduce the aircraft into service.
Fortunately for the airline, the effect is not so serious as might
have been the case had the Vanguard been allocated to a larger
number of routes; in fact, at the outset two aircraft only were to
be deployed on the single London - Paris route. Nevertheless,
BEA's forward bookings are heavy on the whole of the network,
and there is no Viscount capacity to spare for redeployment to
fill in the missing Vanguard capacity. The corporation is therefore
seeking to charter, on a bare-hull basis, four Viscounts to
resolve the situation. The crews who have been converted to the
Vanguard will accordingly be reconverted to the Viscount.
As reported last week, the first Vanguard was due to be handed
over to BEA by Vickers on June 15. The machine which BEA
were to have m the meantime for crew-training, G-APED, was
ready to be handed over last Friday. But, with the seven other
Vanguards so far flown (and Canadair's CL-44s), the aircraft is
suspended from flying. The most bitter pill for Vickers to have to
swallow is that the ARB were expected to grant the Vanguard its
Certificate of Airworthiness yesterday, June 2. But assuming that
the unofficial estimate of three months is likely to prove accurate,
at least the TCA Vanguard programme—which calls for delivery
in August—should not be unduly affected."
In fact the investigation and rectification took until November but integrity testing by BEA in order to make sure all was really fixed took a month or two. Limited services began at Christmas, more at Easter 1961 but it was July1961 before BEA were back on their schedule of the previous year.
Tn May 1960 an hp7 compressor disc burst whilst a re-worked Vanguard engine was on pass-off test at Derby. As a genuine disc failure cannot be contained it is a very serious incident. Flying on route proving and prototype flights still went ahead, with severe restrictions, but passenger flights were off the agenda. 
The figure below from A C Lovesey's paper 'Gas Turbine Development- Thirteen and a half years in Commercial Aircraft' Aeronautical Jnl V68 No 644 August 1964, shows the disc pieced together after the failure. It had a running time of only 68 hours!
Prolonged lab examination determined the initial failure was the vertical fracture seen in the photograph but little useful additional information was unearthed.
A further 5 cracked discs were discovered in discs all running with times close to the first one. The metallurgical team were sure the problem lay in the material itself. Many discussions with experts within and outside the aero industry but to no avail. The probability of failure of another disc was estimated to be 1 in 700 discs- too high to contemplate and so RR decided that no passenger carrying flight could go ahead until the problem was demonstrably eliminated. This decision was taken after many attempts to eliminate faulty discs, including 64 individual disc rig tests, each test being run to 20 times the number of cycles experienced by the first disc to burst. 3,500 discs were scrapped.
Incidentally this disc material was used in the Conway and the engine had 80,000 hrs of airline experience without incidence.
.tbc
The lab had been looking at the improvements that come from vacuum re-melting of this particular steel alloy, and were convinced that the variability of the steel would be significantly reduced by the process. RR had no choice but to 'forge' ahead, as to revert to a lower strength alloy would necessitate a significant redesign and development programme. The steel maker involved had not got the capacity to vacuum remelt sufficient quantities of steel so RR arranged to have this done at their titanium alloy provider who had spare capacity at this moment. Material testing demonstrated that a significant increase in uniformity and increased properties was obtained from material test pieces that are part of each disc forging. A measure of a ,aterial's ability to even out the stress distribution is the tensile elongation. The change from air melted to vacuum melted steel had a dramatic effect on the elongation as shown in the distribution of results from 300 test pieces of each type, plotted below.  The vacuum re-melting process reduces scatter and the improvement in elongation results enabled the acceptance level to be increased one and a half times from 10% to 15%.
Lovesey states that the evidence of improvement outweighed any that could be obtained by other means, particularly as the effort to isolate potentially unreliable discs in the air melted material had failed. It was on this basis that the ARB approved the modification. Subsequent experience has shown their decision to be correct and by 1964 flying hours on Tyne engines stands at one and one quarter million hours with a total absence of any disc material trouble.
« Last Edit: August 07, 2012, 01:01:59 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #188 on: August 07, 2012, 01:52:17 am »
In the early days of development the Tyne had some serious trouble in the form of fracturing of bolts securing the LP Turbine assembly.
Lovesey described how these bolts were sometimes found with fractures originating under the heads. As often happens the circumstances surrounding the failures presented a confusing story. He goes on...
"A first approach to a mechanical failure is to make the component strong enough, by way of showing that the action proposed gives a large increase in life when subjected to loads that produce typical failures of the original design. This, more often than not, is best done independently of the engine. If the 'forced' failure is identical in character with that experienced in the engine we can be pretty sure that the treatment is the same, and one has a yardstick to measure the effectiveness of design modifications.
The evidence of failure origin, in the radius under the head at a point directed closely towards the centreline of the shaft, resulting in eventual fatigue failure. This evidence and that of fretting patterns on the mating face between flange and disc made it clear that, whatever the disturbing force, the consequent flexure of the flange would most likely be the prime source of high bolt stress, and that attention to the flange stiffness might be a powerful factor in preventing further failures.
A Sonntag fatigue testing machine was used to generate the evidence for the before and after situation. The whole LPT assembly is anchored to the table of the machine. a vibrating force is then transmitted via a rod to the shaft. Results for the original and modified design can then be collected. The flange could not just be thickened up as the gap between HPT and LPT assemblies is tight; the flange is thickened between the bolt heads. The results show a 60+ improvement in life as tests were discontinued with no sign of failure.
No failures of the modified flange have been found and much later the LP rear bearing was modified to have improved damping and the source of vibratory forces was removed, having an overall benefit on the engine as well as easing stresses on the flange....
The fourth picture below shows (top) the original LPT shaft and (bottom) the shaft with modified flange.
« Last Edit: August 07, 2012, 02:25:42 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #189 on: August 07, 2012, 07:07:17 am »
Interesting numbers...

The Orion itself would have been a big weight penalty (5600 pounds for 4 bare engines) for the Herk, but then it was a bigger engine even at T/O rating. But if you'd scaled the engine down and used the same philosophy, the weight penalty would have been much smaller, the aircraft would have cruised faster, higher and more efficiently, and the operators would have loved the hot-high-short capability that it would have given you.

Offline tartle

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Re: Early British gas turbine development
« Reply #190 on: August 07, 2012, 04:38:03 pm »
LowObservable... good point... it would lower the penalty... the Tyne of course restored hot/high power by using water/methanol injection at a small weight penalty to restore power to sea level conditions at 10,000 ft and between +15 to +20 deg C.
Just as a first order excercise I have replotted Orion performance curve from the Proteus cruise power and looked to a cutoff of 5050 hp. I btlieve the Orion output was mechanically limited by the main gearbox no thermally limited  so we would have to ask what the turbine entry temperature implications of having a higher than scaled sea level power would be.
We seem to have scaled Orion 8,200 ehp to 6,900 ehp i.e a .841 scale. The mass flow will then be 68 lb/sec which is a massflow scale from Tyne of 1.48 so a linear scale of 1.22... over 20% bigger. The economics of a Herc with such an engine would then have to be done, but my gut feel is that getting the engine rightsized as normal and then using water/methanol may be a more cost effective solution... but if economics do not weigh so heavily it would be interesting. Knowing operators minds a little... I would see mil/civil operators looking to use all the power they could get whenever they could get it so they would have ended up supersizing the load anyway!
But superficial calculations can be misleading!
« Last Edit: August 08, 2012, 06:52:11 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline alertken

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Re: Early British gas turbine development
« Reply #191 on: August 08, 2012, 07:44:53 am »
NBMR.4 was put out to tender in 1961: NATO-Standard (V)STOL freighter, to support NBMR.3 (V)STOL strike fighter. UK tired of infighting, could not wait, so in 1963 took HS.681.
 
Bristol took a C-130E licence and bid that as T.222/Tyne, and again to UK-only Reqt.OR.351 that was met by 681. When 681 was chopped, 2/65, RR chose to dust off desultorily its T.222 installation scheming and submit a slim brochure for Tyne to be shipped to Marietta for C-130K. They put little effort into it because:
- no evident operational benefit; but much more significantly:
- incredible to contemplate such a certification exercise in the very short lead-time to delivery of T56/C-130K.
 
MoS/NGTE put much effort from 1944 into Theseus/Proteus/Orion. Brabazon Committee Type III (ultimately, Britannia) and Vickers Windsor were to have taken Theseus. Bristol's 1946 bid to (by then Medium Range Empire, to be initially Centaurus/, then Proteus/Britannia) was a Centaurus/licenced L-649 to be followed by a Theseus/L.849. Cabinet declined to make $ available: for me, a tragic What If: DC-7Orion, L-1649Orion, 1954-ish. (France negotiated a DC-6 licence, 1946: Communist influence in turgid 4th Republic politics scuppered that. Theseus could have been hung on that, too).
« Last Edit: May 31, 2017, 02:09:50 am by alertken »

Offline LowObservable

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Re: Early British gas turbine development
« Reply #192 on: August 08, 2012, 02:14:20 pm »
Orion-Starliner... that would have been something. Were the Mach limits similar to the Britannia, though? And then there was this project:

http://www.flightglobal.com/pdfarchive/view/1955/1955%20-%201675.html

http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%200925.html?search=britannia%20600%20type%20187

We'd have got to jets eventually, but fast props with better long-range performance could well have held off the competition from early one-stop jets.

And it's a little ironic that the US banned the DC-6 for France just as we shipped Nenes to Uncle Joe. Hey Vlad, how about some royalty payments?

Offline tartle

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Re: Early British gas turbine development
« Reply #193 on: August 09, 2012, 02:11:46 am »
LoeObservable... the birth of the CL44; one wonders whether a differnent sort of political climate might have allowed the high Mach Number mods to appear in that aircraft's development programme which would have made a market niche for the Orion; it seems turbojets killed that engine as the aircraft/engine combinations were not pursued with the urgency needed to take advantage of the high MNo turboprop window... as you pointed out.
The first details of Electra in Flight magazine also had a section on engine selection which I have cut and pasted below:"Powerplants. We have previously described the provision of
power for the Electra as a "nigger in the wood-pile," owing to
the fact that the engine assumed in the original projection of the
design—the Allison 510—is not yet fully developed as an airline
engine. Before describing the installation of this engine it is
therefore worth adding a few notes on alternative units.
The Electra is designed to use any modern turboprop in the
3,000 to 4,500 h.p. class. Into these limits can be fined the
Allison 510, the Rolls-Royce Tyne, the Napier Eland and—fully
developed but of earner conception—the Bristol Proteus.
The Allison suffers from a number of fundamental deficiencies,
which become serious when considering the engine from an
airline viewpoint. At present, it is a constant-speed engine
(13,820 r.p.m.) and even the ground idling speed is as high as
10,000 r.p.m., resulting in a high noise level on the ground.
Allison have put a great deal of effort into perfecting the control
system, and have brought the engine/airscrew combination to the
point at which it can be accepted for service in the C-130 for the
U.S.A.F. General handling, however, is still not as good as it
should be for an airliner.
Another factor which should not be overlooked is that the
Allison 501-D-10 is not yet ready to deliver its full design power in
commercial service. This power is 3,460 sJi.p. (3,750 e.sii.p.)
at sea level, i.s.a., at zero forward speed, and to achieve this the
turbine inlet temperature has to rise to 1,780 deg F (1,320 deg K),
making it one of the hottest engines yet flown. Development
running is going forward with the 5O1-D-12 commercial engine
with a maximum rating of 3,015 e.s.h.p. at 1,625 deg F max.
t.i.tcmp., but the Electra needs more power than this. For future
development, Allison hope to achieve well over 4,000 e.s.h.p. in
the 501-D-8 and D-13, but it would seem that they will be hard
pressed to reach this goal.
From a number of aspects, the Tyne and Eland appear to fit
the requirements of the Electra very well. The former is an
outstandingly efficient unit and will provide more than enough
power. The latter is also well-engineered and efficient, and will
shortly deliver considerably more power than the Allison, using
air-cooled turbine blading. The view of Lockheed, expressed
directly to us earlier this year was that, although the American
Airlines' Electras were to be powered by the Allison 501, it
should not be inferred that this would become the standard, or
even the most common, Electra engine. One Lockheed engineer
said, bluntly, "we want the engine from Derby; and if we can't
have the Rolls engine in time, the Eland has a good chance."
Anyway, for the time being the Electra is wrapped around four
Allison 501s. Each is installed as a complete power package and,
except for certain handed items and accessories, all four are interchangeable.
These Allison engines have the reduction gearbox
mounted remotely from the power section (see detail drawing on
p. 715[below]), thus allowing the air intake free entry to the compressor.
In the C-130 the intake is under the spinner, but various factors
have resulted in the Electra engine being "the other way up," i.e.
the axis of the airscrew lies below the axis of the engine, and the
main air intake duct passes down from the top of the cowling
behind the spinner.....etc"
Reading all the press gives an impression of lots of activity around these engines but due to inaction the opportunity was missed... all one can say about Tyne and T56 is that ultimately they found (military) markets of decent size.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #194 on: August 09, 2012, 08:21:20 am »
Flight's stylebook has changed in the last 57 years...

Interesting stuff about a momentous era. Had Lockheed had the Tyne, they wouldn't have had this problem:

http://www.airspacemag.com/military-aviation/The_Hammer.html



Offline robunos

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Re: Early British gas turbine development
« Reply #195 on: August 09, 2012, 01:09:43 pm »
Tartle,
 In #186 in this thread, in other threads on SPF, and elsewhere online, mention is made of thr Rolls-Royce Tweed.
However other than a purported designation of 'AJ.25', I can find no more information on this engine. As it seems to be truly a 'Secret Project', could you tell us a little more about it...


cheers,
         Robin.
Where ARE the Daleks when you need them......

Offline tartle

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Re: Early British gas turbine development
« Reply #196 on: August 09, 2012, 05:05:22 pm »
Robin.... the AJ25 was a jet engine project of 2500lbt; the AP25 was a turboprop version. The AJ25 had thinking in it that fed into BJ45 that eventually evolved into a Conway and AJ65 that eventually became the Avon.
Until I have found my Tweed info this picture of the mockup  gives an idea of it.
Correction: I have changed AJ45 to BJ45 so the section below is also BJ not AJ!
....tbc
« Last Edit: August 23, 2012, 01:24:42 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline robunos

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Re: Early British gas turbine development
« Reply #197 on: August 10, 2012, 02:14:22 pm »
Many thanks for that...and the AJ.45 is completely new to me...


cheers,
          Robin.
Where ARE the Daleks when you need them......

Offline tartle

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Re: Early British gas turbine development
« Reply #198 on: August 11, 2012, 04:22:42 am »
Robin,
I made a typo.. it is the BJ45 started to be schemed on the 23 Oct 1946. I knew Don Eyre, who was A A Griffith's personal designer, and he had a sense of history and so was happy to chat. The B of course stood for Bypass and this was the first scheme issued around that concept.. much work by the Main Project Office followed and the concept emerged as the Conway. The BJ80 Conway was first schemed out as an engine with the first 4 stages of the AJ65 Avon as the LP Compressor, driven by a single stage turbine and the Tweed compressor spool as the HP system, also driven by a single stage. Note that at this period of understanding RR and others were designing highly loaded turbines in order to minimise engine length and weight. The Dart was another engine that was suffering from single-stage-itis. When it first ran it had a turbine efficiency of 80%, way below target... by attention to losses due to leakage this was raised to 86%.. but that is another story. The RR turbine efficiency curves (that are very accurate and derived from model testing and are corrected for losses- i.e. the leakage factors on model are factored out) show that for a given work output dividing the work over two stages will yield a 4% improvement in overall efficiency, less the losses over the second stage... worth having if the weight issue can be tackled and length is not a critical issue. The history of the early Dart brings this out and is a fascinating contrast to the way the Proteus issues were tackled.....so I'll do that shortly.
Back to the Tweed.
This engine was an exploration of a 2,500 hp turboprop that was pure axial. It was designed by John Reed under the watchful eye of Fred Hinkley and was followed by what John called an AP12½... which, unsurprisingly was a scale-down to 1250 hp during the period  when the MoS was looking for engine schemes at that power. The compressor follows the Metrovick design on the Clyde as it has constant outer diameter and a rising hub diameter. RR favoured this arrangement on the turboprop as accessories were still contained within the intake diameter; but in the case of turbojets the reverse is true, resulting in a tapered outer casing .. as it kept the installed diameter of the engine down when accessories were included in the general arrangement, as they could be included between the inlet and outlet diameters of the casing. The combustion chamber took the best of thinking at Lucas and Derby and was schemed as 8 separate chambers. 2 turbine stages were used as the spool also drove the propeller.
« Last Edit: August 12, 2012, 04:26:31 am by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #199 on: August 12, 2012, 06:26:57 am »
Lionel Haworth was the chief designer on Clyde and Dart:
In his biographical memoir (download here) it was stated:
"In March 1944 he was responsible for the design of the compressor and gearbox of the RB39 Clyde turbo-propeller engine, which first ran in 1945. This was the first two-shaft aircraft gas-turbine engine, using an axial flow compressor followed by a centrifugal derived from the Merlin supercharger on the high-pressure (HP) shaft, the propeller reduction gear being driven from the low-pressure (LP) shaft. The Clyde proved to be a powerful and reliable engine but despite its potential it was not adopted for production. However, valuable experience was gained particularly on fuel and propeller control systems.
THE DART
In 1946 a small team at Derby under Lionel Haworth designed the new and relatively simple turboprop, the RB53 Dart. It was aimed at 1000 shaft horsepower (SHP) to satisfy a Ministry requirement for a trainer aircraft. An engine of this class was also needed for a short-range turboprop airliner under study by Armstrong Whitworth and Vickers.
Haworth chose to use a tandem centrifugal compressor as in the latest piston engine superchargers, mounted on the same shaft as the two-stage turbine, which also drove the gearbox and propeller. From the HP compressor the air passed through seven combustion chambers arranged at a skew angle to reduce length and avoid a right-handed bend in the flow. At the front of the main shaft was a helical high-speed pinion connected by three layshafts to a second stage of reduction gearing with spur gears. The Dart was overweight and down on power when it first flew in the nose of a Lancaster in October 1947. It did not compare well with the
The first flight on 16 July 1948 was a great success, and by then the Dart was meeting its design criteria. Haworth had already planned the RDa3, giving almost 50% more power; this was immediately put to use in stretching the now very promising Viscount to meet the needs of BEA with an increase in seating from 32 to 53. Limited scheduled services started on 29 July 1950, the first revenue-producing service by any gas turbine in the world. An order was placed for 20 V701 Viscounts and this was later increased, followed by many others."

As discussed above, the aerodynamics and structural understanding which was derived from the remorseless development programme on the Merlin... see below for the development drivers that ensured that the Spitfire was at least on par with the Me 109 and later the FW 190. Hooker was key to driving Supercharger performance and Lovesey made sure it hung together.
Lionel Haworth was a practical hands-on engineer and designer and was also very keen on mentoring those who followed his footsteps into RR Design and Development... he therefore was always keen to lecture the new intakes of apprentices to help make sure thay realised why they were being trained so thoroughly and the opportunities that could open up for them. I was too young to have heard him speak but his team that were rising over the years spoke the same message. Lombard and Morley lectured my year.
Back to Haworth.. the notes made for one of his lectures form the backbone of the story below, and it contrasts with the lack of urgency and direction at Bristol 'til Hooker arrived.

Rod Banks in his autobiography 'I Kept no Diary' talks of Peter Masefield and his inspired backing for the Viscount that helped make it a success. Rod wrote in the context of our lack of commercial aircraft success- Trident for instance:
" It could be asked: what about the Viscount? The answer is that the '630', the Viscount prototype, with its Dart engines, was designed and built at government expense ahead of any B.E.A. requirement, experience or thinking. It was Peter Masefield, as Chief Executive of B.E.A., who eventually took it on and had the passenger capacity increased from 32 to 47, i.e. the '701'." An important player, was Masefield- his obituary is here.

Haworth covered the background to the Dart and its development
Towards the end of the War the Government set up a committee, under the chairmanship of Lord Brabazon, to prepare 5  specifications for civil aircraft that the World might need in the 20 years after the War........ of the more succesful aeroplanes within the Brabazon specifications are the de Havilland Comet and Vickers Viscount.

The Viscount was planned as a medium speed (300 mph) airliner of an all up weight of about 40,000lb to carry 36 passengers. For this job it required 4 gas turbine propeller engines of 1000 hp. We commenced work on the RB 53, the Dart, early in 1945, while Armstrong Siddeley commenced work on the Mamba. There were other aircraft competing in this field- Armstrong Siddeley built the Apollo and Handley Page also designed an aircrfat to meet this spec'n.
The RB 53 was to give 1000 hp at the propeller for take off and prop diameter was limited to 10 ft. this was fixed by consideration of wing span, wing loadings, landing speeds, and length and weight of undercarriage.
« Last Edit: August 12, 2012, 04:49:04 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #200 on: August 12, 2012, 04:48:32 pm »
Lionel Haworth went on to say:
"It was natural that we chose for the compressor of the RB.53 a two-stage centrifugal type, the type which in fact we had used on later Merlin and Griffon engines. This was drawing on our previous piston engine experience; we thought that we knew something about reduction gearing since the Merlin and Griffon featured these components, but we had not attempted anything with such a large ratio as .106. The piston engine had a much smaller reduction gear ratio of .442. Having decided on the main construction of the engine, some calculations were made to determine the approximate size of the engine. In order to have 1000 hp at the propeller it was necessary to have a turbine that developed about 3000 hp driving a compressor that absorbed about 2000 hp.Thus the rough basic dimensions were arrived at. With the compressor we were hoping to use our latest knowledge and maybe a little beyond. With the turbine we decided to go beyond our jet experience and have a two-stage turbine. This engine was the first aero engine in the world to feature 2 stages in the turbine.
The engine was then sketched out to produce a design scheme with the main components worked up in enough detail for estimates of weight to be made. The project layout or scheme is then turned into a detail design and a General Arrangement generated."

The RB 53 design project started on or around 25th April 1945 and it took 57,048 man hours over a period of 63 weeks to complete the initial design. Detail design of component parts began 12th June 1946 and took another 29,195 man hours over the next 54 weeks. First detail drawings were issued to the shops on 1st Nov 1945 and the first engine was built and ready for test by July 10th 1946.

Haworth continues:
"As soon as the engine was completely assembled, it was put on a weighing machine. Imagine how we felt when instead of showing the predicted 700 lb, the scales showed over 1100 lb! But this was not the worst blow we suffered during that second week of July, 1946; a few days later the engine was wheeled from the shops to the test bed and the anxiety as to whether it would in fact run was completely overshadowed by an inquest in the design office on the weight analysis. The engine,however, did run even under its own power, but when the next day it was decided to open up to full power we were completely stunned by the news - our 1000hp engine could only achieve a little over 600 hp. It, however, was decided to persevere with the 'heavy' engine and within a matter of a month or so it had completed a 50 hr endurance test. We were now faced with the task of finding the power and reducing the weight and these two design problems occupied us for the rest of 1946 and well into 1947.
Every piece of the engine was carefully examined to see were metal sections could be reduced or avoided all together to save weight. Magnesium was used extensively for castings instead of aluminium, and by a process of pruning every ounce of weight on desin and making certain castings were manufactured to drawing thickness (almost 100 lb of weight was put on through overthick castings) we managed to achieve a saving of some 350 lb.
The loss in power output was  not really surprising on closer examination, for instead of the turbine developing 3000 hp it only achieved about 2800 hp, and instead of the compressor requiring 2000 hp it was taking over 2200 hp leaving only 600 hp for the propeller.
Another version of the RB 53 was produced which gave about 900 hp and weighed 800 lb. This engine was developed up to 1000 hp and in Aug 1947 the first 150 hr Type Test was attempted. It was not until Dec 1948 that a clear run throught the 150 hr test schedule was achieved, at a power of 1045 hp. In April 1949 a 500 hr endurance test was completed at this rating."
An aside: At some point during the War Haworth had visited Dr. R. W. Bailey at MetroVick, Manchester and had been shown  a disc in the laboratory being subjected to steep radial thermal gradients by alternately heating and cooling the rim. Dr Bailey expalined he was simulating the thermal stresses that occur transiently in an engine, saying he planned to find out if the metal would attain what he called a 'cyclic state'. He further said he believed the rim hoop stress alternated between tensile and comprssion in excess of the material yield.
Haworth decided that such punishment would fail the disc and went away to find a design solution to the problem.
The 4th attachment below shows a crack at the bottom of the blade root slot of a Derwent engine. 13 Derwent discs failed in service from cracks like this (typical across the industry at the time). While these failures were occuring Haworth was having a design solutiion fitted to the improved RB 53 being developed. This was the extended root blade.
Back to Haworth:
" The improved power derived from the turbine by blocking up the leaks under the NGVs prompted some thought to be put into the idea of blocking up the leaks over the top of the turbine blade.
This was eventually achieved by designing a turbine blade with a shroud on it and to seal off the hot gas on the front edge of the blade by a very narrow land running against a face with as small a clearance as possible. Hence this engine was the first aero engine to have shrouded blades and, incidentally, long roots. Obtaining the correct clearance was very much more difficult to calculate and we resorted to trial and error, observing the stae of the shroud upper surface through holes in the casing. We adjusted the running clearances until we only had a slight rub.
The improved turbine design gave a substantial increase in efficiency and by Oct 1948 we were able to complete a type test at 1100 hp and an sfc of .867.
« Last Edit: August 13, 2012, 06:09:55 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #201 on: August 13, 2012, 05:54:51 am »
The benefit of the long root blade that Haworth had fitted to the Dart was that, not only did the thermal cyclic stresses reduce, the disc rim temperature profile was so much lower that ferritic steels could be used instead of austenitic steels. The Americans were very slow to adopt the innovation choosing instead to pour money into the manufacture of austenitic and nickel based discs. Incidentally the rim temperatures on the Concorde engine exceeded the limits for ferritic materials and we had to use American Waspalloy material for any practicable design.
Another benefit of the long root blade is that a large radius at the top of the firtree greatly reduces the stress concentration at this point eliminating frequent failures that were happening in that area on conventional blades.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

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Re: Early British gas turbine development
« Reply #202 on: August 13, 2012, 06:09:20 am »
Back to Howarth:
" At this (1100hp) power the shrouded turbine was not fully exploited and a further redesign of the turbine was undertaken as a result of research undertakenon a turbine rig. It was decided to redistribute the work between HP and LP stages, reducing the LP and increasing the HP. This was achieved by altering the annulus and increasing the HP blade speed slightly by arranging the HP blades at a slightly greater effective radius. This configuration gave an equal 'hade' at (inner and outer annulus diameter) and by pressurising the outside of the NGVs with high-pressure air thus stopping any internal gas leakage. The result was an increase in turbine efficiency from 80 to 86% at the altitude cruise condition.
Several refinements were made to the compressors, in particular, aerofoil type diffusers were introduced which raised compressor efficiency from about 74% to 78%. At the same time the mass flow of the engine was increased from 18 to 20.8 lb/sec, of which 20.1 went through the turbine. This engine gave 1400 hp and by Sept 1950 a 150 hr TT was completed at 1400 hp and an sfc of .836. This engine became known as the RDa 3 and was put into production; the first one coming off the production line in April 1952."
It also had the Helical Reduction Gearbox driving the propeller. Fretting problems in the gearbox had once again highlighted the problem of spur gears.
All these comments date from around April 1954 and thoughts on how the Dart might be further developed were included.Testing had shown that further aerodynamic refinement enabled the HP NGV numbers to be reduced from 98 to 84 - worth another 1% on turbine effeciency. A second  seal was provided on the HP Turbine blade shroud and the combustion chamber pressure loss was reduced to increase their efficiency... all this added up to a 150 hp increase with a slight sfc reduction. This RDa.6 engine went into production at 1550 hp and was fitted to a Viscount with an AUW of around 60,000lb and an improved cruising speed (plus 10-15 kts). It was also the engine used to power the Fokker Friendship. The engine first entered service in April 1956
Further research on an even more powerful engine required more radical change.
One idea that went to test was the shrouded impeller. This enabled the air to move through the impeller without scrubbing along a staionary wall, reducing turbulence. Such an impeller was then very expensive to machine. There were also mechanical integrity issues that made practical use of such a design problematic.
Also developed was a three stage turbine which with its improved work distribution resulted in a turbine that not only gave 90% efficiency at sea level, it also delivered a similar figure at cruise conditions, unlike the 2-stage design.
The reduction gearbox was also redesigned for the RDa 6 onwards.... an all-helical gear train ....to accommodate further increases in power. The first redesign, when the helical gears were introduced on the high-speed train, cured the dangerous resonance inputs that were causing problems but still left a great deal of vibration that had to be coped with.  In the words of R. J. Shire, an engineer on the Dart project:
"On our Dart engine the improvement [after fitting the helical low-speed gear train) was quite remarkable, so much so that we felt it would be worthwhile to make the low-speed train also helical. The problem here was to obtain a machine which did not exist, to grind an internal helical annulus. We paid visits to the Birmingham Gear Grinding Company and it was quite a major undertaking to persuade them to design and perfect a machine to grind an internal helical annulus to the degree of accuracy we were demanding. However years of work went into this job and now [1954] we have recently had our first engine on the test bed featuring the helical teeth on the low-speed train. From first observations it appears very encouraging, the engine being much smoother and free from vibration around the front end. This is comforting because over the years we have had practically everything at the front of the engine drop to pieces sooner or later, due to the severity of vibration; so much so that we were obliged to mount on specially designed very small shock absorbers, the front cowling ring, the oil cooler, the propeller spinner extension and various accessories like the torquemeter pressure transmitter.
« Last Edit: August 19, 2012, 04:06:40 pm by tartle »
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Offline alertken

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Re: Early British gas turbine development
« Reply #203 on: August 13, 2012, 11:58:32 am »
Could you in a future attic dig look for Conway conception? This my understanding of that:
 
- 23/12/42: English Electric Co (equity-controlled until 1949 by Westinghouse, USA) bought D.Napier & Son, whose design competence lay largely in its part-time consultant, Halford, who concurrently worked on schemes for DH;
 
- 1/2/44: DH Engine Co. was spun off: MD, F.Halford, severed his Napier function;
 
- 28/4/44: Power Jets Ltd was nationalised, to be confined to research/laboratory (and redefined 1/7/46 as NGTE). MAP diffused PJ Intellectual Property across the established industry, through the Gas Turbine Collaboration Committee. Halford had taken H.1-6 to DH; Napier had licenced Jumo 4 in 1934 before charging disastrously into Halford's Sabre. Now their sole innovations were H.7 (unwanted at DH, becoming Oryx gas generator), and Junkers-inspired compound/diesel E.125 (to be Nomad I). From W.2/700 and LR.1 turbofans, Napier schemed E.132, taken up by EE (naturally) and by Short in May,1947 bids to the Medium Bomber. EE was quickly rejected; Short was awarded low-risk, insurance Sperrin, 11/11/47, with low-risk AJ.65;
 
- 1/48: within MoS-managed industry rationalisation, MetroVick exited aero-engines, and George Nelson sold E.132 to RR. Hives let his Chief Scientist, Griffith, play with it while down-to-earth folk did the practical things you are reporting. But he brought it on, such that MoS, 10/51, ordered 17 Valiant B.2, RB.80 intended to displace Avon asap.
 
Gunston Encyclopaedia of Aero-Engines,1986,P.145 (un)credits AAG: "Following prolonged Griffith studies, Govt. funding was obtained in 1952 for...RB.80 Conway". Did it, in fact, have pedigree back to Griffith, or Napier, or Power Jets?
« Last Edit: August 13, 2012, 12:02:00 pm by alertken »

Offline tartle

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Re: Early British gas turbine development
« Reply #204 on: August 13, 2012, 12:11:38 pm »
Alertkin... the bypass engine that became the Conway was a pure RR affair... we can deal with this shortly! E.131 to E.134 and E. 137 were jet engine projects that only got as far as layouts in the Design Office.
P.S. tea chests are cheap filing systems but are not good at facilitating retrieval.
« Last Edit: August 13, 2012, 12:29:49 pm by tartle »
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Offline alertken

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Re: Early British gas turbine development
« Reply #205 on: August 13, 2012, 01:39:59 pm »
The (sole?) published source for this is the HP Putnam, P.497: (About Spring,1948) "RR undertook further development of the Napier-designed E.132...redesigned it (at Barlic) as RB.80/1 and later it was named Conway."
 
The magic of the name included an institutional aversion to acknowledging Mercedes in Eagle, Curtiss-Wright D.12 in PV.12, Sapphire compressor in fixed Avon 100, (Chrysler block in 1950s' Silver cars), or any RAE/NGTE value in, well, anything. Compare Bulman's account of Govt. infusion of money and RAE wit to get Merlin through type test, with Chairman's 1936 assertions to Ministers that RR "owned" it and would not permit (the word for second-sourcing then was) sub-contracting. Vickers (Aviation) took the same position on their "PV" Spitfire. Both were balderdash: A.M had paid for darn nearly everything upfront and the rest in later overhead. Yet, frustrated at foot-dragging, Air Minister Kingsley Wood nominated the design parent to handle volume production at his factories, Crewe & Glasgow, whereas Bristol aided entry of the auto industry. The auto team co-ordinated by Austin, and later Ford/UK and Packard on Merlin, gave short shrift to the notion that fabrication of aero engines was magical beyond autonauts' wit.

Not until the generation raised by Hives was cleared out after 1971 did "collaboration" enter Directors' lexicon (i.e joint design, as opposed to production licencing). That's why in 1959 Medway could not be taken into Allison for Boeing 727, or teamed with ASM to go into TSR.2, so then Concorde.
 
If C.H.Barnes' Putnam is right, then Conway emerged from a combination of competitor and scientist - both offside to the Derby insiders. That would answer Qs, such as here, on modesty of R&D effort into RB.80, causing the by-pass first mover so rapidly to be beaten by upstart Pratt. Why else re-invent it, as Medway?
« Last Edit: August 13, 2012, 01:47:16 pm by alertken »

Offline tartle

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Re: Early British gas turbine development
« Reply #206 on: August 14, 2012, 06:37:14 am »
Alertkin,
 I have the photos of the Mercedes in the shop at Nightingale Road, Derby in 1914... and the new crankshaft we made for it as the original was not good enough! The basic concept was useful to Rolls but it was a much improved engine that superficilly looked like the Mercedes that emerged... but that is a story for another time. The highly beneficial collaboration between Ford in the UK and RR Deby is a story that shows how Hives was a willing leader in setting that up... the shadow factory at Trafford... where the Temple to retail now sits... came on stream extremely quickly... another story..Note nearly 100 Ford personnel were at Derby to understand and prepare drawings for the mass-produced Merlin, as distinct from the craft-produced Derby ones, and the batch produced Crewe ones.. ideal for reacting to German improvements in their engines and then rolling out in larger numbers. Hopefully this story will get published under the working title of 'Oliver's Merlins' soon...
 So my conversations with Jim Boal and others about working with P&W in the 40s does not necessarily support the general view that has grown up over the years.
 The Conway story started out in Oct 1946 with the start of the BJ 45 and as power requirements increased so iterations (Oct 47, Apr 48) took place around the basic BJ45 configuration. The actual RB.80 designation was a later development... but many pundits assume that because the B stands for Barnoldswick then that is where the design was done. In fact the RB became the general Rolls prefix when design office finally moved to Derby mid-1948 and the Barlic design project register continued to be used. The Avon had started at Derby and then transferred to Barlic only in 1947 to be moved back... due to the appalling performance and the need to get all of Derby's knowledge into solving its problems. The final iteration of the BJ 45 bypass principle was Oct 1948 when it was given the designation RB.80.
The bypass concept originated in RR when Griffith continued to think about jet propulsion he started at Farnborough (as we have discussed elsewhere in the thread)
 Griffith recounted his bypass activities:
 "The first RR scheme exhibiting the bypass principle was CT56, which was done by DE [Don Eyre] in 1940. This was, of course, a multi-spool type. My own first thoughts on the subject were late in 1939, but as DE had not joined me then. ...In 1946, came a two-spool scheme whose compressors were cooked up from the Avon and Tweed compressors. A paper based on this was submitted to the TJR Sub-Committee of the ARC about November or December 1946."
 
 ...tbc
« Last Edit: August 14, 2012, 04:30:47 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #207 on: August 17, 2012, 12:23:40 am »
An aside... as we can see (when completed) above the effort on Dart, and other engines, is about performance enhancement, mechanical integrity and life (tbo) enhancement... This document issued 2008 shows level of support for an 'old' engine.
« Last Edit: August 19, 2012, 01:38:24 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #208 on: August 19, 2012, 02:32:15 pm »
Two other major changes were introduced as the Dart was upgraded form RDa.3 to 6 to 7. The method of attaching the turbine discs to the shaft as the number of turbine discs went from 2 to 3; the transfer of torque from the turbines to the compressor and the propeller gearbox was changed from a single shaft to concentric shafts, one driving the compressor, one driving the gearbox. Both were introduced to improve the reliability of the engine and to ensure that in the event of failure of either an impeller or gearbox did not lead to a turbine overspeed.
The cutaway of the Dart with 2-stage turbine shows the method of location of the two discs via radial dogs midway up between the discs. The cutaway with the 3-stage turbine shows how the discs use a method similar to the Tyne with through bolts; 5 bolts are used to assemble the first two stages and the third stage is attached by a further 5 bolts, concentric and, spaced between the first set, going through all three discs.The section shows how a second shaft arranged concentric with the normal main driveshaft is arranged... it goes on to drive the main gearbox, but as it is splined to the mainshft acts as one. 

In 1957 new revisions to airworthiness requirements for turbine-powered aircraft specified the minimum aircraft climb gradients in the event of an engine failure and which required that the effect ofbient  am temperature on engine performance be taken into account. On the Friendship, for instance this imposed severe limitations to take-off weight under hot day conditions.
The most severe condition was the 'final segement' singl-engined climb gradient when the remaining engine operated at max continuous power. On the  RDa6 the original max cont power reduced with increasing ambient temp and so the Friendship had severe weight restrictions. To alleviate this RR worked had to increase the max cont. rating. Eventually the Mk 511-7E engine version delivered 1600 shp upto 25 deg C ambient. Max continuous was a higher power than T/O without detriment to the engine as it is only used in an emergency. In spite of these increases in power and the short stage lengths flown by the Friendship, the RDa6 had a tbo of 4000hrs and the RDa7 3600 hrs in Jan 1964. The military versions operated at 2470 hp (RDa8) in the Argosy with a life of 1200 hrs. The RDa 7 has a higher mass flow than previous engines (22 lb/sec up 2lb/sec on RDa6) with a second stage impeller 0.4 in greater in diameter at 17.6 in, rotating 500 rpm faster at 15,000 rpm.
Turbine blades now sported 3 seals, 2 on top and the third forward facing
« Last Edit: August 19, 2012, 04:42:01 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #209 on: August 19, 2012, 04:52:37 pm »
Meanwhile over at Allison they were developing a higher powered turboprop that had a twin-spool configuratio. With a seal level static T/O power of 6,102 shp +996 lbt =6,500 eshp, it had a 6-stage lp comp'r with tapered O/Diameter and 8-stage hp comp'r with cylindrical outer casing, 10 flame tubes in can annular format, 1 hpturbine and 3 lpturbines driving compressor and propeller gearbox. The Allison 550 T61 engine was developed from 1955 to '59. Nov 30th 1959 saw the end of USAF funding which had totalled $35 million. 4 engines were on test and one was to go in a YC-130B in No 3 position but never flew before programme ended.
« Last Edit: August 19, 2012, 04:55:20 pm by tartle »
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Re: Early British gas turbine development
« Reply #210 on: August 20, 2012, 04:25:44 pm »
A couple of 'secret projects' that the Dart enabled.

D L Mordell initiated a coal burning gas turbine project at Canada's McGill University and wrote a review (1955) after operating the plant for several hundred hours.
A second application for Darts was in static and rotating rigs for the Rotodyne project
...and in a rerun of the 'restaurant at the end of the universe' here is the third example in the couple... at Pyestock .. a rig for  circulation control.
« Last Edit: August 20, 2012, 04:37:06 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #211 on: August 21, 2012, 10:30:35 am »
We have talked in a different thread about the RB 162 engine, design of the engine started in the Spring of 1959 with a first run in 1965. Early in the synthesis of the design it was called on as the basis for a solution to the requirements growth of the Rotodyne that even swapping from Eland to Tyne could not cope with.
 In ‘Requiem for the Rotodyne Flight 9th August 1962, the article includes this extract about the powerplant for the civil version:
Powerplant The tip-driven rotor is fundamental to the concept. Especially with rotary-wing aircraft of the largest sizes, it is lighter than a geared drive to the hub; but it also has a higher fuel consumption, and so in the Rotodyne was used only for VTOL.
Many types of tip drive are possible. The simplest employ tipmounted rockets, ramjets or pulsejets, but these suffer from inordinate specific consumption. Pressure-jet units may be employed either with or without combustion at the tip of the blade. Without combustion the required duct area makes the rotor aerodynamically unsuited to high-speed operation, and this type of system is likely to be applied only to cranes and other slow-flying craft. With tip combustion, rotor horsepower for a given flow through the blade is enormously increased, and there seems no reason to doubt that the Rotodyne rotor was the most efficient that could possibly be devised.
Like most aeronautical design problems, a tip-driven rotor is the end-product of a series of compromises. The blade profile must be the optimum aerodynamically; the duct must be accommodated wholly within this profile; the e.g. must be located at not more than 25 per cent chord; for peak efficiency, pressure ratio must be correctly chosen; tip speed is limited by Mach number; ideally, jet velocity should be not greater than twice the rotor tip speed, but this would take the size of the duct outside the blade  profile; each pressure-jet unit becomes pure drag and weight in cruising flight; noise from such a rotor may be severe, and of an unfamiliar character; and means must be found to provide for engine-out operation.
Complication is introduced by the need to provide for engine out operation. If two sources of compressed air were connected to a single pipe serving all four blades, loss of either source would result in unacceptable loss in rotor horsepower (much more than 50 per cent). The Rotodyne rotor operated as two opposite pairs of blades, each served by one of the sources of compressed air.
Termination of the supply from either source was automatically countered by increasing the fuel flow to the remaining pair of pressure-jet units, thus restricting the drop in rotor horsepower to below 13 per cent. At maximum weight, this enabled a satisfactory VTOL landing to be carried out. But this could be achieved only by designing the pressure-jet units for severe combustion conditions.
In the Rotodyne Y all power was provided by a pair of Napier Eland engines, each rated at 2,800 s.h.p., driving 13ft Dowty Rotol propellers. The single-shaft Eland also had a gear-tooth coupling at the rear driving an hydraulic clutch and auxiliary compressor.
The hydraulic clutch was a compact unit based on Sinclair principles, and by being either filled with oil or drained provided either a firm drive with very little slip or, with infinite variation, progressively less drive down to zero. The auxiliary compressor could absorb up to 80 per cent of engine power and deliver to its pair of blades a mass flow of 19.51b/sec of air at a gauge pressure of 471b/ sq in (the uprated E.151A could deliver up to 22.71b/sec).
But natural growth of the project caused the shaft-power requirement to rise beyond 4,000 h.p., which Napier regarded as out of their reach. During 1960 it became obvious that a switch would have to be made to the Rolls-Royce Tyne, although even this 60
per cent increase in power barely matched the increase in the requirements of BEA and the Services. Under hot and high conditions, the 5,250 s.h.p. Tyne 550 could only just provide the power required without any stretch in the development schedule or reduction in engine life.
Eventually Rolls-Royce suggested separate air-producing engines. Their solution was to instal in the rear of each nacelle an RB.176. This would have consisted of a lightweight gas turbine with a front extension shaft driving an auxiliary compressor. From the engineering viewpoint this arrangement was in some respects preferable to the previous installation with long shafting and hydraulic couplings. Total powerplant weight would have been about a ton heavier, but the use of separate propulsion and lift engines gave added flexibility under critical flight regimes, and also promised substantial gains in performance under hot and high or off-design conditions. In helicopter flight under the original scheme the Tynes would have been held at constant r.p.m. by the fuel governors to provide optimum propeller control, while air delivery to the rotor would have been controlled by opening or closing shutters in the auxiliary compressor  intakes. In the final scheme the turboprops would have had separate controls, and the RB.176s would have been subject to coarse control from levers bearing the legend Rotor Power Control: Start-Idle-Takeoff. The pilot's collective-pitch twistgrip would have been coupled mechanically to the datum of the governor controlling lift-compressor r.p.m. and fuel-flow; this linkage could aiso be operated by the rotor speed governor. A pressure signal from the air supply would be combined with a fuel/air ratio demand to establish almost instantaneously the correct fuel flow to the tip jets.
Originally the Rotodyne pressure-jet unit consisted of a circular section flame tube, fed by three air pipes and a single fuel pipe,
faired within a streamlined nacelle and terminating in a simple propulsive nozzle. But the BEA Type Specification stipulated an initial climb at zero forward speed at maximum weight not less than 600ft/min with a sound pressure level 600ft from the rotor
axis not exceeding 96db. Ignoring the noise requirement for the moment, this meant that each of the two pairs of blades had to generate 3,850 h.p. with an airflow of 331b/sec and a fuel/air ratio of 0.04. The specific consumption was approximately 1.851b/rotor h.p./hr. It was a requirement that the aircraft should be able to hover at maximum weight with either engine inoperative and the other at 2.5minutes max contingency of 7,390 h.p. (with water/methanol). The remaining engine would feed only one pair of blades, and could provide a maximum airflow of 43lb/sec. Emergency power to the rotor was achieved by selecting maximum engine speed and water/methanol injection with the power levers, and twisting the collective-pitch twist-grip to the limit of its travel. This would allow the rotor speed governor to increase the fuel/air ratio to the two remaining units from 0.04 to the stoichiometric value of 0.065, to increase chamber temperature to 2,200-2,300'K, and raise the power developed by the pair of blades to approximately 6,500 rotor h.p. With RB.176 engines the required takeoff rotor power of 3,850 h.p. per half rotor was achieved using 431b/sec air mass flow and a fuel/air ratio of 0.02. The emergency power to the rotor was achieved partly by an increase in engine power without water/methanol injection to max contingency rating, but mainly by an increase of tip-jet combustion temperature corresponding to an increase in fuel/air ratio from 0.02 to 0.065. This variation of power input was obtained by manually removing a mechanical stop and twisting the collective-pitch twist-grip to the limit of its travel.
Noise from the rotor was severe, and the problem was rendered acute by the fact that it was of an unusual "chuffing" character.
Intensive work on the problem began in mid-1956, but the effort was accelerated owing to both the increase in rotor power and the stipulation of an agreed level for civil operation. In fact, the actual noise of an unsilenced unit at 600ft was approximately 113db.  To achieve the 17db reduction demanded for civil operation would have necessitated a redesign of the pressure-jet into a two-dimensional form occupying the last 48in of each blade.
It was expected that the final unit would have nine circular flame tubes within a combustion chamber submerged within the blade profile. These liners would have been interconnected, with an igniter plug at each end of the chamber, and the exit nozzles would have been fabricated from molybdenum with a diffusion-deposited Si-Cr layer to prevent oxidation. This process required special furnaces which are only now becoming available in this country.
  So the RB176 did not go ahead as the Rotodyne project was cancelled.
However a few years later there was a "STOL Tactical Aircraft Investigation", in the US, for a tactical STOL aircraft and the RB176 design was dusted off as a flap blowing powerplant... as the RB176-11, which was not selected for the later design studies.
We can compare the layout of the power unit of RB176 with the RB162 as it emerged here.
« Last Edit: August 21, 2012, 01:15:00 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #212 on: August 23, 2012, 01:46:27 am »
Returning to the Derby bypass engine story....
In 1947 Derby were looking at straight jet and bypass solutions for the next generation combat engine to replace the Merlin in the factories. Hives did not necessarily see the future in turboprops; they had all sorts of problems when it came to handling over the aircraft performance envelope... especially when things were going wrong.  A great deal of effort in the last 15-20 years had gone into maximising (horse) power per unit frontal area in order to power Spitfires, etc, and Hives could so no reason why this was not still important- especially for combat aircraft. Don Eyre produced a drawing to make the point that axials were the way ahead and Hives was right behind the people who believed this to be true.
On 29th August 1947 the Derby Weight Office issued a report that compared 2 versions of the BJ45 with the AJ45 and AJ65; the difference between versions is that version A incorporated Magnesium where possible, whilst version B had Aluminium but no Magnesium.

Engine                                    BJ45                    AJ45                  AJ65
                                       Ver A        Ver B

Net dry weight lb            1536        1612          1800                 1950
Spec wt lb/lbt sls            0.325       0.341        0.400                  0.300
Frontal Area wt/ft*ft        235           248           300                   184

The report states that the BJ45 is lighter than the AJ45 as the HP compressor spool and combustion equipment is smaller due to the HP system dealing with only part of the total airflow e.g. the AJ45 combustion equipment weighs in at 180 lb whereas the BJ45 weighs only 120 lb. The bypass duct made from 18 SWG sheet dural with stiffeners and expansion joint weighs 30 lb.
A later report dated 30th Oct 1947, the concept had been reworked to deliver a bypass engine with a T/O thrust of 7,500 lb; naturally this was called the BJ75
....tbc
« Last Edit: August 24, 2012, 02:48:21 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #213 on: September 09, 2012, 11:12:26 am »
Napier... oh Napier! It has a strange history of producing aero engines that wow and then not devoting enough energy to kepp wowing its operators. The first really succesful in-house design was the Napier Lion which was a great engine just after the First World War... designed by A J Rowledge, who then fell out with Montague Napier over the failure of the post-WW1 car which was a commercial failure. He left and joined RR, who benefitted greatly from having a man of calibre to help a sick Henry Royce. The success of the Lion kept them in business until the mid 20s with minor variations and Ministry funded versions... but there was no really aggressive development as the production engineers did not want to change anything and they were listened to by the board! Fell aked them to do a rival to the V-12 Curtiss Schneider engine but they declined so he went to Rolls-Royce who were suffering from a fall in car orders in the depression and Royce grabbed the opportunity to get back in aviation with a modern engine... this was the Kestrel... enlarged as the Buzzard... which was the basis of the Schneider winning R engine, and ttaught RR how to do rapid development under extreme pressur... useful less than ten years later in WW2 with first the Merlin then Griffon. In the meantime Napier realised that they needed to do something to survive! Montague's idea for an air-cooled V12 developed instead of the liquid-cooled engine Fell wanted (incidentally Fell's 2 draftsman drew out a scheme maximising the use of Lion components). They went to Halford, who was consulting deHavilland on small engines and so the Rapier and the Dagger were born. Unfortunately Halford had a habit of creating great schemes that needed a lot of development... but he was a bit blasé about telling people so Napier went into production without applying any rigour to development. Both engines had problems.... at the beginning of the War, on Hereford aircraft it would oil up and be difficult (=impossible) to start without taking out the lower sprk plugs and washing the out before refitting .. and don't hang about before opening the throttle! Halford had aslo designed the Sabre.. to be used in the next-generation fighter after the Hurricane, i.e. Typhoon... it turned out to have lousy altitude performance and in spite of work on superchargers was destined to be used in low-altitude  roles only. The probem with, especially, sleeve valves, and other areas meant that Bristol were called in to sort this out and lack of urgency to tackle problems meant the Ministry asked English Electric to take them over. At one time no engines were going to Typhoons coming off the production line as all new engines were diverted to operational squadrons to keep those Typhoons in service in the air... it took till 1944 to sort this out, yet still the develoers kept coming up with even more highly stressed higher performing models. In desparation Derby were asked to do a Sabre replacement just in case... the Eagle II ....it was not a copy but what the advanced Sabre would look like as the Griffon did to the Merlin   
So not surprisingly with that track record they were late into gas turbine development. In the 1930s they had taken a licence for the Junkers Jumo diesel aero engine and had built one or two as the Culverin...the became the basis of the Deltic rail and ship diesel engine series post WW2 and also accounts for why they were keen to do a Griffon replacement for such aircraft as the Shackleton... once again spreading their engine development resource too thinly.
The Ministry began to finance activity in gas turbines as the Sabre work reduced as the war ended... although the Sabre improved and its unscheduled outage reduced its life (tbo) remained short and so it occupied Napier till the last.... so it was late in 1945 when people like Herbert Sammons, H. Barlow and H. A. Penn were assigned to gas turbine development- as chief engineer, chief desiner and compressor expert respectively.
One of their first efforts was E127, soon known as Nymph, a turboprop of 525 eshp, again like Bristol given a small engine to look at. There is a 1946 picture, reproduced below, in the IMechE archive that is labelled Nymph. Looking at it with a close scrute reveals a sign above labelled Naiad; however the mockup? engine in the right of the picture looks too small to be a Naiad so maybe that is it. The design of the Naiad was certainly started early in the summer of 1946, first running in the summer of 1947.
« Last Edit: September 13, 2012, 02:26:11 am by tartle »
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Offline robunos

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Re: Early British gas turbine development
« Reply #214 on: September 09, 2012, 01:48:39 pm »
Quote
The probem with, especially, sleeve valves, and other areas meant that Bristol were called in to sort this out ...

I'd been thinking of starting a topic about this. With hindsight, given all the problems, would it have been better to cancel the Sabre as soon as practicable, and merge Napier's resources with Bristol, and use them on Centaurus development/production?

cheers,
            Robin.
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Offline tartle

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Re: Early British gas turbine development
« Reply #215 on: September 09, 2012, 05:19:55 pm »
We could do a WW2 what-if theme...but this is probably too wide as we could include almost anything!
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Offline robunos

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Re: Early British gas turbine development
« Reply #216 on: September 10, 2012, 02:04:09 pm »
You're right, a WWII topic would be too broad, so I'll start a new topic with my question form above, and another one I'd like to ask...

cheers,
            Robin.
Where ARE the Daleks when you need them......

Offline tartle

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Re: Early British gas turbine development
« Reply #217 on: September 13, 2012, 02:24:32 am »
The Naiad was in the same power class as the Mamba and Dart but was never specified in the civil programme for the Brabazon type IIB short-medium range airliner (resulted in the Viscount  with Dart and Apollo with Mamba). The coupled Naiad was funded as a military alternative to the Double Mamba. The Coupled Naiad was specified for the Blackburn Y.B.5 and Y.B.7 aircraft... the latter a rival to the Gannet. The development programme for the Blackburn was protracted and as Gannet/Dble Mamba was developing reasonably the funding was withdrawn for Coupled Naiad.
The original Naiad had a nacelle design the embraced a ducted intake in the spinner. Flight published a cutaway of the arrangement in 1951, first pic below, and it was estimated that the ram effect was worth 19% more than a standard intake but at the expense of weight and a propensity to icing (tests were conducted on Lincoln..as we have noted the techniques were useful to Bristol when the Proteus on Britannia ran into problems).
....tbc
« Last Edit: September 13, 2012, 07:13:36 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #218 on: September 28, 2012, 12:32:36 pm »
After WW2 The design office at Napier worked on various engine schemes for aircraft English Electric were designing in response to Ministry Specs...none of them resulted in a project progressing beyond the scheme, although work continued on component research that led to various Private Ventures funded by EE. Alan Vessey's book 'By Precision into Power' covers the bicentennial history of Napier from Napier's point of view. The appendix lists the E numbers from the drawing office register started by A J Rowledge when he was chief designer at the Acton Works... E1 is dated 1916 and led to the Lion broad W range of aero engines. AJR left in 1921 and joined RR.
I have scanned the Jet Design Projects. I have no reason to believe RR took on any of these schemes. The bypass for instance was well under way before Napier's first scheme... I think it is just that both were responding to same specs and RR had a good relationship with EE.... so similar thermodynamic calcs would lead to similar solutions... but not the same!
......tbc
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Offline PMN1

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Re: Early British gas turbine development
« Reply #219 on: September 28, 2012, 02:19:09 pm »
Both engines had problems.... at the beginning of the War, on Hereford aircraft it would oil up and be difficult (=impossible) to start without taking out the lower sprk plugs and washing the out before refitting .. and don't hang about before opening the throttle!

From what i've read, the Daggers on Herefords also produced a whine that was intolerable after a very short time.

Offline alertken

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Re: Early British gas turbine development
« Reply #220 on: September 29, 2012, 08:07:10 am »
Let's go back to RR sampling Napier, as RB80 Conway. You discount this. My source, Putnam/HP,P.497 says in full "E.132 designed initially for 7,500lb...expected (soon) to reach 9,000 (about Spring,1948) RR undertook further development of (E.132) redesigned it at B'lick as RB.80/1." Just like you have been able to put right Bulman (on Sabre:Eagle), then mayhap CH Barnes is misled. Or maybe RR chose to broadcast its Napier origin to no-one other than AA.Griffith (who was given by-pass to occupy him, leaving proper folk to try to make AJ65 work).
 
What do we (think we) know? E.132 drew its compressor from Whittle W.2/700 and its by-pass (augmented; compound) scheme from Whittle L.R.1. In July,1947 MoS rejected the Short bid to (Medium Bomber, to be Victor/Vulcan) due to the unproven state of its engine (E.132). The EE bid was also rejected: it, naturally, had (EE) Napier E.132, but reason for deletion was to permit Petter to attend to A1. All this time we had neither money nor enemy. On 14/4/48 we acquired an enemy - Cabinet Tasking Chiefs to contain a Sov. thrust on N.Germany. MoS had organised 1/48 transfer of F.9 from MetroVick to ASM, to be Sapphire. What about me? might have been Hives reaction. Nothing from Brabazon. Hello! Vickers-Armstrongs won the third Medium 16/4/48, with AJ65. That was RR's first win since VJ Day. I have EE's Geo.Nelson selling E.132 to him there and then (where did I get that? Dunno now). So...
 
1. MoS paid for everything. PV R&D in UK aero-engine industry was, essentially, zero, ever. That's why Sapphire compressor later infused Avon, and why Fedden's sleeve-valves went to Napier, and...and...We owned it all.
2. What was ever actually unique, new, mine! And how long before it was sampled? And what do we mean when we say Whittle's this infused Napier's that? Paper schemes, bench/rig components; very little running of engines. What, exactly was passed to AA.Griffith to play with? Foo-foo valves and paper?
3. Let us not forget how modest were Aero's creative design/test resources: MoS considered EE/Preston's design team to be WEW.Petter. That's it.
 
Shall we assume that a (by-pass) pedigree flowed from Power Jets, through Napier, to RR, managed by MoS Gas Turbine Collaboration Committee, such that all Committee Members knew/could obtain access to all? So AA.Griffith could not have initiated Conway (as quickly, or as effectively) without Napier's riff. Barnes word "redesign" is too strong.
(F.Halford, onlie begetter of Sabre, designed H.1(Goblin)“from first principles,entirely independently of the Whittle concept” G.P.Bulman,An Account of Partnership,RRHT,2001,P.324. pace: H.1 “would not have been designed but for the stimulus and information provided by (W.1)” 2/10/47,Royal Commission on Awards to Inventors, awarding Sir FW £100K).
« Last Edit: September 29, 2012, 08:25:24 am by alertken »

Offline tartle

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Re: Early British gas turbine development
« Reply #221 on: September 29, 2012, 10:28:06 am »
Alertkin:
I don't yet know what E.132 looked like but I do know that RB80/1 was a scheme that looks remarkably like the drawings done for BJ 45 one of a series of drawings that to quote Don Eyre "led to the RB80" and I could not imagine Don copying anything .. so I stick with my theme ... Conway was a RR engine... but that doesn't mean they did not see E132 layout. I saw P&W layout when I worked on RB178.. but that is all.. you would not say that one begat the other.
Also there is a book written by Michael Schrage called 'Serious Play' . In one section of the book he talks of 'Model Building: an Invitation to Interaction' :
“The value of prototypes resides less in the models themselves than in the interactions - the conversations, [/size]arguments, consultations, collaborations -- they invite. Prototypes force individuals and institutions to confront the [/size]tyranny of trade-offs. That confrontation, in turn, forces people to play seriously with the difficult choices they must [/size]ultimately make. The fundamental question isn't, What kinds of models, prototypes and simulations should we be [/size]building? but, What kind of interactions do we want to create? The latter question aims at the heart of strategic [/size]introspection. Consequently, the design focus - the value emphasis - must be on the quantity and quality of human [/size]interactions that modelling media can support. Who should be working together? What should they be talking [/size]about? Who should see the model next?”

In conversations with him a sketch or design scheme, the first draft of a proposal would count as models that change conversations.
So as Drawings flow about the industry they have an effect on the people who study them.
You are also right to point out that the Ministry paid for much of this work on a cost plus basis, owning the Intellectual Property that resulted. As you say this means information could be transferred between 'rivals' . The sleeve valve information passed to Napier was proprietary to Bristol and the Board of Directors had to be persuaded to pass it to Napier. They could have refused although that might have been a bad move politically.
The transfer of Sapphire compressor data to RR came about after AS were ordered to do it by the Ministry who, in this case, owned the IP.
   
« Last Edit: September 29, 2012, 04:49:33 pm by tartle »
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Offline LowObservable

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Re: Early British gas turbine development
« Reply #222 on: September 29, 2012, 01:06:49 pm »
From what i've read, the Daggers on Herefords also produced a whine that was intolerable after a very short time.

Sounds like my ex. (Badum-ching, I'm LO and I'll be here all week. Try the veal.)

Offline tartle

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Re: Early British gas turbine development
« Reply #223 on: October 01, 2012, 01:53:39 am »
Alertken....
You are right that there are connections that enabled the industry to sample  and riff their way to some excellent engines.
This chart published by English Electric in a 1959 review of gas turbines written by W A Pennington shows the connections with the Whittle/RAE research centres... hope you like the colours!
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Offline tartle

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Re: Early British gas turbine development
« Reply #224 on: October 16, 2012, 02:08:34 pm »
Returning to the Tweed... a promising line of inquiry is the Saunders Roe archives.... if there are any. M J Brennan Assistant Chief Designer at SARO on the Princess recorded, in 1952, that" The determination of the best power unit whether piston, turboprop or turbojet poses the most fundamental problem of aircraft design and in truth is still subject to the skill and ingenuity of the designer concerned."

I did not realise that Princess did not come out of the Brabazon Committee's efforts, but from a commercial rivalry between Imperial Airways and Pan American.
In 1937 the two airlines were conducting flight surveys of the North Atlantic route with developed Empire Boats and Sikorsky 42s and later in 1939, when Pan Am had opened their first transatlantic service with Boeing 314s. The design staff at SARO were engaged on the study of a flying boat to meet the same requirements. A model, around 50% scale, was built and flown successfully- this was the SR37 with 4 Pobjoy engines. The war saw an end to this work but the data from the SR37 was used in the design and construction of the Shetland. In 1943 Brabazon Committee was determining post-war civil requirements but terms of reference did not cover flying boats. so separately a study was commissioned to provide the best spec for a N. Atlantic flying boat.
Saro's studies covered power arrangements using 6  and 8 Centaurus, and 6 RR Eagles.
Gas turbine's rapid evolution meant a new series of proposals with Clyde, Tweed, Python, Cobra and Proteus installations were worked up.
The final design proceeded in considerable detail with six coupled Tweed installations. But soon the Tweed was discontinued and the final choice of ten Proteus was made, with some hope that Brabazon would be able to build on the work to be undertaken by Bristol.... i.e. the Brabazon II.
So somewhere there may be papers on this original Princess arrangement.... more research continues!
« Last Edit: December 02, 2012, 09:54:53 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #225 on: December 10, 2012, 02:40:57 am »
An aside on the origins of the RB.80 Conway.
The E.132 of 1948 from Napier was the second compound or bypass engine to be designed; the first E.131 of 1947 had 2,000lb less thrust at 5,000 lbt.
Lovesey was working on his compound design in early 1945 and the first illustration made from the general arrangement was dated April 1945 This was the RCA4 which had an 10 stage axial hp spool driven by two turbine stages. The 4 stage LP compressor with by-pass was driven off the front of the HP compressor shaft via a gearbox. There was also a CR2 bypass layout using Griffith's contra concepts dated Feb 1945.
Napier were late into gas turbines as they had severe challenges with the Napier Sabre production and reliability as the engine was in quantity production before many of the the problems were ironed out. It is unlikely that they attended wartime meetings of the GTCC (I am hoping to check minutes of these meetings to confirm who was attending them shortly). So their Gas Turbine work did not really start until the cessation of the wartime effort on pistons. They then worked on turboprops and helicopter powerplants. I suspect work on pure jets/bypass were reference designs to ensure EE understood the offers from Bristol/RR.
The history of the RB. 80 has been described in previous posts.
....research continues!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #226 on: December 16, 2012, 10:47:45 am »
Hermione Giffard published her PhD thesis on 'The Development and Production of Turbojet Aero Engine History in Britain, Germany and the US'. Published in 2011, the researches begin in 1936 when the RAE began to increase its activity on aero gas turbines, leaving out Whittle's pioneering work before then and so biasing the whole story in favour of axials, treating centrifugals as an unimportant diversion [ Korean War??]. That said the factual parts of the research are useful, if not the conclusions drawnfrom them.... which is a shame.
....on Armstrong Siddeley (ASM):
It is clear from the research that  Armstrong Siddeley's entry into the gas turbine world was an eventful one.
MAP wanted to move AS into gas turbine development and persuaded them that it was in their best interests to abandon the Deerhound and Wolfhound and concentrate on gas turbines.
AS had a reputation for low power and reliability and the disappointing Deerhound made them sceptical about their development competence.
The logic of MAP was that ASM needed to sharpen up its development practices and to help them into the jet age suggested a collaboration with MetroVick (MV).  ASM would learn about the new engine form  and MV  benefit from ASM's expertise in lighter weight structures and production techniques necessary in the aero industry; in this way it was hoped the development of the F.2 could be accelerated, as it was promising but overweight.... trouble is if you introduce two dinosaurs you should not expect a gazelle.
ASM was invited to join the GTCC in Nov 1941 and they began to work with MV. The collaboration did not work as the MAP intended.
Metrovick insisted on retaining all the technical reponsibility for the engine and that ASMshould not undertake any redesign or modification work in connection with the actual unit.  This may have contributed to the failure of the F.2 engine to develop sufficiently to become a leading engine but it also prevented ASM learning rapidly about jet engines.
The situation could not have been helped by Heppner's ideas, driven by work on Griffith's concepts for contra-rotating engines, for a simpler layout of the basic concept. These designs were rejected by RAE as still being too complex and optimistic, since Heppner had assumed component performance and efficiencies far in excess of anything achieved by his contemporaries in Britain.
It took until mid-1942 for the MAP to persuade ASM to begin with a simple axial flow engine. The RAE volunteered to help ASM design an engine similar to the F.2 but incorporating their latest thinking. The result was the ASX which we have already discussed.
Heppner persisted with his ideas and ASM were rewarded, at this time, with a contract to start development... but as the RAE inspired ASX got going it was quietly shelved.
« Last Edit: January 22, 2013, 12:52:11 pm by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #227 on: January 08, 2013, 04:21:11 am »
Just thought I would add the very first design scheme that showed the initial layout of Dart.. from RRHT Historical Series No. 18 'The RR Dart pioneering turboprop' by Roy Heathcote. The book is a good description of the development process on the Dart up to the 1980's.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #228 on: January 22, 2013, 05:07:35 am »
The aerodynamic design Dart centrifugal compressors were based on the experimental results obtained from the latest thinking on the Merlin superchargers. The actual design was based on the characteristics used for the Eagle 22 supercharger design. Translated into hardware the imeller looks like the first picture below, taken from a series of articles on the manufacture of Dart components published in Aircraft Production Sept/Oct/Nov 1955.
Thirty years after that article RR having spent years making sure the safety and reliability of the Dart were second to none they realised that the 1980's competitors were more efficient (lower sfc) than their offer. An efficiency improvement  programme ensued leading to the Mk551 and 552 engines in 1984.
Redesigning the lp impeller within existing casing outlines and then rematching the turbines gave an improvement of 10% on the 551 and a further 3% on the 552. The improvement in compressor efficiency came from incorporating the latest small engine technology from the Leavesden team which was part of the assets acquired when Bristol Siddeley were taken over. RRHT HS18 by Roy Heathcote does in fact contain a great rendition of the Dart story ... I bought a copy last week!... the page showing the Leavesden impeller is below... note the grooved back face and integral RGVs on alternating vanes.
« Last Edit: January 22, 2013, 06:34:22 am by tartle »
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Offline tartle

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Re: Early British gas turbine development
« Reply #229 on: February 02, 2013, 01:30:40 pm »
One other thing on my list is the negotiations with DH over production of the gas turbines of MetroVick.. on my next visit to Kew I'll follow this up...unless someone out there already knows what this is about... bearing in mind the Air Ministry's view of how MV treated Armstrong Siddeley!
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline tartle

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Re: Early British gas turbine development
« Reply #230 on: March 13, 2013, 08:17:30 am »
I referred to the Dart compressor design using the latest technology from Leavesden SED; a decade and a half earlier in the late 60s-early 70's SED were facing challenges of their own when trying to develop the centrifugal compressor for the Gem- BS360.
During the same time period AiResearch were facing challenges with ntheir ATF-3 engine. This had a reasonable bypass performance but the core engine had a disappointing performance level. It was agreed that in return for a detail design of the GEM engine RR would redesign the ATF-3 compressor to achieve better core compressor efficiencies. This involved new fan aerodynamics with 30 or 33 blades and resculpting the inner and outer walls of swan neck duct at the rear of the fan hub to reduce losses.. this also involved changing the vane radial aerodynamics to match the new velocity profile. AiResearch carried out a major redesign of the ATF-3 in 1971 to build in RR recommendations as well as other improvements in the light of test bed running of protypes..
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #231 on: March 15, 2013, 07:20:21 am »
Ah, the ATF-3. I always wanted to place a speech balloon somewhere in the cutaway.

"Hi, I'm an air molecule and I am lost. My mommy said to go to the LPT but I don't (sniffle) know where it is."

The chief engineer was Tony DuPont, who later managed to sell DARPA on the concept of a magic engine that would give you runway-launched SSTO in a 50,000 pound vehicle. DARPA then sold it to Reagan's science advisor, and thus was begotten NASP.

Well, at least NASP was excellent cover for...  what's that black Suburban doing outs


CARRIER LOST

Offline tartle

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Re: Early British gas turbine development
« Reply #232 on: March 15, 2013, 06:42:07 pm »
Reminds me of the 'theory of random walks' p3 of this link describes the process that a confused molecule might take.
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline jmkorhonen

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Re: Early British gas turbine development
« Reply #233 on: March 26, 2013, 10:30:17 am »
Hi everyone,

had to register just to say thanks for the great read - or should I say a treasure trove of information!

Altho I do have a question, of sorts: I've been fascinated by the different routes that the German and British jet engine designers took at the time, in particular, the decisions about turbine cooling. I've done some reading on the subject - including the PhD thesis by Giffard mentioned above, which is a fine piece of writing - and know that raw material constraints (apparently, nickel in particular?) had a great impact on the German program, but what I'm trying to find is an explicit answer as to why the Brits didn't use internal cooling until, what, 1952? (RR experiments, mentioned in Gunston's The Development of Jet and Turbine Aero Engines). 

I believe and I guess most of the people in the know believe as well that the reason was the ready availability of creep-resistant alloys - they did the job, and cooling was superfluous - but has this been discussed anywhere in more detail?

Also, is anyone aware of any post-war jet engines or turbines that used the "German-style" hollow blades, i.e. either deep drawn or folded and welded from sheet metal? I've had the impression that post-war engines used forged or cast blades, but was that universal?

PS. part of my interest comes from an academic "hobby" - I'm writing a PhD thesis on the effects of constraints and scarcities on innovation. The German hollow blade designs have sometimes been used as an example of an innovation that was born because of the constraint; I'm trying to sharpen that particular theory a bit.

Offline tartle

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Re: Early British gas turbine development
« Reply #234 on: March 28, 2013, 06:34:10 pm »
The reason the UK did not use turbine blade cooling is because they did not need to! If you consider the thermodynamics of the gas turbine cycle then it becomes obvious that the pressure ratio and top temperature of the engine are related... I'll have to dig out my notes or maybe RR's Gas turbine book has the relevant stuff.... air cooling means bleeding off air  for that cooling which reduces the effectiveness of the compressor so one can weigh the economics of pressure needed for the air to flow through the blades, and exhaust into main gas stream and the cost/weight of the turbine blade with and without cooling passages. As we had better materials the need to cool did not need to be addressed until the early fifties when raising the turbine entry temperature and the pressure ratio was the best way to achieve the thrusts needed by the Hunter, etc.
Another way of looking at the problem is to look at the thermal efficiency of an engine and see how the various factors interplay... The equation for thermal efficiency [i.e. (Actual turbine work output- Actual Compressor work input)/(actual heat input) combines the parameters mass flow,temperatures, pressures, fuel/air ratios, compressor bleed flows, component efficiencies, specific heats so one can play with the relative effects of cooling etc.
....I'll scan in my notes on a way of looking at this... when I have found them!
In the meantime here is a page from a Lovesey paper on an interesting way of cooling a turbine!
In the meantime it might be worth looking at 16th Barnwell Memorial Lecture 'Propulsion Prospects' by G. H. Weir on 12 March 1969... RAeS, Fig 1-7 show how the various thermodynamic and material parameters combine.
To sum up WW" German vs British approaches to engine structural innovation:
The Germans had no option; we had options on whether to use blade and vane cooling.
« Last Edit: March 28, 2013, 06:40:45 pm by tartle »
"... prototypes are a way of letting you think out loud. You want the right people to think aloud with you.” - Paul MacCready, aeronautical engineer.

Offline LowObservable

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Re: Early British gas turbine development
« Reply #235 on: March 29, 2013, 08:51:45 am »
Exactly. I remember being surprised to look at a Jumo 004 (Science Museum or Dayton, can't remember) and seeing cooling holes.

I also recall being told at P&W, when they were just starting single-crystal blades, that one of the benefits was being able to cast the blade in two halves with a lengthwise split (like the wing of a model kit) which made it possible to cast intricate cooling passages into the mating surface, and thus get better cooling without using more air.

Offline jmkorhonen

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Re: Early British gas turbine development
« Reply #236 on: April 02, 2013, 12:09:59 am »
The reason the UK did not use turbine blade cooling is because they did not need to! If you consider the thermodynamics of the gas turbine cycle then it becomes obvious that the pressure ratio and top temperature of the engine are related... I'll have to dig out my notes or maybe RR's Gas turbine book has the relevant stuff.... air cooling means bleeding off air  for that cooling which reduces the effectiveness of the compressor so one can weigh the economics of pressure needed for the air to flow through the blades, and exhaust into main gas stream and the cost/weight of the turbine blade with and without cooling passages. As we had better materials the need to cool did not need to be addressed until the early fifties when raising the turbine entry temperature and the pressure ratio was the best way to achieve the thrusts needed by the Hunter, etc.
Another way of looking at the problem is to look at the thermal efficiency of an engine and see how the various factors interplay... The equation for thermal efficiency [i.e. (Actual turbine work output- Actual Compressor work input)/(actual heat input) combines the parameters mass flow,temperatures, pressures, fuel/air ratios, compressor bleed flows, component efficiencies, specific heats so one can play with the relative effects of cooling etc.

Excellent explanation, thank you! Exactly the answer I was looking for :). If you manage to scan your notes, they would be much appreciated as well!

One question, though: is it absolutely necessary to use compressor bleed air for cooling? I (of course) read Antony Kay's book "German jet engine development 1930-1945," and there is a mention about Porsche 109-005 "disposable" jet engine, intended for longer-ranged V-1's. The text mentions that the turbine blades had internal cooling as per BMW 003's, but that the cooling air was not ducted from the compressor; instead, it was scooped via simple inlet. I would guess that this would be adequate given the short lifetime of the missile, but problematic with larger engines intended for aircraft?

Offline red admiral

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Re: Early British gas turbine development
« Reply #237 on: April 02, 2013, 12:16:24 pm »

One question, though: is it absolutely necessary to use compressor bleed air for cooling?

It helps to have a think back to the gas turbine cycle. The compressor compresses the air so that the highest pressure air is at the end of the compressor just before entering the combustion chamber. Heat is then added and the air is expanded through the turbine. Whilst the air is running through the turbine, the pressure is decreasing.

The turbine stage next to the combustion chamber will require the most cooling airflow, but because of the proximity to the combustion chamber, the air pressure is still high. Hence, a higher pressure cooling air source is required in order to overcome the air pressure at the turbine. Connecting the turbine cooling holes with the atmosphere would result in hot air from the turbine escaping to the atmosphere - exactly the opposite of what is required.

I'm surprised about your mention of the 005 engine having an external ram scoop for cooling air. I could concieve that this would possibly work if the engine flew fast enough and had a very low pressure ratio, but this makes for very poor fuel efficiency - not that this is necessarily required for a disposable engine.

Offline jmkorhonen

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