Any WW2 italian gas turbine?

ceccherini

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In a topic in the "early projects" section, I've seen a reference to a R-2000 Italian turboprop of WW2 vintage. That mention arouse in me a question: why Italy was the first to actively research some kind of jet engine but at the same time the only great power apparently not having some research on gas turbines? It's because they invested hard in the dead end motorjet technology or some studies actually existed but are unreported? I know of the critical shortage of the required metals but having perhaps the largest and most modern prewar aero research center, that of Guidonia Montecelio, spending a vast amount of money to purse record planes, even at the expense of operational ones, and not coming at least with some appreciation of the technical possibility to built a turbojet seems quite strange.
 

Dilandu

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but at the same time the only great power apparently not having some research on gas turbines?

Gas turbines required VERY advanced metallurgy to be efficient and durable. In late 1930s - early 1940s, essentially only one country have the metallurgy level required. It was Great Britain.

A clear demonstration of what happens when you build gas turbines with inadequate metallurgy is Germany's jet program. German WW2 turbojets were hopeless; unreliable, underpowered, with ridiculously short service life.
 

ceccherini

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but at the same time the only great power apparently not having some research on gas turbines?

Gas turbines required VERY advanced metallurgy to be efficient and durable. In late 1930s - early 1940s, essentially only one country have the metallurgy level required. It was Great Britain.

A clear demonstration of what happens when you build gas turbines with inadequate metallurgy is Germany's jet program. German WW2 turbojets were hopeless; unreliable, underpowered, with ridiculously short service life.
I'm just talking of theoretical studies on the subject, something nations with similar technological limitations like USSR, Japan and France and even Hungary notoriously did in late '30/early '40.
 

Dilandu

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I'm just talking of theoretical studies on the subject, something nations with similar technological limitations like USSR, Japan and France and even Hungary notoriously did in late '30/early '40.

Well, from 1930s positions, motorjets represented more available technology, that could be made work in short time. Turbojets were much more theoretical. Logically, motorjets were supposed to be the immediate next step in aircraft powerplant evolution, but World War 2 mixed up the situation...
 

T. A. Gardner

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The Italians could have done quite a bit more with the motorjet to make it more competitive. One reason the CC 2 didn't produce as much thrust as it might have, was the compressor section (shown here)

1616351196918.png

was designed as a ducted fan rather than a turbine so the compression ratio was far lower than it might have been. The Soviet motorjets, like the VRDK (Vozdushno Reaktivny Dvigatel Kompressornyi) used a smaller duct and a compressor more like on a turbojet.

A logical step forward for the Italians would have been to create a much more efficient compressor section based on their extant technology. A more efficient motorjet likely could have gotten them to around 500 mph in an aircraft.

The other issue they'd have to overcome is materials in the combustion and exhaust sections of the engine where heating proved a major issue both for the aircrew and for the engine itself. The Soviets had the same issue with their motorjet designs.

So, while I don't think the Italians managed a turbojet during WW 2, they certainly could have done a lot more with a motorjet.
 

Dilandu

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Actually, motorjet (potentially) have one advantage over turbojet in 1940s - it was more suitable for cruising flight, which could be done on propeller, with jet switched on for combat. Early turbojets were notorious fuel consumers, which seriously limited the range.
 

T. A. Gardner

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Actually, motorjet (potentially) have one advantage over turbojet in 1940s - it was more suitable for cruising flight, which could be done on propeller, with jet switched on for combat. Early turbojets were notorious fuel consumers, which seriously limited the range.
The problem with this is, as the Soviets discovered, was that the added weight of the jet portion of such designs imposed a penalty on the aircraft in terms of performance when it wasn't in use. The Soviet engineers working on the MiG 13 and Su-5 tried various things to make this less of an issue but couldn't work around it in the end.
On the Soviet planes the radiator was put in the duct behind the compressor for more efficient heat exchange and the engine supercharger drew air that had been compressed from it increasing its efficiency. But these were small benefits on the whole.

A pure motorjet like the Caproni N1 on the other hand could have been a viable fighter plane with more development. Since the compressor section isn't prone to stalling and wouldn't need the careful blade profiling turbojets did, it would be a shortcut to a jet fighter of around 500 mph in performance. It's certainly something the Italians could have used in 1942 or 43 and likely could have been developed by then.

Something like the proposed Reggiane Re. 2007 could have used a motorjet rather than a German Jumo 004 turbojet for example

1616378569232.png

Late in WW 2, and in the immediate postwar years, a number of mixed / hybrid propulsion aircraft were tested particularly in the Soviet Union and the US. The same problem kept cropping up. When run on one engine, the other(s) were simply dead weight and drag that hurt overall performance making them undesirable. For a motorjet to work well it would have to be built as purely a motorjet rather than some hybrid aircraft.
 

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This is the Soviet VRDK engine. As you can see, the Soviets built in a much better compressor section that was more like a turbine than a ducted fan

1616392646224.png

Here is the internal layout in the MiG 13. As you can clearly see, one serious issue is the combustion chamber is right under the pilot's seat...

1616392709541.png
Of course, we shouldn't forget that Japan late in the war also developed a motorjet the Tsu 11 for use in MXY 7 Oka Model 22 suicide bomb-plane. This choice while inferior to performance to the rocket powered models, had a much longer powered range meaning it could be released earlier giving it and the mother plane a higher chance of evading USN CAP fighters.
 

sienar

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but at the same time the only great power apparently not having some research on gas turbines?

Gas turbines required VERY advanced metallurgy to be efficient and durable. In late 1930s - early 1940s, essentially only one country have the metallurgy level required. It was Great Britain.

A clear demonstration of what happens when you build gas turbines with inadequate metallurgy is Germany's jet program. German WW2 turbojets were hopeless; unreliable, underpowered, with ridiculously short service life.

Why do you think only the UK had the requisite knowledge? And why do you think it was metallurgy holding the Germans back?
 

archipeppe

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A logical step forward for the Italians would have been to create a much more efficient compressor section based on their extant technology. A more efficient motorjet likely could have gotten them to around 500 mph in an aircraft.
Ing. Secondo Campini worked on such solution up to the War's end.

Anyway as you already pointed out Italians were conceptually at the same level of English and Germans but the general know how was poorer, this explain also why late wartime projects relyed on German jet engines.

This situation continued even after the wartimes and also today, even if Italian propulsion industry (generally speaking) obtained outstanding results in automotive (e.g. Ferrari) it remanined confined in aerospace to turboprop, never developing a true national jet engine (like France or Sweden).

All the 50's and 60's projects (both Aermacchi and FIAT) relyed on British engines.
 

Archibald

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but at the same time the only great power apparently not having some research on gas turbines?

Gas turbines required VERY advanced metallurgy to be efficient and durable. In late 1930s - early 1940s, essentially only one country have the metallurgy level required. It was Great Britain.

A clear demonstration of what happens when you build gas turbines with inadequate metallurgy is Germany's jet program. German WW2 turbojets were hopeless; unreliable, underpowered, with ridiculously short service life.

Why do you think only the UK had the requisite knowledge? And why do you think it was metallurgy holding the Germans back?

-Sensaud de Lavaud and Brunet
-René Anxionnaz et Sedille
-René Leduc

All three worked on turbojets (and ramjets) right from 1937 in France. Sensaud de Lavaud got a prototype running the same year as von Ohain and Whittle, 1937.
 

Archibald

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Now, considering the absolute and complete Kafka-like mess that was 1938 French military aviation at every single level (politicians, engineers, workers, aviators... all equally blind and deaf to the incoming Azincourt / Crecy -class military disasterrushing toward them in May 1940) - there was little time and resources for early turbojet research.
 

Grey Havoc

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Not all of them, but those who could see the oncoming train were generally told to sit down and shut up, so to speak.
 

Archibald

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Fair enough - but I'm not even sure ! Fundamentally, 1938 France main issue was [insert scapegoat here] instead of "solve all the problems sending the country into a brickwall".

Typical conversation in 1938 France

"Nothing works in that damn [country / army / government / industry]"
"Maybe we should try and improve things !"
"Nah, let's blame [insert scapegoat here according to your political feelings]
(Short list:
free masons ! jews ! communists ! fifth column ! laicity ! corrupt politicians ! democracy ! agonizing 3rd republic!)



I don't want to hijack this thread further so I'll stop right here, sorry !
 

Dilandu

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Why do you think only the UK had the requisite knowledge? And why do you think it was metallurgy holding the Germans back?
As far as I know, only Britain was able to produce reliable gas turbines at this time, and its level of metallurgy was truly superior. Even US was forced to rely on British assistance in creating turbojets.
 

T. A. Gardner

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but at the same time the only great power apparently not having some research on gas turbines?

Gas turbines required VERY advanced metallurgy to be efficient and durable. In late 1930s - early 1940s, essentially only one country have the metallurgy level required. It was Great Britain.

A clear demonstration of what happens when you build gas turbines with inadequate metallurgy is Germany's jet program. German WW2 turbojets were hopeless; unreliable, underpowered, with ridiculously short service life.

Why do you think only the UK had the requisite knowledge? And why do you think it was metallurgy holding the Germans back?
On gas turbines, Brown Boveri in Switzerland was at least as advanced, and in some ways ahead of the British. This company produced the world's first supersonic wind tunnel designed by Jacob Ackeret for testing of compressibility of airfoils in steam turbines and turbochargers. This was in the late 20's - early 30's. They were at least as far advanced as Griffith was in England. By WW 2, Brown Boveri had one of the, if not the, largest collections of data on turbine blade profiles in Europe.
While this company had little interest in turbojets, their data proved critical to the German effort to build theirs during the war.

In the US, Stanford Moss at GE arguably placed the first patent on a gas turbine in 1904 and by 1940 had easily the largest collection of data on gas turbine compressor blade airfoils in the world. Moss and GE's interests too were not in building a turbojet but rather something akin to a turboprop--that is shaft horsepower like a steam turbine--and turbochargers for aircraft. In turbocharging this is why the US could make such liberal use of them reliably in aircraft during the war.

GE's database on blade profiles was what made it possible for the US to quickly start turning out reasonably efficient and reliable turbojet designs of their own once the British showed them a working one. It wasn't that the US, or Switzerland, France, etc., didn't have data on the essential components of a turbojet, but rather the application of gas turbines to aircraft was something they hadn't considered.

In France, Rene Armengaud and Charles Lemale at Rateau worked on gas turbines to much the same effect as Ackeret and Moss did. Armengaud died in 1909 and the work at Rateau on these fell to a minimum.

Certainly in metallurgy the US was right with Britain and had access to the necessary metals to alloy these. Germany's issue during the war was simply a lack of sources to get the requisite metals to make high temperature alloys in quantity. It was also a matter of how German laws governed corporations. Monopolies were allowed in Germany at the time for example. This can be seen in the tungsten carbide industry for example.

In Germany, Krupp held patents on manufacture of tungsten carbide. Their subsidiary, Hartzmetallzentral (I think I spelled that right) was the sole supplier of TC in Germany. They made just three grades and would only supply one grade to any company other than Krupp. This pretty much made TC both expensive and inaccessible to most companies in Germany.
In the US there were dozens of companies making TC by the late 30's. With WW 2, the US settled on a standard based on Buick's grading system of fifteen grades of tungsten carbide. This made the product widely available.
The same goes for a whole range of tool steels, high temperature alloys, etc. Germany brought some of their shortage on themselves by government policy.
 

sienar

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Why do you think only the UK had the requisite knowledge? And why do you think it was metallurgy holding the Germans back?
As far as I know, only Britain was able to produce reliable gas turbines at this time, and its level of metallurgy was truly superior. Even US was forced to rely on British assistance in creating turbojets.

German issues with alloys had nothing to do with metallurgy though, it was all about supply mostly of chromium and nickle.

The US was the only country to mass produce turbocharged aircraft during the war. The operating conditions and alloy requirements of turbos aren't that far off centrifugal jets. While it is true that the UK provided plenty of jet development assistance to the US I've never heard of alloys being a part of that.

Lastly it is my understanding that the USSR was something of leader in metallurgy during the 30s. Maybe thats no longer the case by WW2 but they didn't seem to have much trouble making jet copies during and right after the war.
 

T. A. Gardner

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An interesting bit of trivia here is that when Johns Hopkins was looking for a ready made source of high temperature tubing for making ramjet engines as part of project Bumblebee (eventually the Talos missile), they selected P-47 exhaust pipes as their go-to for their Cobra Test Vehicles (CTV).

1616445632042.png
A Cobra or Burner test vehicle (BTV is larger in diameter) at Topsail Island NC circa 1945 - 46

If you note, the FW 190C that was tried with turbocharging failed in part because the exhaust pipes couldn't take high temperatures, whereas the US was using high temperature alloys in their exhaust pipes to avoid this problem. That's some indication of how much more material was available to the US.
 

red admiral

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German issues with alloys had nothing to do with metallurgy though, it was all about supply mostly of chromium and nickle.
I don't understand this. I don't remember any evidence Germany or anyone else outside UK and US developed nickel based superalloys, even in tiny amounts.

But then the early German efforts at blade cooling were innovative

I think that you can probably make the case that high temp stainless steels and maybe a bit of cooling were adequate for your typical WW2 use case


Back to Italian turbojets, I don't think i've seen hints of these before
 

T. A. Gardner

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German issues with alloys had nothing to do with metallurgy though, it was all about supply mostly of chromium and nickle.
I don't understand this. I don't remember any evidence Germany or anyone else outside UK and US developed nickel based superalloys, even in tiny amounts.

But then the early German efforts at blade cooling were innovative

I think that you can probably make the case that high temp stainless steels and maybe a bit of cooling were adequate for your typical WW2 use case


Back to Italian turbojets, I don't think i've seen hints of these before
Exactly. High temperature stainless steels would have been sufficient for German turbojets. With bleed air cooling of the turbine blades as Junkers did in the 004 stainless would have worked fine, particularly when flame sprayed with alumina as the Germans (and others did). It was just their use of regular low carbon steels that was an issue.
 
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