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Aerion SBJ

NUSNA_Moebius

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That bypass is huge for something expected to be supersonic. Can the special mixing nozzle somehow be adding energy to the bypass flow via entrainment of some sorts? Maybe there is a variable bypass system GE is keeping hush hush, or the double fan stage actually is producing the bypass air velocities needed to deliver supersonic achieving thrust, which may require some advanced convergent shaping. The use of a carbon fibre outer casing might be a clue to the kinds of pressures (or technically lack there of taking Bernoulli into account) it's expected to endure with two powerful fan stages driving such an insane amount of bypass air, at supersonic RPMs like some high bypass turbofans do at takeoff power. The noise is of course contained within the casing.

I think the secret is the bypass shoving air down fast enough (read: fast) so that the hot core mixing can keep it energized enough to maintain fast mixed flows. It explains the special core exhaust nozzle shaping. Just look at how deep the exhaust grooves get, almost touching the nozzle cone. What I assume is the slower bypass air flowing along the core casing is being given the most entrenchment into the exhaust so it's given the most exhaust energy. The top of the nozzle tips almost look like they're trying to keep the outer bypass flow from mixing too much, or it could be for efficient bypass flow for subsonic flight.

Too bad GE will probably keep it secret for the meantime. But it's quite 'purdy B)
 

TomS

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More details from AvLeak:

http://aviationweek.com/nbaa-2018/ge-shows-affinity-supersonics

The Affinity is configured with a two-stage fan, a nine-stage HP compressor, a single-stage HP turbine and a two-stage low-pressure turbine. Distinguished externally by an extended, low-drag spinner and a set of fixed inlet guide vanes with movable flaps, the low-pressure system comprises two stages of wide-chord, integrally bladed – or blisked – titanium fan blades.

The aft end of the engine incorporates a sophisticated exhaust mixer resembling the ceramic matrix composite-made design used in GE’s Passport. The annular combustor is designed for supercruising (the term describes sustained supersonic performance without afterburner), while the HP turbine and stator are protected by an advanced thermal barrier coating. To reduce cross-sectional area, the engine is contained in a slimline carbon-fiber casing.
http://aviationweek.com/nbaa-2018/why-ge-s-affinity-supersonic-enabler

While further details are scant, the variable-nozzle design is believed to be centered on an external-expanding, or plug, nozzle which consists of a central axi-symmetric plug that translates fore and aft, depending on the phase of flight. The plug sits in the freely expanding supersonic jet and replaces more usual designs, such as convergent-divergent nozzle, as a means of containing the expansion.
I'm not enough of an aero-engine geek to parse this well, but hopefully it makes sense to someone here who can break it down for the laymen.
 

NUSNA_Moebius

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TomS said:
http://aviationweek.com/nbaa-2018/why-ge-s-affinity-supersonic-enabler

While further details are scant, the variable-nozzle design is believed to be centered on an external-expanding, or plug, nozzle which consists of a central axi-symmetric plug that translates fore and aft, depending on the phase of flight. The plug sits in the freely expanding supersonic jet and replaces more usual designs, such as convergent-divergent nozzle, as a means of containing the expansion.
I'm not enough of an aero-engine geek to parse this well, but hopefully it makes sense to someone here who can break it down for the laymen.
Judging by the pictures of the engine without the extension:



vs with........



........there indeed is core and bypass intermixing before it hits the exhaust nozzle + plug. I think I'll just call it the Zweibel like the Germans did! Though of course previous plugs were essentially part of the engine central assembly and the addition of afterburners made integrating such a thing difficult. Hence convergent divergent nozzles becoming the standard, but I'm somewhat surprised Zweibel nozzles didn't really catch on for non-afterburning engines.

It's only too bad there is going to be a logical limit in speed this engine can deliver, but it provides the subsonic efficiency low bypass types cannot. I wonder if this engine would suit Boom Technologies' needs as they are targeting Mach 2.2, not 1.4.
 

Trident

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http://www.leteckemotory.cz/motory/nk-144/rd36_01.jpg

https://a.d-cd.net/5e44b0ds-1920.jpg

:)
 

Racer

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The Affinity reminds me very much of GE F101 without afterburner.
 

djfawcett

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It should, the Affinity is basically the same core as the F101 with a different fan setup.
 

Archibald

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Ha ! And General Electric F101 core was the basis of the... CFM56, in 1974 ! This caused seemingly endless troubles when the U.S military put pressure on Nixon and Kissinger and they blocked technology transfers to SNECMA. Until Pompidou met Nixon in may 1973 and banged his fist on the table.

So it makes some sense to start from CFM56 - and move back toward the F101 core.

Except that, Aerion now has to assume the cost burden of funding a new engine for its project. This sunk Dassault SSBJ back in 1998, when the M88 core proved unowrkable into a civilian engine. Think Ferrari V-12s for Formula One and road cars - they are essentially separated developments.

So it essentially boils down to finding the best compromise between a CFM56 and a F101. Clever reasonning from both GE and Aerion, let's see if they can pull it out.

...and by the way, I've been ninja'd by TomS over the CFM56 connection. :D
 

Archibald

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Only a casual glance at Wikipedia show the severe limitations of both AS2 and Affinity.

https://en.wikipedia.org/wiki/General_Electric_Affinity

https://en.wikipedia.org/wiki/Aerion_AS2

Noise, speed, range, fuel consumption... all conflict with each others. Hard, very hard tradeoffs. I really wonder if they can pull it out. Technically, yes. Commercially ? I have doubts.

For example, mach 1.2 to mach 1.4 top speed - will it really makes a difference big enough with a mach 0.92 Cessna Citation ? Can't help thinking about Boeing Sonic Cruiser. Speed really didn't paid with this one.
 

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Archibald said:
For example, mach 1.2 to mach 1.4 top speed - will it really makes a difference big enough with a mach 0.92 Cessna Citation ?
Cost wise, being able to fly from NY to London and back in a single day will do the trick. Unless Boom of course succeed in a similar time frame.
 

aeroengineer1

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Often times, things succeed because it is not only the right technology, but also at the right time. Sonic Cruiser was an example of this. It had the tech, but then 9/11 happened, and many, many things changed. In the case of Aerion, they may be able to make it work. I am not too worried about the engine tech. This is essentially a derivative engine. Airframe integration will be the harder part of it.

As for if Mach .92 vs Mach 1.4 will make a difference, well you will get there 40-50% faster. Heck when we drive on the road, we are content to do 10-15% faster. This essentially means that a person can leave the East Coast of the US, and be in London in about 4-4.5 hours vs the typical 7 hours. It is now possible to do the flight, with a couple of hours of meetings, then return in the same day, and only have a 12-14 hour day. This can be done, vs an 18-20 hour day which is less likely. Admittedly, the market is going to be small, but it will be there. The bigger question is if it is financially viable.
 

Trident

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... and lowering ambition to a Mach 1.4 top speed takes care of the airframe integration challenge to some extent, because they get away with fixed normal shock intakes.
 

Sundog

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Trident said:
... and lowering ambition to a Mach 1.4 top speed takes care of the airframe integration challenge to some extent, because they get away with fixed normal shock intakes.
The Aerion does have fixed inlets, but they aren't normal shocks, they're actually swept, so they are 2D shocks, which makes them more efficient. The real savings in terms of keeping the speed in the mid Mach number region, between one and two, is in materials. They don't require exotic materials to handle thermal loads.
 

Trident

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Sundog said:
The Aerion does have fixed inlets, but they aren't normal shocks, they're actually swept, so they are 2D shocks, which makes them more efficient. The real savings in terms of keeping the speed in the mid Mach number region, between one and two, is in materials. They don't require exotic materials to handle thermal loads.
While the cowl is swept, cross section is round, so I'm having some trouble working out how an oblique shock is supposed to form without a conical centerbody? At these low Mach numbers the ramp/cone angle would also have to be extremely shallow (<9.5° wedge) which may conflict with the relatively blunt lip radius seen in the CGI pictures. In this Mach range you seem to get a normal shock if you so much as look at the flow the wrong way, and the total pressure recovery difference between a 5° wedge with oblique+normal shock and a normal shock is only ~1.5% (M=1.4, below this the difference would be even less) anyhow.

I suspect the sweep may be more related to high AoA take-off/landing conditions (and possibly noise, for the inverse sweep intake on the centerline engine). Materials is a good point though!
 

fredymac

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Some details on the engine.

https://www.youtube.com/watch?v=TC6utYmM4_o
 

LowObservable

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You have to give the guys some credit for forming partnerships with Airbus, LockMart, GE and then Boeing before they cut metal.
 

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Except that LM, Boeing and GE came to finalize the design where Airbus jumped out having achieved not much (at least, not the propulsion solution, neither advanced anything around the Laminar wing and not conducted any system integration)...

I wonder if Boeing is not there to provide its expertise in designing large and complex fuselage sections at low cost.
 

Arjen

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FINALIZE the design? Aerion and its predecessor have been at it for decades now, who knows when this will take to the air? If ever?
 

TomcatViP

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I have to admit the use of an assertive form was a big step into the unknown.
 

Arjen

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Does assertive apply to Aerion's design or to your use of language? Honest question.
 

djfawcett

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Has anybody seen the new configuration released by Aerion in the last several days? My understanding it differs dramatically from previous designs.
 

djfawcett

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Looks like Boeing took Tracy's low sweep, ultra thin, supersonic laminar flow wing and threw it out with the baby water. That is what the entire Aerion program was based on since day one ....... Tracy's career work. I wonder if the boys proved that it would not be feasible for day to day operations, or that upper management thought it was too high risk, like excessive software testing ;) .
 

Sundog

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I wonder if they found the market wasn't interested in "no boom" overland at the Mach cut off and said they would simply rather have higher speed over water?
 

djfawcett

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The reasoning could be any or all the above. But I bet a big contributing factor is the way drag of the unswept trap wing in the trans sonic area. Right where they plan to fly boomless over land. I do find interesting that the new plan form is very reminiscent of the JAXA plan form being investigated for supersonic transport, which interestingly been described as having laminar flow.
 

Sundog

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The reasoning could be any or all the above. But I bet a big contributing factor is the way drag of the unswept trap wing in the trans sonic area. Right where they plan to fly boomless over land. I do find interesting that the new plan form is very reminiscent of the JAXA plan form being investigated for supersonic transport, which interestingly been described as having laminar flow.
The trapezoidal wing planform is the best layout (minimum wave drag) for flying near Mach 1. It's why so many fighters use that layout. It's excellent in the transonic region. The only reason to go to the higher swept arrow wing is for higher speeds.
 

djfawcett

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I would agree with you if it is a swept trap wing. But, if it is a low swept leading edge trap, I will have to respectfully disagree. However, you very well may be right about the reason since the intake has been changed to include a shock cone, and no longer is a simple pitot. So higher mach may indeed be the reason.
 

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Meanwhile their website is unreachable. They're probably reworking it with new artwork and such... Hopefully.
 

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...or that upper management thought it was too high risk, like excessive software testing ;) .
Based on recent history, I fear that this is indeed the correct explanation.
 

LowObservable

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It seems unfortunately that the mission requires some form of wide-range variable-cycle propulsion system.
 

Sundog

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I would agree with you if it is a swept trap wing. But, if it is a low swept leading edge trap, I will have to respectfully disagree. However, you very well may be right about the reason since the intake has been changed to include a shock cone, and no longer is a simple pitot. So higher mach may indeed be the reason.
Well, as someone who has designed aircraft like this before, just when I was working on my degree, there isn't a low swept leading edge trap. The Aerion was originally designed for a very low max supersonic speed. The F/A-18, the F-5, and the F-35 were all designed to be faster and they didn't have any problem with low sweep leading edges. The trapezoidal layout is the ideal layout to minimize wave drag at transonic speeds, which is precisely where they were poised to operate with the original design. This new design tells me they are aiming for the heart of the supersonic drag bucket instead.
 

djfawcett

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Again, I agree in part, but also disagree in other parts. With that being said, I have no interest in engaging a none ending discussion like on the JMR & FVL thread, which is now bordering on insanity. What I do have interest in is that Aerion made a dramatic change by moving away from Tracy career research, even after 15 years of design development for the AS2. All along, the secret sauce was the advantages of laminar flow in Tracy's design where he deemed his design superior to high swept wings (delta, cranked arrow, etc.) in everything but wave drag.
 

TomS

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It seems unfortunately that the mission requires some form of wide-range variable-cycle propulsion system.
They've been pretty consistently saying that it needs fairly conventional engines -- initially JT8Ds but now CFM56-derived Affinity medium bypass turbofans. The speed regime isn't terribly extreme, so I don't see what would force anything exotic like variable-cycle engines.
 

TomS

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I wonder if they found the market wasn't interested in "no boom" overland at the Mach cut off and said they would simply rather have higher speed over water?
Article says they are looking at M1.2 boomless over land, exploiting the Mach trap that keeps the boom from reaching the ground. It also gives a maximum speed of M1.6, which I think is a subtle upgrade from the earlier M1.4 and may contribute to the planform change.

(As noted in another thread, the current issue is downloadable here: https://aviationweek.com/awst_current)
 

TomcatViP

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Thank you. Much appreciated.

So, at the end, the 2020s laminar flow strait wing wonder is just a souped-up 1956 Hustler with a cranked delta?
 

Grey Havoc

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Thank you. Much appreciated.

So, at the end, the 2020s laminar flow strait wing wonder is just a souped-up 1956 Hustler with a cranked delta?
That would seem to be Boeing's preferred approach. Of course, they have been making a lot of poor calls of late...
 
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