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By: - 14th April 2015 at 10:59 Permalink - Edited 1st January 1970 at 01:00
Is the promise of adaptive cycle engines all that they're cracked up to be? The pentagon seems sold sold on the idea as a total game changer. Are Russians and Chinese working on their own versions?What would a fully developed adaptive cycle engines allow a 6th generation fighter to do that current design don't. Will the over complication and weight nullify the advantages?
It sounds like you already made up your mind. But, eh, I will give it an answer.
Adaptive cycle engine can adjust its optimum point. In the end, this saves fuel. Fuel is weight and all aircraft would love to be lighter. Even if the actual fuel carried remains the same, if you can eke out another hundred miles of combat radius, it would be very tempting. Of course we will have to see whether the savings outweighs the increased cost and complexity, but Pentagon wants to give it a try. If you don't, well, dunno. What can you do, eh?
By: - 14th April 2015 at 11:14 Permalink - Edited 1st January 1970 at 01:00
From what I understand the adaptive engine will need a lot of airflow to optimize its subsonic regime. That means a large intake so more drag. I would guess the effect would be worse in transsonic/supersonic. But the engine produces more thrust at high speed so it is likely to more than compensate.
My 2 cents...
By: - 14th April 2015 at 12:15 Permalink - Edited 1st January 1970 at 01:00
Is it likely that 6th generation aircraft will incorporate adaptive cycle engines with thrust vectoring and stealth? what other "givens" will the 6th generation fighters have?
By: - 14th April 2015 at 12:37 Permalink - Edited 1st January 1970 at 01:00
http://forum.keypublishing.com/showthread.php?123081-Rise-of-the-6th-Generation-Fighter
By: - 15th April 2015 at 03:52 Permalink - Edited 1st January 1970 at 01:00
That all aside. Are adaptive engines the future of all future fighters?
By: - 15th April 2015 at 14:43 Permalink - Edited 1st January 1970 at 01:00
F135 in F-35B is an adaptive engine. At the push of a button, it goes from low bypass turbofan to high bypass turbofan and back again.
F120 for the ATF program was a valiant attempt at a variable cycle engine. The variable area bypass doors allowed it to vary bypass ratio depending on airspeed, altitude and thrust demand.
By: - 15th April 2015 at 15:32 Permalink - Edited 1st January 1970 at 01:00
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790014913.pdf
Is it likely that 6th generation aircraft will incorporate adaptive cycle engines with thrust vectoring and stealth? what other "givens" will the 6th generation fighters have?
Its a vague question. They have been the "future" since the 80s if not earlier. Similarly, hypersonic has been the future for the last few decades, Ceramic matrix composites have been the future of turbine blades for a few decades as well (and are now showing up) etc etc. Some will claim the J58 was a variable cycle engine. Ultimately, you have to develop it, put it on a platform, test it and build a lot of them. The funding for the ADVENT, AETD and the expected funding for the AETP are very encouraging but the proof is in the eating.
By: - 15th April 2015 at 18:09 Permalink - Edited 1st January 1970 at 01:00
F135 in F-35B is an adaptive engine. At the push of a button, it goes from low bypass turbofan to high bypass turbofan and back again.F120 for the ATF program was a valiant attempt at a variable cycle engine. The variable area bypass doors allowed it to vary bypass ratio depending on airspeed, altitude and thrust demand.
Aswell as M53-P2 btw, not a real new idea.
By: - 15th April 2015 at 23:08 Permalink - Edited 1st January 1970 at 01:00
So what's the big deal? If the basic technology is already proven and and in production. It seems that there is a huge amount of controversy surrounding the funding of the ADVENT and AETD programs. Is it just because they're slated to "save" the F-135 Lightning?
By: - 15th April 2015 at 23:42 Permalink - Edited 1st January 1970 at 01:00
So what's the big deal? If the basic technology is already proven and and in production. It seems that there is a huge amount of controversy surrounding the funding of the ADVENT and AETD programs.
There was absolutely no controversy surrounding either of these programs.
So what's the big deal?
The big deal is their ability to offer 20-30% improvements in fuel consumption and be "adaptable" when it comes to serving multiple mission needs. Most of the questions you are asking hear are easily answered through google or even using the search feature on this forum.
Is it just because they're slated to "save" the F-135 Lightning?
Is this flame baiting? The engines are designed to support the next generation of aircraft. From fighters, to bombers to unmanned aircarft. Needless to say, along the way the F-35 will also in some way benefit from the billions being invested in development. Why should the largest fighter in the US tactical fleet not benefit from these changes 10, 15, 20 years from now? Even if one were to neglect performance benefits, the fuel cost savings over a 2000+ fighter fleet would more then justify the development expense.
By: - 15th April 2015 at 23:45 Permalink - Edited 1st January 1970 at 01:00
No, certainly not flame baiting. It's just that there are congressional hearings regarding the Air Force and Navy appropriations for these programs, neither of which seem to overlap the other.
By: - 15th April 2015 at 23:49 Permalink - Edited 1st January 1970 at 01:00
It's just that there are congressional hearings regarding the Air Force and Navy appropriations for these programs, neither of which seem to overlap the other.
Why would they overlap each other? And what do congressional hearings have to do with separate AFRL run programs?
By: - 16th April 2015 at 05:41 Permalink - Edited 1st January 1970 at 01:00
Do tell, Holloweenie.
How exactly did the M-53 change its bypass ratio ?
It was a fixed, low bypass, single spool turbofan of very simple design.
By: - 16th April 2015 at 08:44 Permalink - Edited 1st January 1970 at 01:00
Why would they overlap each other? And what do congressional hearings have to do with separate AFRL run programs?
The F110 was used by both the Navy and Air Force. Congressional hearings are involved because they appropriate and administrate the armed forces budgets.
By: - 16th April 2015 at 09:18 Permalink - Edited 1st January 1970 at 01:00
Do tell, Holloweenie.
How exactly did the M-53 change its bypass ratio ?It was a fixed, low bypass, single spool turbofan of very simple design.
The M53P2's cold path has a variable section. By decreasing the section the backpressure pushes more air in the hot section and vice versa.
The M53 has a simple architecture to maximize its cost and reliability (single engine fighter pilots tend to appreciate this, ask early F-16 pilots what they think about the F100...). Its design is far from simple however.
By: - 16th April 2015 at 11:58 Permalink - Edited 1st January 1970 at 01:00
The F110 was used by both the Navy and Air Force. Congressional hearings are involved because they appropriate and administrate the armed forces budgets.
Again, read the point I raised. Why would an F-35 hearing, cover an AFRL project?
By: - 17th April 2015 at 07:24 Permalink - Edited 1st January 1970 at 01:00
Could you provide eme with a source for this variable section bypass, Blue Apple.
I don't recall ever seeing or reading anything of the sort, and its not mentioned in Jane's.
Its so simple it doesn't even use variable stators in the compression stages, I find it hard to believe that the bypass would be variable.
By: - 17th April 2015 at 07:55 Permalink - Edited 1st January 1970 at 01:00
Could you provide eme with a source for this variable section bypass, Blue Apple.
I don't recall ever seeing or reading anything of the sort, and its not mentioned in Jane's.
Its so simple it doesn't even use variable stators in the compression stages, I find it hard to believe that the bypass would be variable.
http://www.institut-strategie.fr/Moteurs_10.htm
Les exigences de polyvalence du Mirage 2000 ont conduit aussi à une des caractéristiques les plus originales du M53 : le détendeur à section variable du flux secondaire, qui fait du M53 le premier moteur à cycle variable jamais mis en service.Ce dispositif permet, en effet, d’introduire une variabilité du taux de dilution. Fermé, il augmente la poussée spécifique du moteur au régime maximum, en particulier en supersonique. Ouvert, il favorise une optimisation de la Cs à régimes partiels de croisière basse altitude ou d’attente.
The multirole needs for the Mirage 2000 led to one of the most uncommon feature of the M53: the variable section in the cold flow that makes the M53 the first variable engine ver put in service.
This item enables a variation of the bypass ratio. Closed, it increases the specific thrust of the engine at max settings, especially in supersonic. Open, it optimizes the Cs at medium thrust at low altitudes or during holding patterns.
It's called the DSV (Détendeur à Section Variable) makes the bypass vary roughly between 0.4 and 0.32.
By: - 17th April 2015 at 10:17 Permalink - Edited 1st January 1970 at 01:00
Thanks Blue Apple.
I wasn't aware of that.
By: - 17th April 2015 at 13:03 Permalink - Edited 1st January 1970 at 01:00
the variable section in the cold flow that makes the M53 the first variable engine ver put in service.
The J58 was a variable cycle engine which functioned as both a turbojet and fan assisted ramjet.
http://www.skytamer.com/Pratt&Whitney_JT11.html
The J-58 is what is called a variable cycle engine, meaning an engine that operates efficiently at different airspeeds, such as subsonic, transonic, and supersonic. The engine functioned as a turbojet and as a fan-assisted ramjet, and was one of the first bypass jet engines (although very atypical) put into service. The engine had a 9-stage, axial flow, single spool compressor, a two-stage axial flow turbine and was rated at ~32,500 lbs. of thrust at full afterburner.
http://atomictoasters.com/2012/08/a-look-at-the-pratt-whitney-j-58jt11d-20/
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By: AbitNutz - 14th April 2015 at 05:17
Is the promise of adaptive cycle engines all that they're cracked up to be? The pentagon seems sold sold on the idea as a total game changer. Are Russians and Chinese working on their own versions?
What would a fully developed adaptive cycle engines allow a 6th generation fighter to do that current design don't. Will the over complication and weight nullify the advantages?