Air Force plans to develop revolutionary engine

Well this is cool. What do you all think? I wonder how will this affect the overall performance of the JSF or F22?


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So they are finaly gonna release what they been using for 30 years . Come on , with this project in view they can convince the masses to keep on paying more and more. And with that money they can fund their black budget things.

nice find though !!

If they were going to unveil a black project, they'd do it through the media, not a research project. When they unveiled the F-117, they didn't announce a 5 year program to study stealth, they just called up the media and invited them to come out and see it. So insinuating this is just a whitewash effort to justify more defense spending is actually pretty obviously silly.

Regarding the original question, this will all come in too late to impact the JSF or F-22, unless they do a major overhaul of one of them in about 10-15 years. Presuming they do come up with some workable new technologies (that's not a guarantee), it will take that long at least for a production system to take advantage of them. You can't just cut in a new engine on the assembly line, especially not in a US Government program.

So what I think is that even though we have spent decades refining aircraft engine technology, the stated goal of this project to optimize performance over a broad range of conditions is very lofty. It's a difficult set of problems to overcome, and it's certainly worthwhile to try to overcome them. This would not just be defense technology, it would impact commercial aviation and potentially also access to space.

How would they do this? Some kind of contant speed N1 fan? Don't we already have something like this; variable geometry inlets and exhaust?

My guess on what they might be studying is the concept of Variable Bypass engines. It is well known that the mose fuel efficient Jets use High bypass engines like Turbofans or even turboprops. High speed aircraft either use very low bypass engines, like the F-119's on the F-22, or Turbojets like the J-58's that flew on the Blackbird Spyplane. If they could find a way to combine the advantages of both types into one engine, that would be a major advance in engine technology.

Tim

I just hope the chinese dont try to copy it like they have copied everything else. God hopes the technology stays secure.

How will they do it? If I knew that I'd pitch it to the government and try to snag some of the millions of dollars they'd spend on researching it. Variable geometry is a double-edged sword since it is generally complex with many possible failure points. That doesn't rule it out entirely, but to some extent that kind of technology has already been looked at and in fact implemented in some areas. They could also look at electromagnetic flow manipulation using MHD or some similar technology, but that too has a downside. The whole point of the research would be to investigate some of these ideas or others and see what might actually be feasible and helpful, and I'm not going to pretend to know what answer they will come up with.

Regarding the "don't we already have this stuff" question, of course we've refined aircraft engine technology for decades trying to make engines more efficient at all flight regimes. We've had some great successes, but we're still not to the point that we can design an engine to operate at a wide range of conditions with optimum efficiency. We pretty much pick a design point and optimize for that, then work to make the off-design performance as good as it can be. That's the real challenge that I see: truly optimal performance not only for various atmospheric conditions/altitudes, but also for various (wide-ranging) thrust levels. It's not an easy problem by any stretch of the imagination, and no we're not close to solving it as far as I can tell.

Spot on Tim i agree totally
It would be a exceptional interceptor/fighter

Hmm... well, Tim has kinda outlined the concept I'd imagine they would be working towards.


A variable bypass ratio engine. How they achieve that I'm not 100% sure - maybe use SMAs to vary the compressor inlet area immediately downstream the fan. Problem is keeping the area variation symmetric, so no flow distortions get into the 1st compressor disk.



I'd assume they will be looking at variable pitch blades as a given, I'm not sure if smart materials (SMAs) are at the point where we can look at variable profile blades just yet (especially under such high centrifugal loading), but I'd expect the military to have materials not yet published, so it may be feasible. That way, the blade loading across the fan from root to tip can be varied, and to a large extent, the bypass ratio with it.


There isn't much more in the way of efficiency to come from nozzles or inlets, any competent inlet/nozzle operates at over 95% efficiency already.


Distributed propulsion is an outsider, as it would tend to involve quite alot of weight, not really a useful thing.


Of course, expect the obligatory things like magnetic "bearings" to be in there, they are already lined up for the next gen civil engines (if they aren't already in some today)... newer ceramics that operate at higher temperatures to further increase the pressure ratios in the combustors, further refinement of the combustor itself with greater use DES/LES based CFD instead of RANS models.


But the big gains would come from what I said in the first 2 paragraphs.