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airjampanam
Topic Author
Posts: 243
Joined: Tue Sep 09, 2003 3:06 am

Supersonic Engines

Sat Nov 08, 2003 4:07 am

Now that the Concorde has gone belly up, did research come to a halt on supersonic engines when they got hitched to BA and AF?
Or could they, or some variation return conceivably on some future aircraft?
It's quite a shame to see that aircraft go out of service, environmentalists be damned!
Suing is the new Lotto... if u wanna win u gotta sue!
 
Guest

RE: Supersonic Engines

Sat Nov 08, 2003 4:16 am

The first jet airliners - for 707, DC8 had civilian versions of J-57 and J-75 engines.
The DH Comet had RR Avon engines, initially a military design...
Research will not stop, engine designers work for the military... and airlines...
Maybe the engine for the "future" B-3, or B-4, will be engine for the next SST...
xxx
Happy contrails  Smile
(s) Skipper
 
airjampanam
Topic Author
Posts: 243
Joined: Tue Sep 09, 2003 3:06 am

RE: Supersonic Engines

Sat Nov 08, 2003 4:19 am

B747skipper
You are the MAN!!!
thanks for your reply.
We can only hope we see another SST at some point.
Suing is the new Lotto... if u wanna win u gotta sue!
 
ConcordeBoy
Posts: 16852
Joined: Thu Feb 01, 2001 8:04 am

RE: Supersonic Engines

Sat Nov 08, 2003 4:24 am

NASA continues to study SST engines, as well as the Japanese (though their recent experiments havent gone so well... no data was ever able to be collected)
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
ConcordeLoss
Posts: 382
Joined: Sun Nov 02, 2003 11:50 pm

RE: Supersonic Engines

Sat Nov 08, 2003 4:33 am

They keep talking about "efficiency" with supersonics.
The Concorde was introduced 30 years ago.
And since then they haven't found something that's more efficient????!!!!
"You're not as stupid as you look, or sound, or our best test indicates" Burns to Homer
 
B2707SST
Posts: 1289
Joined: Wed Apr 23, 2003 5:25 am

RE: Supersonic Engines

Sat Nov 08, 2003 5:06 am

Concorde's Olympus 593s are still marvels of engineering. They are optimized for Mach 2 flight and are amazingly efficient in that environment, but the tradeoff is that subsonic flight is quite inefficient and the engines are very loud at takeoff and landing. Hence Concorde actually has more range and lower fuel consumption per mile at Mach 2 than at Mach 0.95.

A new SST will have to clear much more stringent noise standards, so designers will probably go for a low-bypass turbofan rather than a pure turbojet like the Olympus. This means less noise and better efficiency at subsonic speeds, but it will be very difficult to beat the Olympus in supersonic cruise. Most of the efficiency gains on a next-generation SST will probably come from better aerodynamics and lighter materials, not radically more efficient engines (assuming the SSTNG uses jet engines, not SCRAMJETS or pulse-detonation engines).

--B2707SST
Keynes is dead and we are living in his long run.
 
StevenUhl777
Posts: 3281
Joined: Sun Jul 08, 2001 11:02 am

RE: Supersonic Engines

Sat Nov 08, 2003 5:15 am

I have pictures of engines #1 & #2 from G-BOAG, which came to BFI this Wednesday as part of the museum of flight permanent exhibit. Contact info. is updated, send me an email if you'd like them.
And the winner for best actress is....REESE WITHERSPOON for 'Walk the Line'!!!!!!!!
 
sllevin
Posts: 3314
Joined: Wed Jan 30, 2002 1:57 pm

RE: Supersonic Engines

Sat Nov 08, 2003 5:22 am

All engines actually operate subsonicaly -- even the J-58 tubojets of the SR-71. The intakes are used to reduce the speed of the intake airflow down to subsonic speed.

Steve
 
airbazar
Posts: 10377
Joined: Wed Sep 10, 2003 11:12 pm

RE: Supersonic Engines

Sat Nov 08, 2003 5:45 am

I really have a hard time believing that 30+ year-old technology like the Olympus can't be improved on. In my opinion, the only reason it hasn't been done is because no one tried.
 
B2707SST
Posts: 1289
Joined: Wed Apr 23, 2003 5:25 am

RE: Supersonic Engines

Sat Nov 08, 2003 7:04 am

I'm not saying that you could not design a pure turbojet like the Olympus that would be more efficient at Mach 2 - this is probably quite possible. The issue is that a new SST cannot get away with a pure jet engine, because their takeoff noise and subsonic inefficiency are no longer acceptable. The design features needed to reduce noise and boost subsonic efficiency will reduce supersonic efficiency. These are inevitable design tradeoffs.

Once you move into the supersonic speed range, higher bypass ratios become a liability because you want to maximize exhaust velocity. The exhaust speed of a high-bypass turbofan like the CF6 series is too low to provide effective supersonic propulsion, which is part of the reason why you can't hang 4 GE90s on a 747 and call it an SST. The large frontal bypass fans also create tremendous drag. The challenge for engine designers is to create a turbofan with a sufficiently high bypass ratio to provide quiet, efficient takeoffs and landings as well as subsonic cruise over land, but a low enough bypass ratio to provide efficient supersonic cruise. This has proven to be a very difficult challenge.

Current studies show turbofan bypass ratios from 1.4:1 to 2:1 are optimal for a Mach 2-2.4 SST: compare this with 0:1 BPR on the Olympus, the roughly 6:1 BPR on the CF6 and the 9:1 BPR on the GE90. Designers cannot go any higher without compromising supersonic efficiency, which is a do-or-die objective. These low bypass ratios still produce unacceptably high noise levels, requiring extremely complex and heavy silencing systems. NASA's entrained-flow mixer-ejector nozzle, which used secondary inlet doors to mix outside air with the exhaust stream, was the size of an RV and weighed several tons. Even with this system, they could not meet Stage IV limits, which was one reason the HSCT was cancelled.






2-D Bifurcated Mixed-
Compression Inlet
Mixed-Flow
Turbofan Engine
2-D Mixer-Ejector
Exhaust Nozzle


--B2707SST
Keynes is dead and we are living in his long run.
 
GDB
Posts: 14253
Joined: Wed May 23, 2001 6:25 pm

RE: Supersonic Engines

Sat Nov 08, 2003 8:06 am

Not much to add to B2707SST's excellent posts, other to add that Concorde worked as the propulsion system was three modules, all coming together to provide a still unprecedented 43% thermal efficiency at Mach 2, 50,000+ feet.

The BAC intake system, vital for safe and efficient supersonic operation, still a model of elegant and cutting edge design.

The R/R Olympus 593 mk.610 engine, a massively developed version of an engine that had been around for years, early form of FADEC on the Concorde engine too.

Snecma's reheat/nozzle system. The secondary nozzles acting as an expansion chamber at supersonic speeds, as thrust reversers on landing. The expansion chamber config providing 50% of the power at Mach 2.

On take off the Olympus 593's developed 38,000lbs on take off, with 6,000lbs being reheat.
At Mach 2, only 8-10,000lbs of thrust with no reheat.

In the late 1990's our R/R rep had been talking with colleagues involved in R & D, they told him that no one expected to beat the Olympus 593 efficiency in supercruise, they were looking at the subsonic flight region for big improvements, clearly they failed, though funding was limited and no firm application existed.
More was spent in the US, but they had the same issues.

Concorde B would have had an improved Olympus, with 25% more airflow, no reheat, better efficiency in subsonic, much better noise suppression, had that happened it would have been an incremental improvement, nowhere near the step change required.
And this dated from the mid/late 1970's.

Why have we not yet seen a supersonic biz jet after over a decade of talking about it?
Lack of a suitable engine mainly.
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Supersonic Engines

Wed Nov 12, 2003 6:50 am

"It's quite a shame to see that aircraft go out of service, environmentalists be damned! "

Back in the day I am sure it was that and a combination of severe paranoia, I have never heard of so much racism against a machine...nowadays it is everyone's fault for giving up.

"They keep talking about "efficiency" with supersonics. The Concorde was introduced 30 years ago. And since then they haven't found something that's more efficient????!!!!"

Concorde was not efficient, she burned 16 times more fuel that a 747, I think we can do away with afterburners in the future because those engines will have hi-bypass ratios in place of it, something like 2 or 3 would be nice.

" NASA's entrained-flow mixer-ejector nozzle, which used secondary inlet doors to mix outside air with the exhaust stream, was the size of an RV and weighed several tons. Even with this system, they could not meet Stage IV limits, which was one reason the HSCT was cancelled. "

They insisted on a turbojet to reduce complexity, turbojets have the exhaust speed but are notoriously loud. It would be a miracle if they have decided on turbofans without a burner. The reason the NASA cut off the HCST was because Boeing, their ONLY partner to the project with the interest in building one, dropped off due to a difference in market research from 1996 to 1999; people suddenly decided that they were not willing to pay 25% extra to go supersonic. Stupid grinches.

NASA can't do jack on their own without "community cooperation" (which was why NASA dropped off the X-30, the US Air Force had an interest in it called "Copper Canyon" which they pulled out of in 1995). The government doesn't give NASA any money -- hence nobody gets payed and nothing gets done. I honestly do not believe it is an issue of technology, just lack of investment by stupid people that need to get smart.


Hey G-dub, weren't those Olympus 593's the most powerful turbojets on the planet?


[Edited 2003-11-11 23:13:23]
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
mattg21iah
Posts: 55
Joined: Tue Oct 28, 2003 11:22 am

RE: Supersonic Engines

Wed Nov 12, 2003 7:02 am

It’s not a matter of technological difficultly; it's who is willing to spent the money on such an undertaking to meet strict restrictions and requirements. The day an SST is finished will be another revolution in aviation history just as concord was and still is.
 
timz
Posts: 6581
Joined: Fri Sep 17, 1999 7:43 am

RE: Supersonic Engines

Thu Nov 13, 2003 10:50 am

"I honestly do not believe it is an issue of technology, just lack of investment by stupid people that need to get smart."

Definition of "smart": "enjoys building bonfires with $100 bills."


"Hey G-dub, weren't those Olympus 593's the most powerful turbojets on the planet?"

The J93 was rated higher, wasn't it?


 
JetRanger2000
Posts: 227
Joined: Sun Feb 13, 2000 8:21 am

RE: Supersonic Engines

Thu Nov 13, 2003 11:00 am

I've heard ideas such as having 2 efficient subsonic engines and 2 efficient supersonic engines on a SST
 
ConcordeBoy
Posts: 16852
Joined: Thu Feb 01, 2001 8:04 am

RE: Supersonic Engines

Thu Nov 13, 2003 11:02 am

...which (unless they've found some way to tuck them a la landing gear) each respectively become two efficient sources of drag, during the different stages
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
JetRanger2000
Posts: 227
Joined: Sun Feb 13, 2000 8:21 am

RE: Supersonic Engines

Thu Nov 13, 2003 11:05 am

Thats what I was thinking too. Unless they can make the engines share a air duct or something...

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