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"Superjet" variable cycle jet engine could power future fighter aircraft

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January 6, 2013

Cross-section of the GE ADVENT engine design

Cross-section of the GE ADVENT engine design

GE Aviation is developing a revolutionary new jet engine that aims to combine the best traits of turbojet and turbofan engines, delivering supersonic speed capability and fuel efficiency in one package.

The new engines are being developed under the USAF ADVENT project, which is seeking 25 percent fuel saving which will in turn lead to an increase in mission capability.

There are two main species of jet engines for aviation: low-bypass turbofans, usually called turbojets, and high-bypass turbofans. Turbojets are optimized for high-performance, pushing fighter jets to above Mach 2 (and the SR-71 "Blackbird" to well over Mach 3), but pay for that performance with terrible fuel efficiency. The performance outcome of a conventional turbojet is dominated by the operation of the high-pressure engine core (compressor, combustion, turbine, and exhaust nozzle).

In contrast, high-bypass turbofans are the heavy lifters of commercial aviation, being optimized for subsonic thrust and fuel efficiency, but performing poorly at supersonic speeds. A conventional turbofan adds lower-pressure airflow from an oversized fan which is driven by the jet turbine. The fan airflow bypasses the combustion chamber, acting like a large propeller.

In an ADVENT (ADaptive VErsitile ENgine Technology) engine, the high-pressure core exhaust and the low-pressure bypass streams of a conventional turbofan are joined by a third, outer flowpath that can be opened and closed in response to flight conditions. For takeoff, the third stream is closed off to reduce the bypass ratio. This sends more of the airflow through the high-pressure core to increase thrust. When cruising, the third bypass stream is opened to increase the bypass ratio and reduce fuel consumption.

The extra bypass duct can be seen running along the top and bottom of the engine. This third duct will be opened or closed as part of a variable cycle to transform it from a strike aircraft engine to a transport-type engine. If the duct is open the bypass ratio will increase, reducing fuel burn, and increasing subsonic range by up to 40 percent, leading to 60 percent longer loiter times on target. If the ducts are closed, additional air is forced through the core and high pressure compressor, enabling thrust and speed to increase and providing world-class supersonic performance.

GE's ADVENT designs are based on new manufacturing technologies like 3-D printing of intricate cooling components and super-strong but lightweight ceramic matrix composites. These allow the manufacture of highly efficient jet engines operating at temperatures above the melting point of steel.

Engineers also designed the new engine to be easy to fly. “We want the engine to take care of itself and let the pilot focus on the mission,” says Abe Levatter, project manager at GE Aviation. “When the pilot says ‘I’m out of danger, I want to cruise home,’ the engine reconfigures itself. We take it upon ourselves to make the engine optimized for whatever the pilot wants.”

GE is now testing the engine’s core components and plans to run a full test in the middle of 2013. The video below provides additional visual description of its operation.

Source: GE Aviation

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer.   All articles by Brian Dodson
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12 Comments

Advent huh? Nice idea but every time you open one of the engine doors you get a chocolate? (Scandinavian joke) As the name is a holiday here of sorts..its the count down to Christmas. But the engine idea seams good, all for improved engines, hope it don't also make it super fragile/delicate.

Toffe Kaal
7th January, 2013 @ 08:49 am PST

The J-58 used in the SR-71 mach 3 spyplane had a very similar arrangement, but for a different purpose. At subsonic and low supersonic speeds, all the compressor air went through the combustion chambers. At higher mach numbers, the bypass ducts were opened and some air bypassed the later stages of the compressor and the combustion chambers and was fed into the afterburner. That had the effect of turning the engine into a partial ramjet, which is more efficient at very high mach numbers than a turbojet.

William R. Mosby
7th January, 2013 @ 09:02 am PST

Good to see a very obvious application being made reality...

Sorry, a Low Bypass Turbofan is still a turbofan. NOT a turbojet

I don't think there has been a single Turbojet used in any aircraft (at least in the aircraft we know about, and are told about) for a while now, they all appear to use turbofans....

J-58 = Turbo Ramjet

All (there may be an exception) US and European FighterJets use TurboFans (Sure Low bypass, but still described as such... Just Wikipedia it for goodness sake, it ain't too hard to get facts right.)

For Super cruise that thing called an afterburner is used..

Please PM me on information on any modern advanced aircraft using turbojets.

NOTE: Low-Bypass TurboFan =/ TurboJet, (Turbo Jet is a Zero-bypass Turbofan, but that is a paradox)

MD
7th January, 2013 @ 09:31 am PST

Their marketing department could use some extra funding, and, I got to say, the concept doesn't seem new. In fact, I think some of the European and Japanese companies or agencies have developed similar concepts,.. Though I have no citations to make.

Thing is, with recent studies in owl feathers, I am surprised I don't see any manufacturer developing something along these lines. After all, a noise reduction, is a drag reduction, which makes it a fuel efficient design. Engines could spin to higher rpm and the noise would definitely be suppressed by such design, rendering flight a bit less noisy even in turboprop designs... In theory anyway.

Nitrozzy Seven
7th January, 2013 @ 11:01 am PST

Bad news is the F-35 just doubled in price,again & again.

chidrbmt
7th January, 2013 @ 12:21 pm PST

The idea of a veritable bypass turbofan engine is not new but the trick is to get it to work reliably.

Slowburn
7th January, 2013 @ 01:04 pm PST

GE designed an operational variable-cycle engine in the late 1980s for the program that led to the F22. I think it was called the GE YF120 and flew in both the YF22 and the YF23 black widow. Installed in the latter it was said to be very efficient and very fast.

mommus
7th January, 2013 @ 01:56 pm PST

The Chinese probably have a working model already.

Ron Evans
7th January, 2013 @ 02:46 pm PST

Like someone mentioned, this process is a lot like what the Blackbird did several decades ago...except it used the ramjet process which made it go faster then this.

But regardless, I hope the engine works great during it's testing, and 10-15 years from now it might be a USAF 6 gen fighter.

Derek Howe
7th January, 2013 @ 04:05 pm PST

Test in older Cold War jets: F14, F15, FA18.

Be radical for Exec Jet use.

Stephen N Russell
7th January, 2013 @ 05:12 pm PST

MD, the definition of "super cruise" is supersonic flight without the use of an afterburner. I just googled "supercruise definition" and the top 4 or 5 results confirmed that. The F-22 can supercruise at about mach 1.5.

I know the J-58 was a turbo-ramjet, I just didn't mention that term.

William R. Mosby
7th January, 2013 @ 05:56 pm PST

Essentially this is what the Harrier Jumpjet and its engine does! Amazing how ideas come back around and hardly anyone realises!

Alan Bradbury
5th April, 2013 @ 06:46 am PDT
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