FARNBOROUGH 2008: New engine LEAP X to power passenger airliners - CFM

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CFM is the first of the world’s major engine companies to break cover and announce an entirely new engine – Leap-X – designed specifically to power the next generation of single-aisle 100+passenger airliners.

Joint owners GE and Snecma will also develop an open rotor engine – with similar thrust of 20,000 to 30,000 lbs – using much of the same newly-developed third generation core technology.

Leap-X will be completely new with “not one single part carried over from today’s CFM 56 engines”, says CFM’s president and CEO Eric Bachelet. Featuring a bypass ratio 85% higher at 9:1 (today’s CFM engines have a 5:1 ratio), the new powerplant will provide 16% lower fuel consumption versus today’s best ‘tech insertion’ CFM –5B and –7 models.

It will be environmentally friendly too, with noise at 10-15dB less than Stage 4 and NOx emissions more than 60% lower than CAEP6.

But despite the game-changing 3-D woven 71in diameter composite fan blades and case; the 50%-plus higher core pressure ratio; the TAPS II combustor and the variable area fan nozzle, “there will be absolutely no compromise on reliability or serviceability”, says Bachelet.

CFM says it would be impossible to build this engine without advanced materials. It will weigh much less than today’s power-plants, largely due to its woven fan blades - 18 blades weighing just 168lb - as opposed to today’s CFM56-5C with 36 72-in blades weighing 330lb.

 cfm-ceo
 CFM’s president & CEO Eric Bachelet talks Leap-X and open rotor

Half-scale rig tests are happening now and it’s intended to have a full-scale demonstrator running by Q4 2008. The low-pressure turbine will go to full rig test in Q1 2010 and will feature titanium aluminide blades – once again with less weight.

The core components will be tested individually between now and the end of Q3 2009 before a full core is ready for test in Q4 2009. Once these tests are complete, revisions will be built into a second core that will test in Q3/4 2011. A full engine demonstrator will run in mid-2012.

In conjunction with the Leap-X engine, GE and Snecma will also research an open rotor engine, which will offer a further 10% reduction in fuel burn and featuring much of the Leap-X advanced core technology.

The trade-off between reduced fuel burn and the increased noise generated by open rotors is at the root of research as GE/Snecma/CFM spend billions of dollars with NASA and similar research establishments in Russia (TsAGI) and France (HERA) to achieve Stage 4 minus 10 noise levels by Q3 2011.

But it’s not only increased noise that comes with the open rotor territory. The Leap-based open rotor engine has a diameter of 168-in, 40in more than a GE90 115B. So installation will be a huge issue, “and we will do this in conjunction with the airframers”, says Bachelet.

Precisely what airframes these new composite-nacelled engines will power remains to be seen – but the time between now and 2016 will be interesting as GE and Snecma on one hand, and Rolls-Royce on the other, develop both conventional and open rotor engines, while Pratt & Whitney, somewhere in the middle, concentrates on its GTF engines.

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