12/27/2020

GE and the Geared Turbofan

There was quite a lot of hype in the last days around a story, first reported by Bloomberg, saying that GE talked with Airbus about a new engine for “a narrow-body jetliner in development”. In the article (and many that followed that first story) there is a lot of speculation about the aircraft: If it would be a successor of today's A320, a future stretched variant of the A220 or if that aircraft would in the end be the ZERO E (E for Emissions) aircraft announced by Airbus in September and the engine GE and Airbus discuss here would be an engine that would be used for that aircraft until a ZERO E engine (technology) would be available.

To make it short: this last consideration is – sorry to say it that way – bullshit! Whatever the source of energy of the future ZERO E aircraft would be – hydrogen or electricity comes to mind- the aircraft has to look very different from the design of a jet fuel powered aircraft and it would make no sense at all to hang a Geared Turbofan on an aircraft designed and optimized for zero emissions.

The fact that GE and Airbus talk about a new narrowbody is not a big story in the first place, as there are always discussions between airframers and engine companies about all kinds of possible future projects. But Bloomberg made a lot of noise due to the fact, that the design proposed by GE would be a geared turbofan, which is the engine design that today only Pratt & Whitney uses. GE always more or less dismissed the geared design in public because of the added complexity of the gear. Rolls Royce began developing their own geared engine concept called Ultrafan a few years ago.

So does GE not believe in the conventional turbofan anymore?

Not necessarily: believe it or not, but it is not the first time that GE proposes a geared design to an aircraft manufacturer. For the B777X, today's B777-9, GE also pitched a geared design towards Boeing, as did P&W at that time (I believe RR proposed a 3 spool design). But obviously Boeing went down the low-risk path of the GE9X engine, an evolution of the GE90-115B and the GENx engines, although the geared engines would have had a better fuel burn.

For the now (forever?) dormant NMA, Boeings reference engine was a geared turbofan. This makes sense, as at least in the beginning two of the three possible engine provider offered a geared design (P&W and RR), so we can only guess that GE (or CFM) also offered both variants (geared and non-geared) to Boeing. Later RR went out of the discussions as the aimed EIS timing was too early for the UltraFan.

So when today GE talks with Airbus about a geared engine, there is nothing sensational in there. Most likely the geared engine is just one out of two or more designs. And it most likely not more than a paper study, in which P&W and RR are involved as well. It is not more than the usual business of the future concept groups of all parties involved.

So do not expect an announcement of a new aircraft in the near future. Even a stretched A220 (-500) seems not to be on the horizon too soon...

2 comments:

  1. I don't agree on the zero emission point. Airbus hydrogen projects will certainly use conventional turbofan engine burning H2 instead of carbon fuel. Only the combustion chamber, ignition, injectors, fuel pumps and tubing will have to be modified. It's like a flex-fuel engine in your car, or dual fuel engine in ships, all the heavy machinery stay the same. Of course, for commercial aviation, it's a bit more tricky because the engine has to be certified, but it's a low risk approach compared to electric driven engines or even fuel cells.
    I'm quite sure GE (or Pratt or RR) will never launch a new engine program from now that would not be compatible with hydrogen fuel. It's a too short time to get return on investment before zero emission engine comes to reality, especially since GE Leap and PW Pure Power are still new on the market and don't have pay back the money invested.

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    1. The engines for hydrogen might not be too different, but the aircraft would and this is my point. Also, a hydrogen powered aircraft would not be a ZERO E aircraft. It would still emit NOx.

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