May 30, 2023, © Leeham News: “The need for radical fuel improvements will only increase over time.”
That’s the definitive conclusion of Arjan Hegeman, GE Aerospace’s general manager of advanced technology.
GE is working on Performance Improvement Packages (PIPs) of its current engine lineup used on Airbus and Boeing airliners. It’s also developing the GE9X, now in testing on the Boeing 777X, and concepts of a hybrid-electric and hydrogen-fueled engine.
But the big bet is on the Open Fan “RISE” (Revolutionary Innovation for Sustainable Engines). “The Open Fan technology—it’s a go,” Hegeman declared earlier this month at a press briefing in advance of the Paris Air Show next month.
The Open Fan is an evolution of the Open Rotor engine tested in the 1980s. The concept shows a dramatic reduction in fuel consumption compared with the engines of the day. But the counter-rotating rotor design was very noisy. Coupled with other technical challenges and a sudden drop in fuel prices, GE (and rival Pratt & Whitney) dropped the concepts.
But research and development continued. Today, PW thinks its Geared Turbo Fan engine will suffice for the future. Rolls-Royce is also pursuing traditional engine designs. But GE believes the problems of the Open Rotor have been solved for the Open Fan.
It comes down to supercomputing, said Mohamed Ali, GE Aerospace vice president of engineering.
Supercomputing is going to be key to improving engine designs and working toward greener aviation, Ali said during the same press briefing. “We have access to supercomputing capabilities and we are privileged to be working with the Department of Energy. It’s by invitation only. We are designing RISE using that.”
Using Supercomputing power is advancing shape, fuel efficiency, and acoustics, Hegeman said. Whereas the Open Rotor was too noisy for use on an airplane even under the less stringent regulations then in place, the Open Fan has a lower decibel level than the LEAP engine. “The single fan was a design breakthrough. It’s better for weight, better for costs.” The RISE has only a single whirling fan instead of the counter-rotating fans of the Open Rotor. There are fixed blades aft of the rotating fan that helps dissipate noise. Supercomputing led to this breakthrough.
There was a second big breakthrough Hegeman wasn’t authorized to reveal.
The Open Fan is the most recognizable feature of the new narrowbody concepts, said Hegeman. “There’s a laundry list of technologies that will be in RISE. It’s how do we get that core smaller and smaller to burn less and less fuel, whatever that fuel is, whether it’s Jet A, SAF, or hydrogen.
“We have a narrowbody engine that has a fan similar to the size of the GE9X.” It’s a narrowbody engine able to move the air the size of an engine on the 777. But there is no casing around it, so it’s not that much bigger in diameter than today’s LEAP, Hegeman said. If you combine it with a core that is the size of a business jet engine, moving the amount of air of a 9X engine but very efficiently with narrowbody level-type thrust. “That is what RISE is.”
In the past decade, GE replaced all its commercial airliner engines. The CFM 56 was replaced with the LEAP, the CF6 with GEnx, the GE90 with GE9X, and the CF34 with the Passport, Hegeman said.
“All had one thing in common: the fuel improvement was 10-15%. That’s been the name of the game in the industry. Each generation gets better fuel efficiency. It wasn’t so much for emissions in the past but for pure economics for the operator. Pratt and Rolls have been doing the exact same thing. When we started the LEAP 1B in 2011, the price of oil was at an all-time high. We had to meet or beat the 15%.”
But, oil prices fluctuate, at times relieving immediate pressure for changes. Today, Hegeman said, “We are convinced that with climate change, and the price of fuel, whether it’s carbon-based, synthetic, bio-mass or completely alternative fuels like hydrogen, the cost of carbon emissions and the cost of fuel will increase over time. It is no longer tied to the price of a barrel of oil.”
Hegeman said that investing in fuel efficiency is not only the right thing to do for the planet, but for following generations. It’s also going to be a much more economic differentiator for the operators compared to what it was.
Boeing CEO David Calhoun publicly stated several times that the next generation of airplanes and engines must be a 25% to 30% improvement over today’s aging airframe and modern engines. When GE announced the RISE in June 2021, it said the goal for fuel reduction was 20%. There are skeptics in Boeing who think this might fall to 10% once the engines are installed. But last week, GE’s target fuel reduction is more than 20% (without specifying what “more” is). And Hegeman reaffirmed that this is after installation.
“A new engine has to get at least 20% or more fuel efficiency, which ties directly to the amount of carbon you emit,” Hegeman said. “The overall integration of the next airplane with engine and airframe needs to be 25%-30% better than today’s airplanes. We’re looking at the aircraft level, what do we achieve? We don’t worry too much about what is on the aircraft side and what is on the engine side. It’s got to work as a system.”
GE is working with Airbus and Boeing and their engineering teams on future concepts. “We know the numbers they are coming up with for the aircraft,” he said.
“We also need to look at alternative fuels. SAF, synthetic. A whole new era is the electrification of flight. In the past, we always got our efficiencies through propulsive efficiencies—how efficient does the propeller, the forward fan, provide thrust? And thermal efficiency—the core—how little fuel can you burn?”
GE is doing studies in these areas. We’ll have more reporting in future articles.