Airbus and CFM are developing dedicated technology demonstrators for hydrogen combustion (left) and open-fan propulsion (right), exploiting the A380’s large-scale internal capacity and ground clearance, respectively.
Airbus has provided more details about the accelerating design work underway on two A380 technology demonstrators targeting advanced propulsion evaluations for next-generation single-aisle aircraft planned for the 2030s.
The multinational OEM is collaborating with CFM International—the joint venture between GE Aerospace and Safran Aircraft Engines—on two major flight-test programs that will run almost concurrently. One A380 will be used to evaluate a GE Passport engine modified for direct combustion of hydrogen fuel while the second will flight-test the open-fan propulsion system being developed under CFM’s Revolutionary Innovation for Sustainable Engines (RISE) program.
- Hydrogen tested as separate system
- Loads and noise part of open-fan tests
Although neither aircraft is due to enter flight testing until after the middle of this decade, work on the two sophisticated demonstrators is underway, says Frank Haselbach, head of propulsion engineering at Airbus. “The teams are spooling up,” he adds. “We’re having good cooperation with CFM on both programs, so we’re quite happy about that.”
The RISE and hydrogen flight-test campaigns form part of Airbus’ technology push toward a “ZEROe” carbon-neutral airliner for entry into service by 2035. The modified A380s will be used to conduct tests in the second half of this decade at the company’s flight-test facility in Toulouse. Before the A380 test flights, CFM will perform engine ground tests, along with flight-test validation on GE’s Boeing 747-400 flying testbed at GE Aerospace’s Flight Test Operations center in Victorville, California.
Haselbach says the hydrogen test effort is aimed at understanding “how we actually make sure that we have a safe or safer operation than today with such a sustainable aircraft—and that includes things like liquid hydrogen, because with gaseous hydrogen you wouldn’t get the range.” Speaking to Aviation Week on the sidelines of an International Society for Air Breathing Engines meeting in Ottawa, he adds that areas of focus will include tests of higher-density liquid hydrogen, storage tank and fuel system distribution technology, ground and flight operations, fueling infrastructure and combustor design.
“But to really make this meaningful, we decided to put it toward a flight test,” he adds, “which also helps to drive the teams together and gets us thinking about how we get this integrated into the aircraft [and] how we make it safe for flight, even in an experimental environment. So that was the key decision here.”
Haselbach stresses that the A380 hydrogen testbed—modified to carry the Passport engine on a pylon projecting from the aft fuselage of the A380 while the interior will be equipped with liquid hydrogen tanks—is still “a technology demonstration” and by no means a product. “It will give us the answers we need, and working toward a flight demonstration helps to actually do it with the right focus,” he says.
“We could have done it on a smaller platform than an A380, but it will be good to actually have more space,” Haselbach adds. “Also the layout of the fuselage structure enables us to have a reasonably short distance between the tank and the engine, so all of that actually helped a little bit. In addition, you can almost set up the entire hydrogen test system as a separate section or area on the aircraft. We’re not going to be interacting with any of the other systems, so rather than modify the fuel and propulsion system on an existing aircraft, it made a lot more sense to develop this as a pure flying testbed.”
The RISE demonstrator on the A380 is aimed at testing the potential fuel-burn savings from CFM’s open-fan configuration and will be the first single rotating and stator-stage tractor configuration of its type to be flight-tested at full scale. “We’ve seen the fairly promising concept of the open fan before in the 1980s and 2000s, so this is really the third time,” Haselbach says. “Clearly, it is a promising offering because you have a single fan rotating rather than two counter-rotating. That makes noise management easier, and the mechanics are simpler.”
Building on previous open-rotor and propfan concepts and demonstrators, the RISE takes the approach to new levels, he adds. “Now you have the adjustability of the fan and the stator, and that gives you effectively a high-performance sort of low-pressure system at a good sort of cruising Mach number,” Haselbach says. “The second stage takes the swirl out, so that’s the key benefit. Otherwise, a normal turboprop would actually fall off [in performance] at around Mach 0.6 or thereabouts.”
The open-fan demonstrator will be fitted with a large support pylon on the No. 2 inboard left engine test position. The inboard wing structure and adjacent areas of the fuselage will also be reinforced to accommodate the CFM engine, which is currently expected to feature a rotor diameter of about 13 ft.
“We will be looking at the aerodynamic integration of that concept because it’s quite a big fan,” Haselbach says. “So, specifically, this means studying how it will interact with the lift-drag ratio of the wing and the structural interaction in terms of the moments [when] an open fan generates extra forces.” Other areas will include acoustic evaluations in terms of community and cabin noise as well as monitoring interactive noise generated between the fan and the stator.
“From what we have seen so far of this in simulation, the first set of work is quite promising,” Haselbach says. “Not everything is solved, but it’s actually good enough to say: ‘Okay, let’s have a closer look.’ And that’s exactly what we have decided to do together.”
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