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Baseline performance of a Passport 20 was assessed prior to the start of modifications for upcoming power extraction tests.
For a commercial aircraft industry strangely bereft of all-new single-aisle jet airliner designs in the wings, there is a surprising and growing groundswell of advanced propulsion systems under study and development.
Nearest to realization is CFM’s RISE (Revolutionary Innovation for Sustainable Engines) initiative—an open-fan technology demonstrator program in the 30,000-lb.-thrust class launched three years ago by joint venture partners GE Aerospace and Safran.
- Supercomputers are playing a key role
- Passport 20 engine modified for hybrid-electric small core tests
“We’re in an unprecedented time for GE Aerospace with a number of demonstrators that we’re doing to mature the technology,” says Arjan Hegeman, general manager of future-of-flight technologies. “We consumed all the technologies that we basically have ready to go on the current engine programs. So the mountain of work that we’re in today is for these demonstrators to mature [technology for] that next generation.”
The next demonstrator planned to run in the U.S. will be the Turbofan Engine Power Extraction, which is to operate later this year under Phase 2 of NASA’s Hybrid Thermally Efficient Core (HyTEC) program. Fitted with multiple electric motor-generators, the program is based on a modified Passport 20 engine and forms part of the efforts to develop technology for small, high-power-density cores for integration with larger lower-pressure fans—thereby enabling higher bypass ratios.
A follow-on series of demonstrators is slated to include a flight-test version of the 130-in.-dia. open-fan system under study for RISE, also with a Passport 20 gas generator. In parallel, the high-power-density core targeted at the eventual production engine to emerge from the RISE program will be tested in the ground demonstration of the full-up HyTEC core, elements of which are likely to include the hybrid-electric technology from the Power Extraction program.
GE meanwhile says the results of its unprecedented use of large-scale supercomputing to design, test and analyze aspects of the RISE design continue to build confidence in its ability to deliver an engine with 20% better fuel efficiency than today’s Leap 1. GE has been using Frontier, a recently commissioned supercomputer at the U.S. Energy Department’s Oak Ridge National Laboratory to model elements such as the open fan and high-pressure turbine.
Initial evaluations of the first rotating components of RISE began 2023 when tests of the first full high-speed, low-pressure turbine stage began at GE’s Evendale, Ohio, facility using an F110 military donor engine.
Mohamed Ali, vice president and general manager of engineering for GE Aerospace, says the results of the supercomputing tests on the new-technology turbine blades in the F110 were “incredible, not just in its ability to improve the fuel burn, but also the durability.” He says the open-fan installation performance and noise predictions from supercomputer runs and wind tunnel data also were matched perfectly.
This advanced computing capability “is shortening the cycle and enabling us to get accurate results faster,” Ali notes. “We have been doing joint testing with Airbus at the noise-testing facility in Hamburg, [Germany,] and we validated that we can achieve lower noise with an open fan than today’s engines, and it will meet the noise requirements.”
GE is undertaking “a lot of ongoing testing as we speak right now to validate the durability [of the open fan],” he continues. “For certification, we are working with the airframers on that together and also with the regulatory agencies, and the testing results so far—whether it’s ingestion testing or vibration testing—are quite encouraging about the durability and the capability of the open fan. So we are increasingly confident about our ability to achieve 20% fuel-burn improvement and really set the standards for what the future will be.”
The first full demonstrator engine is expected to start ground testing in 2025-26, and another pair of powerplants are due to start flight testing around two years later. The RISE program also will include a recuperating system to preheat combustion air with waste heat from the exhaust as well as the application of advanced materials such as ceramic matrix composites in the hot section and resin-transfer-molded composite fan blades.
Recent tests by Safran include static and dynamic tests of a 1.5:1-scale open-fan blade set at French aerospace research agency ONERA’s S1MA transonic wind tunnel in Modane Avrieux, France. The latest phase focused on high-speed performance for cruise conditions and whether this is compatible with a low cabin noise. Low-speed performance, representing takeoff, initial climb and landing, was tested late in 2023. Noise targets for next-generation commercial aircraft will have to be 5-7 EPNdB quieter than current ones, according to Safran, which is targeting a reduction of 10 EPNdB.
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