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Two years after announcing the CFM RISE open rotor technology demonstrator program, GE Aerospace and Safran have made significant progress with the design and are fully engaged in component testing. And the initial results look fascinating, the engine makers said today during a pre-Paris Airshow media presentation. CFM RISE is no longer just a paper concept engine.
The event was scheduled almost two years to the day on June 14, 2021, when GE and Safran announced they would go disruptive for the next generation of civil aero engines. Called Revolutionary Innovation for Sustainable Engines (RISE), the engine would be 20 percent more efficient than a LEAP and 60 percent over the first-generation of jet engines. Running on 100 percent sustainable aviation fuel (SAF), carbon emissions should be 80-100 percent lower.
Since then, it has been a bit quiet on RISE. Until today. GE Aerospace’s Mohamed Ali and Safran’s Michel Brioude, Vice President of Engineering for Research and Technology with the two companies, went through the steps since June 2021. In 2022, the concept design review was completed and the program has now entered early part-level testing.
Over 100 tests have been completed of subsystems, models, and parts, which confirmed that each part works as designed. This includes static and dynamic tests of the fan blades with simulations of ingestion and vibrations. The high-speed Low-Pressure Turbine (LPT) also entered testing in a facility near Paris and the first long-lead parts have been ordered and some manufactured. The open rotor model also has been in the wind tunnel.
RISE will have a super compact core. “If you would make a comparison: it is an engine with the fan size of the GE9X (that powers the Boeing 777X) coupled with a core of a small business engine,” said Mohamed Ali. This gives the engine a by-pass ratio of 40 to 60:1 compared to 12:1 for the LEAP.
Fascinating results on the rigs
NASA is involved in the design of this compact core. “We are working on the compressor, combustor, and high-pressure turbine (HPT) to achieve breakthrough improvements while at the same time sticking with reliability. (…) For the HPT, we designed new foils, nozzles, and blades that used supercomputing. We have got fascinating results on the rigs as durability.” GE is extensively using ceramic materials on RISE, learning from lessons its use in the LEAP and other GE engines.
GE is actually testing the next generation of turbine blades in Evendale on an F110-engine “as we speak,” said Ali. This engine shares the same core with the CFM56 and is an ideal platform for testing. Tests are also being done on heat exchangers that have made produced using additive (3D) technology, again showing superior results, Mohamed Ali said.
RISE turbine blades have been tested on an F110 engine right this week. (GE Aerospace)
Supercomputing capabilities are also combined with a state-of-the-art system of Airbus to test the engine noise of the open rotor. GE and Safran are using an advanced noise-testing facility of Airbus in Hamburg. While the unducted fans of General Electric and Pratt & Whitney of the late 1980s were known to be very noisy, Mohamed Ali pointed out that supercomputing models demonstrated that levels are lower on RISE than the LEAP. More work will continue to study how to improve cabin noise levels. Later this decade, an Airbus A380 flying testbed is used to validate the concept.
Open rotor safety
This also applies to studies on safety of the open rotor. In the event of a blade failure, the engine doesn’t have a fan case to contain the blade. This increases the risk that the blade could penetrate the fuselage and aircraft systems, with potentially lethal results. There are two rows of blades on RISE, with just one of them spinning and the other able to change camber, with each blade the size of a fan blade of the GE9X.
Ali is not concerned about blade safety: “We have over 100 million flying hours with composite fan blades. Touch wood, but so far we have never lost one. Keep in mind too that the blades are rotating at a slower speed (thanks to a gearbox), so there is less stress on them.”
The RISE engine will include a one MegaWatt hybrid-electric powertrain, which is being developed under NASA’s Electrified Powertrain Flight Demonstration (EPFD) program. It is an important ingredient to achieve the 20 percent efficiency gain. GE and NASA said last year in Farnborough that this hybrid-electric system has been successfully tested in tests that simulated high altitude at 45.000 feet. The next phase is preparing to get to flight-testing readiness, for which Boeing has sourced a SAAB 340 turboprop that will be converted. Another avenue is adding hydrogen to the RISE concept, both with direct injection and fuel cells. This is studied through a Clean Aviation program supported by the European Union.
As Ali and Brioude said: “RISE is not anymore on paper, it is for real. We are on track for the flight test demo and the ground test demo by the middle of the decade.” But it is up to the airframers Airbus and Boeing to decide if they think an open rotor is the preferred option for the new airliners they plan to introduce in the mid-2030s or if they go for a less disruptive but also advanced concept as the Rolls-Royce UltraFan. “We are getting for a mid-decade entry into service and maturing the technology, to make sure that they are readied and matured.”
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