CFM RISE open rotor
UPDATE – While Airbus needs at least four more years to finalise the specifications of its Next-Generation Single Aisle (NGSA) aircraft, the engine that is in pole position for this plane is making steady progress. GE Aerospace and Safran stress that they are doing everything to have the CFM RISE open rotor be ready when Airbus decides about NGSA in 2030.
Specialists from GE, Safran, and CFM shared updates of the RISE program during a pre-Farnborough Airshow media briefing in London. While AirInsight wasn’t present, details were also presented in a media release. We have kindly been shared a transcript of the meeting since then by FlightGlobal colleague Dominic Perry.
Five years since unveiling the open rotor concept, RISE had completed the Preliminary Design Reviews of the compact core system, the open fan and outlet guide vanes (OGV). The vanes are static objects placed directly behind the rotors that help direct and optimise the airstream over the engine. “This is a very important milestone in our world because it means that we can now start manufacturing the parts that will be built, that will be assembled into the grounded demonstrator of the object”, says Arjan Hegeman, GE Aerospace Vice President of Future of Flight Engineering.
CFM intends to build a demonstrator for ground tests, sometime before the end of the decade. “We’re not giving more details on the exact points in the near future here on what we’re going to deliver. We’re aiming to have technology readiness level six by the turn of the decade”, Hegeman said. A second open rotor engine will be flight-tested on a converted Airbus A380, but GE repeated previously shared information today that this engine will be based on a Passport business jet engine and not have the new, small core that is still in the design phase.
Already tested, however, is the low-pressure turbine that is part of the open fan system. It has already done over 1.000 hours, with engineers validating the aerodynamic design and aerothermal performance. Wind tunnel tests have confirmed the aeroacoustics performance of the open rotor, with noise levels being at the same level as a CFM LEAP, the engine maker said earlier.
Sand ingestion
Since engine makers have been confronted with durability issues in harsh environments, all are paying particular attention to simulating sandy, hot conditions. GE has been doing so with the GE9X that powers the Boeing 777X, while CFM has gone to great lengths to improve the durability of the LEAP. RISE is benefiting from this, with sand ingestion and durability tests having already been done in over 2.000 cycles with a newly designed high-pressure turbine airfoil.
RISE also incorporates hybrid-electric elements, which have been tested during two ground tests. It builds on the data gained with the Phileas full-scale demonstrator that is being developed by Safran. “Hybrid electric will provide us ways of improving the gas turbine by removing some constraints, and it will allow us to meet the new employment in terms of power extraction. The two parent companies of CFM have made a lot of progress in the last few years, going really into the ground testing phase of these technologies. Safran is about to launch in the coming days a new series of tests on our Silvercrest engine that will include the whole electrical system developed by our sister company Electrical and Power.”
In total, over 500 test campaigns and 3.000 endurance cycles have been completed since last June, when CFM shared the number of 350 campaigns at the Paris Airshow. “We have accumulated more than 500 hours of wind tunnel testing and more than 5,000 cycles of endurance and just ingestion tests on the core. These tests are relevant to all the modules of the engine, fan and OGV, of course, core. We have covered a whole range of testing: aerodynamic testing, acoustic testing, icing testing, and that’s only part of the list.” It is preparing tests of a full-scale, four-meter-wide front module of the open fan rotor in the new Villaroche test cell.
As mentioned, the jury is still out on whether Airbus will fully embrace the open rotor concept for the successor of the A320neo family. “What we made sure of is that we have the technologies matured and ready to go to kick off a program when the airframers start pulling on”, Hegeman said.
CFM will have to demonstrate in the coming years that the concept is not just delivering the advertised 20 percent fuel burn advantage, but is doing it reliably and durably. As reported here before, airlines have recently gone vocal that engine performance needs to improve significantly and that a repetition of the Geared Turbofan, Trent 1000/7000 and LEAP issues must be out of the question.
“We do deep dives with customers that I personally am involved in, so to get the opportunity to really kind of walk them through some of the technical details. Some of those sessions are a day long. Some of those sessions are an hour, and at large, everybody is excited about the potential step changes that this engine can offer.”
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