A $20 million investment announced this week by GE Aerospace to add a new test cell and equipment at the Electrical Power Integrated Systems Center (EPISCenter) in Dayton, Ohio, underscored the company’s commitment to hybrid electric powerplant technology in the coming years.
What will become the facilities’ seventh test cell will add another 2 MW of testing capacity to support NASA’s Electrified Powertrain Flight Demonstration (EPFD) program. Plans for EPFD call for ground and flight tests of the hybrid-electric system this decade using a modified Saab 340B aircraft and GE’s CT7 engines in collaboration with Boeing. NASA also previously awarded GE Aerospace a contract for the Turbofan Engine Power Extraction Demonstration under the Hybrid Thermally Efficient Core (HyTEC) project.
Speaking with reporters in Dayton on May 16, GE Aerospace hybrid-electric systems leader Christine Andrews listed three essential tenets of the EPFD program. “One, we’re going to pull power off the battery to run electrically; two, we’re going to pull power off the engine and charge the battery; and, three, we’re going to move power from the left-hand side to the right-hand side and do a power-transfer test,” she explained. “And that power-transfer test is really the altitude integration testing that we had announced as a success last year at [the] Farmborough [Airshow.]”
At the Farnborough event in July 2022, turbofan engine manufacturer GE and NASA announced they became the first to successfully test high-power, high-voltage hybrid-electric aircraft engine components in high-altitude conditions. Specifically, GE and NASA ran a megawatt-class, multi-kilovolt hybrid-electric system in conditions simulating altitudes to 45,000 feet. The test took place at NASA’s Electric Aircraft Testbed (NEAT) facility, the only installation capable of simulating high-electric and high-altitude conditions also large enough to fit an electric powertrain.
Andrews noted that her team will spend two years testing at the component level and systems level in Dayton to get ready for ground and flight tests. Next, GE will partner with Boeing subsidiary Aurora Flight Sciences to test the system in the air on the Saab 340. Andrews declined to name a target date for the first flight, however. “We, in a typical hybrid fashion, as we progress the technology, talk about it much later after it's already been done,” she explained. “We're just releasing today, but I did a [preliminary design review] last year, so that should give you an idea of where we're at.”
GE and NASA performed systems-level testing at NASA’s NEAT facility, and Andrews reported that the results proved promising. “The system and component have only gotten better from that test,” she said. “We've gotten better in quality and understanding and have done more testing, but we're looking at that as our full system test. When we look at the aircraft piece here, this is why we have [Boeing] involved to bring in their knowledge at the bird side of it, and then NASA certainly as a third party and bringing it together.”
The point of GE’s studies, of course, isn’t limited to exploring the potential of a standalone hybrid-electric airplane, but it will also inform the development of elements of CFM’s RISE engine program. Studies into RISE, which stands for Revolutionary Innovation for Sustainable Engines, center on an open-rotor concept conceived by the GE-Safran CFM partnership as a bid to deliver at least 25 percent better fuel efficiency at the airframe level over today’s most efficient engines. The RISE program includes research into integrating the open-fan design into a hybrid-electric system to optimize engine efficiency and enable electrification of aircraft systems.
GE Aerospace general manager of advanced technology Arjan Hegeman explained that the hybrid-electric application to RISE would happen at a systems level, effectively allowing designers to make the engine core smaller.
“It's hard to describe from a propulsive efficiency or a thermal efficiency [perspective] because it's really a third system-level type technology that allows you to run a slightly smaller core and still get the same thrust levels and responsiveness that you need,” said Hegeman. “So it's an additional system-level technology that sits in that engine that will allow us to undersize the core just a little bit more.”
Hegeman described the exercise as “definitely an aircraft-integrated technology,” the efficiency gain from which will come partly from the engine. “We can do a small part on it on the engine itself, independent from the aircraft, and get quite a few points of efficiency out of it,” he explained. “But then clearly once you do that, you have an architecture in place that when the aircraft technologies and energy storage technologies continue to mature, you can start getting more and more efficiency out of the architecture. So it's definitely a step-up type approach.”