GKN Aerospace expects a clear path to bringing hydrogen-powered airliners into commercial service open by 2025 in terms of optimum propulsion system architectures and their effective integration with airframes. Working with multiple partners, the aerostructures and engine components specialist says it has made important discoveries from both the H2Gear and H2Jet programs, which respectively focus on hydrogen-electric fuel cell-based powertrains and direct combustion of liquid hydrogen fuel in turboprop and turbofan engines.
According to chief technology officer Russ Dunn, GKN and its partners expect to have completed the preliminary design for a hydrogen-electric propulsion system by the end of this year. “We have defined the architecture for a number of different aircraft with 19, 48, and 96 seats, and it scales [up in size] really well and actually becomes more attractive than we thought for larger aircraft,” he told a pre-Farnborough show press briefing.
From GKN’s perspective, failure to decarbonize flights is not an option for the air transport industry. Dunn said that aviation’s portion of global emissions will inevitably rise in the coming years as flight volumes increase and other industries reduce their emissions. “If we don’t do this, we’ll see a suppression of global flights through measures that we don’t want, such as taxation, so it is in our interests to ensure we can achieve sustainable growth,” he said.
The UK-based H2Gear team endeavors by next year to attain technology readiness level (TRL) 4 and complete testing of the cryogenic electric motor and fuel cells. The following year should see the start of sub-system detailed design and testing as the program reaches TRL5 and then in 2025 the culmination of work with ground-based testing of a full system-level propulsion system.
Work on the £54 million project takes place at GKN’s Global Technology Center in Bristol, UK. With government funding behind it, the partners include fuel cell specialist Intelligent Energy, electric motors and control systems group Aeristech, Newcastle University, the University of Manchester, and the University of Birmingham.
Advances in the understanding of cryogenic technology perhaps have proved the most significant results of the work so far. Dunn explained that reducing the temperatures of electrical wiring lowers resistance, thereby supporting greater power density by limiting the amount of voltage needed to generate more current as the powertrain scales up for larger aircraft. The approach offers the added benefit of eliminating the risk of electric arcing at altitude, which has presented a safety concern for new aircraft.
In the £2.8 million H2Jet project, which gets run from GKN’s facility in Sweden through 2023, the partners evaluate how engine and airframe architectures will need to adapt to support the direct combustion of hydrogen. Potential applications could include new medium-range, single-aisle aircraft, like those conceived through Airbus’s ZeroE program, which GKN says it would like to join. Other H2Jet partners include the Swedish Energy Agency, Chalmers University of Technology, Lund University, KTH Royal Institute of Technology, University West, Research Institutes of Sweden (RISE), and Oxeon.
Environmental sustainability ranks as GKN’s top research and development priority, said the group’s CEO, David Paja. In 2021, even as it weathered the financial impact of a 30 percent drop in sales caused by Covid, the company invested more than £100 million ($121 million) in such work and it expects to at least maintain the same level of commitment over the next few years.
In the rapidly-emerging advanced air mobility (AAM) sector, GKN (Stand C630) partners with four electric aircraft start-ups. For Eviation’s fixed-wing Alice aircraft, it has designed the wing, tail, and electrical system, delivering all of those elements in a nine-month window to get the first prototype ready to start flight testing. UK-based Vertical Aerospace uses GKN’s Bristol manufacturing plant to construct the first prototype of its VX4 eVTOL vehicle, which the company plans to start flying before the end of this year. GKN also partners with rival eVTOL aircraft developer Lilium of Germany
Ultimately, Dunn maintained, all-electric propulsion using batteries will do the most to eliminate all categories of harmful emissions, including carbon dioxide, nitrogen oxides, contrails, and water vapors. That belief largely explains GKN's involvement with new electric aircraft, but the company also wants to be ready to help commercialize other new propulsion options and doesn’t see the solution as involving a binary choice between the various options now under evaluation.
Alliances with existing aircraft engine makers further exemplify its holistic approach to advancing sustainability. GKN serves as a technology demonstrator partner for Pratt & Whitney in its work to develop the next-generation Geared Turbofan. Meanwhile, for the future of unducted fan engines, it works with CFM International on its Revolutionary Innovation for Sustainable Aviation program.
In the realm of aerostructures, GKN’s engineers have focused on achieving a step-change in manufacturing efficiency for increased production rates through Airbus’s Wing of Tomorrow project, for which it already has begun delivering wing spars. That project involves the novel use of resin transfer molding that allows for the production of spars all at once outside an autoclave. The approach reduces the size of the factory floor space required and also energy consumption.
As part of efforts to reduce the volume of materials required to make aircraft structures, GKN plans to extend the use of additive manufacturing. “This can bring a significant environmental benefit in reducing the amount of materials consumed by 60 to 70 percent, while also making production times shorter and the structures lighter [cutting fuel burn in flight],” explained Dunn.
With research and development work bearing fruit in terms of understanding where and how it can achieve progress, the next big decision for GKN and its aerospace partners centers on how exactly to apply the new technology and generate commercial returns. Dunn was coy when asked whether the various projects could see the company expand its product range to include complete new propulsion systems. He expressed confidence in his ability to present the right opportunities to his boss David Paja, who quickly concluded, “but we haven’t yet finalized exactly where we want to play in the whole system.”
