UK-based global major propulsion and power systems group Rolls-Royce announced on Monday that it and its partners had achieved a significant breakthrough in making hydrogen a practical fuel for aeroengines.

In what the group described as a “world industry first”, tests using a Pearl 700 jet engine’s full annular combustor and employing 100% hydrogen fuel had established that hydrogen could be combusted under conditions representing an aircraft’s maximum take-off thrust.

It was the successful design of advanced fuel spray nozzles (which control the combustion process) which enabled the breakthrough. Hydrogen burns at far higher temperatures, and faster, than kerosene, so the development of the nozzles required the overcoming of “significant” engineering problems. The new nozzles employed a new system to control the flame position, which progressively mixed air with the hydrogen, to manage the reactivity of the fuel. Emissions and combustor operability were both in accord with expectations.

Rolls-Royce’s partners in this research programme are UK-based low-cost airline easyJet, Loughborough University (also in the UK) and the German Aerospace Centre (Deutsches Zentrum für Luft- und Raumfahrt, or DLR). Initial, intermediate pressure tests of the individual nozzles were run at Loughborough University. The full-pressure tests of the complete combustor were run at the DLR facility in Cologne.

“This is an incredible achievement in a short space of time,” enthused Rolls-Royce chief technology officer Grazia Vittadini. “Controlling the combustion process is one of the key technology challenges the industry faces in making hydrogen a real aviation fuel for the future. We have achieved that, and it makes us eager to keep moving forward. I want to thank easyJet, Loughborough University and DLR for their dedication and support to reach this milestone.”

“This is an outstanding success story and we are more than happy to have contributed our hydrogen testing capabilities,” affirmed DLR divisional board member aeronautics Markus Fischer. “It was very exciting supporting this technology journey and seeing the burner technology mature in various rigs at our Institute of Propulsion Technology. This underlines again DLR’s capabilities in complex applied research and the achievement, at such a high pace, was supported by our experience in real-scale testing of ground-based gas turbines.”

The next stage in the test programme will see the full ground testing of a Pearl engine using gaseous hydrogen as fuel. This will be followed by the full ground testing of a Pearl engine using liquid hydrogen fuel. Both easyJet and Rolls-Royce hope to follow this with a flight test programme.

“We believe hydrogen is the future of short-haul aviation and the success of this test and progress being made demonstrates that this is becoming ever closer,” stated easyJet CEO Johan Lundgren.

Meanwhile, work is continuing on systems to deliver hydrogen fuel to engines, and on integrating those systems with the engines.