Rolls-Royce has achieved a key milestone in its hydrogen combustion engine research project. Both Rolls-Royce and its partner easyJet are committed to being at the forefront of the development of hydrogen combustion engine technology capable of powering a range of aircraft, including those in the narrow-body market segment, from the mid-2030s onwards.

Now, working with Loughborough University in the UK and the German Aerospace Centre Deutsches Zentrum für Luft-und Raumfahrt (DLR), Rolls-Royce has proven a critical engine technology that marks another significant step in the journey to enabling hydrogen as an aviation fuel.

Hydrogen testing at DLR, Cologne

Tests on a full annular combustor of a Pearl 700 engine at DLR in Cologne running on 100% hydrogen have shown the fuel can be combusted at conditions that represent maximum take-off thrust.

Key to that achievement has been the successful design of advanced fuel spray nozzles to control the combustion process. This involved overcoming significant engineering challenges as hydrogen burns far hotter and more rapidly than kerosene. The new nozzles were able to control the flame position using a new system that progressively mixes air with the hydrogen to manage the fuel’s reactivity. Rolls-Royce confirms that combustor operability and emissions were both in line with expectations.

The individual nozzles were initially tested at intermediate pressure at Loughborough’s recently upgraded test facilities and at DLR Cologne before the final full-pressure combustor tests took place at DLR Cologne.

Last year, easyJet and Rolls-Royce also set a world first by successfully running a modern aero engine, an AE2100, on green hydrogen at Boscombe Down, UK. These recent tests mean the combustion element of the hydrogen program is now well understood, while work continues on systems to deliver the fuel to the engine and integrate those systems with an engine.

Grazia Vittadini, Chief Technology Officer, Rolls-Royce

The technologies tested at Loughborough and DLR will now be incorporated into the learning from the Boscombe Down tests as Rolls-Royce and easyJet prepare for the next stage of testing—a full gas hydrogen ground test on a Pearl engine.

That will in turn lead to a full ground test on a Pearl engine using liquid hydrogen; both easyJet and Rolls-Royce have a shared ambition to then take the technology to flight.

Rolls-Royce receives support for hydrogen research through the UK’s Aerospace Technology Institute HyEST program, Germany’s LUFO 6 WOTAN program, and the European Union’s Clean Aviation CAVENDISH program. Loughborough is a partner in HyEST and CAVENDISH. DLR is a partner in WOTAN and CAVENDISH. easyJet has provided investment to support the development of hydrogen combustion engine technology for narrow-body aircraft.