British airplane engine expert Rolls-Royce says it has proven a critical engine technology that marks a significant step in enabling hydrogen as an aviation fuel. “Tests on a full annular combustor of a Pearl 700 engine at DLR in Cologne running on 100% hydrogen have proven the fuel can be combusted at conditions that represent maximum take-off thrust.”

The tests were done with Loughborough University in the UK and the German Aerospace Center (DLR) in Cologne. Rolls Royce says that successfully designing advanced fuel spray nozzles to control the combustion process is critical to that achievement.

Burning hotter than kerosene

That isn’t as easy as one would think, as hydrogen burns at significantly higher temperatures and more rapidly than today’s kerosene. Kerosene is a lighter diesel oil extracted from crude oil before diesel. The lighter weight means it contains slightly less energy. Hydrogen plays in a whole different kind of league.

The new nozzles on the Pearl 700 engine could control the flame position using a new system that progressively mixes air with hydrogen to manage the fuel’s reactivity. “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.”

Turboprop airplane engine

In November 2022, the British airplane engine manufacturer Rolls Royce, with the same name as the car but no other than historical connections, already marked the world’s first by running a modern turboprop airplane engine on green hydrogen. It didn’t fly yet, but it was a successful ‘ground test’ with the British low-budget airline easyJet.

After having the converted AE 2100-A to hydrogen combustion, a turboprop engine known to equip the Saab 2000 regional airliner, among others, the partners plan a series of rig tests leading up to a full-scale ground test with a Rolls-Royce Pearl 15 jet engine.

The Saab 2000 is a twin-engined high-speed turboprop airplane built by Swedish aircraft manufacturer Saab, which can carry 50 to 58 passengers and has a range of 1 549 nautical miles (2 869 km).