Rolls-Royce and partners have run a Pearl 700 business aircraft engine on 100 percent hydrogen fuel as part of longer-term work to develop a hydrogen combustion engine for narrowbody airliners by the mid-2030s. Working with the UK’s Loughborough University and German aerospace research agency DLR, the aero engines group said tests on a full annular combustor proved that hydrogen can produce maximum takeoff thrust.
According to Rolls-Royce, the breakthrough is based on new fuel spray nozzles that control the combustion process. “This involved overcoming significant engineering challenges as hydrogen burns far hotter and more rapidly than kerosene,” the company explained in a statement issued on September 25. “The new nozzles were able to control the flame position using a system that progressively mixes air with the hydrogen to maximize the fuel’s reactivity.”
The individual nozzles were initially tested at intermediate pressure at Loughborough University’s new test facilities at the National Centre for Combustion and Aerothermal Technology. Then the hardware was tested at the DLR’s facility in Cologne, Germany, where the final full-pressure combustor evaluation was conducted using rigs at the agency’s Institute for Propulsion Technology.
“This is an incredible achievement in a short space of time,” said Rolls-Royce’s 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 of the future. We have achieved that and it makes it easier to move forward.”
Rolls-Royce is working with low-cost carrier EasyJet to develop a larger hydrogen propulsion system. Last year, the company successfully ran an AE2100 turbofan engine on green hydrogen at the Boscombe Down research facility in southern England. Airbus is also involved in the newly formed UK Hydrogen Alliance.
The next step for the partners is to incorporate the learnings from both sets of tests to develop a full gas hydrogen ground test on a Pearl engine. Beyond that, they intend to conduct ground tests on the same type of turbofan using liquid hydrogen.
The Pearl 700 engine powers Gulfstream’s G700 long-range business jet. Rolls-Royce has also developed the Pearl 10X for Dassault’s new Falcon 10X aircraft and the Pearl 15 for Bombardier’s Global 5500 and 6500 models.
First Test Run With Turbine For Hybrid-Electric Powertrain
Also this week, Rolls-Royce reported that it has conducted the first fuel burn test on a new small gas turbine it is developing for hybrid-electric powertrains. The company said the test confirmed the effectiveness of the compact, power-dense turbine that is to be integrated into a lightweight scalable turbogenerator system delivering between 600 kW and 1,200 kW of power.
Rolls-Royce is targeting new hybrid-electric applications including both eVTOL and eSTOL aircraft, as well as regional airliners with up to 19 passenger seats. The new small gas turbine itself could also be used for helicopters, auxiliary power units and military aircraft.
The aero engines group said it could run on sustainable aviation fuel as an initial step to reduce carbon emissions while delivering longer range than is currently possible with all-electric propulsion. In the future, it envisages the turbine running on hydrogen fuel.
For the ground tests, the Rolls-Royce team integrated 14 subsystems in a design, procure, and build process that took just under a year. The test set-up comprises commodity components such as valves and hoses, as well as systems for fuel injection, oil and ventilation, engine mounts, and water brakes. The research and development work is being partly funded by the German Ministry for Economic Affairs and Climate Action.
According to Rolls-Royce, its turbogenerator will be suitable for both serial and hybrid powertrain applications. This means it can both recharge batteries and provide direct power to electric propulsion units so that aircraft can switch between power sources during flights.
