Rolls-Royce is on course to perform ground runs later this year of a Pearl 15 business jet engine adapted to run on gaseous hydrogen.
UK-headquartered Rolls-Royce has already completed a series of system and component tests that will pave the way towards the full engine trials.
These include hydrogen tests of an annular combustor from a Pearl 700 last year, and earlier work on fuel nozzles and actuation. The project also builds on the November 2022 ground runs of an AE 2100 turboprop on gaseous hydrogen.
Simon Burr, Rolls-Royce group director of engineering, says the project is “all coming together – we are on track”.
Runs of the 15,125lb (67kN)-thrust Pearl 15 burning gaseous hydrogen will take place “later this year”, he told a pre-Farnborough air show briefing on 11 July: “We are all set to run.”
“I’m confident we’ll execute on this. Hydrogen likes to burn – it’s not combusting it that’s the problem,” he adds. Challenges include changes to how the engine is shut down, he says, with nitrogen purging seen as a likely solution.
Further out, if liquid rather than gaseous hydrogen is used then “heat-exchanger technology becomes the most challenging bit.
“But we are just going carefully, because what we need to do is see what the market wants,” says Burr.
“There’s no point getting too far ahead of the market. What we are trying to do is make sure we are ahead and understand the technology challenges but we are not going to forge ahead and put something on the shelf if people don’t want it.”
However, he points out that “at least 50%” of the technology being developed for the hydrogen demonstrator also has a use on conventional gas turbines: “It’s not all unique to hydrogen.”
Rolls-Royce’s German unit, which makes the Pearl 15, is also leading a Clean Aviation-funded project that is charged with developing the technologies necessary to run a modern turbine engine on liquid hydrogen.
Called CAVENDISH, the initiative kicked off in January 2023 and runs until December 2026. Besides Rolls-Royce, the 19-strong consortium working on the project includes airframers Dassault Aviation, Embraer and Fokker Next Gen.
In addition to the ground-test activity, CAVENDISH will also work on “system and powerplant aircraft integration” and “define certification pathways and formulate a route to permit to fly”, according to Clean Aviation project documents. Flight testing could take place in Clean Aviation’s second phase, in the years after 2026.
“Our programme targets the delivery of mature technology in time to support potential future airframe decisions and be ready to serve as preparation for, and feed into, Clean Aviation Phase 2 which is currently in the configuration phase,” says Rolls-Royce.
Having three airframers as part of the project means it is “well placed to allow all consortium members the ability to consider the opportunities and challenges of hydrogen propulsion at platform level”.
