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Rolls-Royce is the latest engine builder to begin testing liquid hydrogen combustion and wants to use many of its current powerplants in a project that might lead to the flight of a hydrogen-powered Pearl 15 business jet engine.
As a first step, ground runs of an AE 2100 turboshaft driven by liquid hydrogen – the same engine previously used to test its PGS1 turbogenerator system – will begin in the United Kingdom later this year.
Alan Newby, director of aerospace technology and future programmes at Rolls-Royce, explains that this “early concept feasibility” phase will provide a “really good early indication of hydrogen combustion, how we control it, and how it can work, and it will give us clues about some of the other areas we need to work on.”
Rather than a total redesign of the combustion chamber, he adds that only a “very straightforward change of the fuel injector itself” will be necessary to allow the engine to run on hydrogen.
The AE 2100 tests will be followed by ground runs of a Pearl 15 business jet engine adapted to run on the fuel using a “far more typical system” at an unspecified date.
First, Rolls-Royce will demonstrate that the hydrogen system can be decoupled from non-combustion services performed by conventional fuel, such as heat management.
“Once we’ve accomplished that, we’ll run the engine on hydrogen,” he says.
This will give us great confidence in our ability to comprehend all of the issues associated with a liquid hydrogen-powered gas turbine.
Several locations are being considered for this portion of the program, including the Rolls-Royce test site at the Stennis Space Center in Mississippi, United States.
Newby asserts that the initiative could eventually lead to flight trials of the hydrogen-burning Pearl 15 on the company’s Boeing 747 flying testbed.
However, the manufacturer has yet to commit to this program aspect. “We must determine if there are further advantages to conducting a flight test on the engine.
“The question for us is whether operating a hydrogen engine at altitude teaches us more at the system level. Internally, we are conducting a great deal of research to determine what further benefits exist beyond ground testing.”
Newby asserts that the Pearl 15 is ideal for the tests because it combines the compact size of a smaller engine with the internals of a larger engine.
“There are certainly more options for flight testing with this engine than with a larger engine,” he argues.
The engine manufacturer is seeking further funding from the UK’s Aerospace Technology Institute and the EU’s Clean Aviation program for the project.
Rolls-Royce has been involved in a number of studies with airlines, including as EasyJet and Wideroe of Norway, and research organizations to better understand the operational and technological issues of using hydrogen as a fuel.
Newby states, “We have exerted a great deal of effort to comprehend the principles.”
Newby emphasizes that Rolls-research Royce’s is customer-agnostic, despite the fact that numerous aircraft manufacturers, including Airbus, have already committed to hydrogen power for future aircraft.
However, he notes that its test program is generally in accordance with Airbus’s stated timescales for aircraft development under the ZEROe initiative.
In a project involving long-term narrowbody propulsion supplier CFM International, the airframer has already committed to flight testing a hydrogen-powered engine.
Rolls-Royce “respects” this decision, according to Newby, who adds, “What we want to make sure of is that when [Airbus] reach the stage where they say they will produce a new aircraft in year x… that we have the necessary technology and they have a choice of powerplants.”
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