Despite the growth of electric motors for aviation, the gas turbine engine will continue to provide power for many years to come, according to Rolls-Royce. One of the “big three” players in the global aircraft propulsion field, Rolls avers that only gas turbines can provide the necessary power density to propel large aircraft over long ranges. Even for small aircraft on shorter ranges, the gas turbine plays a part in providing power as part of a hybrid-electric propulsion system, such as the 600- to 1,200-kilowatt turbogenerator announced by the company this week at the Paris Airshow.
Tackling sustainability stands at the heart of Rolls-Royce technology efforts, including the development of electrical power units. For the gas turbines, however, the company is focusing on efficiency and adapting them to cleaner and ultimately zero-carbon fuel sources.
The UltraFan demonstrator, which began testing last month, showcases the company’s commitment to more efficient engines. With a 140-inch fan, it is the largest aero engine ever built. Early tests have proved encouraging, with full power tests due for later this year following a pause to install a dynamic X-ray for examining engine behavior while it runs. The UltraFan’s geared architecture and optimized turbine/case clearances form part of a technology drive to create an efficiency increase of 10 percent over the Trent XWB series, which itself improved on the preceding Trent 700 by 15 percent. The company also has a number of associated technology demonstrations aimed at increasing overall gas turbine efficiency.
Rolls-Royce has begun clearing its engine range for 100 percent sustainable aviation fuel (SAF) use while preparing alongside Boeing and Virgin Atlantic for a 100 percent SAF transatlantic flight later this year with a Trent 1000-powered Boeing 787. Blended SAF essentially serves as a drop-in replacement for traditional jet fuel. Adoption of 100 percent SAF is more an issue of gaining approval rather than clearing technical hurdles. For the future, however, the brightest promise comes from liquid hydrogen fuel. The main challenges involve the transportation of a cryogenic liquid held at very low temperatures (-253 deg C) and turning it into a gas that can combust with minimal emissions of gases such as nitrogen oxide at room temperature.
Rolls-Royce, in partnership with EasyJet, has already tested hydrogen fuel in gaseous form in an adapted AE2100-A turbine, the engine that powers the Saab 2000 regional airliner. The November 2022 test, which used hydrogen produced in the Orkney Islands by EMEC using renewable energy, was the first run of a modern engine using hydrogen.
Now the company has embarked on a test campaign using a Pearl 15 engine that will initially clear 100 percent SAF for use, before moving to trials with gaseous hydrogen fuel. Ultimate plans call for the campaign to demonstrate operation with a liquid hydrogen fuel source.