Rolls-Royce chief technology officer Grazia Vittadini recently characterized the UltraFan engine architecture designed for ultra-high bypass ratios as “literally bristling with cutting-edge technologies from the front all the way to the back.”
The company tested the UltraFan technology demonstrator at its Derby, UK site for the first time last month and will now put it through its paces in an effort to start developing a scaled range of engines. The manufacturer’s vision for UltraFan technology centers on a portfolio of two-shaft, three-shaft, direct-drive, and geared propulsion systems ranging in thrust from 25,000 to 110,000 pounds.
Designed to power new narrowbody and widebody aircraft entering service in the 2030s, Vittadini said the initial testing program would last several months, during which time the engine maker will carefully start integrating a host of technologies to help deliver a 10 percent efficiency improvement over the Trent XWB.
The Rolls-Royce engineering executive told reporters that the regime would make purposefully slow and steady progress to support opening the engine’s operational envelope, which she admitted “at times [was] difficult.” Nevertheless, she insisted the team will make rapid progress.
That begs the question: when will airframers be ready to present their airline customers with a new aircraft to exploit the benefit of such new engine technology? While Rolls-Royce goes to pains to stress that the UltraFan technology demonstrator not only heralds the engines of tomorrow but also helps improve the engines of today, the radical propulsion technology still awaits a similarly advanced airframe on which to showcase what Rolls calls a compelling clean-sheet advantage. “Dear airframers, give me an aircraft and you will have your engines,” said Vittadini, who has also served as Airbus’s chief technology officer and executive committee member.
Rolls-Royce director of aerospace technology and future programs Alan Newby told AIN that the manufacturer believes the industry needs such advanced technology to reach a state of readiness for future aircraft types.
“We talk to all airframers all the time, quite frankly,” he said. “We’re in continual dialogue, not just with Boeing and Airbus, but with Embraer, with Gulfstream—all our customers. They’re the ones that go to market and we work with them to determine what is the optimum time because it has to fit with their product strategy. We’re just making sure we’ve got the technology ready when that time comes.”
At a time the development of electric- and hydrogen-powered aircraft steal headlines, Newby insists that gas turbine technology remains central to the engine maker’s development plans. “If you look at any projection out to 2050, you will see SAF, efficiency improvements, and possibly even hydrogen being featured,” he explained. “Yet 90 percent-plus of those applications will still need gas turbine engines in that part of the market that will burn the vast majority of the fuel. That is why we continue to innovate the gas turbine.
“What we’re going to do under the EU Clean Aviation program is to take that a stage further,” he explained. “The obvious one is to push the bypass ratio higher, go for bigger fans that will require further advances in materials technologies, and then continue to develop the aerodynamics. We’ve done some work on aspects like shortening the inlet without damaging fan performance…so we’ll continue to look at fan aerodynamics.”
Until the energy-density challenge for propulsion gets solved, engineers aim to help reduce an aircraft’s CO₂ footprint in an approach termed micro-hybridization, where instead of relying on the gas turbine to completely power the aircraft, electrical power can relieve the engine in certain operations.
“We’ve done some work on micro-hybridization in Bristol on one of our smaller engines where we’ve embedded electric starter generators,” said Newby. “That gives us the ability to take power off the shaft, but also allows us to put it back in. When you combine that with stored electrical power, you can use that to optimize performance around the flight envelope. So, for example, during certain transient conditions or during very low power conditions we could allow the engine to spool right down or, in arduous operating conditions, it could receive a slight boost of electric power.”
Newby added that Rolls believes it can exceed its stated 10 percent efficiency improvement “if you push all the way.”
“The hybridization [results in] probably a single-digit [improvement] but when you combine that with higher bypass ratios and so forth, then you’d be looking at probably going beyond 10 percent,” he concluded.