Guy Norris Despite supply chain slowdowns, the UltraFan demonstrator comes together as supporting tests continue.
Guy Norris
The large scale of the UltraFan is apparent as titanium outlet guide vanes are fitted into a test version of the composite fan case. Credit: Rolls-Royce
As components for the first Rolls-Royce UltraFan demonstrator continue to come together at the company’s Derby, England, headquarters, the gearbox assembly at the heart of the new high-bypass engine has set a record-breaking level of power transmission during preinstallation checkout tests.
The gear system transfers power from the fast-spinning intermediate-pressure (IP) turbine to drive the slower-turning fan, allowing both to operate at their optimum speeds, and that is key to meeting the enhanced propulsive efficiency targets of the UltraFan. The new engine will be the first Rolls large turbofan to incorporate a power gearbox (PGB) and represents the first fundamental change to the company’s direct-drive three-shaft architecture since the RB211 was designed in the 1960s.
Developed in partnership with Liebherr-Aerospace through the Aerospace Transmission Technologies joint venture, the standard PGB transmitted 64 megawatts—the equivalent of 85,800 hp—during tests at Rolls-Royce’s dedicated facility in Dahlewitz, Germany. “[The power level is] a massive tick in the box to say it’s ready to support the engine demonstrator program,” says Andy Geer, chief engineer of UltraFan product development and technology at Rolls-Royce.
“The PGB operation extended beyond the sea level maximum takeoff power levels that would be associated with a product of around 80,000-lb.-thrust capability in order to cover the needs of the upcoming UltraFan demo sea level engine-test regime,” Geer says. “This will take test engines beyond service-representative thrust levels to fully explore capability. So far, the PGB has operated to conditions about 10% beyond a service maximum takeoff thrust condition,” he adds.
For the high-power test, Rolls engineers ran the unit until it was fully thermally stabilized—a test that typically takes about 10 min. to reach the target condition. “One of the other things we’ve done with the power gearbox is a demonstration flight cycle in which we simulated a flight from London to New York,” Geer says. “This was representative of a flight cycle, including takeoff, climb, cruise and descent and all the operating conditions of that cycle.”
Pictured from the core side, the demonstrator’s combined power gearbox and front bearing housing are instrumented prior to preshipment tests in Germany. Credit: Rolls-Royce
The gearbox for the first demonstrator, UF001, is meanwhile set to begin a final pass-off test in Germany in early September before being shipped to the UK for integration into the engine. “The size of the thing is impressive—the power gearbox module with its surrounding engine structure is about the same size as a Tay engine—so it’s a big brute,” he continues. “We are desperately keen to get the unit over and built into the engine now.”
Like many other parts of the demonstrator, Rolls originally hoped to induct the module by midyear. But delays caused mostly by supplier disruption attributed to the COVID-19 pandemic have inevitably pushed back the schedule for final engine assembly. “It has been an unprecedentedly difficult period of time to be bringing lots of parts through the supply chain, and we continue to struggle with that,” Geer adds. “I’m not going to count my chickens, but hopefully we’ll be there by the end of the year. If not, we’ll be very close, and it’ll be into early next year.”
Trial installation of the composite fan case, with titanium outlet guide vanes and metal support ring, is also underway in advance of the unit’s arrival for the demonstrator engine from Rolls’ composite production site in Bristol, England. “That is going through some instrumentation attachment and will be brought up to Derby and take over where this one leaves off quite shortly,” he says.
Assembly of IP and high-pressure compressor modules is also underway in the company’s DemoWorks facility—a refurbished experimental build shop in Derby where a center of excellence has been set up for building the UltraFan demonstrator engines. “We did that very consciously to have focus and to wrap a team tightly around the engine so that they get to know the parts very well,” Geer explains. “It’s obviously different than a Trent, both in the component parts and its build sequence. So we wanted to have a team that [could] rapidly get familiar with it and [become] experts in its construction.”
All 18 composite fan blades for the initial demonstrator are now assembled and undergoing instrumentation work for the installation of strain gauges. The fan set will be one of the final parts of the engine buildup sequence to be completed late this year, Geer says.
Multistage drum assemblies of the first UltraFan high-pressure compressor are pictured prior to integration in the DemoWorks. Credit: Rolls-Royce
Other supporting efforts for UltraFan technology test and development, meanwhile, continue in parallel with the main engine demonstrator. These measures are mainly centered on the high-temperature turbine (HT3) demonstrator and Advance3 engine tests. The HT3 is based on a modified Trent XWB-97 and is “about to run,” Geer says. Designed to prove out hot-section technology for the UltraFan, the high-pressure turbine of the donor engine has been replaced with a new module that incorporates advanced blade and vane configurations with enhanced cooling channels produced through the company’s cast-bond process.
“It’s essentially a production-standard engine into which we introduce these novel parts,” he adds. “It’s got no instrumentation in it because the engine is intended to be a durable platform to do cyclic and high-temperature proving of these new pieces of technology.” In addition to supporting UltraFan, the initiative could pave the way for future Trent upgrade packages, Geer says.
Rolls is also rebuilding the Advance3 demonstrator, which is being used to prove out the new high-pressure core for the UltraFan. Sandwiched between the conventional fan system of a Trent XWB-84 Airbus A350 engine and the low-pressure turbine of a Trent 1000 Boeing 787 engine, the core is about to enter its second major test effort. “The second phase of Advance3 is to precede the first test of the UltraFan engine,” Geer says. “Risk-wise, it makes sense to learn what we can get from this vehicle, before we run UltraFan, so the race is on to do that. It’s going through the DemoWorks organization to be built up [and be] ready for test again very early in 2022.”
“We learned a lot from Advance3 in the first build, and this is a chance now to push the engine harder beyond the operating envelope we ran it through before,” he says. “We shall give it more challenges and a bit more ‘rough stuff,’ if you like, in terms of pushing the engine beyond its normal operating steady-state data collection mode.” Testing will include transient operation handling characteristics and other non-normal conditions.
