UK industrial technology group Rolls-Royce gives high priority to research and development (R&D), particularly with regard to aero engines. “We are focused on pioneering the power that matters and are at the forefront of research into the future of flight,” affirms Rolls-Royce VP customers: Africa Kevin Evans. Currently, the group’s two major civil aero engine R&D programmes are the UltraFan and the Accel Project.
The UltraFan is a next-generation gas turbine design. “It will offer a 25% fuel efficiency improvement over the first generation of the Trent engine,” he reports. “Testing continues to proceed extremely well, with a new set of tests on composite fan blades and fan cases taking place right now. The gearbox for the engine has already set a new world power record for an aerospace gearbox while on test at our facility in Germany.”
UltraFan is the second stage of a turbofan R&D programme, the almost concluded first stage of which is designated Advance 3. While Advance 3 should be launched next year, UltraFan is scheduled for launch in 2025. Both build on the more than 100-million operating hours of experience that Rolls-Royce has gained from its Trent family of engines. Both further develop the group’s three-shaft engine architecture, first developed for the RB211 engine in the 1970s; this architecture is currently unique to Rolls-Royce in civil applications. ‘Three shaft’ means that the engines have an intermediate compressor and turbine stage, as well as high pressure and low pressure compressor and turbine stages. The three stages are mounted on separate shafts which run concentrically with one another. Other companies’ civil turbofan designs use only two stages: the high and low pressure.
Advance 3 will provide the greatest overall pressure ratio of any commercial turbofan, increasing efficiency, thereby reducing fuel expenditure and costs, and also reducing carbon dioxide emissions. UltraFan will add a major increase to this in the engine’s bypass ratio, which will further increase efficiency and decrease costs, emissions and noise.
A turbofan engine is fronted by a large fan; this fan has a larger diameter than the gas turbine behind it, so not all the air drawn in by the fan – and given initial compression – goes through the gas turbine; some bypasses it – hence, the term ‘bypass ratio’, that is, the ratio between the air that goes through the turbine and that which, after going through the fan, bypasses it. This bypass air adds to the thrust of the engine. The higher the bypass ratio, the more efficient the engine.
The UltraFan will be based on a scaleable design, which will be available in versions with thrust ranging from 111 kN to 446 kN. This will allow the design to be used to power both single-aisle and long-haul wide-body aircraft. “We also continue to research how gas turbine and airframe integration can be further improved to create greater efficiencies,” he adds.
“We are also at the forefront of research into electrification, which we regard as the third wave of aviation,” he highlights. “We are working with partners on the Accel project to build a high-performance electric aeroplane that will fly for the first time, in the UK, in 2020. It will reach speeds of 300 mph (almost 483 km/h), and quite likely [faster], making it the fastest all-electric plane in history.”
Accel is an acronym for ‘accelerating the electrification of flight’ and the project is partially funded by the British government. Rolls-Royce’s partners in Accel include the Aerospace Technology Institute (a public–private partnership between the UK government and UK aerospace companies), YASA (a manufacturer of electric motors and controllers) and Electroflight (an aviation startup company). The Accel aircraft, a single-seat propellor-driven low-wing monoplane with a carbon-fibre airframe, will draw its power from a battery pack, with 6 000 cells that will have the greatest energy density of any aircraft battery ever assembled. It will have a maximum power of 750 kW and a range of almost 322 km (enough to fly from London to Paris).