Rolls-Royce Pushes Its New Technology Horizon Beyond 2020
A composite fan blade, a real Rolls-Royce Trent 1000 high-bypass powerplant and a model of the Trent XWB being developed for the Airbus A350 are on the manufacturer’s stand here at Farnborough (Hall 4 Stand H3, and Innovation Zone) to illustrate the state of the engine maker’s art and where the company expects to go next. In what the UK-based group calls a “relentless pursuit of technology,” Rolls-Royce is “always looking at 15 to 20 different designs beyond 2020,” according to strategic marketing vice president Robert Nuttall. As the manufacturer continues various engine core and systems demonstrator programs, it is considering the technologies required for future commercial and large corporate aircraft.
Rolls-Royce studies alternative applications for its research results, so future programs must accommodate different possibilities, said Nuttall. Some research addresses outside requirements, a current example being the RB3025 project geared to a Boeing request about an engine for a future 777-size aircraft (see box); other work is driven by internal needs.
Underlining the long-term nature of research and development, Nuttall said tomorrow is “six or seven years away, so it will be [that long] before [a newly launched project] enters service, plus a ten-year development program.”
A key element in Rolls-Royce philosophy is its three-phase Vision program. “Vision 5” describes available, off-the-shelf technologies that could beincorporated into new products or used to update existing engines. Developments at the validation stage and due to be commercially available in the medium-term (up to 10 years ahead) are dubbed Vision 10, while technologies at the emerging (or unproved) strategic research stage and aimed at future generations up to two decades hence are classed as Vision 20.
Unconvinced of the business case for commercial aircraft re-engining programs such as the Airbus A320neo and Boeing’s 737 MAX (and having failed two years ago to dissuade the two airframe manufacturers otherwise), Rolls-Royce officials remain adamant that the future lies in developing projects that match airframes and engines from the start. “We want to design an airplane and an engine that are made for each other, to focus on driving a level of technology that is not going to be available in 2014 or 15 [for new designs planned to enter service in mid-decade],” Rolls-Royce senior vice president Dominic Horwood told the U.S. Pacific Northwest Aerospace Alliance last year.
Accordingly, the engine maker is looking much farther into the future, having dissolved its interest in International Aero Engines (which continues to make V2500 engines as a Pratt & Whitney, JAEC and MTU partnership) in favor of a new 50:50 joint venture with P&W to develop engines to power the next generation of mid-sized airliners (120 to 230 seats).
Smaller members of a family of such engines also could be used on future regional airliners and medium- and large-size business jets. Focusing on high-bypass-ratio geared turbofan technology, the joint venture will collaborate on studies for future propulsion systems, including advanced geared engines, open-rotor technology and other advanced configurations.
For some time, it has been working on new Advance2 and Advance3 two- and three-shaft engine series. Led by German subsidiary Rolls-Royce Deutschland’s two-shaft center of excellence in Stuttgart, Advance2 work considers requirements for aircraft from medium-sized business jets up to 150-passenger narrowbodies. Rolls-Royce believes it can produce a good engine by using a fan derived from its large engines attached to a core based on the E3E efficiency, environment and economy technology-demonstrator that entered test four years ago.
A slightly smaller fan would be used for large corporate and regional jets; removal of a compressor stage will permit the basic core to be used for midsize business aircraft. Advance2 features a “world-leading” 22:1 high-pressure compressor ratio and two-stage HP turbine.
The Advance3 program is based on the Trent 1000-derived environmentally friendly engine (EFE) technology demonstrator core and is aimed at providing three-shaft engines for commercial widebodies such as the prospective Boeing 777X expected to enter service around the end of the decade. Advance3 incorporates “lean-burn” combustion and technology from the advanced low-pressure system (ALPS) demonstrator project.
EFE is part of the UK National Aerospace Technology Strategy program that aims to develop measures that will reduce noise, fuel burn and emissions. One element of EFE includes an active blade-tip clearance-control system. Nuttall said that a “most sensitive area” of engine technology is loss of efficiency because of leakage around blade tips.
The active control senses dynamically what is happening, compared with current systems that sense temperature and control fuel flow to pre-set parameters. According to Nuttall, “The question is: ‘Can you sense the [blade-tip clearance] in real time and adjust it as necessary?’”
The LP system uses a composite fan and casing (for comparison with established titanium equipment) and is on schedule for testing beginning in 2014. Other demonstration work also planned for testing in two years’ time includes the advanced low-emissions combustion systems (ALECSYS) “lean-burn” demonstrator program that has been under way for “some considerable time.”
The program uses an “advanced active-control”system involving valves to meter fuel flow and an “innovative” thermal-management system to reduce mean peak temperatures and the time engine parts are exposed to that level of heat. Nuttall said that ALPS and ALECSYS work involves two separate engines for two separate flying-testbed programs.
Rolls-Royce does not see any imminent move into the application of open-rotor technology, but it has been working on such a powerplant that could become available during 2020-25. The manufacturer wants first to complete any related flight-testing “so that we can have an informed design.” It is not proposing open-rotor flights before the second half of this decade, according to Nuttall.
After completion of wind-tunnel tests with potential open-rotor blade designs, Rolls-Royce became convinced the technology will be quieter than current equivalent-size engines. Using generic round numbers, Nuttall said such designs are expected to offer 10 percent better fuel consumption but would be 10 percent “less quiet.” Meanwhile, the company sees open-rotor propulsion as “the only real game-changer relative to an advanced turbofan, and the only thing that can deliver clear daylight–10 percent better.”