Initial results from crucial tests of two key elements of Rolls-Royce’s future large civil engine strategy – a new core and a high-power gear system – are positive and on track says the powerplant manufacturer.

Providing first details of results from test runs of the Advance3 high-pressure core at the heart of the company’s future UltraFan concept, Phil Curnock, chief engineer for Civil Aerospace Future Programs, says “We have done a significant amount of testing and all technologies are performing well.” 

The core is the common element of the company’s plan to succeed the long-running Trent family with a new gear-driven engine architecture. The new core, which began tests in November in a hybrid demonstrator, will run initially in the Advance, a direct-drive turbofan with a fuel-burn level at least 20% better than the current Trent 700. However the Advance is a stepping-stone to the UltraFan, a very high bypass design that marries the same core to a large gear-driven fan to improve fuel burn by at least another 5% over the Advance. 

In the Advance3 demonstrator the core is sandwiched between the conventional fan system of a Trent XWB-84 Airbus A350 engine and the low-pressure (LP) turbine of a Trent 1000 Boeing 787 engine. “We are in Phase 1 of testing and it is progressing extremely well,” says Curnock. Tests have quickly reached the point where the P30 pressure (at the rear of the high pressure compressor) has “got to 450psi. . . . That means we have got to about 90% of core power.”

Key tests include measurements of the bearing loads to assess the impact of Rolls’ design choice to place more work on the high-pressure spool and reduce the load on the intermediate compressor. “When you change the work split between the compressors it gives different axial forces to the bearings so we need to manage and monitor that,” says Curnock. Other tests on the new core include water ingestion, a noise survey and an X-ray examination.

Tests of the core’s lean burn combustor, which is also a new design to reduce emissions and boost efficiency, have also been positive with no signs of an aero-acoustic effect known as a ‘rumble’ that can sometimes occur with these designs. “We haven’t seen any rumble at all, which is quite satisfying,” says Curnock, who adds that tests for other typical lean-burn-related concerns such as starting issues and fuel scheduling have “gone really well.”

Rolls-Royce has also begun tests of the third power gearbox (PGB) at its Dahlewitz facility in Germany. Evaluation of the unit, which is a planetary-style gearbox with a ring gear on the outside and five planet gears inside rotating around a central sun gear, follows the news in September 2017 that the first PGB had been tested at its maximum rating of 70,000 hp. This rating is designed to enable the gear to be mated with the Advance3 demonstrator, which is aimed at the 70,000- to 80,000-pounds-thrust bracket.

Further components of the future engine family are also being tested in a parallel series of focused demonstrators. These include the advanced low-emissions combustion system (ALECSys), which is dedicated to testing the lean-burn combustor design at a full-scale engine level in a modified Trent 1000. The engine, which made its initial run in the weeks running up to the Singapore Airshow, will shortly be shipped to the company’s test site in Manitoba, Canada, for cold-day and cold-soak starting as well as ice shedding and ingestion testing. Curnock says the engine will later go to Rolls’ site at NASA Stennis in Mississippi for noise testing and “in the next couple of years” will be flown on the company’s 747-200 flying testbed.

Rolls-Royce is also poised to begin runs of the advanced low-pressure system (ALPS) engine, which, for the first time on one of the company’s powerplants, combines tests of a composite fan with a composite fan case. “We have just got to pop the fan blades in the front and we will be putting that on test later this year. That’s a good step forward because that is all about understanding not just the composite blade but also the performance of the composite case with the fan,” says Curnock. Testing is expected to be complete by year-end.