Rolls-Royce has frozen the design for a demonstrator version of its UltraFan future engine programme, which is to be run in ground tests in 2021.
The step marks the end of the programme's first development stage and represents a "significant and exciting point" in the technology effort, said Andy Geer, project director for the UltraFan demonstrator programme, during a 5 July briefing.
As the powerplant's basic architecture has been locked, engineers can now concentrate on detailed design and, subsequently, on the manufacture of first components, he says.
Meanwhile, R-R is proceeding with demonstrator testing of individual sections of its future engines. At its Derby base, the manufacturer is conducting ground trials of its Advance 3 demonstrator to assess a new engine core with higher thermal efficiency than current-generation equipment.
Compared with R-R's latest large engine – the Trent XWB – the new core will have a larger high-pressure compressor, a shorter intermediate-pressure compressor and a lean-burn combustor featuring two separate fuel-flow systems intended to optimise combustion in cruise versus high-thrust flight phases.
The core has been equipped with the fan system from a Trent XWB-84 and a Trent 1000's low-pressure turbine. Ground tests began in November 2017. R-R intends to have the core ready for a potential new engine programme that could enter service from 2020.
Additionally, the core will be employed on the future UltraFan engine family, which will have a geared, IP turbine-driven fan and no low-pressure turbine. The UltraFan is scheduled to be available for service entry from 2025.
Geer says the new core has performed "really well" in tests, during which the engine operated at maximum take-off power, representing output from the Trent XWB-84.
New technologies employed in the core – including ceramic matrix composites in the HPT and additive-layer-manufactured components in various areas – have performed in line with R-R's expectations, Greer says. He notes that the team is "carefully stepping through... a complex series of tests" – including bearing load measurements, noise evaluations, x-ray examinations, thermal surveys and water-ingestion trials – as just a single demonstrator engine is available for the programme.
Particular attention is being paid to using data from the trials to verify R-R's capability to predict the new engine's performance and behaviour through simulation and digital modelling, Geer says.
Separate evaluations of the lean-burn combustor on another modified Trent 1000 – named ALECSys, or advanced low-emission combustion system – were completed earlier this year. In January, that engine finished ground testing in Derby and was then transferred to Manitoba in Canada for cold-weather rig trials.
Later, the engine underwent water-ingestion tests at the same site. Geer says the effort allowed a "really good exploration of learn-burn performance under tough conditions".
Back in Derby, the manufacturer is preparing ground tests for its advanced low-pressure system (ALPS) demonstrator on a further modified Trent 1000, to assess a composite fan system. The carbon-titanium (CTi) fan blades were previously tested on R-R's Boeing 747 flying testbed in 2014. But the forthcoming ground tests will concentrate for the first time on the entire fan system, comprising blades and fan case.
Geer says the engine is ready for the trial, but has been put on hold because of limited test cell capacity. The assessment is scheduled to begin during the fourth quarter and will be focused on performance and interactions between the fan blades and case, Geer says.
He thinks it is unlikely that the ALPS will undergo further flight tests. Instead, he believes the next time the composite fan will take to the air will be as part of flight tests for the UltraFan demonstrator. R-R has not disclosed a flight timetable for UltraFan, but says ground trials of the fully integrated demonstrator engine are set to begin in 2021.
Meanwhile at R-R's German facility in Dahlewitz, near Berlin, the manufacturer is testing the fan gearbox for the UltraFan demonstrator. The purpose-built test facility features an attitude rig to simulate pitch and roll movements, which is aimed, in particular, at assessing oil flow – crucial for both lubrication and heat absorption – in different phases of flight. Additionally, the site includes a power rig to assess the gearbox's capability to handle shaft speeds and loads.
The planetary gearbox for the UltraFan demonstrator has an approximately 80cm (31.5in) diameter and has been designed to transfer power up to 70,000hp (52,200kW). Trials on the power rig began in 2017 and more than 150 test hours have been logged to date. Geer says that tests on a fourth gearbox started in June, and that a fifth article is currently being assembled, scheduled to begin tests in September.