Rolls-Royce is pursuing its Vision strategy with a raft of future engine concept studies stretching forward more than 20 years. Under the strategy, which was first unveiled in early 2014, work is under way on a rolling program of technologies to meet expected requirements in what the manufacturer terms “exciting times ahead,” according to civil large engines future-programs chief engineer Phil Curnock.

Planned Rolls-Royce demonstrator testing covers the previously revealed Advance and UltraFan engines (including the latter’s power density gearbox [PGB]), and advanced low-pressure system (ALPS), advanced low-emissions combustion system (ALECSYS), and high-temperature turbine technology (HT3) full-scale demonstrator programs. The Advance concept is scheduled for readiness in “2020+,” about five years ahead of the UltraFan, which will introduce bypass ratios of more than 15:1 and more than 70:1 overall.

Beyond the next decade, the 2030s should see further new Rolls-Royce powerplants evolve as part of the trend towards more integrated engine and aircraft systems, with more embedded technology and distributed propulsion. Along the way, the manufacturer hopes to develop technologies that can be put “on the shelf” in intervening years and “chosen to fit,” while also using some for Trent family applications.

Current work involves at least 10 elements: intermediate- and high-pressure compressor (IPC and HPC) rigs, Advance3 core, PGB, ceramic-matrix composites (CMCs), lean-burn combustor (LCB), carbon-titanium (CTi) fan, research centers, UltraFan, and high-temperature technologies.

IPC rig testing begun in early 2016 has been supported more recently by related HPC work, as Rolls-Royce uses advanced sub-system architecture to confirm compressor operability. The “Advance-style” IPC and HPC rigs involve comprehensive aerodynamic demonstrator test programs aimed at proving “the design, efficiency, and stability” of new four- and 10-stage compressors, respectively, says Curnock.

Tip-clearance, vibration, and noise tests have been successfully completed on the IPC, while HPC testing should be complete soon after the Farnborough International Airshow, with Rolls-Royce planning to deploy both units in Advance and UltraFan applications.

Construction of Rolls-Royce’s “next-generation” Advance3 core demonstrator, which contributes to future Advance/UltraFan family HPC and IPC spools, started before April this year, with ground testing planned to begin during October-December and second-phase testing set for the second quarter of 2017. Advance3 uses the Trent XWB-84 fan from the Airbus A350 and the Boeing 787’s Trent 1000 low-pressure turbine (LPT).

Rolls-Royce’s next testing milestone involves the PGB, which the UK company is developing with German joint venture partner Liebherr-Aerospace. Initial unit PGB1 should start rig testing in the current quarter, with PGB2 earmarked to follow before mid-2017, both at a new centre at Dahlewitz, south of Berlin, that was completed earlier this year. The PGB will enable future high-bypass ratio engines to deliver efficient power over a range of take-off thrusts, say the partners. Located in Friedrichshafen, the joint venture will provide production engineering for the PGB drive-train components.

Also scheduled shortly is a brisk round of testing for Rolls-Royce’s lean-burn combustor (LBC), starting with full-engine groundwork. A feature of the LBC is its unconventional dispersion of nozzles to mix fuel at an earlier stage in the combustor.

Two ground-test engines are being built for ice, noise, and other testing before the LBC is flown on the engine manufacturer’s Boeing 747 testbed. Full-engine ground running and ice testing of Rolls-Royce’s carbon-titanium (CTi) fan, developed from Trent hollow-titanium wide-chord fan-blade technology, are planned to begin toward the end this year.

By mid-2017, Rolls-Royce expects to have frozen the concept for the UltraFan demonstrator engine, for which Curnock says “the Advance core reads straight in.” The UltraFan Program is said to be “on track” with the low-speed fan rig test among those already completed. The engine is expected to fly in 2021, about four years before entry into service.

Architecturally, the UltraFan concept—to which the Advance design provides a stepping-stone—represents a major step away from Rolls-Royce’s hallmark large-engine three-shaft structure introduced more than 40 years ago and still successfully championed by today’s Trent powerplants. Whereas in those engines, the low-pressure turbine (LPT) drives the fan, and the IP and HP turbines propel the IP and HP compressors (respectively), the UltraFan’s “enhanced” IP turbine will drive the fan—eliminating the LPT and creating what R-R has dubbed a “2.5-shaft” design.