ANALYSIS: Rolls-Royce harvests a decade of research for new engine projects

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As Rolls-Royce prepares to build and begin testing next year its seventh member of the Trent family – the 7000 for the Airbus A330neo – it is harvesting the fruits of a decade’s worth of research and development projects into two studies that could form the basis for a new generation of widebody – and even possibly narrowbody – engines in the 2020s.

The UK propulsion specialist wants to develop technology and products that will secure a 50% share of the twin-aisle market, as well as – perhaps more ambitiously – help it break back into the growing single-aisle sector, vacated when it abandoned the International Aero Engines consortium in 2012, just when a host of new narrowbody programmes were arriving on the market.

The company earlier this year revealed its Advance and UltraFan designs. Although both are far from being formal programmes, they are based on the three-shaft structure of the successful widebody Trent family, in particular the Airbus A350’s Trent XWB. R-R says they could, in theory, be ready to enter service as production engines as early as 2020 and 2025, respectively.

R-R says Advance and UltraFan are about highlighting its progress in a range of technologies, from composite fans to lower-emissions combustion systems. The company’s timescale for bringing these to market, however, means the engine studies are more than simply “what-might-be” concepts. It has already proved, or is currently testing, many of the engines’ novel elements.

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The advance's carbon/titanium fan system has been tested on a Trent 1000 at the Stennis centre

Rolls-Royce

Advance and UltraFan are not just Trents with tweaks, stresses Alan Newby, chief engineer, future programmes and technology. Although they rely on the same three-shaft architecture, the first of the two engines, Advance, will have a new core – with a larger high-pressure compressor and smaller intermediate compressor – as well as a composite fan and casing.

Other changes include an adaptive cooling system, a lower NOx combustor, “dynamic sealing” to minimise leakage and a wider use of ceramic-matrix composites. “Advance is the next generation in three-shaft engines and brings together a lot of the technologies that we’ve been working on for the past 10 years. There are a lot of differences. The HP and IP compressors are very different,” he says.

There is a clear commercial goal too. “We are getting the technology bricks in place, and when we get the call to develop [Advance] for an aircraft programme, we will,” adds Newby. “We won’t launch a programme until we have a requirement, but we think we will have de-risked all the technologies by 2015 or 2016 and be ready with a new application from 2020 onwards.”

The test or “slave” engine for many of the new core technologies is a Trent XWB, with its core removed and replaced by the trial HP and IP system. “It’s a good platform for testing. We have quite a big project team up and running on it,” says Newby. R-R has started machining components for the engine and other elements have been ordered from the supply chain.

Although the company has no plans as yet to fly the adapted Trent XWB independently, it will undertake ground tests next year. Separately, a carbon/titanium fan system, which will be used on both Advance and UltraFan, has just completed a phase of testing – on a Trent 1000 engine – at the company’s outdoor jet engine test facility at the John C Stennis Space Center in Mississippi.

While R-R plans to test elements of its Advance engine separately, it intends to build a whole engine demonstrator for the UltraFan, with a vision of it taking to the air on a flying testbed by the end of the decade. “Given the amount of changes, we would need to verify it in flight,” says Newby. “Four or five years before entry into service is when you’d want to be maturing the technologies.”

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Several engines are dedicated to research

Rolls-Royce

These technologies include a variable pitch fan, with gearbox, and a high-speed IP turbine, as well as possible adaptations to the core. “UltraFan takes the core configuration we will have developed for Advance and adds a lower-speed fan,” explains Newby. “This turns at a relatively low speed, so it makes sense to add a gearbox.”

Although UltraFan retains the Trent’s three-shaft compression system, the enhanced IP turbine drives the fan via a power gearbox, allowing the LP turbine to be eliminated. The gearbox is “critical technology”, says Newby. “We have experience through our work on the JSF [Lockheed Martin F-35 Joint Strike Fighter] and elsewhere on the military side. We are not starting from scratch.”

The engine manufacturer has already allocated more than a dozen engines to the various technology projects that have led to Advance and UltraFan. Many of these have been supported with research and development funding from the EU and R-R’s “home” governments: the UK, USA and Germany.

Its ALPS study, intended to come up with a lightweight LP system, has used three Trent 1000s. The first phase of engine testing was completed in 2013 and the second has just finished at Stennis. A third Trent 1000, fitted with the composite fan, has been shipped to Tucson, Arizona, for flight testing on a Boeing 747 by the end of the year.

A second project, EFE, running since 2010, focuses on “hot end technologies” and also uses the Trent 1000. Testing on a fourth engine has just ended at R-R’s Bristol facility. A final study, ALECSYS, is about developing a “robust lean-burn combustion system” and involves flight testing two Trent 1000s converted with a lean-burn combustor in 2015 and 2016.

R-R claims that the bundle of technologies on Advance and UltraFan could improve efficiency by 20% and 25% respectively, compared with the first Trent, the Trent 700. Newby adds that the technology is scalable and could cover a range of thrusts from 30,000lb (134kN) to more than 100,000lb, a much broader band than the current family’s 53,000-95,000lb range.

However, the company is quick to point out that this does not offer a direct clue to how it might re-enter the single-aisle market in the next decade. “Scaling down is possible, and in theory these technologies could form the basis of a new narrowbody engine,” says Newby. “But this is not necessarily the route we will take.”