The next 18 months are destined to be a busy period for Rolls-Royce’s research and development engineering teams as the UK-based engine manufacturer ramps up test activities on its next generation of turbofan engines.
Its technology road-map, referred to as the Vision strategy, was launched two years ago, and 2016 is the point "where the Powerpoint comes to life”, says Phil Curnock, chief engineer future programmes.
R-R is working on two demonstration programmes, Advance and UltraFan, in order to mature technologies for future propulsion systems – for widebody and, potentially, narrowbody aircraft – which deliver better specific fuel burn and lower nitrous-oxide (NOx) emissions.
“It is really about putting technology and architecture on the shelf so that when an aircraft comes along we have got them demonstrated and available so we can integrate them into product offers for our customers,” says Curnock.
For Advance, its Vision 5 near-term effort, the basket of technologies under evaluation include ceramic matrix composites, a lean-burn combustor and control system, a 304cm- (120in) diameter composite/titanium fan, and a new three-spool architecture that redistributes workload from the intermediate- to the high-pressure compressor. Curnock describes this move as “a step-change for large engines”.
That architecture will be ported across to the UltraFan engine, which is scheduled to begin flight testing in around 2021. However, UltraFan also gains a power gearbox – similar to that on the Pratt & Whitney PW1000G series – allowing the fan to rotate at an optimum speed, rather than at the same rate as the low-pressure turbine (LPT). In fact, R-R goes one stage further and entirely removes the LPT on UltraFan, creating a highly compact engine.
Ground tests are scheduled to begin in the fourth quarter of 2016 of a full-scale Advance3 demonstrator, which marries the new 10-stage HPC and four-stage IPC with the fan system from the Trent XWB-84 and the low-pressure turbine from the Trent 1000. That powerplant is currently in build at its Bristol site, ahead of transfer to its Derby test cell.
Trials of the IPC concluded earlier this year, with rig evaluations of the HPC due to finish by the end of July and have so far yielded “positive results” and “good stability”, says Curnock.
Maturation work on its CTi fan – which features composite blades with titanium leading edges – continues this year, following flight trials aboard the company’s Boeing 747 test bed in 2015. Further ground-rig runs, including ice testing are planned over the next six months, running into 2017, “to mature our understanding of the technology”, says Curnock.
After completing initial trials of its lean-burn combustor in December 2015, additional tests, including cold-weather starts and ice-shedding performance, are planned for the component and its associated control system this year, ahead of a 2017 first flight. The combustor uses a larger spray nozzle to enable mixing of the fuel and air earlier to achieve a more efficient fuel-burn producing less NOx. In addition, the new design features two separate fuel flow systems “that we are able to turn up or down accordingly”.
And 2017 will also see the first run of R-R’s Trent XWB-97-based HT3 (high-temperature turbine technology) test bed. This features metallic components that use a next-generation cooling design made possible by manufacturing advances, specifically the company’s CastBond process, alongside use of CMC parts that are lighter and able to withstand higher temperatures than metal alternatives.
Rival GE Aviation has already pioneered the application of CMCs in the shrouds and combustor liners of the Leap engine produced by its CFM International joint venture, but R-R is taking a slightly different approach. It will employ the material in seal segments in the high-pressure turbine, but sees “more than 10” applications in the combustor and turbine blades and vanes.
“We see most benefits in the turbine area. It’s a journey through seal segments to guide vanes into blades,” says Alan Newby, R-R’s director aerospace technology for future programmes.
“This is a journey in high-temperature development – we just keep adding more and more high-temperature-capable materials,” adds Curnock.
And with the tests taking place on a modified Trent XWB, Curnock admits that it raises the possibility of technology insertion upgrades on existing engines. “It’s part of our strategy to feed this back at the appropriate time into our fleet.”
All of these advances will also feed into the UltraFan development, which will be ready for production in 2025. Tests of the engine’s key power gearbox, a part that must be capable of handling around 100,000hp, are due to kick off in the third quarter at a newly built facility at its Berlin site.
The initial powerplant will also feature a high bypass ratio of around 15:1: “That’s what the geared concept gives us the opportunity to do,” says Curnock. However, the final production ratio will vary depending on the application, adds Newby.
It is also designed with fixed-pitch blades “but we retain the option for variable pitch”, says Curnock, along with the potential for a “variable area nozzle”, but it is yet to be decided whether it is included in the final product.
Further out, Curnock admits the future of engines and aircraft is harder to read, but its near-term goals are much clearer, not least for the rest of 2016.
“It is a packed year where Advance and UltraFan are starting to become a reality. That [future engine] strategy is really starting to come to life.”
Meanwhile, Rolls-Royce is preparing to build the first production examples of the engine that will exclusively power Airbus’s A330neo. Both the A330neo and the Trent 7000 were launched at the Farnborough air show in 2014, and the widebody is scheduled to enter service with TAP Portugal towards the end of next year.
The UK propulsion specialist has two engines in test – the first engine run was in November 2015 – and a further two in development. L71 has completed altitude and icing tests, L73 has had its first run, L72 is in module build and L74 – which will do the bulk of cyclic and ETOPS testing – is being kitted.
Rolls-Royce has released more detail about the engine, which is a development of the Trent 700 for the original A330 and uses technology from the Trent 1000 TEN for the Boeing 787. Additions include a new engine electronic control, gearbox and air bleed system.
The first Trent 900 for the Airbus A380 to go into service with Emirates later this year will be the first to come with the engine maker’s latest “enhanced performance” specification, Rolls-Royce has disclosed.
The engine maker has been building Trent 900 to the new standard – known as EP3 – since May and has delivered the first two shipsets for the Dubai airline to Airbus.
EP3 – which follows EP and EP2 packages of enhancements introduced in 2012 and 2014 – includes elliptical leading edges on the fan blade, changes to the engine’s intermediate compressor and “optimised” cooling air in the centre of the engine.
The Trent 900 – which competes with the Engine Alliance GP7200 – has been in service since 2007 and powers 77 A380s. Emirates is the biggest customer for both the airliner and the engine, having switched its allegiance from the US joint venture last year, when it selected the Trent 900 for its 2013 order of 50 A380s, as well as another pair of superjumbos signed for in March this year.
Emirates had opted for the GP7200 for its first 90 A380s, and its switch propelled Rolls-Royce into a market share lead.
Source: Flight Daily News