Rolls-Royce’s Advance family of demonstrator engines is the first planned step in the company’s transition from the Trent XWB – today’s state of the art – to the engine families they envisage for the future large civil engine market. Rolls-Royce is using the Advance3 demonstration programme to conduct high-level system integration and new technology de-risking at a whole engine level. Andy Geer, Rolls-Royce’s Chief Engineer and Head of Programme for the Advance3 engine demonstrator provides an update on the progress made and challenges faced by this programme.

“Advance puts a new core architecture in place, to allow us to move overall gas generator pressure ratio from 50-odd to one in the latest Trent families to 60-odd to one, in pursuit of further fuel-burn improvement. It also acts as a stepping stone on to the geared engines of the future – such as UltraFan™ –  which have a gas generator pressure ratio of 70-odd to one and better propulsive efficiencies associated with higher bypass ratios enabled by a very different fan system. The UltraFan engines need a different core architecture – you have to do more work in the high pressure system to sustain core efficiency in that geared architecture. So the Advance engine family is two things: it’s an improvement step in its own right; and it’s an enabling step for the UltraFan” explains Andy.

The Advance3 programme was born in late 2013 and is Rolls-Royce’s first whole engine-level demo engine in support of a technology step-change for a long time.  Andy describes the “architectural change away from a Trent to something different is big. We don’t do that very often, so there’s a lot of implicit risk.  We concluded: let’s run a demo – design, build, test and analyse a one-off engine with that new architecture to flush out all those risks.”

He describes his role as being to build a team and to treat Advance3 as a mini-NPI [New Product Introduction] programme. “We did this for a couple of reasons – to give us focus to deliver a demonstrator engine for de-risking, but also to explore some of the processes we might use to be leaner and quicker in bringing a future NPI programme first engine to test. When we do the UltraFan demo – which is another step up because it’s a five engine demo programme and includes a FTB [flying testbed] – we’ll use a lot of the process learning gained from Advance3.”

The Advance3 is a hybrid vehicle marrying some existing components with new developmental ones. Andy describes the Advance3 as follows “It  takes the fan system from a Trent XWB, because that’s got about the right core inlet flow area; it takes the Trent 1000 LP turbine because that’s got about the right turbine throat area; and then we design a brand new core in the middle. That enables us to put a whole engine to test sensibly from a cost-to-completion point of view – for instance, we can use other projects’ existing expensive slave equipment.”

 

HP/IP spoke structure

The Advance3 engine includes a couple of specific areas of new technology that Andy draws attention to: “There’s lean burn, which we’ve run before on a Trent architecture, but not with this architecture.  There’s also high-temperature capability in the turbine – ceramic matrix composite first stage seal segments and cast-bond first stage vanes.  These technologies are essentially new in the civil arena. They were originally developed for the Joint Strike Fighter programme and operated briefly on the EFE [Environmentally Friendly Engine] demonstrator, but this is the first time they’ve been included from the outset as a key enabler for a new architecture.  Less headline but no less important is the inclusion of hybrid main-line bearings (that is bearings with ceramic rolling elements running on metallic races) which will be required in future engine designs to manage high bearing load environments inside cores that are getting progressively smaller at an engine thrust level.”

Advance3’s intercase structure

The Advance3 programme will not include a flying phase. “We’ve made Advance3 a ground-based demonstrator only” says Andy. “We took that decision for a couple of reasons. Firstly we wanted to open up a broader supply chain than we’ve typically used in the past and, because the engine will only ever run in a controlled test cell environment, we don’t need to use ‘flight worthy’ certified suppliers. Secondly we can get most of the understanding of the engine’s performance and operability at sea level, without the expense and complexity of a flight-test vehicle. The engine will have about 2,000 lines of instrumentation which would be beyond the capacity of a flying testbed, so that’s another reason for sticking to a ground-based programme of work.

Taking a slightly different view for a second, we’ve stayed focussed on the fact that the main demonstrator deliverable is risk reduction and the engine and its delivery programme are the means to achieving that.  We’ve been focussed as a team on capturing risks to the company around the new architecture.  We’ve systematically recorded the risks; identified mitigation using a structured verification approach; and fed that into the way we design both the test vehicle and the experiments and how we analyse the data. Having gone through the detailed design process we’ve already identified and eliminated a lot of risk.  We're feeding learning forward into the early design of the current round of Future Programme study engines including the UltraFan.”

 

HPC1-3 blisk

Andy summarises the current status of the Advance3 Demo as “We’ve got all of the detailed design work done and are in the build instruction and kit launch cycle. We’ve got all but the last few parts delivered from the supply chain to allow us to start the first build. We plan to get the engine to test in the summer. It’s not likely we’ll get this new architecture vehicle perfectly cycle-matched first time, so the plan assumes we’ll do a rebuild in late 2016 into early 2017 to finesse turbine capacities. Aspects of the build process will be significantly different to the Trent, so we’ve got lots to learn as we enter this next major stage of the programme.” 2016 and 2017 promise to be exciting and challenging times for Andy and his engineering team.