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The UHBR engine flight testing programme gathers momentum

The Ultra High Bypass Ratio (UHBR) engine demonstrator, UltraFan® for large aircraft is being developed within the framework of Clean Sky’s ENGINE ITD, and its flight testing is one of the major flagships of Clean Sky’s Large Passenger Aircraft (LPA) Innovative Aircraft Demonstration Platforms (IADP). The magnitude of work represents a major investment in innovative activities and the program has ambitious environmental targets that will deliver long term benefits for the future of European aviation.

“Here in LPA we are working on the integrat ion of t he UHBR engine demonstrator onto an aircraft and to ensure that we will be minimising the potential negative coupling effects throughout that integration, which means working out the impact of close-coupling effects and examining all the elements that interface between the engine and the aircraft – and to prepare the integration of such an engine onto the aircraft, with the design of the different junction systems which will sustain the engine“ says Sebastien Dubois, LPA Project Officer at Clean Sky.

The UltraFan demonstrator is in development at Rolls-Royce; a key focal point in the project is the analysis of the aero-coupling effects of the UltraFan engine and the wing because the fan of the UltraFan has a much larger diameter than conventional engines.

“Our objective is to design the pylon, thermal management and the nacelle aspect, but also to perform the calculations and tests on significant components such as the thrust reverser unit, the nacelle coupling effect of the engine and the wing, and also the aero-acoustic characterization of this engine as well as the jet noise and exhaust coming out from the engine“ says Dubois. “In terms of potentials we are talking about a fuel improvement of 9% to 10% compared to reference aircraft from 2014.“ Gary Way, Head of the EU R&T programme with responsibility for the Clean Sky 2 programme of activity at Rolls-Royce, explains that “over a number of years we have had funding for that programme – originally from Clean Sky 1, and now Clean Sky 2 – and that has enabled Rolls- Royce to make considerable progress with the design, development and demonstration of the key elements of technology that are going to be required in the UltraFan demonstrator that ultimately will take us through to the flight test activity“.

Standout technologies in the programme are the composite titanium fan blades which have taken a lot of weight out of the engine design compared to the previous standard, the power gearbox technology which has been introduced into the UltraFan demonstrator to get the best optimum operating efficiency of the engine core and fan.

“The engine is going through a series of gearbox tests at the moment and there’s been a new test facility created, with funding from the Federal State of Brandenburg, at Rolls-Royce’s site in Berlin to facilitate that. Additionally there’s work underway – which is being progressed through Clean Sky 2 funding – on the Advance3 core and that introduces, at the right scale in terms of size and technology, the core engine attributes that are needed to make the UltraFan demonstrator work in combination with the new fan system. That Advance3 core testing has completed its first phase of activity“ adds Way.

The core testing included a series of starts and tests for over 100 hours which is fundamental for attaining confidence that the technologies will work together. All that work with the fan, gearbox and core has enabled the concept design freeze of the UltraFan demonstrator in May 2018, all of which leads up to the actual flight testing programme.

“The first flight is scheduled for 2023“ says Martin Shelley, Programme Manager of LPA at Rolls-Royce. “A lot of the work in Clean Sky 2’s Large Passenger Aircraft is about how we attach the engines to the aircraft, the nacelle, and the test bed itself. That is what we are currently progressing“.

As for the airframer’s checklist, at Airbus the current focus is around the integration of the engine, which, while being much more efficient in terms of noise, fuel burn and pollutant emissions compared to the current technology, presents, literally, an enormous challenge. The significant increase in the fan diameter, compared to existing engines, has necessitated the design of new architecture and technology enablers to allow it to be integrated onto an aircraft.

“Together with Rolls-Royce, and in the frame of Clean Sky 2, Airbus has produced a number of innovative nacelle and engine architectures that are compatible with UltraFan from Rolls-Royce, and those nacelle and engine architectures have now reached the concept freeze, so we’ve now attained TRL3“ says Dr. Marc Maurel, Clean Sky 2 Powerplant Business Manager and CTO Business Development XLGE at Airbus.

“It also has to be noted that we’ve developed further key technology bricks up to the concept freeze at TRL3 and beyond, and the partial test bricks for some of the technologies are being produced and tested, and this is ongoing in Clean Sky 2. We have also developed a portfolio of architectures and technologies for the pylon which will be tested on a rig in 2022, so the technologies for the plan are consolidated“ says Maurel. “It should be emphasized that the collaboration and partnership between Airbus and Rolls- Royce through Clean Sky 2 is essential to develop and integrate the UHBR engine onto an aircraft, and the support of research partners including ONERA and DLR are also a big part of this“.

Looking at the project and its merit in a European context, Gary Way of Rolls-Royce says that “the value of these projects to European aviation, and more broadly to Europe and the citizen, is clearly through a number of different angles. At an industry research capability level this support that we get from the Clean Sky 2 funding mechanism enables us to fundamentally maintain our competitiveness in what is clearly a global environment. That funding enables us to take a bigger perspective in terms of where we can push our strategy, because it allows a number of activities to be run concurrently and in an integrated way to enable something like the UltraFan demonstrator – and ultimately a product – to exist. If we didn’t have the funding in terms of size and in terms of its construction it could limit European aviation, so it is very powerful in terms of maintaining our competitiveness“.

As for the broader benefits to Europe and globally, Way adds that “it’s the ability of this technology to deliver continued step changes in efficiency of the product in terms of reduction of fuel burn, which then leads to reductions in CO2, NOx emissions and noise. Within all of that in terms of how we package the entire engine, technology and airframe together are all part of the journey that we all need to go on to meet the ACARE goals and Flightpath 2050. Clearly that’s at a point in the future, but the work that we are doing now with the UltraFan demonstrator through Clean Sky 2 over this decade will surely make a substantial impact along the journey“.

Next steps for the UltraFan demonstrator flight testing programme include a series of supporting ground tests to consolidate the concept. As Rolls-Royce’s Martin Shelley points out: “there is a number of ground test demonstrations that will be held both on the engine side at Rolls-Royce and also in collaboration with Airbus in wind tunnels. The first wind tunnel tests will take place for the fan inlets in 2019 at ONERA, with a further test in 2020 for jet engine noise and installation assessment“.