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EU-funded ‘ANTLE’ and ‘CLEAN’ projects see successful conclusion

Two major five-year research initiatives aimed at cleaning up European air transport have been completed successfully. Together, the ANTLE and CLEAN projects make up the ‘EEAFE’ initiative, targeting reduced aircraft engine CO2 and NOx emissions, improved reliability, lower ownership and life cycle costs and shorter time to market.

Testing ANTLE engine © Rolls-Royce
Testing ANTLE engine
© Rolls-Royce

In the aerospace sector, good environmental performance is a key business driver. In fact, the industry has done a good job since the jet engine revolutionised air travel more than half a century ago, reducing environmental impact by 75% while increasing power by a factor of 50. But the industry’s growth now demands even more rapid and radical change, and the Advisory Council for Aeronautics Research in Europe (ACARE) has called for improvements at twice the historic pace. The industry has committed itself to reduce perceived external noise by 50%, lower fuel burn (and carbon dioxide emissions) by 50%, and to slash the production of nitrogen oxides (NOx) by 80%, relative to 2000 levels, by 2020.

Two EU-funded projects, ANTLE (Advanced near-term low emissions) and CLEAN (Component validator for environmentally friendly aero-engine), both launched in 2000, have just been completed.


ANTLE coordinator Rolls-Royce

Rolls-Royce is actively involved in many international, national and domestic initiatives aimed at lowering the environmental impact of its products, some collaborative, others under its own auspices.

The company uses formal legislative targets and the most authoritative advisory organisations to benchmark performance requirements, and then sets its own environmental course, pursuing programmes under its ‘Vision’ technology strategy in the areas of emissions and noise.

The Rolls-Royce Vision strategy defines three periods for the development of technology:

  • Vision5 includes technologies that exist ‘off-the-shelf’ and can be applied immediately to new and existing products.
  • Vision10 describes a range of technologies currently at the validation stage and likely to be commercially available in a five- to ten- year time frame.
  • Vision20 comprises a broad range of emerging or unproven technologies aimed at a future generation of products for the ten- to 20-year timeframe and beyond.

ANTLE background

According to Gary Atkins, Communications Manager for Rolls-Royce, “ANTLE has made a vital contribution on the road to meeting the ACARE goals. The project has broadly met objectives that included reducing CO 2 by 12% and NOx by 60%, improving reliability by 60%, and lowering cost of ownership by 20% and time to market and life cycle costs by 30%. Technologies developed and proven as part of this programme will set the foundation for new engine programmes and will provide a considerable step towards the environmental goals.”

The demonstration hardware that successfully concluded the ANTLE programme in 2005 will be reassembled and used in the European-funded ‘POA’ (Power optimised aircraft) project, led by Leibherr. POA is looking at the greater use of electric systems across the whole airframe, and will rely on embedded generators, taking the place of gearbox driven generators.

ANTLE was one of two specific projects under the European-funded ‘EEFAE’ (Efficient and environmentally friendly aero engine) research project that ran between 2000 and 2005. It was designed to demonstrate and validate a suite of new aero-engine technologies, and comprised 16 industrial companies, two universities and one research institution.

A high-flying co-operative effort

Rolls-Royce had overall management responsibility for EEFAE throughout its five-year life and led the ANTLE project. “Environmental and cost goals have been key success factors for the ANTLE programme,” says Ian Ritchey, Chief Engineer, Research and Technology – Civil at Rolls-Royce and lead engineer on ANTLE.

Demonstrator testing this year at maximum engine conditions at a facility, near Madrid, marked the culmination of the project. The test results are now being analysed in detail, but were largely positive and, in some areas, even better than expected. Key technologies will undoubtedly emerge from ANTLE that can be used in the next generation of engines. Some, says Ritchey, are already finding their way into the latest Rolls-Royce engines in development – the Trent 900 and Trent 1000.

“While the ANTLE vehicle was nominally based on a Trent 500 engine, virtually the whole rear section was packed with new technologies. It had fewer stages of blading and fewer blades per stage in both the compressor and turbine areas, resulting in a much lower parts count, less complexity, weight reduction and lower cost. Advanced aerodynamics rig testing on the high-pressure compressor and turbines improved the understanding of how to achieve parts count reduction without losing efficiency.”

Hitting all targets

The fundamental goal of improved emissions performance was met by a lean-burn combustor designed to halve today’s NOx levels. The new combustor has shown promising results in terms of emissions and performance, while also increasing understanding of combustion stability and acoustics behaviour.

ANTLE also incorporated new distributed engine control and actuation systems – a foundation for more electric engines. The project was highly collaborative: Rolls-Royce was responsible for the compressor, combustion system and HP turbine; Spain’s ITP produced the low-pressure turbine; Techspace Aero of Belgium undertook the electric oil system; Italy’s Avio provided the intermediate-pressure turbine; Hispano Suiza of France supplied the gearbox; a fabricated tail bearing housing came from Sweden’s Volvo; the control system was supplied by UK-based Goodrich Engine Controls, and electric engine actuators came from Goodrich Actuation Systems.

The CLEAN project

Aeroplane engine
CLEANing up Europe’s air transport
© Peter Gutierrez

Under the CLEAN project, which is the second half of the EEFAE initiative, comprehensive testing was carried out on technologies required for geared turbofan engines. The project was aimed at reducing fuel consumption, and with it CO 2 emissions, by as much as 20 percent. Also investigated was a novel combustor that has the potential to reduce NOx emissions by as much as 80 percent.

The CLEAN demonstrator was developed under the coordination of MTU Aero Engines. In September 2004, the technology demonstrator made its first run at the University of Stuttgart's altitude test facility. At the international Paris Air Show in 2005, project partners displayed a successfully engine-tested rear turbine frame developed and manufactured by Volvo Aero using CLEAN technologies.

In addition to the rear frame, Volvo Aero was responsible for the turbine case and the assembly of the entire CLEAN engine. Other key components, including the high-speed low-pressure turbine, the heat exchanger, and the turbine center frame, were developed by MTU. “We demonstrated that our high-speed low-pressure turbine was technologically fully mature," says Dr. Günter Wilfert, who oversaw the CLEAN project at MTU. Testing also involved novel materials and design variants.

The CLEAN engine validates technology for future engines with new thermodynamic cycles, such as intercooled, recuperated and geared fan cycles. The rear frame was designed to withstand higher temperatures than today's engines. All components performed well during engine testing, and the CLEAN engine met all targets regarding performance and emissions.

The CLEAN budget was €50 million euros, divided among seven partners.


CLEAN coordinator MTU Aero Engines

MTU Aero Engines is a major player in the development, manufacture and repair of commercial and military engines. It is Germany's leading manufacturer of engine modules and components and of complete aero engines. Internationally, it holds a strong position in all significant regions and markets, thanks to co-operative efforts and joint ventures.

MTU partners include manufacturers and operators of engines and industrial gas turbines across the world. The quality and reliability which characterize the company's products and services, as well as its regional presence in many parts of the world, make MTU a preferred partner to customers worldwide.

Leading a coordinated air transport strategy

ANTLE and CLEAN are certainly not the only examples of EU-funded projects aimed at reducing environmental impact in the aerospace sector. The EU-funded ‘SILENCER’ initiative, for example, is looking to reduce noise levels, as have a number of earlier initiatives including the ‘Quiet Technology Demonstrator’, a project carried out in co-operation with American aerospace giant Boeing.

SILENCER is also a major collaborative effort, involving Airbus as well as engine companies, key suppliers and academic outlets. It incorporates new application of liner material, a new low-noise fan, a circumferential ‘splitter’ in the fan outlet guide vane and a negatively-scarfed intake that directs fan-generated noise upwards rather than towards the ground.

A test vehicle incorporating some of these innovations has been tested at the Rolls-Royce special outside noise test facility at Hucknall, UK. Over the longer-term, Rolls-Royce is now collaborating in the Airbus-led NACRE programme, looking at novel aircraft concepts and their propulsion.