Sustainable and Green Engines

The Air Transport Action Group (ATAG), a not-for-profit association, has stated that worldwide, flights produced 781 million tonnes of carbon dioxide (CO₂) in 2015, while overall humans produced 36 billion tonnes. The global aviation industry produces around 2 per cent of all human induced CO₂ emissions. Aviation is responsible for 12 per cent of CO₂ emissions from all transport sources compared to 74 per cent from road transport. Around 80 per cent of aviation CO₂ emissions are emitted from flights of over 1,500 km for which there is no practical alternative mode of transport.

Jet aircraft in service today are well over 80 per cent more fuelefficient per seat kilometre than the first jets in the 1960s.

From this it is very clear that the aviation industry, despite its low levels of emission, continues to work aggressively to be a responsible environment friendly player. At the forefront of these technological advancements is Clean Sky, the largest European research programme developing innovative, cutting-edge technology aimed at reducing CO₂ , gas emissions and noise levels produced by aircraft. Funded by the EU’s Horizon 2020 programme, Clean Sky contributes to strengthening European aeroindustry collaboration, global leadership and competitiveness.

Cleaner Skies

The objectives of Clean Sky are to develop integrated technologies contributing to the engine sector ACARE environmental targets for the engines sector. Engine sector targets for Clean Sky are up to -20 per cent CO₂, up to -60 per cent NOx, up to -20 EPNdB noise relative to year 2000 baseline. The players in the Sustainable and Green Engine (SAGE) are Rolls-Royce plc and Safran (participation from Airbus and Alenia Aeronautica), MTU Aero Engines GmbH, Turboméca, AVIO, ITP, Volvo Aero Corporation, Rolls-Royce Deutschland, Hispano-Suiza, Aircelle, Techspace Aero, Volvo Aero Norge, and Alenia Aermacchi.

Since the SAGE programme was launched on June 1, 2008, it has defined in detail five engine demonstrator projects, including leaders’ and associate work shares and opportunities for partners. The objective of the SAGE ITD (integrated technology demonstrators) of Clean Sky is to demonstrate engine technologies across all sectors of the civil aerospace market, including regional, narrow-body and wide-body fixed-wing aircraft and rotorcraft.

Five Demonstrat ion Vehicles

The ITD comprises demonstration vehicles, segregated by application such as helicopter, regional, narrow-body and wide-body and by engine architecture namely 2-shaft, 3-shaft, geared and open-rotor, and exploits the significant range of competencies and facilities of all the European aero-engine manufacturers.

The demonstrations deliver new solutions for the complete range of the market, whereby for fixed-wing aircraft, particular focus will be applied to novel engine architectures such as open-rotor and geared-fan engine that offer opportunities for step-change reductions in CO₂ emissions relative to current turbofans in narrow-body and regional markets. Open rotor propulsion offers particular promise in energy efficiency; but also presents strong challenges in integrating novel subsystems, engine and aircraft systems and addressing noise emanating from the unshielded propellers.

The primary focus of engine demonstration will be ground/flight testing to deliver proven architectures for advanced engines and mature “ready to use” technologies, and the target across all demonstrators is to deliver technology demonstrations that attain technology readiness level (TRL) 6. In other programmes, the technologies to be demonstrated will typically have been developed to lower TRLs. The value of SAGE is in providing the engine vehicles and environments to take them to a higher TRL and accelerate their introduction into the market.

The Engines ITD will build on the success of SAGE ITD of Clean Sky 1, working towards radical engine architectures and new engine technologies to power the aircraft of the future. All the activities under the Engines ITD in CS2 have a common goal: to increase fuel and energy efficiency of the engine and reduce environmental impact, regardless of whether the engine is powering a large airliner or just a small utility aircraft, meaning more thrust while burning less fuel and emitting less CO₂, NOx and noise.

Challenge for Players

The challenge for the players in the Engines ITD Programme of Clean Sky 2 is to use the achievements gained in Clean Sky 1’s SAGE programme to advance aeroengine technologies to a state of eco-compliance and technological readiness that can be employed in a whole range of aircraft that will take to the skies in the 2025 to 2050 time frame.

THE GEARED TURBOFAN ENGINE IS THE CULMINATION OF OUR DREAM TO PUSH THE BOUNDARIES OF SCIENCE, TECHNOLOGY AND INGENUITY

In Clean Sky 2, the Engines ITD will build on the success of Clean Sky 1’s SAGE. The main objectives are to deliver substantial improvements in engine technology. In particular, it will develop full engine and major engine system solutions that can deliver a step change reduction in emissions. It will also take a step-by-step approach to progressing the technology’s maturity or ‘TRL’, utilising design studies and rig tests to explore and understand the technologies under development, their system interactions and the risks associated with their implementation. The ultimate goal of the project is to achieve TRL 6.

Huge Opportunity

Rolls-Royce’s Market Outlook for the period 2014-23 sees a need, globally, for 27,000 new aircraft, requiring 55,000 engines, spanning large passenger aircraft, regional planes and business jets. It’s a huge market opportunity for the EU aviation industry to maintain and extend its global leadership, but also a major challenge to deliver radical new engine architectures and advanced technologies which are much needed to continue the emissions reductions and to meet overall sustainability targets to comply with ACARE and Flightpath 2050 Goals.

US Manufacturers are Up There

While Europe is working on Clean Sky, engine manufacturers in the US are also working on smart, sustainable technologies. Pratt & Whitney’s PurePower Geared Turbofan engine is one of the sustainable brands. Reaching new sustainability milestones relative to conventional engines, the geared turbofan engine lowers fuel consumption by 16 per cent while also delivering a 50 per cent reduction in regulated emissions and a 75 per cent reduction in noise footprint.

Pratt & Whitney, a unit of United Technologies (UTC), has invested two decades and $10 billion to develop this gamechanging engine technology and bring it to the industry. The result is the world’s most sustainable large commercial jet engine, which is now powering commercial flights with airlines on two continents.

“This engine changes everything. The geared turbofan engine is cleaner, greener and quieter than anything available in the industry today,” said UTC Chief Sustainability Officer John Mandyck. “The geared turbofan engine is the culmination of our dream to push the boundaries of science, technology and ingenuity.”

Progressive LEAP

Meanwhile, CFM International LEAP has made enormous progress. The LEAP is a high-bypass turbofan engine. It is produced by CFM International, a 50-50 joint venture company between GE Aviation of the United States and Safran Aircraft Engines of France. It is a modernised replacement for the successful CFM 56, intended to compete with the Pratt & Whitney PW1000G in the single-aisle jetliner market.

The LEAP’s basic architecture includes a scaled-up version of Safran’s low pressure turbine used on the GEnX engine. The fan has flexible blades manufactured by a resin transfer molding process, which are designed to untwist as the fan’s rotational speed increases. While the LEAP is designed to operate at a higher pressure than the CFM 56 (which is partly why it is more efficient), GE plans to set the operating pressure lower than the maximum in order to maximise the engine’s service life and reliability. Currently proposed for the LEAP is a greater use of composite materials, a blisk fan in the compressor, a second-generation twin annular pre-swirl (TAPS II) combustor and a bypass ratio around 10-11:1. GE is using ceramic matrix composites (CMC) to build the turbine shrouds. These technological advances are projected to produce 16 per cent lower fuel consumption.

The engines of the future are indeed in alignment with global concerns, to reduce air and noise pollution and engine manufacturers continue to invest time and money to deliver engines that are sustainable by leaps and bounds.