‘Generation Engine’: How Innovation in Propulsion is Fuelling a Bright Future

Over the past 2-3 years, the focus from large aerospace manufacturers has been on developing new engine derivatives of popular platforms to satisfy the desire from airlines for more fuel efficient and environmentally friendly aircraft. Last year, I blogged about the focus on ‘re-engining’ and how this not only helps to foster innovation but also promotes supply chain continuity.

However, despite the important strides made in offering ‘new engine options’ – the long term policy goals of initiatives such as the EU’s Flightpath 2050 will require real game-changing technology to be developed and industrialised.

So what key, long term, innovation breakthroughs in civil aerospace propulsion are currently on the radar of engine and component manufacturers – to ensure industry meets the ambitious targets of a 75% reduction in CO2, a 90% reduction in NOx and perceived noise reduced of 65%, by 2050?

Rolls-Royce – Ultra Fan and Formula 1

The Ultra-Fan is RR’s new long term civil engine programme – set for completion and service entry between 2025 and 2030 and with the goal of achieving a 25% fuel burn reduction compared to a Trent 700 engine. The UltraFan’s most critical technology breakthroughs will include:

  • Composite fan blade technology – which could help reduce engine weight by up to 1,500lb per aircraft; the equivalent of carrying seven more passengers at no extra cost.
  • A new ‘power gearbox’ – which improves on current geared turbofan technology to increase efficiency.
  • Variable blade pitch (in all phases of flight) – mirroring variable fan blade pitch on open rotor aircraft, to help reduce noise and improve fuel consumption.
  • Removal of ‘thrust reversers’ – the introduction of variable blade pitch to slow down the aircraft on landing, rather than the standard diversion of engine exhaust to the forward direction, will help to improve design, weight and maintenance cost, due to the high stress and demand required of the engine.

The power gearbox may also derive technology from current Formula One engines and their use of energy recovery systems, due to a recent £14m fund from the UK’s Aerospace Technology Institute (ATI), led by RR and McLaren Racing.

Composite and ‘Zero-Splice’ Nacelles –Bombardier/ Aircelle

The noise generated by an aircraft’s airframe and the nacelle (the casing which holds the engine together) can be as significant as the jet and fan noise of the engine itself. The focus on improving the ‘splices’ of an acoustic liner with a nacelle (the number of joins in the liner due to the number of parts required to make it) is part of the EU’s Clean Sky 2 initiative – with Bombardier in Belfast recently announcing the successful completion of a zero-splice, carbon fibre acoustic liner.

Whilst zero splice has been used on the A380 Trent 900 engine, it is the use of carbon fibre composites which presents technology and manufacturing challenges – but also presents the opportunity for large scale improvements to reduce the weight of the engine, improve efficiency, and improve the distribution of noise around the engine itself.

Just as Bombardier in Belfast are leading on the Clean Sky project, Aircelle in Burnley has recently announced it will become a ‘Centre of Excellence’ for Nacelle technology development – backed by a £12m award from the Department of Business. The will further enhance the UK’s reputation as a global leader in Nacelle R&D.

Pratt & Whitney – Reverse Tilted Geared Turbofan

As recently highlighted in last week’s Aviation Week article, US engine manufacturers Pratt & Whitney have revealed details of their ‘Reverse Tilted Geared Turbofan’ concept, for 2030 and beyond. In essence, the new technology has 2 interesting elements:

  • Separating the propulsion and core sections of the engine – by doing this, the cores of two engines can be angled relative to each other; allowing both engines to be placed directly next to each other and still comply with the “1 in 20” rule of the FAA (which states there should only be a 1 in 20 chance of debris from an uncontained engine failure causing a second engine to fail).
  • Changing the way in which the air flows through the engine – instead of air entering the front of the engine and continuing directly to the compressor stage, P&W’s design ducts the air around the side of the compressor and back into it from the opposite direction.

Why do these changes help improve engine efficiency? By being able to mount engines next to each other, an aircraft can therefore place them in optimum locations – such as on top and at the back of a fuselage. In this position, the engines can directly use the air flow and kinetic energy which passes over the fuselage and is previously wasted on traditional aircraft. In addition, by taking the engines off the wing, the whole aircraft can improve its efficiency through lower weight wing materials, new swept wing design, or even more effective laminar flow. It is hoped that such measures could improve efficiency by 60% from current single aisle engine platforms.

Despite these innovative designs, even longer term innovations following the recent media focus on the successes of Solar Impulse 2 and Airbus’ E-Fan project, show that the game changing technology listed above is only the start.