What’s Fuelling the Future of Aero-Propulsion?

By Editor 11-May-2018


The Paris convention to battle climate change has in turn forced the hands of the International Civil Aviation Organization (ICAO) to narrow the noose on air and noise pollution from aviation. As aviation emissions contribute close to 2% of the global atmospheric pollution, with an annual Carbon and Nitrogenous oxide emissions increase of 3 - 4%, ICAO is aiming a 2% annual fuel efficiency improvement and carbon-neutral growth from 2020 onwards.

Also, from 2020 onwards the Committee on Aviation Environmental Protection (CAEP) standards will certify every airplane before delivery, while from 2026 onwards the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) framework will mandate a new global market-based measure to control CO2 emissions from international aviation. Amongst all others, these are the densest dark clouds gathering on the horizon of sustainable profitability for airlines and (Original Equipment Manufacturers) OEMs alike. With the majority of the existing technologies based on fossil fuels that are getting costlier by the day and stand chance to run dry in the near future, there’s a burning need to develop sustainable alternative aviation fuels and commission research into quieter commuter airplanes, aerodynamic aero-structure designs, and greener propulsion systems.

Flight plan for course correction

Despite the polarisation of the market between Boeing and General Electric (GE) Aviation versus Airbus and Rolls-Royce on wide body aircraft, the integration of products and services at multiple levels are re-shaping the aerospace industry. With the internal combustion architecture attaining a very mature stage of design development, there is hardly any scope left for competition over the engine, unless the advances in material technology are leveraged accordingly. For instance, if the melting temperature of the turbine space could be increased with advanced materials, the three shaft Trent architecture or the Roll-Royce’s two and half shaft power gearbox, could be further improved. Just like in the defence sector, engines should be integrated with airframes to boost efficiency, rather than just hanging an efficient engine on a wide-bodied aircraft as in the commercial aviation sector which changes the entire aerodynamic profile and fails to be a truly radical solution. Blade craft is key here – the smaller the fans, the smaller the core, the smaller yet thermally efficient the turbine is, resulting in lesser drag created to ultimately boost the engine’s efficiency. Besides, to lighten the aircraft for further optimizing fuel efficiency, advanced composite material, coating systems and bionic mechanisation is also imperative.

Starting cruise control

Traditional turbofan engines dominating the aero-engine sector since the 1960s had felt the first disruptive tremors with Pratt & Whitney’s Geared Turbofan engines that optimized fuel efficiency by 20% with larger fans. GE and Safran’s joint-venture - CFM International responded by attaining similar results with the LEAP engine deployed in Boeing airplanes that used carbon fibre blades for weight reduction. Such corporate competition for excellence has reduced an aircraft’s average fuel consumption from 6 litres per 100 passenger kilometres in the 90’s to the A380 burning only 2.9 litres for the same today.

Even UTC Aerospace Systems (UTAS) has initiated the Ecological Integrated Propulsion System (EcoIPS) program for next-generation ultra-high bypass ratio propulsion systems with short, integrated fan duct thrust reversers that maximize efficiency yet reduce noise. They have also innovatively designed carbon brakes, SmartProbe Air Data system and electrical actuators to replace heavy pneumatic systems.

In order to arrive a scalable solution for both widebody and narrowbody aircrafts by 2025, Rolls-Royce and Airbus have collaborated to develop the UltraFan demonstrator engine. With Airbus developing the nacelle and pylon while also integrating the innovative architecture and technology enablers, this demonstrator would be trialled on a Rolls-Royce flying test-bed using Boeing 747. By leveraging advanced manufacturing technologies such as high-deposition-rate 3D printing, welded assembly, and high production-rate thermoplastics, the UltraFan could be 25% more fuel efficient than the Trent 700. Moreover, in February 2018’s Singapore Airshow, the IntelligentEngine concept revealed by Rolls-Royce with quantum leaps in processing power, big data analytics, connectivity, and cloud computing paves the path for integrated digital avionics technology across design, manufacturing, and aftermarket for the aero sector.

Battery power ALERT

With a vision 2020, Siemens, Airbus and Rolls-Royce have collaborated to flight-test E-FAN X, a BAe 146 regional airliner customised with a 2-megawatt, serial-hybrid propulsion system. Through a battery-boosted take-off and pure electric propulsion for landing, it aims to minimize noise levels, fuel burn and polluting local emissions. However, all-electric propulsion systems can only power small planes for regional commute. The fact that today’s most advanced batteries pack lesser energy per unit of weight than the standard gasoline is what’s holding back OEMs from being able to design all-electric airplanes capable of flying around the world in eighty hours.

Feasible Hybridisation ACTIVATED

In 2017 NASA has broken ground in distributed turboelectric propulsion with its novel STARC-ABL design that could increase fuel efficiency by 7-12%. ABL or Aft Boundary-Layer propulsor is a turbofan behind a Boeing 757 sized airplane that collects the air currents moving over the fuselage and accelerates it using 3 megawatts of electricity generated by the smaller wing-mounted turbofans. However, due to the conservative nature of the aerospace sector and its paramount need for safety, such disruptive innovations should not be rushed into deployment. Possibly within a decade’s time-frame we could see airplanes with avionics driven by generators rather than from the engine bleed-off.

We shall overland

For the evolution from the internal combustion engine to the fully-electric engine, OEMs need to find an essential stepping stone in hybrids by leveraging multi-disciplinary approaches. OEMs would need to take a cue from successful use-cases of battery-power development and hybridization in sectors such as rail transport, automotive and power generation. The key would be in sourcing and collaborating with specialised engineering service providers with capabilities across these sectors.

Even if it now seems that the pace of change is already so great that it can’t possibly be getting any greater, the natural fact is that rate of change is exponential. The fact that the aerospace sector is very different from what used to be a decade ago, proves that the future of aero-propulsion and integrated aviation is yet to unfold in myriad ways. However, even if time alone is unable to resolve all these, we shall still continue our QuEST to find the turnkey solutions.

The author Lawton Green is Associate Vice President for Strategic Clients at QuEST Global Services which is a focused global engineering solutions provider and production engineering partner serving the product development & production engineering needs of high technology companies in the Aero Engines, Aerospace & Defense, Automotive, Oil & Gas, Power, Medical Devices, Industrial and other high-tech industries.