A revolution driven by small advances on many fronts
Achieving net zero for the UK aviation sector by 2050 is a complex challenge. The good news is that the UK leads the world in delivering innovations in partnership with industry that will help secure this goal.
But no single technological breakthrough, whether sustainable fuels, electric aircraft, green energy sources such as hydrogen, or advances in cleaner and more efficient propulsion and flight systems, will lead this aviation revolution.
Professor Carol Eastwick’s stimulating career as a mechanical engineer at the University of Nottingham shows that advances can steadily be made across many fronts, with progress powered by experts coming together to puzzle over the detail.
At the Gas Turbine and Transmissions Research Centre (G2TRC), Professor Eastwick and her colleagues including Dr Chris Bennett (solids and materials characterisation) and Professor Seamus Garvey (vibration and dynamics), have helped make jet engines and transmission systems more efficient, with transformative environmental impact.
“We work in the margins, pushing for steady improvements that incrementally make these systems more efficient, reducing the amount of fuel that you need, which in turn reduces the amount of CO2 released into the atmosphere. The actual changes appear tiny, but when you’ve got transatlantic flight, a 0.1% increase in engine efficiency translates to saving millions of tons of fuel, and globally multiplies up in terms of the reduction of CO2 emitted.”
Professor Eastwick’s expertise lies in thermofluids, the transfer of thermal power from gas, liquids or vapours and how this can be applied to energy and transport. In aviation, understanding these processes is key to improving how engines transfer energy to propel the aircraft.
Thermal management also takes in electric motors, which are becoming increasingly important for systems on board sustainable aircraft.
“Electric motors are being used in a lot of different contexts, and they all have the same problem - when you pass current through electric wiring it heats up, its resistance changes and it loses energy. It’s a hurdle for aviation – to increase the amount of power from an electrical machine without prohibitively increasing its weight, we have to improve how heat is managed and removed. I work with electrical engineers on this challenge – the Power Electronics and Machines Group is one of several research groups I sit within.”
"When you’ve got transatlantic flight, a 0.1% increase in engine efficiency translates to saving millions of tons of fuel."
This expertise, combined with input from specialists in chemical, materials and manufacturing engineering, has shaped the design of successive generations of Rolls-Royce aircraft engines.
The latest, the Rolls-Royce Ultra Fan, is up to 25% more fuel efficient than the company’s first generation Trent engine, with successive models all being developed in collaboration at the Rolls-Royce University Technology Centre (UTC) in Gas Turbine and Transmission Systems, which sits within the G2TRC.
Professor Eastwick and her colleagues are also exploring how gas turbines could run continuously at full capacity, rather than variably according to the aircraft’s needs. This would increase efficiency and generate power to run systems such as electric motors on the wing, bringing closer sustainable long-haul flight. Another project is studying the benefits of electrification by using an electrical generator to power ancillary pumps and valves.
Such incremental advances have collectively transformed the design and efficiency of aero engines, with the next step changes likely to come from emerging and future energy vectors such as electrification, sustainable aviation fuel, or hydrogen.
All will have part to play, she added, but no one power source has all the answers.
Short-haul, regional and ‘taxi’ flying with electric aircraft is already close to reality. For transatlantic, long-haul flights, sustainable aviation fuels (SAFs) are likely to feature, not least because new generations of engines, including the Rolls-Royce Ultra Fan will be able to burn on 100% SAF.
Hydrogen fuel cells – which offer three times the energy per kilogram than kerosene – are a tantalising possibility. But hydrogen has 1,000 times the volume, and the mass of equipment to compress it (either at 400 times atmospheric pressure or at -250°C) would literally outweigh the benefits for sustainable flight.
"To achieve zero carbon aviation demands true systems engineering, looking at the whole problem, and having a multidisciplinary team to attack it."
But any new technology has hurdles. “From a university perspective, what we do is make sure that we've got an understanding of all potential solutions.”
Professor Eastwick’s work with advanced liquid fuel systems takes in disciplines including chemistry, chemical engineering and electrical engineering, while Professor Pete Licence, Director of The GlaxoSmithKline Carbon Neutral Laboratory, and bioengineer Professor Alex Conradie of the Green Chemicals Beacon, are leading the way in the development of sustainable aviation fuels derived from bacteria and biomass.
Professor Eastwick believes such a holistic research approach is key to delivering net zero aviation by 2050.
She added: “One of the reasons I've enjoyed being here 30 years is because I've had the opportunity to work across disciplines, and we have a truly collegiate philosophy.
“I've even got a paper in a psychology journal, which for an engineer is a bit weird. I've worked with physicists, chemists, psychologists. Social scientists give us insights into barriers to the acceptance of new technologies or understanding of the interaction between policy and delivery. We had a problem in a power station with clouds of fungi, so we asked biologists to identify them. Being able to draw on that expertise across the whole university is absolutely brilliant.”
“To achieve zero carbon aviation demands true systems engineering, looking at the whole problem, and having a multidisciplinary team to attack it.”
Carol Eastwick is Professor of Mechanical Engineering in the Faculty of Engineering and heads the Gas Turbine and Transmissions Research Centre