A major new research partnership between Rolls-Royce and three UK universities is aiming to develop the technologies needed to allow the aerospace industry to switch towards all-electric flight.
The aerospace industry has been investing heavily in the search for alternatives to combustion engines, in a bid to cut carbon dioxide emissions and reduce its dependence on Earth’s decreasing fossil fuel reserves.
But the great distances aircraft must travel between refuelling stops has made this a considerable challenge, with battery technology not yet sufficiently developed to cope with long range journeys, for example.
The new £6.1m EPSRC-funded project, called Cornerstone, which includes researchers from Nottingham University, Imperial College London and Oxford University, will undertake research into areas of mechanical engineering that will help the industry move towards electrification, according to the project’s principal investigator Seamus Garvey of Nottingham University.
“There is an assumption that moving towards electric flight requires electrical engineering only, and that is utterly wrong, some of the biggest challenges are in fact mechanical engineering challenges,” he said.
The project will focus on six areas of mechanical engineering research. These include an attempt to better understand high power-density contacts, or those locations within an engine where there are very high stresses occurring between two surfaces, such as gear teeth.
“The whole area of understanding how long those contacts will last before cracks start to develop, then those cracks propagate and result in fatigue failure, is as yet an incomplete science, and one of the things we will do through Cornerstone is try to complete that science,” said Garvey.
Some of the biggest challenges are in fact mechanical
The researchers will also investigate the effect of impacts, such as a bird strike, on engines, and attempt to better understand the load and vibration dynamics of aero-engine assemblies, as well as the way in which air interacts with structures such as fan blades, turbine blades and compressor blades.
Of particular importance to hybrid-electric and all electric aircraft will be an investigation of new ways to manage heat without increasing the mass or complexity of the system, said Garvey.
“That is particularly relevant for all-electric flight, because all electrical machines are fundamentally limited by the ability to get heat out of them,” he said.
This will build on work the research team at Nottingham have previously undertaken to investigate the use of oil as a coolant in gas turbines, he said. “We want to upgrade our methods for analysing thermal management with oil, but we also want to develop some new methods for removing heat from engines,” said Garvey.
So, for example, the researchers will investigate the use of fine oil mists for thermal management, as well as cooling components using internal heat pipe elements. The team will also consider the use of materials such as graphene and diamond-like carbon within aircraft components. These materials have extremely high thermal conductivity, he said.
“If we can build those into our engine components, the heat can pass through the parts much more easily than it would do otherwise.”
Finally, the researchers will investigate the interactions between the electrical and mechanical machines within the aircraft, which can be a considerable advantage of electrification, said Garvey.
“When we design a rotating machine one of the things we worry about a lot is whether the machine will shake itself to pieces through vibration,” he said.
By putting an electrical machine on the rotor, it can help to take vibration out of the system, preventing damage, he said.
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A considerable amount of research has been done on the use of high pressure bubble skins on ship hulls to reduce viscous friction losses. However, I have read very little on the equivalent plasma skinning for aircraft wings and fuselage, which could potentially provide considerable increases in range with existing battery technology.
Some of the biggest challenges are in fact mechanical.
I am reminded of the exactly same comment from a university colleague -who eventually went to become a Public Company as a Civil Engineer contractor who opined that most of his civil engineering issues were also mechanical. I hope that young Engineers recognise this.
In ‘my’ industry most of the garment problems are thread or fabric issues, most of the fabric issues are yarn issues, most of the yarn issues are fibre issues -and in the end blame the Sheep! for not growing their wool more uni formally. In my experience, and many experiences, few problems occur where the result shows. Look up-stream! Young Engineers should be told that throughout their education -and afterwards!
The success of electric flights will happen when engineers stop trying to modify internal combustion engines and turbines to run on electricity. You need to look outside of the box and develop new technologies that run on electricity and permanent magnets. Obviously solar panels can be fitted to the top of the fuselage and wing surfaces, and some can be stored in batteries, but remembering that most commercial flights fly above the cloud levels, the solar panels would operate continuously, the issue is what you do with the electricity to create forward movement and lift, in a new and creative way. So spending time on the mechanical issues of conventional turbines and ICE motors may prove to be a waste of time and effort.
Ummmm night flights?????
I think that many of the problems of engineering cross the boundary; indeed a major issue for many electronics and electrical devices thermal AND thermal stress management is a major issue (think of the high power densities and high thermal gradients and stresses in much modern electronics – such as LEDs or lasers….); which might be good for innovation.
And I believe that for wind-turbines stress and failure/fracture is a major issue; though is not clear if that is what is meant by “high power density contact” (or do they mean electrical?) – and if this is relating to fretting and surface failure in gear teeth or surface induced fracture; in either case improved contact and the further development of stress management techniques will have significant impact.
There is definitely a need for good thermal management in electromagnetic devices (solenoids, transformers & motors) but the implication is that putting in more conductive materials (such as graphene) will help; surely this will tend to short out the current flows (induced or in the coil)?
Reducing friction is not only applicable to battery powered aircraft it would be beneficial for all aircraft. In the past several military aircraft had “blown” wings where exhaust gas and or/air was ejected through tiny holes on the surface of the wings to reduce drag without loss of lift. I don’t know if this was ever applied to civilian aircraft.