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Down to the wire for eco flights

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16.10.2007

It may be only a plastic sheath, but the covering round the wires in any cable, circuit, plug, component or appliance is the difference between success and disaster, particularly when it comes to aviation.

If there’s a short circuit machines stop and systems break down. When the wiring is inside a jet engine, generating power for all the electrics in an aircraft, this thin coating becomes a life-support system for all on board.

This is why careful research goes into every aircraft component. And with the 21st century bringing about a new era of air travel where safety is joined by environmental concerns, the issue has become a government concern and has led to the UK’s former Department of Trade & Industry (DTI) funding a major technology research project with 16 companies, including Rolls-Royce plc and Goodrich Power Systems, and academic teams from several universities.

The overall research programme called Advanced Electric Machines through Materials sets out six key challenges, all concerned with the two principal requirements for motors and generators – magnets and coils of wire.

Wiring insulation is one of the key concerns and scientists and engineers at the University of Teesside are working on the solution - a new nanocomposite material, part-plastic, part-ceramic, to replace traditional coatings, explained Professor Simon Hodgson, Dean of the University s School of Science & Technology and head of its IDEAS Institute.

This will be important because designs for future aircraft, such as the Boeing 787, will have to be more eco-friendly and carry a much greater range of electrical and electronic systems, for example, in place of the heavy hydraulics that operate flaps on the wings.

These changes will reduce weight, improve fuel efficiency and help reduce emissions. They will also result in more responsive, safer and ultimately cheaper systems.

But they need a significantly bigger on-board source of power. The best place to locate the generators is inside the jet engine, but with traditional materials and methods, the magnets and wiring used for generating power cannot withstand the high temperatures which could exceed 500°C. Existing exotic plastics will go as far as 200°C and to date this has been an insurmountable obstacle for designers and engineers.

The Teesside team, led by Professor Hodgson is developing a coating that will work in such extreme conditions.

His team started work on the DTI project at Loughborough University but moved as a group to Middlesbrough, both to be nearer the chemical process industries and manufacturing opportunities, and to take advantage of new University research facilities.

“To meet the extreme demands of this application we have devised a new material, known as a ‘ceramer’, incorporating characteristics of ceramics and polymers. The coating needs to be thin but strong, and stable both at high temperatures and under the high forces produced in a rapidly-rotating generator.”, says Professor Hodgson.

Professor Hodgson likens the properties of the ceramer to ‘a soft pencil-lead’ that covers the core copper wire to micrometer-scale thickness – a fraction of a hair’s-breadth.

It is being developed in a high-precision chemical engineering operation. This is Teesside’s speciality and is known as a sol-gel process. It takes individual molecules of polymer and ceramic and constructs them chemically in solution, where they react together. Initially the product of the reaction is flexible like a polymer, and is suitable for coating the copper and allowing the completed wire to be coiled. In the high temperatures inside the engine, it undergoes a chemical change, ‘a controlled decomposition’, and the hard ceramic-like qualities take over.

Nic Mitchell | Source: alphagalileo
Further information: www.tees.ac.uk/sciencenews

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