Jet engines shape up

Rolls-Royce is brining together researchers from India and the UK in a bid to develop shape-changing alloys that could operate at high temperatures inside aircraft jet engines.

These innovative materials, known as shape memory alloys, could replace the numerous heavy, complicated mechanical actuators used in modern jet engines. The project may also aid the aerospace industry’s development of ‘more-electric’ planes — next-generation aircraft in which hydraulic and pneumatic systems are cut to a minimum.

Imperial College London is working with the Indian Institute of Science in Bangalore on the three-and-a-half-year project. The research has received a £200,000 award from the newly-formed UK-India Education and Research Initiative, which was set up to foster closer ties between the countries.

Dr David Dye, lead researcher at Imperial’s department of materials, said there is huge scope for the use of shape-memory alloys in modern jet aircraft, particularly in the engines.

‘Micromechanical actuators, which are hydraulically driven using fluids or fuels, are used in all sorts of places in engines and airframes,’ he said. ‘They weigh a lot and make the engine and airframe very interdependent.’

Electrically actuated shape memory alloys change shape with the application of heat or a magnetic field — a less complicated approach than mechanical actuators and one requiring far fewer moving parts. The result, according to Dye, could be a more robust and far lighter aircraft.

In this project, ‘self-actuating’ components are likely to be applied initially to noise and emissions reduction systems.

Higher temperatures

One goal of the joint research project is to develop shape memory alloys with a much higher actuation temperature than existing materials. Current alloys that use phased transformation operate at temperatures between -20ºC and 100ºC, changing shape as their crystal structure alters.

Alloys that actuate at higher temperatures could be used further inside Rolls-Royce’s aircraft jet engines. However, Dye said it will be a long time before the technology can be used in the hottest part of the engine, where temperatures often reach 1,600ºC.

‘We’re trying to improve the capability of these things,’ he said. ‘It could mean that these actuators are used in new parts of the engine. If you want more electric actuation and want to use these design concepts all over the aircraft, then you need alloys that can function at all these temperatures.’

The researchers will use synchrotronic X-ray diffraction at the European Synchrotron Radiation Facility in Grenoble to study candidate alloys, as well as the new diamond light source facility in Oxfordshire. Here, materials will be placed within X-ray beams and put through temperature and strain cycles to see what happens as the materials change. This approach is more useful than carrying out standard microscopy tests and gives researchers an insight into the physical changes as they occur within the material, said Dye.

During the project a number of different alloy compositions will be analysed simultaneously using a variety of technologies, including a nano-indenter, a tool that allows researchers to analyse the composition of a material on the nano scale. This work will be undertaken in Bangalore at the Institute of Science.

Dye’s team aims to deliver possible shape memory alloys to Rolls-Royce by the end of the project, as well as gaining a better understanding of the micro-mechanics of these materials.

The project will also develop a shape-memory alloy that can operate in a component with more than one function, for example one with a ‘cruise’ and an ‘idle’ setting.

While the project’s main goal is to develop alloys for Rolls-Royce, Dye said the company is also interested in widening its network of collaborators outside the UK.