Inside the jet engine

Fibre optic pressure sensors developed at Edinburgh’s Heriot-Watt University could lead to more aerodynamic and longer lasting jet engines.

The sensors, that can be used inside jet engine test rigs, should allow engineers to collect valuable information on the internal aerodynamics of jet engines.

Speaking at Cardiff’s recent Photon02 Conference, Dr. Matthew Gander, a member of the Heriot-Watt research team, described how five sensors were used to make the first ever pressure measurements at the trailing edge of a stator blade, the stationary blade behind the rotor, in a jet engine turbine simulator.

Each tiny sensor contains a diaphragm that flexes in response to a pressure change. The sensors were then attached to the ends of optical fibres.

The devices work because a tiny air gap, called a Fabry-Perot cavity, exists between the diaphragm and the optical fibre. Light resonates in this cavity and the position of the diaphragm determines the phase of the resonance. This phase signal is recorded via the optical fibre.

‘Our sensors are smaller than the competing electrical gauges and making them by micromachining techniques is potentially very cost-effective,’ says Dr. Jim Barton. ‘The small size allows them to make measurements that were not previously possible, which can contribute to an improved understanding of the aerodynamic processes in an engine, with benefits for future design.’

However, Dr. Barton warns that as the sensors have not been built to work in real engines, because of the extremely high temperatures, it may be some time before they are approved for usage in aircraft.

The team now plans to run the sensors in a scale model of the ‘Beagle 2’ Mars lander, which is due for launch next year.