Pressure relief for jet engines – Photon02

The aerodynamics inside jet engines are not completely understood due to the unpredictable nature of the air flowing through the turbine. However, a research team led by Dr Jim Barton from Heriot-Watt University, has developed tiny fibre optic pressure sensors that can for the first time be used inside jet engine test rigs. These sensors should allow engineers to collect data that will enable them to make more aerodynamic engines, which will improve fuel efficiency and engine performance, ensuring longer component lifetimes and saving in maintenance costs.

Speaking at the Photon02 Conference in Cardiff on Tuesday 3 September Dr Matthew Gander, a member of the Heriot-Watt research team, will describe how five optical 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. The experiment was performed at QinetiQ`s Isentropic Light Piston Facility, a research turbine test facility in Pyestock.

The sensors were fabricated on silicon wafers using the micromachining facilities at the Central Microstructure Facility at the Rutherford Appleton Laboratory. Each sensor, which is smaller than the size of a half-millimetre cube, contains a diaphragm that flexes in response to a pressure change. The Fibre Optics group at Heriot-Watt University completed the sensors by attaching them 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.

Dr Jim Barton said: “Our sensors are smaller than the competing electrical gauges and making them by micromachining techniques is potentially very cost-effective. The small size allows them to make measurements that were not previously possible. Sensors with this capability are opening up areas of flow measurements, which can contribute to an improved understanding of the aerodynamic processes in an engine, with benefits for future design.”

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

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. These test will take place in a hypersonic tunnel at Oxford University`s aerodynamics laboratory.