Jet engine condition monitoring using radar

Abstract

At the 2000 IEEE Aerospace conference a paper was presented on the work that had been undertaken at the Advanced Technology Centre, Gt. Baddow to detect and classify potentially damaging foreign object debris (FOD) as it is ingested by a jet engine. The impact of a damaging item of FOD on a highly stressed compressor blade may often not produce visible damage, but the impact will have altered the stress within the blade. This can drastically alter the life of the blade and possibly instigate early fatigue failure, often with catastrophic effect. The blades of a jet engine have natural resonant frequencies and will vibrate at certain points in the engine speed curve. Any change in this characteristic vibration frequency can provide an early indicator of High Cycle Fatigue (HCF). This paper describes work undertaken at Rolls Royce, Filton to investigate the ability of a low power microwave radar to measure the vibration characteristic of compressor blades of a Pegasus jet engine. Initial results are presented that show how the engine radar spectra changes as a function of engine speed. These have been displayed as a Campbell Diagram which enables key features in the data to be analysed as a function of engine speed. (5 pages)