The Use of Eddy Current Sensor Based Blade Tip Timing for FOD Detection

Abstract

Deterioration of rotor blades due to foreign object damage (FOD), erosion by sand/water, low cycle fatigue (LCF) and high cycle fatigue (HCF) all limit blade life, but cannot always be detected before a failure. The advent of tip-timing systems makes it possible to assess turbomachinery blade vibration using non-contact systems. However, these systems are still largely optical based and therefore suffer from contamination problems, further development of these systems is difficult due to problems associated with keeping the sensors clean. Experimental measurements have been carried out using an alternative eddy current sensor that has been validated in a series of laboratory and engine tests to measure rotor blade arrival times. A series of engine trials have been conducted to assess their capability for detection of pre-existing damage and the capture of dynamic foreign object damage (FOD) events. The results show that it is possible to acquire high quality blade timing data for use in engine condition monitoring. In addition for the detection of FOD created damage and FOD damage as it occurs.