An integrated measurement method of blade tip clearance and blade vibration based on blade tip timing technology

Structural parameters measurement of rotating blades is an important issue to ensure long-term safe operation of turbomachinery. Blade tip clearance (BTC) and blade tip vibration (BTV) are essential parameters of rotating blades. Typically, BTC and BTV are measured by two separate systems, which poses a challenge to the available space for the sensors. This paper proposes an integrated measurement method of BTC and BTV base on blade tip timing (BTT) technology. On the hardware side, two focusing lenses with different focal lengths are used to form two tapered optical paths. On the software side, a new protocol is designed where both the time-of-arrival (ToA) and time-of-leaving (ToL) as a blade sweeps across the light cone are recorded. Finally, a new data processing algorithm was developed. This method was validated on a newly calibrated test bench, which had an adjustable clearance and could provide a vibration displacement benchmark. The experimental results show that simultaneous measurements of the BTC and BTV can be achieved without calibrating the blade parameters.