Measurement of multiple physical quantities based on blade tip timing

Novel methods are proposed to expand the capability of a blade tip timing (BTT) system. Simultaneously measurement of blade tip clearance (BTC) and blade tip velocity (BTV) is realized. In terms of hardware, a convex lens is used at the emitting end of the laser fiber to adjust the optical path. In the software part, a new BTT protocol is designed where both the time-of-arrival and time-of-leaving as a blade sweeps across the detecting region are recorded. Meanwhile, new algorithms are developed to process the data. The methods are studied experimentally from various aspects. It is demonstrated that when a speed sensor is not available, the BTC and BTV can be measured by a double-lens sensor. The random error of BTC on a steady operational occasion is within 30 pm. Subtle dynamic responses during accelerations can be accurately captured. When a speed sensor is available, a single-lens sensor can be used to measure the BTC. Besides, a double-lens sensor can be automatically calibrated using a Kalman-filter-based algorithm to maintain high precision during long-time online measurement. All the methods have been validated on a compressor rig.