Analysis of a Signal Preprocessing Method for Blade Tip-Timing without the Once-per Revolution Sensor

Blade tip-timing is an effective method for blade vibration online measurement of turbomachinery. The majority of tip-timing systems require a once-per revolution (OPR) sensor installed close to the shaft to generate timing reference. In this article a tip-timing signal preprocessing method which requires no OPR sensor is analyzed. The method presented uses only tip-timing signal to obtain the vibration information of the blade and the rotating speed of the rotor. Error analysis indicates the method is less sensitive to the bend and torsional vibration of the shaft and the rotating speed measurement error can be limited. The measurement error of vibration displacement difference is analyzed and compared with the method which requires the OPR sensor. Experiments are conducted and the results indicate that the method is feasible for BTT signal preprocess without the OPR sensor and has good accuracy.