Simultaneous Measurement of Blade Tip Clearance and Blade Tip Timing With Microwave Sensor

Microwave sensing approach has attracted growing interest in the field of measurement of blade tip clearance (BTC) and blade tip timing (BTT) owing its the applicability in harsh environments and insensitivity to rotation speed and pollution. However, there is now a lack of demonstration of the feasibility of simultaneous measurement of BTC and BTT via a single microwave sensor. Moreover, for the close-range measurement in this scenario, the critical baseband signal calibration remains challenging. In this article, a simultaneous measurement method of BTC and BTT with a single microwave sensor termed amplitude and phase joint analysis (APJA) method is proposed. The method leverages the amplitude component of the baseband signal as the timing signal to realize BTT measurement and extracts the tip clearance value from the phase component to realize BTC measurement. In addition, a signal calibration method for quadrature imbalance and dc offset based on relative motion in the close-range measurement is proposed and the detailed implementation procedures are illustrated, which is significant to reduce the measurement error of APJA. Finally, experimental validations are carried out to demonstrate the accuracy of signal calibration method and the effectiveness of the APJA method, offering a promising approach for blade health monitoring with a microwave sensor.