Wide-Range Self-Calibrating Blade Tip Clearance Measurement Using Microwave Sensor

Blade tip clearance (BTC) measurement is crucial for testing and health monitoring of gas turbine engines. Among various measurement methods, the emerging microwave sensing-based solution has gained growing attention due to its high sensitivity and reliability, but accurate BTC measurement still has several challenges, including DC offset variations caused by environmental factors and the inherent trade-off between measurement range and sensor size. To address these issues, this paper proposes a wide-range self-calibrating microwave measurement method (WSMM) based on a single-frequency continuous-wave microwave sensor, providing a high-accuracy, low-cost, and versatile solution for BTC measurement. The method begins with a simplified static calibration process to determine sensor static parameters that are independent of environmental changes. Then, during dynamic measurements, the tricky DC offset variations are compensated through automatic signal classification and peak extraction algorithms. Finally, it automatically compensates for BTC jumps caused by phase ambiguity, thereby extending the sensor’s measurement range without increasing its physical size. Experimental validations on a high-speed fan for drones demonstrate a dynamic measurement accuracy of ±30 μm within a range of 0-5 mm, effectively monitoring the independent BTC of each blade and the blisk's overall radial vibration.