Enhanced Calibration Method for Microwave Blade Tip Clearance Measurement

Accurate measurement of blade tip clearance is crucial for ensuring engine safety and enabling active clearance control systems. Despite advancements in sensor technology, testing techniques for measuring tip clearance still pose challenges. This paper introduces a novel measurement method utilizing a low-cost microwave sensor for precise tip clearance measurement, with on-site calibration capabilities. The method refines the calibration process of the microwave sensor by moving the sensor over a fixed known distance using a simple device, eliminating errors caused by DC-offsets and carrier wavelength. With this method, the microwave sensor for blade tip clearance measurement could be more compact, user-friendly, and maintaining high precision. Experimental results on high-speed fan blades demonstrate the real-time monitoring capability of the proposed method, achieving a measurement accuracy within 30 μm in static tests.