A Microwave Sensor for Real-Time Online Monitoring and Measuring the Blade Tip Clearance of Aero-Engine

In this article, a microwave sensor for real-time monitoring and measuring the blade tip clearance (BTC) of an aero-engine is proposed. It comprises a ceramic cap, a resonant cavity, an inner conductor, and a cross-coupling ring (CCR). In the real-time monitoring and measuring process, the different loading states of BTC will endow the proposed sensor with different additional capacitance, shifting the resonance frequency. By introducing a high-temperature-resistant metal and high-temperature permittivity stability ceramic cap, the proposed sensor has good high-temperature stability and an excellent ability to overcome the interferences of the attached carbon deposition and oil stain. In addition, the proposed sensor has a probe size of only 7.1 mm while maintaining an operating frequency of below 10 GHz (9.524 GHz). Meanwhile, the simulated and measured results not only confirmed the feasibility of the proposed sensor but also indicated that the designed sensor has a reliable BTC of aero-engine monitoring range of 3000 mu m with an accuracy of 100 mu m (average accuracy better than 0.75 MHz/ mu m).