Structure and operation algorithms of the systems for measuring of radial clearances with temperature self-compensation

The paper is dedicated to the principles of construction of the systems for measuring of radial clearances in compressors of gas-turbine engines. The methods realized in such systems are based on using of single-coil eddy-current sensors with sensitive elements made as a conductor strips and self-compensation of temperature influences on the sensor. The method also involves the using of only one sensor (it provides work and compensation functions) and as a result only one hole in the engine stator. The selfcompensation procedure is carried out in operation mode during rotation of the rotor. It involves measuring and fixing of extreme values of equivalent inductance of primary winding of matching transformer of single-coil eddy-current sensor at the moments when the controlled blade is in sensor sensitivity area and when the blade is out of it (when sensor’s sensitive element is in interblade zone) and further difference calculation between obtained results. This difference doesn’t depend on temperature influence on sensor constructive elements. Because of this self-compensation there is no need in additional sensor for temperature correction an as the result there is no need to make additional hole in engine stator. Hence the proposed method is better compared to existing. The article considers the general structural and functional scheme of the system that realized the method with temperature self-compensation. The main operation algorithms of the system such as the algorithm for seeking of extreme codes in interblade zone, the algorithm for difference calculation between codes with the removal of “non-compensated” temperature influences on the sensor and the algorithm for blades numbers detection during asynchronous sensors surveying are given too.