Research Of Turbine Blade Tip Clearance Measuring Technology Based On Capacitive Sensor

Since gas turbine blade tip clearance acts as one of the most important parameters when toevaluate engine performance, real-time monitoring of rotating blade tip clearance can ensurethat engine operates efficiently and safely, which makes blade tip clearance measurementtechnology a research hotspot in recent years both at home and abroad. By analyzing andcomparing the current research home and abroad, this paper proposes the design of blade tipclearance measurement system based on capacitive, besides, after testing on parts ofhardware and software, the validation of the system is verified.The main target of the paper is to protect capacitive sensors from miscellaneousinterference in practical application, and realize the hardware system design including A/Dconversion and data acquisition circuits, and find the signal processing method from blade tipclearance signal to voltage signal converted by capacitive, finally display the results on PCscreen.The main research work is shown as followed:(1) Signal processing circuits based on the principle of carrier frequency tracking torestrain carrier frequency drift because of capacitive miscellaneous are designed, and throughtheoretical analysis the validation of the design is verified.(2)Circuits such as preamplifier in conversion between capacitive and voltage, alow-pass filter and logarithmic amplifier are designed and made.(3)The tip clearance signal’s high-speed data acquisition PCI is designed, with which thehardware and virtual instrument LABVIEW are combined to realize the collection and displayof the tip clearance analog signal.It shows that in this paper the tip clearance measurement system based on capacitive,along with carrier frequency tracking technology works well in solving the interferenceproblem of stray capacitance and other factors on the clearance measurement. The real timedynamic measurement of gas turbine tip clearance can be realized when to combine capacitivesensors and high temperature high pressure probe structure and drive cable technology,aswell as a complete data acquisition system.