비접촉식 계측 시스템을 이용한 터빈 블레이드 진동 특성 분석

Abstract

Blade tip timing technique is measurement of vibration using a non-contact type sensor mounted on the case of a rotating blade. The sensors measure the blade vibration by detecting the time interval passing the sensor. When measuring a signal using the BTT method, the arrival time of the blade is measured by a sensor installed in the rotor case with an even or uneven gap. Since the oscillation frequency always appears as an integer multiple of the sampling rate, the aliasing phenomenon cannot be avoided. Therefore, in order to measure vibration, non-uniform vibration data must be secured through sensors installed with uneven gaps and signals must be reconstructed through various curve fitting techniques. In addition, since the sampling frequency of the BTT-based vibration signal determined by the disk rotation speed and the number of non-contact sensors is always smaller than the Nyquist frequency, the BTT-based vibration signal has undersampled characteristics. Therefore, in this study, we reconstruct the vibration signal through the SDOF Curve Fitting method and the Circumferential Fourier Fitting (CFF) method and analyze the vibration phenomenon of the blade by using each data processing technique