Blade damage monitoring method base on frequency domain statistical index of shaft’s random vibration

Abstract

The shaft vibration based blade damage monitoring method has become another research focus in addition to tip timing technology because of its simple testing system. However, how to extract the accurate and effective blade damage information from the vibration response of the shaft is the key to the implementation of this method. In this paper, a blade damage monitoring method based on the frequency domain statistical index of shaft’s random vibration is proposed. Firstly, a continuum dynamic model of blade disk shaft system is established and verified for the statistical feature analysis of rotor system with blade damages, in which the coupling among shaft’s bending, torsion and blade’s bending is considered. Then, base on the vibration response from the dynamic model, a blade damage monitoring method is constructed, in which the harmonic components of forced vibrations are removed, the random vibration component is retained, and the mean frequency and bandwidth index in the resonance frequency band of the random torsional vibration is adopted as the blade damage monitoring index. After that, a blade-disk-rotor system test bed is designed and the vibration measurement system is constructed. The experimental results verify the effectiveness of the proposed methods and indicators. To sum up, the verified dynamic model can provide abundant simulation data under various working conditions and various fault parameters for the research of diagnosis index and methods. The random excitation is inherent in the running rotor system, so the random vibration based blade damage monitoring method is easy to implement. The statistical index based method is a simple and effective way to extract the damage information of blade in random vibration. Therefore, the research results of this paper can provide important supplements to the blade damage monitoring.