Investigation into the Noise Characteristics Based on Rotating Instabilities Mechanism in a Multi-stage Axial Compressor

Rotating instability can be observed in the tip flow region of axial compressor stage while stable operation. In order to investigate the noise characteristics in a multi-stage axial compressor, the noise inner compressor casing is measured simultaneously with the vibration of the rotor blades on a high pressure compressor component rig testing. An azimuthal mode analysis and theoretical formulation of the rotating source mechanism are applied to the unsteady pressure at the casing wall immediately upstream of the inlet plane of the rotor. It is shown that RIs might be described by a group of superimposed modes. This is the reason why RIs can be identified as an amplitude increase in a frequency band. The mode orders of RI are consecutively numbered riseing with frequency. The frequency in the source frame (omega(N)) closed to the frequency in the rotating frame (omega(R)) can be got well recovered. The results presented in this paper can be a reference for further understanding of the characteristics of unsteady flow field and the effects of the high intensity sound waves on the rotor blades.