Study on instability evolution at different rotation speed in a transonic compressor

In order to study the physical mechanisms of the occurrences of different instability precursors, it is necessary to figure out instability behaviors of compressor at different rotation speed. Experimental investigations are carried out to study the instability evolutions at different rotation speed in a transonic compressor. High response transducers are mounted at both rotor tip region and stator outlet hub region to measure the whole instability evolutions data. After that, FFT (fast Fourier transform), WFT (window Fourier transform), filter are used to analyze data in both frequency domain and time domain. So that, the rule of instability evolution in this compressor is obtained. The instability evolution changes with the increasing of rotation speed. At low rotation speed (subsonic) such as 65% of design rotation speed, the compressor turns into instability because of rotating stall driven by spike. At high rotation speed (transonic) such as 88% of design rotation speed, a disturbance of low-frequency, axisymmetric, large amplitude, localized at hub region leads into instability. It is called as partial surge. As a critical rotation speed (78% of design rotation speed), partial surge and rotating stall nearly occur at the same time.