Unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of unsteady P-Q performance, casing wall pressure fluctuations and their wavelet analyses. The feature of the test compressor is a capacity tank facility connected in series to the compressor outlet in order to supply a compression wave from the compressor downstream. Research attention is focused on the post-stall characteristics of surge and rotating stall which occurs simultaneously. The behavior of the test compressor on the unsteady P-Q characteristic map shows that the surge cycle changes irregularly and the results of wavelet analyses of wall pressure fluctuations suggest increasing and decreasing of cascade flow blockage by variation of the rotating stall cell structure. The surge cycle may selectively determined by the rotating stall cell structure within the rotor cascade. The peculiar unsteady behaviors of the cascade flow by injecting the compression wave are also discussed.
