Numerical investigation on rotating instability phenomenon in tip flow field of transonic compressor rotor

Numerical simulations were performed on tip unsteady flow field of a transonic compressor rotor with different work mass flows. The results show that no oscillation occurs in tip flow field of rotor under high mass flow condition, which can be regarded as steady flow field for analysis, and the oscillation of tip leakage vortex is intensive under low mass flow conditions. Furthermore, periodical interference within the tip leakage flow between adjacent blade passages emerges. As a result, a phenomenon called "rotating instability" caused by the oscillation of tip leakage vortices and its circumferential propagation, is found in stationary frame. The dominating cell number of "rotating instability" flow field is nearly 40% of the blade passage number, and the cell size in circumferential direction is 2-3 pitches.