Investigation of Tip-leakage-vortex Breakdown and Its Role in Rotating Stall in a 1.5-stage Low-speed Axial-compressor

April 10-15, 2016 Abstract A whole-annulus unsteady numerical simulation is carried out to investigate the mechanism of the rotating stall in a 1.5-stage low-speed axial-compressor. By comparing the experimental and numerical results, the numerical results are validated. The numerical simulation captures the most features of the rotating stall of the 1.5-stage compressor observed from the experimental results. The unsteady bubble-like breakdown appears in the tip leakage vortex at the near stall condition. With the compressor throttling, the modal wave appears, increases in intensity and induces the part of the breakdown-vortex flow spilled over the adjacent blade leading-edge unsteadily, which form a spike. Consequently, the spikes emerge around the compressor annulus at the same time and the intensity and size of the spikes is increased rapidly during the inception period. At last, the spikes are merged into a large stall cell, which propagates around the annulus with 30% rotor speed.