Role of leakage vortex behavior on stall inception in an axial compressor rotor

Steady and time-accurate three dimensional viscous flow calculations are applied to look deep into the steady and unsteady natures of tip leakage flow in a small-scale high-speed axial compressor rotor. Steady numerical simulations indicate that the breakdown of tip leakage vortex occurs inside the rotor passage at near stall condition. The vortex breakdown results in the low-energy fluid accumulating on the casing wall spreads out remarkably, which has a large blockage effect on incoming flow. Time-accurate simulations verify that leakage vortex breaks down massively as the mass flow rate decreases. The resultant low-velocity area builds up rapidly and moves towards pressure side and upstream until the unsteady equilibrium solution limit. At this point, the interaction of the massive vortex breakdown with the blade suction boundary layer occurs, and the low energy fluid in the blade suction boundary layer is rolled up into the leakage vortex, which further intensifies the blockage of tip blade passage.