Evolution of the tip leakage vortex in an axial compressor rotor

The evolution of tip leakage vortex is analyzed at both design and near stall conditions based on instantaneous and averaged velocity and vorticity distributions in cross flow sections measured with Stereoscopic Particle Image Velocimetry (SPIV) in a large-scale low-speed compressor facility. Formation, becoming unstable, and interaction of small-scale vortices and mainstream characterize the evolution of the tip leakage vortex in the compressor rotor. These processes influence the mainstream in very different ways. The process of leakage vortex becoming unstable is relatively smooth at design condition and vortex breakdown occurs at near stall condition for the case in the experiment. The main reason is that the critical condition occurs only in the core of tip leakage vortex at near stall condition. The effect of Coriolis force and centrifugal force on the stability of tip leakage vortex is analyzed theoretically with hypothesis of incompressible, inviscid and quasi-cylindrical swirling flow.