Visualizations of the leakage flow in a compressor cascade with different tip geometries

This paper presents flow visualization of the leakage flow in a compressor cascade at the incidence angle of 0°. The experiments were performed in a water tunnel using the hydrogen bubble technique. Three kinds of tip geometries are investigated, including flat tip, the suction side squealer tip and tip with a closed cavity on it. The evolution of the tip leakage vortex is observed clearly. The interaction of the leakage vortex and the corner vortex is also observed. On the endwall, it can be seen bubbles move along a streak which indicates the separation line of the leakage flow. For the tip with a cavity, a streamwise vortex is generated immediately when the flow entering the cavity. The evolution of the streamwise vortex in the cavity also can be observed. Compared to the case of the flat tip, the onset of the rolling-up of the leakage vortex of the suction side squealer tip occurs earlier. A streamwise vortex is observed at pressure side of the squealer. It may contribute to the secondary vena contractor of the leakage flow.