Influences of groove-type casing treatment on the tip leakage flow behaviour in linear compressor cascades at different tip clearances: influence of single groove at mid-chord

Abstract

In this study, the influences of the single groove installed at the mid-chord – which is known to have a large expansion effect on the stable operating flow range of low-speed axial compressors – on the flow behaviour and the loss generation in a linear compressor cascade were investigated numerically at different tip clearances. Reynolds-averaged Navier–Stokes simulations of the incompressible flow in the test cascade were performed, with the computed results clarifying the following remarkable phenomena, which are common to both small and large tip-clearance cases. The single groove locally weakens the tip leakage flow by the decrease in the blade loading and the streaming of the flow near the blade pressure side into the groove, consequently reducing the distance between the tip leakage vortex and the blade suction surface. Meanwhile, although the groove decreases the loss due to the tip leakage vortex generated from the blade leading edge, the loss generation in the entire cascade passage is almost the same as that in the cascade without the groove due to the additional loss generation resulting from the presence of the groove.