Experimental Study of Effects of Grooved Tip Clearances on the Flow Field in a Compressor Cascade Passage

This paper presents an experimental investigation of effects of grooved tip clearances on the flow field of a compressor cascade. The tests were performed in a low-speed large-scale cascade, respectively, with two tip-clearance configurations, including the flat tip and the grooved tip with a chordwise channel on the blade top. The flow field at 10% chord downstream from the cascade trailing edge was measured at four incidence angles using a mini five-hole pressure probe. The static pressure distribution was measured on the tip endwall. The results show that the pressure gradient from the pressure side to the suction side on the blade tip is reduced due to the existence of the channel. As a result, the leakage flow is weakened. The high-blockage and high-loss region caused by the leakage flow is narrower with the grooved tip. In the meantime, the leakage flow migrates to lower span-wise position. The combined result is that the flow capacity in the tip region is improved at the incidence angles of 0 deg and 5 deg with the grooved tip. However, the loss is slightly greater than that with the flat tip at all the incidence angles.