Boundary Layer Control in a Compressor Cascade Using Distributed Suction

Abstract

An experimental study in a low speed compressor cascade was carried out to investigate the effect of distributed suction (aspiration) on the cascade performance. Unlike suction used conventionally, distributed suction requires lower mass flow rates and is achieved by suction through holes of very small diameter distributed over the surface. A set of 5 NACA - 65(18)10 blades were used in the experiments that were carried out at a Reynolds number of 1.6 × 105. Detailed measurement of surface static pressure, total pressure loss in the wake of the blades and boundary layer thicknesses were taken at incidence angles in the range −10 to +6 degrees. Significant effect of suction was observed on the total pressure loss distribution at the trailing edge of the blades. The mean total pressure loss coefficient reduced in the range 14 to 36 percent for the various configurations tested. Higher performance improvement was observed at negative incidence angles. Boundary layer measurements revealed that the effect of suction was prominent in the mid-span of the blades. Reduction in boundary layer momentum thickness in the range 8 to 20 percent was observed for the various configurations. The calculated diffusion factor also showed improving trends in line with the observations of total pressure loss and boundary layer thicknesses. The mass flow ratio for the best configuration was only 0.15 percent of the primary mass flow. This experimental study demonstrates the effectiveness of distributed suction (using only a fraction of the primary mass flow) on compressor cascade performance.