Experimental Investigation in Annular Compressor Cascades at Transonic Flow Conditions

Abstract

The paper describes flow measurements in an annular compressor cascade at sub- and supersonic inlet flow conditions. The investigation is concentrated on the evolution of the flow field along the blade passage. A homogeneous flow could be realized in the test section at midspan with carefully directed suction by a splitter downstream of the blade passage. Two typical compressor cascades (Multiple circular arc profile (MCA) and controlled diffusion (C.D.)) have been investigated at similar inlet flow conditions in the whole operating range with a maximum relative inlet Mach number of about 1.3. Detailed flow measurements have been performed over several axial and radial positions along the whole blade passage. The velocity vectors have been measured with a Laser-2-Focus anemometer and the total pressure with miniature pilot-probes. Cascade overall performance, blade-surface-pressure-distributions and flow-visualization are presented. The obtained results show that the blade shape has a strong influence on the loss behavior especially at off design conditions and on the shock system influencing the whole flow field of the blade row. Different boundary layer evolution on the suction side (measured with Laser-2-Focus) causes the shock to be fixed or in fluctuation resulting in different losses (shock-, profile-, overall losses).