EXPERIMENTAL AND NUMERICAL INVESTIGATION OF CORNER STALL IN A HIGHLY-LOADED COMPRESSOR CASCADE

Three-dimensional collier stall is one of the most important factors limiting compressor performance. This paper presents a complementary experimental and computational study of corner stall in a highly-loaded compressor cascade subjected to three inlet boundary layer thicknesses, two levels of freestream turbulence intensity and two Reynolds numbers. Experiments included seven-hole pressure probe traverses, airfoil loading and surface oil flow visualization. Measurements were supplemented with the numerical predictions from a commercially available CFD code. It was found that the low momentum boundary layer on the endwall was unable to overcome the large streamwise adverse pressure gradient in this high-lift profile and turned sharply towards the midspan due to the strong cross-passage pressure gradient. The corner stall, with distinct regions of three-dimensional reversed flow, started at 50% chord and occupied a large area of the suction surface as well as the dbwnstream passage. Only a small region of the inlet boundary layer, very close to the endwall seemed to play a role in the corner stall. As such, the flow in the endwall region was found to be nearly independent of the inlet boundary layer thickness, freestream turbulence intensity and Reynolds number. Based on the endwall flow structures, a new topology of corner stall for compressor cascades with high airfoil diffusion factor and high flow turning has also been proposed.