Flow Control in a Compressor Cascade at High Incidence

Flow control has been applied on the suction surface of blades within a compressor cascade to remove a turbulent boundary-layer separation that occurs at an incidence of 12.5 degrees. Vortex generator jets and boundary-layer suction through discreet holes have each been applied to the suction surface to push the point of separation from 54% chord to the trailing edge. Corner separations also occurring at this incidence have been controlled by means of endwall suction. The mixed-out stagnation-to-stagnation pressure loss coefficient was measured in each case tested. The measured loss coefficients were used, together with an endwall suction-loss coefficient and a boundary-layer control loss coefficient, to estimate the total loss coefficient for a compressor blade with a representative aspect ratio of 3.5. For such a blade, endwall suction and vortex generator jets on the suction surface were found to yield a 20% reduction in the total loss coefficient relative to the uncontrolled case. Endwall suction, together with boundary-layer suction on the suction surface, was found to yield a 33% reduction in the total loss coefficient. Flow control was also applied to the suction surface at a range of incidences from 0 to 15.5 degrees. Only boundary-layer suction was able to achieve a loss reduction at 15.5 degrees.