1 ARCHIVES EFFECTS OF HUB TREATMENT ON COMPRESSOR ENDWALL FLOW FIELDS

An experimental investigation was carried out to examine the influence, on stator passage endwall flow of a slotted hub treatment rotating beneath an axial compressor stator row. The main focus of the investigation was better understanding the mechanism of operation of the treatment. To obtain this, a detailed mapping of the three dimensional, unsteady velocity field near the hub endwall was done, using hotwire anemometry for both a solid hub endwall and an endwall treated with axial skewed slots.The velocity measurements indicate that, with the smooth wall, a large region of blockage occurs near the rear of the blade passage. This blockage is seen to be associated with the hub endwall rather than either the suction surface or the pressure surface of the blade. With axial skewed slots, the blockage is eliminated, and the stalling flow coefficient is reduced by 12%. The measurements showed that the hub treatment induces both a region of removal near the rear of the passage and a strong flow injection, or jet, near the front. The data appears to support the idea that it is the region of removal, and not the jet, which is responsible for the improvement in stall margin. To my parents, Chuck and Jan, for their continual support. ACKNOWLEDGEMENT