Hub aspiration strategies and flow loss analysis of a shock-in type supersonic compressor rotor with negative inlet pre-whirl

Large-scale corner separation is one of the key factors that limit the performance improvement of high-load compressors. In this paper, the hub aspiration method was applied to a supersonic shock-in type compressor rotor with negative inlet pre-whirl to suppress the hub corner separation. Six suction schemes composed of aspiration slots with different locations and orientations have been designed and numerically tested. The results revealed that the aspiration location is better to be placed starting from the post-shock point and extending to the deep separation zone. The streamwise slot satisfying such conditions could effectively suppress corner separation but narrows the rotor stable mass flow range by increasing the pitchwise secondary flow. The circumferential skew slot could exactly remedy such defects. The streamwise slot combined with a downstream skew slot is the optimal aspiration strategy that effectively improves the rotor performance without reducing mass flow range. At the design and near-stall operating point, the rotor efficiency (EF) and total pressure ratio (TPR) could be improved by 1.3% and 5.0%, 3.3% and 7.2%, respectively. Consequently, the stall margin was increased by 2.0%. According to the flow loss analysis, the combined aspiration scheme mainly alleviated losses from hub to middle span by reducing the shock strength and the magnitude of separation as well as its radial migration. But in the tip region, it strengthened the leakage flow and its interaction with shock waves, thus increasing the flow losses.