Corner separation control in compressor cascade based on L-shaped endwall groove

To overcome the shortcomings of current vortex generator techniques used to control corner separation in compressors, we investigate the mitigation of corner separations using the streamwise vortex generated by the L-shaped endwall groove in a high-speed compressor cascade. First of all, a convenient and universal parametric modeling method for the L-shaped endwall groove has been proposed by introducing the standard modeling space and function superposition strategy, and the L-shaped endwall groove optimization was conducted based on this method. The simulated flow fields of the baseline cascade and a Pareto-optimal case have been compared. It was found that the groove separation vortex generated by the L-shaped groove could effectively block the endwall cross flow, cut off the supply of low momentum endwall fluid to the corner region, and therefore significantly mitigated the reverse flow in the corner region and avoid the formation of the corner separation vortex, remarkably improving the cascade performance within a wide range of incidence. Calculated results of different Pareto-optimal cases have been compared. The results show that the strength of the groove separation vortex determines the control effect of the groove on the endwall cross flow and the severity of additional loss and blockage caused by the groove, and thus is the key factor influencing the control effect of the L-shaped endwall groove. Secondly, the influence of design parameters on the L-shaped endwall groove and its mechanism have been analyzed through the combined use of the Sobol indices-based sensitivity analysis method and conventional control variate method. It was found that the control effect of the endwall groove was significantly influenced by four design parameters including the pitchwise location of the groove, groove depth, the width and length of the upstream groove. The pitchwise location of the groove determined the distance between the groove separation vortex and suction-side corner region, while the other three mainly influenced the strength of the groove separation vortex. Finally, a guideline for selecting design parameters of the L-shaped endwall groove has been summarized based on the above analyses.