Large eddy simulation and combined control of corner separation in a compressor cascade

Abstract

Due to the demand for higher aerodynamic performance of compressors, thoroughly investigating the high-loss flow in the corner region and effectively controlling it are important. In this paper, a novel parameterization method based on the extended free form deformation (EFFD) technique and the constraints for EFFD's control points is proposed. Then, considering the features of typical control techniques and the degrees of freedom of both the blade and hub geometries, the combined control approach is implemented in the corner region of a linear cascade. Furthermore, large eddy simulation is used to simulate the flow, verify the effects of the combined control approach, and explore the underlying physical mechanisms of corner separation. The numerical results show that the combined control can significantly decrease the mean total pressure loss. The loss reduction at the design point reaches 6.05%, while it decreases by almost 2.5% near the stall/blockage operating conditions. The combined control increases the radial pressure gradient at the rear of the blade by depressing the hub and stretching the suction surface. Consequently, although the radial flow slightly increases the mixing loss in the mainstream at large incidences, the accumulation of low-energy flow in the boundary layer and the corresponding development of the corner vortex are significantly restrained. Moreover, by redistributing the static pressure on the hub, the combined control weakens the migration of crossing flow and obstructs the low-velocity flow from the pressure side involved in the separation. Overall, the combined control contributes to reducing the corner separation and improving the aerodynamic performance.