Corner stall control in linear compressor cascade by blended blade and endwall technique based on large eddy simulation

Abstract

Under the influence of a strong adverse pressure gradient, secondary flow, and other factors, compressor cascades are prone to corner separation and even to corner stall, which seriously affects aerodynamic performance. In this paper, large eddy simulation is used to investigate the effects and mechanisms of corner stall controlled by the blended blade and end wall (BBEW) technique. Based on this technique, three BBEW control schemes with different chord-direction positions of the maximum BBEW width are designed for the suction side root of a modified NACA (National Advisory Committee for Aeronautics) 65 blade. The influence of the chord-direction position of the maximum BBEW width on control corner stall and the differences of physical mechanisms are deeply explored. The numerical results show that the BBEW technique can improve the flow field structure and aerodynamic performance of a compressor cascade under corner stall conditions to a certain extent. When the maximum BBEW width is located near the leading edge, it provides the most significant reduction in the spanwise height of corner separation and effectively weakens the intersection of boundary layers, so that the boundary layer losses are reduced by 6.27%, and the overall performance is improved. These effects can be attributed to the axial and spanwise forces generated near the maximum BBEW width, with the former increasing the kinetic energy of the surrounding fluid, while the latter transports low-energy fluid upward to reduce accumulation on the end wall. In addition, the increased dihedral angle weakens the intersection of boundary layers and restrains the development of the corner vortex, which is also one of the underlying physical mechanisms. When the maximum BBEW width is located in the middle of the chord, it most effectively delays the corner stall. When it is located near the trailing edge, it is most effective at controlling the development of corner separation, reducing the accumulation of low-energy fluid in the three-dimensional corner region, and reducing corner separation losses by 4.73%. The effect of the increased dihedral angle in weakening the intersection of boundary layers and the corner vortex is the main reason why these two design schemes can improve the aerodynamic performance of the compressor cascade.