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With the advancement of aerodynamic design techniques for turbomachinery, the high-loss flow in the end wall region has emerged as a bottleneck, limiting further improvements in the aerodynamic performance of fans and compressors. In this study, the end wall region of a linear cascade is flexibly parameterized using the advanced extended free-form deformation method and subsequently optimized through adjoint optimization, enabling an integrated design of the entire end wall region. A refined design featuring flexible hub deformation and a smoothly corner region is achieved. The results demonstrated that the finely integrated design significantly reduced the loss coefficient by 16.81% and effectively controlled corner separation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]