Effectiveness of Bowed Blade on Suppression of Corner Separation in Linear Compressor Cascade Demonstrated by DES

Abstract A 3-dimensional blade stacking is one of the effective technologies to improve the aerodynamic performance of axial compressors. Particularly, the circumferentially bowed blade with the positive dihedral angle is well-known to suppress the corner separation generated in a corner of a blade suction surface with a hub endwall. However, the effectiveness of the bowed blade has been studied by mainly using the Reynolds-averaged Navier-Stokes (RANS) simulation which may give less accurate prediction especially for the corner separation. In this study, to achieve further improvement of the compressor performance such as the stall margin by applying the bowed blades, its accurate effects on the corner separation formation are examined by using the detached eddy simulation (DES). The RANS simulation is also conducted to verify the superiority of the DES in the comparisons with both the steady and the unsteady experimental data. In this paper, it is concluded that the present DES method possesses higher prediction accuracy of the corner separation formation compared with the RANS. And the computed results clarify the following: The bowed blade suppresses the corner separation in the DES results. However, its suppression effect is smaller than that in the RANS one because of the following facts: The high loss region caused by the corner separation in the cascade with the bowed blades in the DES result is increased compared with that in the RANS one. This is caused by the fact that the DES captures the formation of the relatively large-scale vortices generated around the boundary between the corner separation and the main flow.