Numerical Investigation of Flow Separation Control of Low-Pressure High-Lift Blade With Different Grooves and Protrusions

Abstract

The shear stress transport (SST) turbulence model and γ-Reθ transition model were employed when solving the Reynolds-averaged Navier-Stokes (RANS) equations. The flow separation in the suction side of the typical high-lift low-pressure gas turbine PakB blade was investigated. Different sets of mesh were adopted and the results of grid independence study show that the precision is maintained when the grid system of 126,780 is adopted. And the computational results were compared with the existing experimental and computational results, which indicate that the numerical method can predict the separated transition flow reliably. Different kinds of structures including V grooves and protrusions, curved grooves and protrusions, rectangular grooves and protrusions were used to passive control of the flow separation in the suction side of the PakB blade. The structures have the same locations including 65%Cax, 68%Cax and 71%Cax on the suction side of the blade as well as length and height for better comparison. All of these cases are compared with the flow of PakB cascade without control with Re = 86,000 and FSTI = 1%. The shear layer is uplifted when the flow passes the passive device. And the separation bubble inside the grooves almost occupies the whole groove space which makes the length of the separation shorter than that in the case without control. The separation inside the grooves joins into the downstream separation in the case of grooves located in 71%Cax. The flow starts to separate in the leeside of the protrusion wherever the protrusion locates. And the attachment point moves forward significantly in the comparison with the case of without control. However, it brings in more flow loss because of the protrusion’s resistance to the boundary flow. In the total pressure loss coefficient comparison with the case without control, the grooves produce less flow loss while the protrusions at all the locations bring more flow loss. The nearer the groove is away from the separation point in the case without control, the higher the efficiency could be in the view of total pressure loss coefficient. The rectangular grooves are considered as a more effective structure for the flow separation control of PakB blade. Moreover, the flow separation bubble length and the total pressure loss coefficient decrease as Reynolds number increases in the cases without control. The total pressure loss coefficient in the different Reynolds numbers cases with rectangular groove is lower than that in the cases without control and the flow control performance gets much better when Reynolds number increases.