Abstract
Under the influence of secondary flow, the film cooling deviates from the flow direction on the turbine blade, which directly results in undesirable uneven film coverage. On the pressure side, the film appears divergent, while on the suction side, it is bunched. To solve this problem, a kind of subregional compound angle is proposed, in which the angle in the spanwise direction is different in different regions depending on the strength and direction of the secondary flow. Four rows of film holes with five kinds of subregional compound angles are provided on the pressure side, while two rows of film holes with different subregional compound angles are provided on the suction side. The Reynolds Average Navier–Stokes (RANS) method of the SST k–ω turbulence model is chosen to solve the above blade arrangement. The results show that a significant improvement can be achieved by the introducing subregional compound injection of the film coolant compared to the case of simple injection. In compound injection, the injectant maintains sufficient momentum to prevent the coolant from being swept away by the secondary flow. This was found to be largely the case for most holes on the pressure side, and some holes on the suction side. However, for holes near the downstream section of the suction surface of the blade, where the passage vortex is strongest, no value is found for the compound angle that could redirect the coolant along the blade profile without radial deviation. In some cases, excessive values of the compound angle led to jet liftoff rather than spreading the film along the surface.
