Exit plane and suction surface flows in an annular turbine cascade with a skewed inlet boundary layer

Abstract The flow in the exit plane and on the suction surface of an annular turbine cascade was examined experimentally for conditions of inlet boundary layer skewing similar to that found in a real turbine and for the collateral inlet as found in most cascade tests. Skewing was introduced by rotating the nose cone ahead of the cascade. At the cascade exit, the loss distribution pattern, as measured by a 3 hole cobra probe, showed that the corner vortex at the hub is displaced radially to almost a mid-span position by the skewed inlet boundary layer. This movement was attributed to the stronger endwall crossflows being radially directed as they strike and rise up onto the suction surface. The radial displacement and endwall crossflow effect was also seen in surface flow visualization studies. The overall cascade loss coefficient and deviation angle are significantly reduced by skewing. Traverses taken on the suction surface confirmed the separated flow effects seen in the flow visualization pictures. The general conclusion is that skewing plays a significant role in determining the flow phenomena in turbine cascades and that these effects should be borne in mind when interpreting the results taken from plane cascades.