THE INFLUENCE OF SECONDARY FLOWS NEAR THE ENDWALL AND BOUNDARY-LAYER DISTURBANCE ON CONVECTIVE-TRANSPORT FROM A TURBINE BLADE

A naphthalene sublimation technique is used to investigate convective transport from a simulated turbine blade in a stationary linear cascad e. In some of the tests undertaken, a trip wire is stretched along the span of the blade near the leading edge. The disturbance produced by tripping the boundary layers on the blade near the leading edge causes early boundary layer transition, creates high mass transfer rate on t he pressure side and in the laminar flow region on the suction side, b ut lowers the transfer rate in the turbulent flow region on the suctio n side. Comparison is made with other heat and mass transfer studies i n the two-dimensional region far from the endwall and good agreement i s found. Near the endwall, flow visualization indicates a strong secon dary flow pattern. The impact of vortices initiated near the endwall o n the laminar-turbulent transition extends three-dimensional effects t o about 0.8 chord lengths on the suction side and to about 0.2 chord l engths on the pressure side away from the endwall. The effect of the p assage vortex and the new vortex induced by the passage vortex on mass transfer is clearly seen and can be traced along the suction surface of the blade. Close to the endwall the highest mass transfer rate on t he suction surface is not found near the lending edge. It occurs at ab out 27 percent of the curvilinear distance from the stagnation line to the trailing edge where a strong main flow and the secondary passage flow from the pressure side of the adjacent blade interact. The influe nces of some small but very intense corner vortices and the passage vo rtex on mass transfer are also observed on both surfaces of the blade.