Heat Transfer for a Turbine Blade With Non-Axisymmetric Endwall Contouring

Complex vortical secondary flows that are present near the endwall of an axial gas turbine blade are responsible for high heat transfer rates and high aerodynamic losses. The application of non-axisymmetric, three-dimensional contouring to the endwall surface has been shown to reduce the strength of the vortical flows and decrease total pressure losses when compared to a flat endwall. The reduction of secondary flow strength with non-axisymmetric contouring might also be expected to reduce endwall heat transfer. In this study, measurements of endwall heat transfer were taken for a low-pressure turbine blade geometry with both flat and three-dimensional contoured endwalls. Endwall oil flow visualization indicated a reduction in the passage vortex strength for the contoured endwall geometry. Heat transfer levels were reduced by 20 percent in regions of high heat transfer with the contoured endwall, as compared to the flat endwall. The heat transfer benefit of the endwall contour was not affected by changes in the cascade Reynolds number.