Effect of profiled endwall on nozzle guide vane with coolant purge flow

Abstract

The aerothermal performance of a gas turbine could be improved by applying endwall profiling to the nozzle guide vane. In this study, various thermal performance factors of flat and profiled endwalls with purge coolant flow were investigated using adequate experimental methods. Each experiment was conducted under same exit Reynolds number (300,000) for the flat and profiled endwalls. Because secondary vortices in the nozzle passage were weakened by the endwall profiling, the upstream purge coolant covered the endwall surface wider and further with the profiled endwall. Moreover, the heat transfer coefficient in upstream region could be reduced with the weakened secondary vortex. The experimental results indicated that the area-averaged film cooling effectiveness on the profiled endwall was 67.7 % higher and the area-averaged Sherwood number was 18.3 % lower than those on the flat endwall. Although the downstream region of the profiled endwall exhibited a negative cooling performance, the overall area-averaged net heat flux reduction was 169 % higher than that on the flat endwall. Thus, if an additional cooling system was applied to the downstream region of the passage, the profiled endwall could effectively improve not only the aerodynamic performance but also the cooling performance of the nozzle guide vane.