Influence of Inlet Swirl on Film Cooling of the Turbine Leading Edge

Abstract

The swirling flow is used to increase mixing and decrease nitrogen oxide emission in the combustor. Meanwhile, the swirling incoming flow has a significant effect on both aerodynamic and heat transfer characteristics of the downstream first-stage turbine. This paper conducts a numerical investigation on the influences of the inlet swirl core on the film cooling performance of a leading-edge model. Besides, the trenched holes are employed to improve the cooling performance under conditions of different swirl numbers and blowing ratios. The results show that the inlet swirl benefits the generation of downstream detrimental vortex structures and increases the mixing between coolant and mainstream. Although the trenched holes cannot absolutely change the flow patterns of swirling mainstream, they can guarantee the lateral spread of coolant and suppress the downstream coolant rotation. At different swirl numbers, the trenched cases all provide a better cooling performance, especially on the rows away from the stagnation line. Besides, the trenched cases show incremental cooling performance with the blowing ratio increasing from 1.0 to 3.0. However, for the round holes, the highest averaged cooling effectiveness is obtained at blowing ratio of 2.0, which is still lower than the trenched cases.