Swirl impact on the overall cooling characteristics of an effusion -cooled combustor liner with cylindrical and fan-shaped holes

Abstract

The swirl impact on the overall effusion cooling characteristics is investigated. Two typical hole configurations, cylindrical and fan-shaped holes, are studied under different blowing ratios (BR). The overall cooling effectiveness is obtained by IR camera and the flow features are analyzed by simulations. The result shows that the typical cooling characteristic is the existence of low-effectiveness regions at where the swirl impact the wall. The reason for this is that the swirl flows destroy the cooling film and suppress the cooling air, resulting in poor cooling effectiveness. At the plate beginning, the cooling effectiveness is high because the corner recirculation pushes the cooling air upstream to cover the wall. The ending of the plate has the best cooling performance due to the gradually superimposed cooling film. Increasing the BR weakens the influence of the swirl impact and improves the cooling effects, therefore the area average cooling effectiveness of the cylindrical holes increases from 0.334 to 0.688 and the cooling effectiveness unevenness decreases from 0.042 to 0.036. The fan-shaped holes have a maximum of 0.063 higher cooling effectiveness due to better film coverage. However, the fan-shaped holes have a stronger cooling effectiveness unevenness, which is 0.012 higher. And the lowest cooling effectiveness is 0.133 and 0.146 lower than the area average value for the cylindrical and fan-shaped holes, respectively. The reason for this is that the fan-shaped holes have similarly poor film cooling in the swirl impact zone but better film cooling effectiveness in the other regions.