Effects of Injection Angles and Aperture Ratios on Film Cooling Performance of Sister Holes

In this paper, to analyze the influences of the injection angles and aperture ratios (AR) of the primary hole and the side hole on the film cooling performance of a flat plate model, pressure sensitive paint (PSP) technology was used to study the forward and backward jet of a single hole and four sister holes, and a numerical simulation was supplemented to explore the flow structure of the sister holes. The sister holes had a better film cooling performance than the cylindrical hole at all blowing ratios (BR). The backward jet of the primary hole or the side hole could increase the spanwise film coverage of the sister hole. In this study, with the primary hole featuring a backward jet and the side hole featuring a forward jet, the film cooling performance was the best, 11.9 times higher than the areal mean film cooling efficiency of the cylindrical hole when AR=1 and BR=1.5. At a low blowing ratio, the counter-rotating vortex pair (CRVP) of the side hole could suppress the strength of the CRVP of the primary hole. At a high blowing ratio, when the primary hole featured a backward jet and the side hole featured a forward jet, the CRVP of the side hole had the optimal performance for suppressing the CRVP of the primary hole.