Investigations Of Film Cooling Characteristics Of Sister Hole With Back Jet In Combustion Chamber

Film cooling has been widely used as the most effective cooling solution in the protection of the hot end parts of a gas turbine combustor now.In this study,pressure sensitive paint（PSP）technology was used to build the flat film cooling experimental platform for measuring the film cooling efficiency of the sister hole.And in order to study the mechanism of film cooling,a numerical simulation was supplemented to explore the flow structure of the sister hole.the influences of the injection angles of the primary hole or the side hole on the sister hole film cooling performance of a flat plate model were comparatively analyzed.The area mean film cooling efficiency of the sister hole CASE6 with the forward jet and the spanwise angleβ₁=15°of the side hole was the highest,4.07 times higher than the area mean film cooling efficiency of the single hole at the medium blowing ratio（BR=1）.At the high blowing ratios（BR=1.5,2）,the sister hole CASE4 with the forward jet of the side hole had the highest film cooling efficiency,the increase of 575%,736%.The counter rotating vortex pair（CRVP）of the side hole could suppress the strength of the CRVP of the primary hole at all blowing ratios.the film formed by the backward sister hole CASE4 and CASE6 of the primary and the side holes was guaranteed.The gas film had a higher spread,and it had better adherence and the best cooling efficiency at the medium and high blowing ratios.The film cooling efficiency of two kinds of backward sister hole with the spanwise angleβ₁=15°was studied under three kinds of hole spacing.The study found that the average spanwise film cooling efficiency of backward sister hole decrease fast with the increase of hole spacing at low blowing ratio（BR=0.5）,but with the increase of hole spacing,the backward sister holes with forward jet of side hole flowing in the same direction can obtain better film cooling efficiency at high blowing ratios.The vortex core height of the sister hole decreased with the increase of the hole spacing,and it had better adherence and the best film cooling efficiency at the high blowing ratios.Compared the film cooling efficiency of 4 kinds of sister hole without spanwise angle when the aperture ratio（AR）is 1 or 2.When AR=2,The film cooling efficiency of standard forward sister hole was the best at the low blowing ratio.With the side hole featuring a forward jet,when AR=1,the film cooling performance of the backward sister hole was the best,11.31times higher than the areal mean film cooling efficiency of the single hole at the medium and high blowing ratios.Compared with the sister hole with the AR=2,when AR=1,the CRVP of the side hole has the optimal inhibitory effect on CRVP of the primary hole at high blowing ratios,the vortex core was closer to the wall surface and the film cooling performance was better.