Experimental And Numerical Investigations Of Film Cooling Performance With Anti-vortex Film Hole In Gas Turbine

The continuous increase of the outlet temperature of the gas turbine combustor puts higher requirements on the temperature resistance of the parts in the gas turbine.The film cooling technology is an important means to achieve efficient cooling.In this paper,a flat film cooling test bench and test system were built,and the cooling effectiveness of the film was measured by using an infrared camera.In order to master the film cooling mechanism,the simulation explored the cooling characteristics of various hole shapes under different aerodynamic parameters.Firstly,the steady numerical simulation was used to compare the flow field structure and heat transfer characteristics of the bean-shaped hole,NEKOMIMI and the C-shaped hole,which reveals the cooling mechanism and analyzes the discipline of discharge coefficient.NEKOMIMI is superior in cooling performance.The discharge coefficient of the bean-shaped hole is significantly higher than that of NEKOMIMI.However,under the condition of mediumhigh blowing ratios,the cooling effectiveness is lower due to the phenomenon of jet lift-off.At the blowing ratio of 2.0 and 3.0,the cooling effectiveness of the C-shaped hole is higher than that of the bean-shaped hole,with the values of 267.8% and 239.7% respectively,and C-shaped hole also have a high discharge coefficient.In addition,from the perspective of cooling performance,stability,and aerodynamic performance,the adoption of C-shaped hole in consideration of actual working conditions is an ideal choice.Secondly,the basic experiments was carried out by using the built flat film cooling test bench to investigate the effect of the blowing ratio and the mainstream turbulence on the cooling effectiveness of the NEKOMIMI and the C-shaped hole.The results show that under the same mainstream turbulence conditions,with the increase of the blowing ratio,the NEKOMIMI and C-shaped hole show a tendency to improve the film cooling effectiveness,and the highest film cooling efficiency occur at the blowing ratio of 2.0 and the turbulence intensity of 1%.Finally,the transient simulation explores the vortex structure and turbulent flow information downstream of the dumbbell hole,and the influence of vortex structure on the heat transfer of the downstream wall is analyzed in the turbulent flow field.The hairpin vortex is the main feature at the downstream of the dumbbell hole: the hairpin vortex head(rolling vortex)promotes the interaction between the cooling jet and the high temperature mainstream,which deteriorates the film cooling performance.The upper throwing effect of the hairpin vortex is same as the kidney vortex,which reduces the wall cooling effectiveness.Due to the exchange of kinetic energy between the vortex systems at medium and high blowing ratios,the vortex structure gradually dissipates and fills the downstream space after being away from the film hole.