Investigation On Flow And Cooling Characteristics Of The Cratered Film-Cooling Hole Combined With Ribbed Cross-Flow Channel

High efficiency cooling of high temperature turbine blade is the key technology to improve the performance and life of gas turbine.Film cooling can effectively isolate the high temperature gas from the blade surface,which is an effective way to realize blade cooling.Researchers have been working to develop more efficient hole patterns,in which dimple holes can be contoured with thermal barrier coatings and have higher cooling performance.At present,many studies have been carried out on cratered holes,and the results show that cratered holes have better cooling performance,but all the studies are carried out under the cavity inlet environment.However,the performance of cratered holes in perpendicular cross-flow channels has not been studied,and the mechanism of the effects of perpendicular cross-flow and rib structure on the cratered holes is not clear.Therefore,the film cooling characteristics of cratered holes in a perpendicular cross-flow channel are studied by numerical method.In this paper,the cooling performance of cratered hole in perpendicular crossflow channel is studied by numerical simulation.The effect of ribs on the cooling performance of cratered hole is analyzed in detail by comparing the cross-flow channel with and without ribs.The influence of Reynolds number and rib angle on the shape of the cratered hole is analyzed.The shape of the cratered hole is optimized by using the neural network genetic algorithm with the structure parameters of the cratered hole as variables and the area average cooling efficiency as the objective function.The results show that the cratered hole still has a good cooling performance in the perpendicular cross-flow channel.The cold air moves spirally in the hole under the influence of crossflow,which makes the cold air downstream of the cratered hole appear double peaks.The existence of the rib structure in the ribbed channel can weaken the influence of cross-flow on the rib and improve the cooling efficiency.The cooling performance of cratered holes is influenced by the Reynolds number of crossflow.The cooling air with high Reynolds number will carry more momentum,which will weaken the disturbing effect of the rib structure and reduce the cooling efficiency,the Reynolds number of 8800 has the best cooling performance.The influence of rib angle on the cratered hole is mainly reflected in the aerodynamic loss,and the difference in efficiency is small.After the cooling air passes through the 135 degree and 120 degree ribbed channels,a vortex structure is formed behind the rib,and the rotating direction of the vortex is the same as the inclination angle of the cratered hole,so the aerodynamic loss is small,among which the 135 degree ribbed channel is the best match with the film cooling hole,and the 45 degree ribbed channel has the largest aerodynamic loss.Neural network and genetic algorithm are used to optimize the shape of the dimple holes at blowing ratios of 1.5 and 2.5.Compared with the reference holes,the optimized holes have wider coverage in the span direction,and the overall efficiency is improved by 27% and 20% respectively.meanwhile,on the basis of optimizing the holes,the shapes of the holes are designed asymmetrically again,so that the uniformity of cold air coverage is enhanced.