Optimization Design And Investigation On Conjugate Heat Transfer Of The Cratered Film-Cooling Hole

Film cooling is a key method applied to modern gas turbine blades.Maximizing the film-cooling effectiveness has always been the primary research objective both at home and abroad.The main approach to achieve this goal is to develop highly efficient cooling holes.However,only two kinds of cooling holes,i.e.,cylindrical hole and fanshaped hole,are utilized for turbine cooling blades for practice.In recent years,a cratered film cooling structure with excellent cooling performance and low machining cost was proposed and verified by preliminary experiments.However,the flow mechanism of improvement on the cooling effect and the regularities of cooling performance for the cratered hole are not fully understood.The superiority of this hole should be validated in the cascade environment and the conjugate heat transfer environment.The optimal cratered hole to improve cooling effectiveness as much as possible needs to be further investigated.The computational fluid dynamics method is used to resolve the problems mentioned above.The flow mechanism of the cratered hole was analyzed to improve cooling effectiveness,and the cooling effectiveness and discharge coefficient with various blowing ratios were investigated under different coolant flow directions.Taking the geometric characteristics of the cratered hole as the optimization variables and the maximum adiabatic average film cooling effectiveness as the optimization goal,combined with neural network and genetic algorithm,the shape optimization of the cratered hole is carried out at blowing ratio M=0.5 and 1.5.The film cooling performance of the cratered holes is evaluated in the adiabatic cascade environment and the conjugate heat transfer plate environment.The results show that the expansion structure and the arc-shaped block of the cratered hole increase the velocity of the coolant jet in the lateral direction,and the anti-kidney shaped vortex pair generated by the interaction between the coolant and the block weakens the influence of the kidney vortex pair and enhances the ability of the coolant to adhere to the wall.The interaction of asymmetrical coolant and crater for perpendicular coolant channel will greatly increase the lateral velocity of coolant and spanwise coverage area.Moreover,the increase of the angle between the coolant flow direction and the mainstream will raise the flow loss at the entrance of the film cooling hole,resulting in a decrease in the discharge coefficient.The crater structure optimized by the BP-GA method reduces the momentum and penetration height of the coolant,enhances expansion of the film in the mainstream and the lateral direction.And the adiabatic cooling effectiveness of the optimized holes obtained at blowing ratios M=0.5 and 1.5 is improved by 17.21% and101.96% respectively.Besides in the cascade environment,the film cooling effectiveness and pressure loss coefficient of the optimized holes are higher than the reference.In the conjugate heat transfer analysis,the comprehensive cooling effectiveness of the cratered hole is higher,and the surface and internal temperature distribution of the plate is more uniform.However,with the continuous heating of coolant in the hole,the film cooling effectiveness will be reduced...