| The increase of gas turbine inlet temperature is the most intuitive and effective way to improve its cycle power and thermal efficiency,but the current rate of increase of inlet temperature has far exceeded the development rate of high temperature resistant materials for turbine blades,and the heat resistance of turbine blades has also put forward higher requirements.Compared with the development of new materials or processes,the use of more advanced and rational cooling technology brings more significant results.Therefore,efficient cooling technology becomes the key to ensure reliable operation of gas turbines.A variety of cooling forms,including external cooling,internal cooling and internal and external combined cooling,have been developed in modern gas turbine blade cooling.Among them,the film impact combined cooling is one of the advanced cooling methods applied to the modern gas turbine high temperature components.The effect of conjugate heat transfer between multiple cooling forms is not a simple superposition,and detailed investigation is required to prove the actual cooling performance.In this paper,the cooling performance of film is first investigated under adiabatic condition.The influence of the protrusion structure of cratered film holes on the cooling performance was investigated by numerical calculation method,while the shape optimization of cratered holes with larger hole spacing was carried out by combining neural network and genetic algorithm under the condition of multiple blowing ratios.The results show that the cratered hole protrusion structure is a key factor affecting the flow of coolant and generating vortex pairs.The protrusion structure that can form a certain scale strength anti-renal vortex pair suppresses the negative effect of the renal vortex pair near the centerline,which can better guide the coolant to attach to the wall,enhance the effect of the film coverage in the middle and downstream of the cratered hole,and enhance the film cooling effectiveness.The crater geometry of the optimized hole possesses a larger spreading extension and depth with a smaller flow length.The area average cooling effectiveness is improved by 16.58%,51.17%,70.81%,58.81%,73.78% compared with the reference hole under the conditions of blowing ratio M=0.5,M=1.0,M=1.5,M=2.0,M=2.5 respectively,which ensures the cooling effectiveness under the conditions of multiple blowing ratios to some extent.Then the film impact composite cooling structure was investigated under the conjugate heat transfer condition,and the numerical calculation method of conjugate heat transfer was used to evaluate the combined cooling performance of the cylindrical hole and cratered hole combined cooling structure under different blowing ratios,and the effect of the impact hole structure on the combined cooling performance in the cratered hole combined cooling was investigated.The results show that the overall cooling effectiveness in the cratered hole impact combined cooling structure is higher and more uniformly distributed,the shape of the film hole has a greater impact on the overall cooling performance,and the laterally-averaged overall cooling effectiveness gradually increases with the enhancement of the blowing ratio.The impact hole arrangement and the impact hole diameter have a greater effect on the overall cooling effectiveness of combined cooling,and the effect of the impact hole expansion way and impact distance is not obvious. |
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