Influence mechanism of impingement and film on the flow and heat transfer of turbine outer ring with composite cooling structure under different operating parameters

Abstract

Two typical turbine outer rings with impingement-film composite cooling structure and single film cooling structure are selected as the research object, the mechanism of temperature ratio (τ = 1.2 ∼ 1.6), blowing ratio (M = 0.7 ∼ 3.0) and Mach number (Ma = 0.2 ∼ 0.8) on the flow and heat transfer of the two outer rings under engineering application is explored, which serves as a foundation for designing turbine outer ring cooling of aero-engine with different thermal load characteristics. It is indicated that compared to single film cooling, impingement-film composite cooling improves the cooling performance on the outer ring surface, while also effectively reduces the localized regions of low cooling property, enhancing the even distribution of cooling effectiveness. In the impingement-film composite cooling structure, film cooling is the primary factor determining the cooling property of outer ring. Among the influencing factors, Mach number has the greatest impact (64 % ∼ 83 %), followed by blowing ratio. Under different temperature ratios, film cooling accounts for approximately 80 % of the cooling property. At high blowing ratio, impingement-film composite cooling outperforms single film cooling in terms of cooling enhancement and effectiveness. Increasing blowing ratio (0.7 ∼ 2.0) enhances the cooling contribution of impingement in composite cooling, while the cooling contribution remains constant at 18 % as the blowing ratio enhances from 2.0 to 3.0. When Mach number increases, impingement-film composite cooling experiences a smaller decrease in cooling effectiveness compared to single film cooling, leading to better cooling uniformity. At high Mach number, impingement cooling effectively mitigates the decreasing cooling trend in the middle region of the outer ring. Additionally, the proportion of cooling performance in composite cooling increases, thereby reducing the adverse impact of the sharp decrease in film cooling property with elevating Mach number on the overall performance of composite cooling.