A combined cooling structure consisting of serrated trench and V-shaped surface for film holes: Flow structure and effectiveness improvement

Shaohua Han,Runsheng Zhang,Jiangjiang Xing,Na An,Yuanyuan Song,Tianyi Huo,Leping Zhou,Li Li,Hui Zhang,Xiaoze Du

doi:10.1016/j.ijthermalsci.2023.108267

Abstract

Film cooling is a commonly used thermal protection technology for turbine airfoils. However, due to the counter-rotating vortex pair (CVP) generated by the interaction between the cooling jet and the mainstream, the coolant gradually breaks away from the wall, which is particularly evident at high blowing ratios. For the sake of improving the film cooling effectiveness (FCE) under high inlet temperature conditions, a novel film cooling structure (SerrTrench-VSS) that combines serrated trench film holes with shark skin-inspired V-shaped surface (VSS) is proposed. The RANS method and realizable k-ε model are used for the simulations. The flow characteristics, adiabatic FCE, and resistance loss are analyzed in detail when the blowing ratio (BR) is 0.5–1.5 and then compared with the traditional cylindrical film hole and transverse trench film hole. In addition, the impact of VSS height on the cooling performance is investigated and the best height of the structure is determined. The results show that the SerrTrench-VSS has better FCE. The serrated trench can destroy the CVP and improve the spanwise spreading ability of the coolant. Also, the VSS can converge the cooling jet downstream of the film hole toward the centerline, thereby improving its extension ability along the flow direction. In the studied range of blowing ratio, the SerrTrench-VSS has the best FCE, and the spanwise-averaged FCE increases by up to 10.50% when BR = 0.5. The empirical correlations between the globally-averaged FCE and the height ratio within the range of the present study are also given. For the serrated trench, the cooling jet has the best spanwise spreading and flow extension ability when the VSS height is 0.5D. The proposed novel film cooling structure (SerrTrench-VSS) can effectively improve the FCE and provide feasible means for the efficient cooling of a turbine blade under practical conditions.

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