Film cooling technique is commonly adopted in modern gas turbine to protect high temperature components from erosion and damages caused by thermal stress. To improve film cooling effect, many efficient prediction tools have been developed and shown promising results, which are helpful for turbine aero-thermal design. For the film cooling, evidences have shown that it is strongly affected by the momentum and heat transport in the boundary layer when hot gas and coolant are mixed downstream the ejection. From the view of resolution accuracy in boundary layer, structured grids will be the primary choice in fluid domain. However, the high pressure gas turbine blade usually has several hundreds of cooling holes with different configurations and arrangements. Numerical simulations often face a big challenge in multi-block structured-grid generations when a large number of cooling holes are involved on curved hole-to-mainstream interfaces. Conventional block-splitting and meshes-generating for all holes are quite time-consuming and cumbersome, because the copying, translating and rotating manipulations cannot be applied on curved hole-to-mainstream interfaces directly. To solve these difficulties, this paper presents a novel mesh generation strategy, which is a background-grids based mapping (BGBM) method, to generate multi-block structured grids for film-cooled blade efficiently without modifying the existing meshing tools and solvers, which is much convenient for the CFD users, especially for the beginners. It consists of three main steps: At first, the relations between physical space and computational space are established by two sets of background grids. Then, the sectional curves of geometry features in physical space are projected to the computational space. With these treatments, the curved hole-to-mainstream interfaces are flattened in computational space, where grids can be quickly generated with feature copying, translating, rotating and merging manipulations. Thereafter, meshes in computational space are mapped back to the physical space based on the relations between physical and computational spaces, and high-quality structured-meshes can be obtained for numerical simulations. To demonstrate the presented meshing strategy, several typical cases with film cooling are selected for testing, including single cooling-hole on curved surface, multiple rows of cooling-holes on curved surface and NASA C3X blade with multiple hole-arrays. In these cases, different holes, including the cylindrical holes and shaped holes with different ejection angles and arrangements, on curved interfaces are taken into considerations. The quality of generated structured grid for each test case is illustrated, which is able to meet the requirement of CFD solver. With the generated meshes, heat transfer in a turbine blade with different cooling arrangements is computed and also validated with the existing experimental data.


Background-Grid Based Mapping Approach to Film Cooling Meshing: Part I \u2014 Strategies and Test Cases

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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