Abstract

To cool a high-pressure gas turbine blade, many rows of cooling holes with different arrangements and configurations are manufactured to achieve higher cooling effect and lower aerodynamic loss. To evaluate the heat transfer and film cooling effect in the full-cooled turbine blade, efficient numerical simulations are required in the design and performance optimization processes. From the view of numerical accuracy, the structured grids have to be employed because of higher resolution in flow and heat transfer than the unstructured grids. Because many splitting, attaching and merging manipulations are involved in meshing the cooling features and curved boundaries, it is very complex and time-consuming for a researcher to generate multi-block structured grids for a full-cooled gas turbine blade. As a result, in the industrial applications, almost all researchers preferred to generate unstructured grids instead of structured grids for the full-cooled blade.

Unlike the previous research, the aim of this study is to apply the Background-Grid Based Mapping (BGBM) method proposed in Part I to generate multi-block structured grids for a full-cooled gas turbine vane. With the strategy of BGBM method, meshes were conveniently generated in the computational space with simple geometrical features and plain interfaces, and then were mapped back into physical space to obtain the multi-block structured grids which can be used for numerical simulations. With the experimental data, the present numerical methods and BGBM strategy were carefully validated. Then, the flow and film cooling performance in the full-cooled NASA GE-E3 nozzle guided vane were numerically investigated. The effects of coolant mass flow rate and land extensions on film cooling effectiveness were discussed. The results show that film cooling effectiveness near the stagnation point is the lowest and film cooling effectiveness on the pressure side is slightly higher than that on the suction side. When the coolant mass flow rate increases up to the value of 1.5 design flow, the relative outflow mass flow rates of cooling hole arrays and slots are no longer affected by the increase of the coolant flow rate. At half design flow, the outflow mass flow rates of No.5 hole-array to No.10 hole-array are almost zero, and the area-averaged film cooling effectiveness on vane surface is as low as 0.268. Compared with the cases of half design flow and double design flow, better film cooling performance is obtained in the cases of design flow and 1.5 design flow. Compared with the vane without lands, the area-average cooling effectiveness on vane surface is slightly higher for the vane with lands. Land extensions have a considerable influence on film cooling performance in the cutback region.

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