Investigation on cooling characteristic of the novel double-wall with the hollow pin fin

The double-wall structure has attracted wide attention, especially in the cooling design of the turbine vane, because of its excellent cooling performance. However, extreme flow resistance becomes the main obstacle limiting the application of double-wall structure. Previous studies focus on further improving the cooling performance of the impingement/effusion cooling system, and few improved schemes have been made to reduce the flow resistance. In this paper, a novel cooling structure with hollow pin fins is proposed, which takes into account both the improvement of the cooling effect and the reduction of flow resistance. The three-dimensional steady-state numerical simulation obtains the film cooling effectiveness, Nusselt number, overall cooling effectiveness, and coolant flow coefficient of the novel and traditional double-wall structures. The gird uses tetrahedral elements, and the turbulence model selects the shear stress transport (SST) k-ω model for numerical calculation. The effects of different hollow pin fin arrangements on the cooling performance and flow resistance characteristics are investigated to study the novel cooling structure. The main conclusions are as follows: In terms of external cooling, placing pin fin holes near the film holes can reduce the vortex intensity and improve the film coverage. The surface-averaged film cooling effectiveness is increased by 112.5% compared to the traditional cooling structure. In internal cooling, the novel cooling structure has a more considerable spanwise distance between the impingement holes and a lower impinging jet velocity, reducing the target plate's heat transfer. However, the novel cooling structure still has excellent internal cooling owing to the increase of heat transfer area by the pin fin. The novel cooling structure maintains internal cooling and significantly improves external cooling, increasing the surface-averaged overall cooling effectiveness by up to 14.5%. In terms of coolant flow resistance, adding the hollow pin fin provides a lower total pressure loss option for coolant outflow. The novel cooling structure brings the maximum increase of flow coefficient of 32.4% and reduces the flow resistance significantly.