Numerical investigations on flow and heat transfer of swirl and impingement composite cooling structures of turbine blade leading edge

•A novel swirl and impingement cooling structure is proposed.•Four swirl and impingement cooling configurations are reasonably established.•Flow and heat transfer of swirl and impingement composite cooling are revealed.•Comparisons are conducted at fixed total mass flow rate.•This paper provides a reference for the gas turbine blade leading edge cooling. In this paper, four swirl and impingement composite cooling structures are established to deeply study the flow and heat transfer characteristics, where the swirl nozzles and impingement nozzles are reasonably arranged. Numerical simulation is conducted by solving the Reynolds Averaged Navier-Stokes (RANS) equations with the standard k-ω model. Meanwhile, numerical results are compared with the cooling behaviors of swirl cooling and impingement cooling under the same condition. Results revealed that the pressure distribution of four composite cooling structures is quite different from that of swirl cooling and impingement cooling. Hence, the nozzle mass flow ratio distribution of composite cooling structures displays a large fluctuation with the variation of the nozzle location, which has an influence on the flow and heat transfer characteristics. Moreover, the heat transfer characteristics of swirl and impingement composite cooling combine the advantages of impingement cooling and swirl cooling, where there both exists extremely high local heat transfer regions and uniform heat transfer regions. As for composite cooling 3 and composite cooling 4, the alternate locations of impingement nozzles and swirl nozzles could effectively increase the band-shaped high heat transfer area. Meanwhile, the low heat transfer area caused by the continuous arrangement of impingement nozzles is reduced. Among four composite cooling structures, the composite cooling 4 has the highest average heat transfer coefficient and the minimum pressure loss. The globally average heat transfer of composite cooling 4 is 3.49% lower than swirl cooling but is 19.12% higher than impingement cooling. Its total pressure loss is 4.29% lower than swirl cooling and is slightly lower compared with impingement cooling.