Analysis of flow characteristics and heat transfer regulations for gas turbine blade middle double swirl cooling under different nozzle numbers

In this paper, the gas turbine blades middle double swirl cooling structure under diverse number of nozzles N are constructed to explore the heat transfer and flow behavior. The k-ω turbulence model are applied and the inlet coolant Reynolds number is 12500. The N vary by 4 to 11 and two cases are investigated. For case 1, the cross-sectional area of each nozzle is 6 mm2 for all structures. For case 2, the cross-sectional area of total nozzles stays the constant at 42mm2 when the N is varied. Results show that, in case 1, when the N increases, the area of the high heat exchange zone decreases but the distribution is more uniform. Moreover, the thermal performance factor ξ gets larger, but the average Nusselt number Nua decreases significantly. In case 2, when the N increases, the ratio of inclination to nozzle length increases for the jet near the outlet, Nua is almost constant but the heat transfer uniformity is improved. The best ξ is obtained when the N is 8. For case 1, as the N is increased, the Nua decreases significantly. Therefore, heat transfer and ξ should be considered by case 2 to select the optimum N.