In this article, a compound unit of swirl and impingement cooling techniques is designed to study the performance of flow and heat transfer using multi-conical nozzles in a leading-edge of a gas turbine blade. Reynolds Averaged Navier-Stokes equations and the Shear Stress Transport model are numerically solved under different nozzle Reynolds numbers and temperature ratios. Results indicated that the compound cooling unit could achieve a 99.7% increase in heat transfer enhancement by increasing the nozzle Reynolds number from 10,000 to 25,000 at a constant temperature ratio. Also, there is an 11% increase in the overall Nusselt number when the temperature ratio increases from 0.65 to 0.95 at identical nozzle Reynolds number. At 10,000 and 15,000 of nozzle Reynolds numbers, the compound cooling unit achieves 47.9% and 39.8% increases and 63.5% and 66.3% increases in the overall Nusselt number comparing with the available experimental swirl and impingement models, respectively. A correlation for the overall Nusselt number is derived as a function of nozzle Reynolds number and temperature ratio to optimize the results. The current study concluded that the extremely high zones and uniform distribution of heat transfer are perfectly achieved with regard to the characteristics of heat transfer of the compound cooling unit.

This paper numerically simulated a swirl cooling system to study the influences of the slot area ratio and slot angle on the flow field and heat transfer performance. Numerical simulations were performed for different coolant inlet to outlet slot area ratios (1, 2, 3, and 4) and slot angles (60°, 75°, 90°, and 105°) at different Reynolds numbers. Results indicate that large-scale vortices and small circular or oval vortices are generated in the cooling channel at different slot area ratios and slot angles. At identical Reynolds numbers, the cooling system achieved 30% and 23% increases in global Nusselt number and thermal performance factor, respectively, when the slot area ratio increased from 1 to 4. Although the system obtained only a 7.5% increase in global Nusselt number, it achieved a 29.8% increase in thermal performance factor when the slot angle increased from 60° to 105° at fixed Reynolds number. The applied cooling system is recommended for the internal swirl cooling of a gas turbine blade leading edge at optimum values of design parameters at a slot area ratio of 4 and slot angle 105° at high Reynolds number.