Effects of Target Channel Shapes on Double Swirl Cooling Performance at Gas Turbine Blade Leading Edge

In order to further study the effects of the target channel shape on the cooling performance of the double swirl cooling (DSC), five double swirl channels formed by two overlapping elliptic cylinders with different length ratio between the vertical semi-axis and the horizontal semi-axis are applied. Numerical studies are carried out under three Reynolds numbers. The flow characteristics and heat transfer performance of five DSC cases are compared with the benchmark impingement cooling case. The flow losses, cross-flow development, generated vortices, and velocity distributions inside target channels are illustrated, analyzed, and compared. The spanwise averaged Nusselt number, Nusselt number distributions, and thermal performance are discussed and compared. Results indicate that the largest length ratio between the vertical semi-axis and the horizontal semi-axis of the target channel yields the lowest flow loss, largest overall averaged Nusselt number, and best thermal performance. With the decrease in the length ratio, the heat transfer distribution on the target surface becomes more uniform. The maximum enhancement of overall averaged Nusselt number and thermal performance in DSC is about 30% and 33%, respectively.