Enhancement of the film cooling performance by the combination of droplet/air coolant and upstream micro-vortex generator

In this study, a combination of Euler-Lagrange method is adopted to investigate the effect of upstream micro-vortex generator (VG) on the film cooling performance of two-phase droplet/air film cooling. The droplet trajectories and flow field are also simulated to reveal the flow mechanism related to the improvement effect of micro-VG on the droplet/air film cooling performance. The results indicate that the anti-counter-rotating vortex pair (anti-CRVP) induced by micro-VG can expand the spreading region of droplets in spanwise direction, and also force the droplets to approach the wall, delaying the separation of droplets from the wall under high blowing ratios. As a result, the micro VG can effectively enhance the improvement effect of droplets on film cooling effectiveness in both spanwise and streamwise directions, thereby enhancing the overall cooling performance of droplet/air film cooling. In addition, the size and flow rate of droplets are also investigated to reveal the influence of droplet parameters on the performance of droplet/air film cooling. It was found that there is an optimal droplet size for the enhancement of droplet/air film cooling efficiency.