Film Cooling Performance Enhancement by Upstream V-shaped Protrusion/Dimple Vortex Generator

Abstract

Film cooling is an effective technique to isolate the heat flux from high-temperature mainstream, but the counter-rotating vortex pair (CRVP) generated by the interaction between film jet and mainstream leads to serious jet-off and poor film coverage. To enhance film cooling performance, a v-shaped protrusion/dimple vortex generator is arranged at the upstream location of film hole for suppressing the CRVP. The flow and heat transfer characteristics of film cooling with four kinds of vortex generators, v-shaped protrusion vortex generator (VSPVG), v-shaped dimple vortex generator (VSDVG), anti-v-shaped protrusion vortex generator (AVSPVG) and anti-v-shaped dimple vortex generator (AVSDVG), are investigated in detail over the blowing ratio ranging from 0.5 to 1.5 by solving three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Realizable k-ε turbulence model. Results indicate that both the v-shaped vortex generators can generate additional anti-counter-rotating vortex pairs (ACRVP) to weaken the CRVP, while both the anti-v-shaped vortex generators will enlarge the CRVP. The arrangement of VSPVG or VSDVG is proved to enhance film cooling performance significantly, especially the VSPVG, which improves the adiabatic film cooling effectiveness by 82.3%, 187.9%, 157.7%, 162.2% and 145.2% respectively corresponding to the BR=0.5, 0.75, 1, 1.25 and 1.5 compared with Baseline case. Considering the total pressure loss, it is found that the enhancement of film cooling effectiveness comes at the cost of slightly increased total pressure loss. In further study, the effect of VSPVG height on film cooling performance is also discussed. It is observed that the adiabatic film cooling effectiveness increases with an increase of the height, and the total pressure loss also inescapably increases, but it is worth celebrating that compared with Baseline case, the higher film cooling effectiveness and lower total pressure loss coefficient is obtained when the height is lower than 0.15D.