Overall cooling performance evaluation for film cooling with different winglet pairs vortex generators

Previous studies have shown that the film cooling effectiveness can be improved by using a winglet pair vortex generator upstream or downstream of the film hole, but these studies merely focused on rectangular and delta winglet pairs and the overall performance evaluation has no heat transfer results. In this study, the overall film cooling performance of a cylindrical film hole with four types of winglet vortex generators upstream of the film hole was numerically investigated. The numerical simulation with the realizable k-epsilon turbulence model was performed by commercial software Fluent, solving steady Reynolds-average Navier-Stokes equations. The film cooling effectiveness with vortex generators is one or more times higher than that without the vortex generators owing to the downwash vortices generated by the vortex generators. The downwash vortices mitigate the negative effect of the counter-rotating vortex pair. There is a competitive mechanism between the downwash vortices and the counter-rotating vortex pair, so the beneficial effect of the vortex generators will weaken with the increase of the blowing ratio. The heat transfer coefficient of film cooling with vortex generators is higher, with a maximum augmentation of 11.45%. The heat transfer distributions of different vortex generator configurations are similar. Results prove that the case with the rectangular winglet pair vortex generator is the optimal configuration since it provides 0.08-0.29 higher net heat flux reduction than the case without the vortex generators.