The overall film cooling performance of crescent holes

This study proposes two crescent cooling holes based on favorable vortex structures to enhance the film cooling effectiveness. Large eddy simulations and laser-induced fluorescence were conducted. An up-convex crescent hole (UCC) was established first, which uses an anti-counter-rotating vortex pair (anti-CRVP) to prevent the coolant from lifting off the surface and another CRVP to achieve better cooling uniformity at the centerline. Then, a down-convex crescent hole (DCC) was further optimized based on the vortex of the UCC. The results show that the film cooling effectiveness of the DCC increases by 48 % at BR = 1.6 compared to the UCC. Apart from the time-averaged results, the instantaneous flow field of DCC was analyzed in detail, and the distribution and breakdown of hairpin vortexes highly affect the cooling effectiveness. Besides, the heat transfer coefficient and net heat flux reduction were analyzed to overall evaluate the film cooling performance of DCC.