Numerical investigation of film cooling performance of a thin-wall thermal shield with disturbing pin fins

For thin-wall heat shields in afterburner chambers, this study proposes an improved design by adding pin fins upstream of the film-cooling holes on the coolant side. This addresses the limitation of using inclined or shaped holes to enhance cooling. Numerical simulations were used to investigate the effects of pin fin height on the film hole exit momentum, film attachment, coolant-side convective heat transfer, and overall cooling effectiveness. The results show that when the pin fin height is less than 5 mm, downwash at the fin base and tip vortices deflect the coolant flow, enhancing the vertical momentum component at the hole exit. This increased vertical momentum causes the coolant jet to penetrate deeper into the mainstream, leading to premature liftoff and deteriorating film attachment, thereby reducing local and overall film-cooling efficiency. When the pin fin height exceeds 5 mm, the exit momentum decreases, the film attachment improves, and the convective heat transfer is enhanced. Consequently, the overall cooling effectiveness increases. The simulations indicate that the flat-spoiler shield can achieve a maximum 13.03% increase in overall cooling efficiency and a 39.72% increase in coolant-side convective heat transfer, outperforming flat heat shields of the same weight. The results show that the improved structure reduces flow losses and enhances heat protection without a significant weight penalty. This study demonstrates that the flat–pin fin heat shield is a highly efficient, lightweight design capable of improving thin-wall shield cooling under demanding thermofluidic conditions.