Numerical Investigation on Film Cooling Mechanism with Different Coolant Delivery Configurations

Kidney vortex has significant impact on film cooling effectiveness, and different kinds of film cooling hole geometry and configuration are developed to weaken or eliminate kidney vortex. This paper is focus on the mechanism of eliminating kidney vortex by optimizing the coolant delivery configuration, seven coolant delivery configurations are designed to conduct a comparative study with different blowing ratios. At high blowing ratio, the strong kidney-shaped vortex is formed outside the film cooling hole causing the low cooling effectiveness for β≤0˚. For β>0˚, the coolant ejection interacts with mainstream hot gas, and the coolant gas in low momentum region of upstream bypasses the large jet momentum coolant to attach film cooling surface at downstream. It increases the distance between the vortexes to weaken mutually reinforcing effect, resulting in high film cooling effectiveness. When the blowing ratio is 1.5, the average adiabatic film cooling effectiveness of β=+15˚ and β=+30˚ is increased by about 130% and 70% compared to case of β=-60˚, respectively.