Analysis of mist/air film cooling performance of trenched holes with shaped lips

Abstract

Mist-assisted film cooling has exhibited great potential for efficient cooling of a turbine blade. Trench structures can significantly affect the film cooling performance of air, while their impact on the adhesion characteristics of the droplets and thus the mist-assisted film cooling performance is unclear. This work highlights the combination of these two aspects by exploring the improvement of the mist-assisted film cooling performance for trenched holes with shaped lips using 3-D computations. The results show that the upper lip structure plays a significant role in the adiabatic film cooling effectiveness, whereas the lower lip structure has little effect on it. It is found that the effect of upper lip structure on the adiabatic film cooling effectiveness increases with increasing blowing ratio. The Coanda effect makes the droplets more attached to the wall of the upper fillet lip structure and upper bevel lip structure. Meanwhile, the concentration of mist and the diameter of droplets are crucial for significantly improving the adiabatic film cooling effectiveness. In general, better adiabatic film cooling effectiveness values are observed for both 10 ?m diameter droplets at a specified concentration of mist and larger concentration of mist at a specified droplet size. This work proposes a novel and efficient means of enhancing the cooling performance using mist/air mixture and trenched holes with shaped lips.