Effect of mist concentration on the cooling effectiveness of a diffused hole mist cooling system

Abstract

Cooling the blades of gas turbines is essential for extending the life of the blades. Conventional gas turbines use air-film cooling. With the increase in turbine inlet temperatures, novel cooling methods are required. Recently mist cooling started to gain prominence for high-capacity gas turbines. Mist cooling involves adding water droplets in the form of a fine mist to the air in conventional film cooled systems. This paper numerically investigates the performance of mist cooling at various mist concentrations for two different hole configurations. The cooling effectiveness for a coolant injection hole with diffusion angle of 10° and 15° was analyzed with mist concentration varied from 1 to 7%. The results show that with a low mist concentration of 1%, the cooling effectiveness improved drastically for both configurations. A maximum of 69% improvement was observed for 7% mist concentration and 10° diffused hole. Mist concentrations above 5% did not offer any significant improvements as with lower concentrations.