Computational Study of Film Cooling With Mist and Air for a Flat Plate

The inlet air temperature of turbines are significantly high which may result in the damage of the blade material. As a consequence, it is required to cool the turbine blades and a number of cooling techniques are introduced in the past. The cooling technique involving evaporation of water droplets is the motivation and focus of this work. When the water droplets are injected along with the dry air, the existing concentration difference between the water droplets and dry air results in the evaporation leading in the drop of the coolant temperature. This phenomena does not occur when the coolant is dry air and this part is addressed for the first time in this study. The cooling performance is investigated on wall of straight channel in the presence of a film cooling hole. Dry air along with water droplets are supplied through the film cooling hole and the computations are carried out for different droplet diameters and mist concentrations. Results showed that, the overall cooling effectiveness is always larger for the mist-air case compared to that for the dry air case. Also, the cooling effectiveness increases with the percentage of mist in the mist-air system for a specific droplet diameter. At a specific mass flow rate and specific mist percentage, the increase in droplet diameter results in the decrease of cooling effectiveness.