Analysis of water droplet evaporation in a gas turbine inlet fogging process

Abstract

To increase power output and improve thermal efficiency of gas turbines, recourse is often had to inlet air-cooling during hot periods. In some cases, a cost-effective way to accomplish inlet cooling consists of evaporatively cooling the air stream in the inlet duct. In this method, a fine mist of water is created at the compressor inlet, and as the mist droplets evaporate the mixture temperature decreases. This cooling process is analyzed using four simultaneous heat and mass transfer models: (A) diffusion, (B) natural convection, (C) Stokes convection, and (D) perturbed Stokes. Special attention is paid to the critical water injection ratio dividing the low and high fogging cases. Air and droplet temperatures and droplet diameters as evaporation proceeds are obtained for different values of inlet temperature and relative humidity of air, initial droplet diameter, and water injection mass ratios. The results of the computations show good agreement among the models considered in this work. (C) 2011 Elsevier Ltd. All rights reserved.