Ambient temperature strongly influences gas turbine performance with power output dropping between 0.5 to 0.9 % for every 1 °C of temperature rise. This is accompanied by a significant increase in the heat rate, resulting in increased operating costs. As an increase in power demand often coincides with high ambient temperatures, power augmentation during the hot part of the day is of value to gas turbine operators. This is true for both the utility industry, where peak-rate power payments often apply, and to the petrochemical and process industries, where throughput can be improved or held constant as ambient conditions change. Evaporative fogging and wet compression are relatively low-cost solutions for recovering reduced gas turbine output.
This paper addresses the important design considerations for fogging and wet compression systems for different sized gas turbines with different duct configurations. These design considerations include the selection of appropriate ambient psychrometric design conditions, selection of appropriate fog nozzles and the optimization of fog nozzle manifold locations in the inlet ducts. For this research, Computational Fluid Dynamics (CFD) software is used to analyze the interaction between the atomized water droplets and the airflow within the confined geometry of inlet air ducts. The location of the nozzle manifolds is simulated in the inlet ducts for four different inlet duct configurations. Experimentally obtained spray data is used to simulated water atomization in the inlet ducts. The effect of the duct geometry is analyzed in term of fog-spray cooling efficiency based on both nozzle manifold location and droplet size distribution.