Energy efficiency analysis of wet compression systems through thermo-fluid dynamic considerations

摘要

Wet compression systems are deployed in gas turbine power plants for energy savings in the compressor. The system works by injecting fine water droplets in the form of mist into the air stream ahead of the compressor. The water droplets evaporate both before entering the compressor and within the compressor and reduce the air temperature by absorbing latent heat of evaporation. In this study, an analysis is done on two-phase compression of air-water droplet mixture. The work is focused on understanding the fundamental concepts associated with two-phase compression. Hence, a simple piston cylinder system is used as the domain to simulate the compression of air-water droplet mixture. During the processes, the pressure, temperature and relative humidity inside the cylinder have been monitored. Parametric studies are then performed for various values of starting relative humidity of the air, over spray percentage of water droplets, droplet diameter, and compression speed of the piston. In these studies, the deviation of PV and TV curves from the dry air compression curves, resulting from latent heat of vaporizing droplets are investigated. The studies show that smaller droplets, higher overspray and slower compression speeds significantly reduces the compressor work requirement, thereby increasing cost savings and environmental benefits of power generation. Interestingly, it is seen that the effect of initial relative humidity of the working fluid on energy savings is minimal. The corresponding efficiencies achieved through wet compression process are determined and tabulated. (C) 2018 Elsevier Ltd. All rights reserved.