Inlet air fogging strategy using natural gas fuel cooling potential for gas turbine power plants

Abstract

Fogging is an effective cooling system used for gas turbine (GT) inlet air cooling. In this study, three fogging strategies were tested: direct fogging, fogging with a natural gas (NG) heat exchanger (FNGE), and FNGE using a storage tank (FNGET). The discrete phase model (DPM) with the standard k-ω turbulence model was used. A computational parametric study was conducted using the standard k-ω turbulence model on a GT compressor inlet duct to optimize the effect of the FNGET cooling strategy. The effects of duct length, number of nozzles, uniform droplet diameter, and nozzle angle on the compressor inlet air temperature and relative humidity (RH) were examined in this parametric study. A duct with 15 m length, 48 nozzles in each half, 100 μm droplet diameter, and 60° nozzle angle exhibited the maximum decrease in the temperature of the compressor inlet air. The minimum (maximum) reduction in temperature was 5.54 °C (15.77 °C), which was observed at 30 °C (40 °C) ambient dry-bulb temperature (DBT) and 60% (15%) RH. The minimum (maximum) increase in the GT output power was 8.99 MW (26.44 MW), or 3.87% (11.15%), which was under the ambient conditions of 34 °C (30 °C) and 60% (15%) RH. The maximum enhancement in GT thermal efficiency was 1.47%, which occurred under the ambient conditions of 30 °C DBT and 15% RH. The maximum decrease in GT specific fuel consumption (SFC) was 4.30%, which was seen under the ambient conditions of 30 °C and 15% RH. FNGET was the most effective cooling strategy in terms of GT output power, thermal efficiency, and SFC. This novel cooling strategy can be applied to various GT models.