Numerical and Thermodynamic Study of a Gas Turbine Cycle with Evaporative Cooling

It has been demonstrated that thermal efficiency can be improved and Nox emission can be reduced in gas turbine cycles by inlet air evaporative cooling. For this method, few studies have been performed using numerical simulations due to the complexity of the combustion and evaporation process. This study numerically and thermodynamically investigated the effect of inlet evaporative cooling on the thermal efficiency and NOx emission of a V94.2 gas turbine. The compressor and turbine are simulated using thermodynamic modeling. However, thermodynamic modeling could be able to calculate the temperature only at the inlet and outlet of devices. Analysis of evaporating cooling effect on combustion chamber temperature distributions and species distribution could be achieved by numerical method. Therefore, the combustion chamber was simulated by numerical modeling using Ansys Fluent 16. The process was simulated at four humidity ratios, including, 0, 25%, 50%, and 75%. Combustion was assumed to occur in a diffusion-type flame. The mass flow rate of fuel and air was 3.64 kg/s and 214.2 kg/s, respectively. Results show that Numerical and thermodynamic solutions have a good agreement with the empirical result. Also, it is observed that the accuracy of the numerical solution is better than the thermodynamic solution. Results indicated a 0.44% improvement in thermal efficiency and a considerable 33.5% reduction of NOx emission at the highest humidity ratio.