Effect of Operational Parameters on Combustion and Emissions in an Industrial Gas Turbine Combustor

Enhancing a combustion system requires increased combustion efficiency, fuel savings, and reduction of combustion emissions. In this paper, the combustion of CH₄ in the combustor of an industrial gas turbine is studied and NO and CO formation/emission is simulated numerically. The objective of the current work is to investigate the influence of combustive parameters and varying the percentage of distributed air flow rate via burning, recirculation, and dilution zone on the reactive flow characteristics, NO_x and CO emissions. The governing equations of mass, momentum, energy, turbulence quantities Renormalized group (RNG) (k–ε), mixture fraction and its variance are solved by the finite volume method. The formation and emission of NO_x is numerically simulated in a postprocessing fashion, due to the low concentration of the pollutants as compared to the main combustion species. The present work focuses on different physical mechanisms of NO_x formation. The thermal-NO_x and prompt-NO_x mechanism are considered for modeling the NO_x source term in the transport equation. Results show that in a gaseous-fueled combustor, the thermal NO_x is the dominant mechanism for NO_x formation. Particularly, the simulation provides more insight into the correlation between the maximum combustor temperature, exhaust average temperatures, and the thermal NO concentration. Results indicate that the exhaust temperature and NO_x concentration decrease while the excess air factor increases. Moreover, results demonstrate that as the combustion air temperature increases, the combustor temperature increases and the thermal NO_x concentration increases dramatically. Furthermore, results demonstrate that the NO concentration at the combustor exit is at maximum value in a swirl angle of 55 deg and a gradual rise in the NO_x concentration is detected as the combustion fuel temperature increases. In addition, results demonstrate that the air distribution of the first case at laboratory conditions is optimal where the mass fractions of NO and CO are minimum.