Study on combustion and emission characteristics of a heavy-duty gas turbine combustor fueled with natural gas

Abstract

In this paper, the ignition delay and laminar combustion characteristics of natural gas were tested in a chemical shock tube and a constant volume combustion reactor, respectively, and simulated with the Gri_3.0, USC_2.0 and NUI_Galway models, respectively. It is proved that the ignition delay and laminar combustion characteristics of natural gas simulated with the Gri_3.0 model are in better agreement with the experiment than the USC_2.0 and NUI_Galway models. Furthermore, the simulated variation trends of the mole fractions of main species, especially NO and NO2 with temperature by the Gri_3.0 model are in better agreement with the experimental data in the oxidation of natural gas. The combustion process and pollutants generation characteristics in a single flame tube of a heavy-duty gas turbine burning natural gas were simulated by coupling the Gri_3.0 model with the computational fluid dynamics. It is shown that the simulated average temperature and the NOx concentration at the outlet of the flame tube are slightly higher than the experimental value by 8.06% and 5.08%, respectively. Because the NOx emission is higher than the designed value, fuel flows in the annular, main, and pilot combustion zones of the flame tube were reassigned and effects of the fuel redistributions on the NOx emission characteristics were investigated. It is shown that the NOx concentration at the outlet of the flame tube increases from 157.1 mg/m3 to 175.5 mg/m3 when the fuel flow in the pilot combustion zone is redistributed to the main combustion zone, and decreases from 157.1 mg/m3 to 139.51 mg/m3 when the fuel flow in the pilot combustion zone is redistributed to the annular combustion zone. The research results will provide theoretical basis and technical support for the optimization of this gas turbine operation.