Add In The Effects Of Diluent No_x In Combustion Of Methane Research

Adding diluents in the gaseous fuel combustion is one of the effective ways to reduce emissions of NOx. Because combustion is a complex physicochemical process, the diluted combustion on the effect of NOx formation is investigated by some foreign experts in order to discuss and improve the mechanism of NOx formation in combustion. However, few domestic researches involves in this field. Based on the background, the effect of diluents addition on NOx formation in an axisymmetric laminar CH4/air coflow diffusion flame is investigated by experiment and numerical simulation and the results are analyzed in detail. In this paper, five diluents with different properties have been studied to ascertain their effects on the formation of NOx. While N2, CO2and CO are chosen for their prevalence and potential relevance to recirculation of burned hydrocarbon flue gases, Ar is selected for its definite lack of involvement in chemistry, H2is chosen for its improvement in combustion as an kind of new energy resource. This paper consists of the following parts:The system of the axisymmetric laminar CH4/air coflow diffusion flame is set up and the effect of diluents addition with different concentration and at different side on NOx formation in an axisymmetric laminar CH4/air coflow diffusion flame is investigated by experiment. The numerical model of the axisymmetric laminar CH4/air coflow diffusion flame is completed to compute the temperatures, the concentrations of free radicals and NOx emission index. Under the same conditions, good agreement between the simulation results and the experimental data is reached. The results indicate that the addition of N2, CO2or Ar, whether at fuel side or at oxidation side, can reduce the formation of NO. On the other hand, the addition of CO or H2can improve the formation of NO. The addition of CO2is much more effective to reduce NO emission compared with other diluents. The effect of the addition of diluents at oxidation side on NO formation is more obvious than at fuel side. Further, the addition of CO2, CO or H? reduces the formation of NO2while the addition of N2or Ar has little effect on it. However, the formation rate of N2O increases when any kind of diluents except H2is added.The content of the paper not only helps to reveal the mechanism of NOx formation in methane combustion, but also promotes practical applications of the diluted combustion in curbing emissions. Therefore, it can be treated as a basic work of realizing the low-NOx natural gas combustion.