Effects of natural gas composition on the nitrogen oxide, flame structure and burning velocity under laminar premixed flame conditions

Abstract

Nitrogen oxide (NO x ), flame structure and burning velocity for Egyptian natural gas–air flames have been investigated experimentally and computationally for a laminar premixed flame. Experimentally, CO, O 2 and NO x concentrations as well as the gas temperature were measured throughout a flat flame on a matrix burner at an equivalence ratio, φ, of 0.5, atmospheric pressure and initial temperature of 300 K. Peak concentrations of CO and NO x were also measured at different φ. Computationally, a kinetic program has been developed to predict the above parameters for the premixed laminar natural gas–air mixture. The kinetic mechanism consists of 59 reactions, 25 chemical species as products and eight species as reactants. The results show that there is good agreement between the measured and computed NO x , CO, O 2 and gas temperature profiles. The results predicted from the model were used to interpret the kinetic factors responsible for the observations. Moreover, the effect of natural gas composition on NO x , flame structure and burning velocity was studied computationally. The results show that an increase of ethane concentration in the natural gas leads to an increase in the lean flammability limit, burning velocity, CO and NO x at very lean flames. The burning velocities of Egyptian natural gas–air flames were correlated at 300 K, 1 atm and different φ by: U l=0.37φ −0.35 exp[−5(φ−1.1) 2] (m s −1).