Numerical study on CH4 laminar premixed flames for combustion characteristics in the oxidant atmospheres of N2/CO2/H2O/Ar-O2

Abstract

The freely-propagating laminar premixed flames of CH4–N2/CO2/H2O/Ar-O2 mixtures were conducted with the PREMIX code. The effects of the equivalence ratio and various oxidant atmospheres on the basic combustion characteristics were analyzed with the initial pressure and temperature of 1 atm and 398 K, respectively, O2 content in the oxidant of 21%. The chemical reaction mechanism GRI-Mech 3.0 was chosen to determine the effects of the oxidant atmospheres of N2/O2, CO2/O2, H2O/O2, and Ar/O2 on the adiabatic flame temperature, laminar burning velocity, flame structure, free radicals, intermediate species, net heat release rate and specific heat of the fuel/oxidant mixtures. The numerical results show that the maximum adiabatic flame temperatures and laminar burning velocities are at Ar/O2 atmosphere. The mole fractions of CO and H2 increased fastest at CO2/O2 atmosphere and H2O/O2, respectively. The mole fractions of CH3 and H follow the order Ar/O2> N2/O2>H2O/O2>CO2/O2. In addition, for 4 oxidant atmospheres, the peak mole fraction of C2H2 is following the order H2O/O2>Ar/O2>N2/O2>CO2/O2 and the net heat release rate is following the order Ar/O2>N2/O2>H2O/O2>CO2/O2 for all equivalence ratios.