The Computational Simulation of a Stoichiometric CH₂CI₂/CH₄/Air Flat Flame

ABSTRACT

A flat flame simulation was performed to model experimental data from a dich-loromethane/methane/air flame. A detailed elementary reaction mechanism was used to carry out the simulation and to obtain insights about key chemical processes occurring in various regions of the flame. The flame was at stoichiometric conditions with a CI/H ratio of 0.34. The PREMIX flat flame program was used to obtain the calculated results. Comparisons between calculation and experiment were good for the three reactants and five of the seven stable intermediates for which experimental data were available. Calculated CO₂ and CO profiles were also good, but were found to be offset from experiment by 0.02 cm, with the calculated profiles occurring too late in the flame. A reaction rate analysis found that the flame developed in three stages, an initiation stage, a chlorine inhibited oxidation stage, and finally CO burnout by the reaction CO + OH. The initiation stage was dominated by chlorine abstraction of H atoms from the fuel species and recombination of dichloromethyl, chloromethyl and methyl radicals to C₂'s. This initiation stage was found to occur in the flame at temperatures of 1070 K to 1500K. The oxidation stage was characterized by temperatures between 1500 K and 1660 K. CO₂ formation from CO + OH was found to be inhibited in the initiation stage and oxidation stage. Once the temperature reached 1660 K OH radicals became available through the endothermic reactions O + H₂O and O + HCI, and CO + OH became the dominant pathway for CO ₂ formation.