Laminar burning velocities of trifluoromethane-methane mixtures: Experiment and numerical simulation

The laminar burning velocities of trifluoromethane(CHF₃)- methane(CH₄)-oxygen(O₂)-diluent mixtures were determined over extensive fuel concentration ranges using the counterflow flame technique. Numerical simulation was performed by employing a detailed kinetic model compiled on the bases of the GRI-Mech for methane combustion and a recent CHF₃ reaction kinetic model. Comparisons between the experimental data and numerical results indicate that while the qualitative experimental trends are well predicted by the model, there exist significant numerical disagreements between model and experiment. Through sensitivity and flux analyses, we identified several rate parameters which are influential to burning velocity predictions, and proposed reasonable adjustments to these parameters either based on new experimental measurements or by considering their associated uncertainties. The effect of CHF₃ addition on the reduction of CH₄ burning velocities was also experimentally and numerically examined. By substituting the inert gas in the unburned CH₄-O₂-inert mixture with CHF₃ while maintaining a constant adiabatic flame temperature, both burning velocities and mass burning rates decrease with an increase in CHF₃ substitution, thus demonstrating positively the combined kinetic and transport effects of CHF₃ on burning velocity reduction and in flame inhibition.