Experimental and computational study of the effect of C2F6 on premixed methane flames

Abstract

The objective of this work was to specify the mechanism of flame inhibition by compounds that do not contain bromine. Mole fraction profiles have been measured by molecular beam-mass spectrometer technique in a stoichiometric CH 4 /O 2 /Ar low-pressure flame seeded with and without 1% hexafluoroethane (C 2 F 6 ). For both flames, stable and reactive species concentrations have been computed and compared with experimental results in order to validate a detailed mechanism. Extension of the mechanism to atmospheric pressure was carried out by substituting the rate constant of a few reactions by high-pressure values. Mole fraction profiles computed in 1-atm-pressure stoichiometric methane-air flame were in very good agreement with Bechtel's experimental results. Thus validated, the mechanism was used to compute the reduction in flame velocity that results from the addition of increasing amounts of the inhibitor to a methane-oxygen-nitrogen flame. Calculated flame velocities are in very close agreement with experimental values obtained with a premixed flame stabilized on an open tubular burner. This shows that inhibition efficiency of fluorinated compounds can be predicted very accurately.