Intermediate species profiles in low-pressure methane/oxygen flames inhibited by 2-H heptafluoropropane: Comparison of experimental data with kinetic modeling

Experimental profiles of the intermediate species H, OH, CH, CF, CF2, and CHF are obtained in a 10 torr premixed hat flame of methane/oxygen in a 1:2 molar ratio, inhibited by a 4% mole fraction of 2-H heptafluoropropane (HFP, CF3CHFCF3). These data are compared to calculations using a recently published kinetic mechanism describing the consumption of this fire suppression agent. The profiles in the flame inhibited by HFP are compared to previously published data for flames containing CHF3 and CH2F2 under the same conditions of stoichiometry and Bur of fluorine atoms. The species profiles relative to the flames containing the fluoromethanes are accurately predicted and atmospheric pressure flame speeds are fairly well predicted by the kinetic mechanism. Under equal fluorine loadings, profiles of temperature and of H and OH mole fraction are virtually identical between the flames containing HFP and CHF3. The flame inhibited by HFP, however, has approximately twice as much CH* emission as the flame containing CHF3. The kinetic model predicts that thermal decomposition, rather than H atom abstraction, is the primary destruction mechanism for HFP under the conditions studied. (C) 1999 by The Combustion Institute.