INHIBITION EFFECTIVENESS OF HALOGENATED COMPOUNDS

A numerical study of the inhibition efficiency of halogenated compound s was carried out for C-1-C-2 hydrocarbon-air laminar premixed flames. The inhibition efficiency of CF3Br, CF3I, CF3H, C2HF5, C2F6, and CF, additives was interpreted using an additive group method. In agreement with measurements, the calculated burning velocity decreased exponent ially with increasing additive concentration over a wide concentration range. The inhibition parameter Phi proposed by Fristrom and Sawyer i ndicating inhibition efficiency was modified to take into account the exponential dependence of burning velocity on inhibitor concentration. The inhibition indices for halogen atoms and groups important in the inhibition process were determined for stoichiometric conditions. The physical and chemical effects of the additives were studied. With incr easing additive concentration, the chemical influence of an inhibitor saturates and the physical influence increases. Therefore, use of a co mposite inhibitor composed of a mixture of an effective chemical inhib itor with a high heat capacity diluent may be beneficial. The contribu tion of physical and chemical components on inhibitor influence are es timated near extinction. A procedure for determination of a regenerati on coefficient, which indicates an effective number of catalytic cycle s involving inhibitor during the combustion process, is suggested. The regeneration coefficient of HBr in stoichiometric methane-air flame w ith 1% CF3Br added is approximately 7. (C) 1998 by The Combustion Inst itute.