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Inhibition of Premixed Methane Flames by Manganese and Tin Compounds.


pdf icon Inhibition of Premixed Methane Flames by Manganese and Tin Compounds. (437 K)
Linteris, G. T.; Knyazev, V. D.; Babushok, V. I.

Combustion and Flame, Vol. 129, No. 3, 221-238, May 2002.

Keywords:

premixed flames; manganese; tin; experiments; flame extinguishment; fire suppression; halon alternatives; kinetic mechanism; organometallics

Abstract:

The first experimental measurements of influence of manganese- and tin-containing compounds (MMT, TMT) on burning velocity of methane/air flames are presented. Comparisons with Fe(CO)5 and CF3Br demonstrate that manganese and tin-containing compounds are effective inhibitors. The inhibition efficiency of MMT is about a factor of two less than that of iron pentacarbonyl, and that of TMT is about twenty-six times less effective, although TMT is about twice as effective as CF3Br. There exist conditions for which both MMT and TMT show a loss of effectiveness beyond that expected due to radical depletion, and the cause is believed to be particle formation. Kinetic models describing the inhibition mechanisms of manganese- and tin-containing compounds are suggested. Simulations of MMT- and TMT-inhibited flames show reasonable agreement with experimental data. The decomposition of the parent molecule for the tin and manganese species is found to have a small effect on the inhibition properties for the concentrations in this work. The inhibition effect of TMT is determined mostly by the rate of the association reaction H+SnO+M <-> SnOH+M and the catalytic recombination cycle is completed by the reactions SnOH+H<->SnO+H2 and SnOH+OH<->SnO+H2O. The inhibition mechanism by manganese-containing compounds includes the reactions: MnO + H2O <-> Mn(OH)2; Mn(OH)2 + H = MnOH + H2O, and MnOH(H2) and the burning velocity is most sensitive to the rate of Mn(OH)2 + H <-> MnOH + H2O.