Inhibition of premixed methane flames by manganese and tin compounds Official contribution of NI

Abstract The first experimental measurements of the influence of manganese- and tin-containing compounds (MMT, TMT) on the burning velocity of methane/air flames are presented. Comparisons with Fe(CO) 5 and CF 3 Br 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 26 times less effective, although TMT is still about twice as effective as CF 3 Br. There exist conditions for which both MMT and TMT show a loss of effectiveness beyond that expected because of 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 + H 2 and SnOH + OH ↔ SnO + H 2 O. The inhibition mechanism by manganese-containing compounds includes the reactions: MnO + H 2 O ↔ Mn(OH) 2 ; Mn(OH) 2 + H ↔ MnOH + H 2 O, and MnOH + OH (or H) ↔ MnO + H 2 O (or H 2 ), and the burning velocity is most sensitive to the rate of the reaction Mn(OH) 2 + H ↔ MnOH + H 2 O.