Laminar flame speeds of DEMP, DMMP, and TEP added to H2- and CH4-air mixtures
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abstract
Organophosphorus compounds (OPCs) have long been known to have significant fire suppression capabilities but were outclassed by Halon 1301 due to toxicity concerns. Recent interest in finding replacements for Halon 1301 has provided an impetus to reconsider OPCs. To better understand the mechanism by which OPCs suppress flames, more information about how they interact with fuel/air mixtures via chemical kinetics is needed. In this study, dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and trimethyl phosphate (TEP) were added to hydrogen/air and methane/air mixtures to assess their suppression capabilities at 0.1% and 0.3% (DMMP only) of the total mixture volume. Laminar flame speed experiments were performed in an optically tracked, spherically expanding flame setup at 1 atm and 120 C. The resulting laminar flame speed data are the first to be recorded using these compounds. Results show a 30% decrease in laminar flame speed for all OPCs at 0.1% on the methane/air parent mixture, and the laminar flame speed curves, as a function of equivalence ratio, tend to be broader than for un-doped mixtures. For the hydrogen/air mixtures, the OPCs differentiate themselves by having an increasing suppression effect corresponding with higher carbon moiety, i.e., TEP (15% overall reduction) > DEMP (13%) > DMMP (9%). The OPCs also have an increasing effect with increasing equivalence ratio on hydrogen/air, but with methane/air, they have a non-monotonic effect. The reduction of laminar flame speeds is comparable to twice the concentration of Halon 1301 and 10 times as much for previously investigated Halon 1301 replacements. These results are ideal for improving existing OPC chemical kinetics mechanisms, and possible applications include both fire suppression technologies and destruction of dangerous OPC compounds.
