Experimental and modeling study on the effects of dimethyl methylphosphonate (DMMP) addition on H2, CH4, and C2H4 ignition

Dimethyl methylphosphonate (C3H9O3P, DMMP) is considered both a surrogate of Sarin, a chemical weapon of mass destruction, and a fire suppressant. In this study, new ignition delay time measurements were taken in a heated shock tube for a mixture of DMMP/O2 in 99% Ar and for diluted mixtures of H2, CH4, and C2H4 doped with DMMP. These data can be used to validate and refine a detailed kinetics model for DMMP. Results showed that the DMMP addition did not modify the ignition delay times obtained with the C2H4 mixture, while a strong promoting effect was observed with CH4. Results were compared to detailed kinetics models from the literature, and it was shown that these models need to be significantly improved. A tentative model was assembled based on a modern hydrocarbon mechanism from the group of Curran and on updated phosphorus chemistry and thermochemistry recently proposed. Computations using this tentative model exhibited the need to revise several aspects of the DMMP oxidation chemistry, such as the rate coefficients of the reactions describing the rapid thermal fragmentation of DMMP and potentially the interactions between the phosphorus chemistry and radicals and molecules in the C2 chemistry.