Shock-tube studies of Sarin surrogates

Abstract

To further refine the existing high-temperature combustion chemistry mechanisms of Sarin surrogates or to develop new ones, the ignition delay times of mixtures containing various Sarin surrogates have been studied in the authors’ laboratory, namely dimethyl-methylphosphonate, diethyl-methylphosphonate (DEMP), and triethylphosphate, and the results are compared for the first time herein. They were each measured in a heated shock tube, with the DEMP-related ignition delay times being the new data reported in this paper. The Sarin surrogates were studied in neat mixtures with oxygen or seeded to baseline mixtures of hydrogen or methane at around 1.5 atm. Noticeable differences were observed between the ignition delay times of the three simulants, whether sole or mixed with a fuel. Comparisons of OH* time histories obtained from each surrogate highlight the similarities and differences in chemical structure among the different compounds. In mixtures with oxygen and Ar, the three surrogates present similar ignition delay times below 1380 K, whereas the ignition delay time results rapidly diverge above this temperature. When the surrogates were added into $$\hbox {H}_{2}/\hbox {O}_{2}$$ or $$\hbox {CH}_{4}/\hbox {O}_{2}$$ mixtures, large changes in the reactivity of the mixtures were observed. These changes in reactivity are however dependent on the surrogate, for each fuel investigated.