Thermochemistry and Reaction Mechanisms of Nitromethane Ignition

Abstract
The thermochemistry and reaction mechanisms of nitromethane initiation are modeled using detailed chemical kinetics. Initial conditions correspond to gaseous nitromethane at atmospheric and liquid-like densities and initial temperatures between 1100 and 2000 K. Global reactions as well as elementary reactions are identified for each of the two stages of ignition. The chemical steps to convert the nitro group to N₂ involve a complex set of elementary reactions. The time-dependence of the ignition steps (ignition delay times) as a function of temperature and pressure is used to determine effective activation energies and pressure dependencies to ignition. The ignition delay times range from several nanoseconds to tens of microseconds. At atmospheric conditions, the delay times for both ignition stages are in excellent agreement with observed experimental data. At the high densities, the ignition times at these elevated temperatures appear to be dominated by the same reaction mechanism that occurs for atmospheric gaseous nitromethane initiation. This is to be contrasted with lower temperature, condensedphase ignition studies where it appears that solvent-assisted reactions dominate.