An experimental and modeling study of nitromethane + O2 + N2 ignition in a shock tube

The ignition of nitromethane/O2/N2 mixtures was investigated via shock tube experiments in the temperature range 947-1333 K at reflected shock pressures near 8, 16 and 32 atm. The ignition was recorded as the intensity maxima of unfiltered luminosity in the range 240-530 nm. Under the experimental conditions of the present study, ignition was found to proceed via a two stage process. Dependencies on concentration, pressure and temperature were examined and discussed. The two ignition stages were separated in time, with individual concentration and temperature dependence. The two experimentally determined ignition stages were found to be pressure independent over the pressure range investigated. The activation energy was derived to be 16.15 ± 1.57 kcal mol−1 for the first stage ignition and 20.89 ± 0.82 kcal mol−1 for the second stage. Modeling using the mechanism by Brequigny et al., published in Proceedings of the Combustion Institute (2014) 703-710, could predict the magnitude of the ignition delay times at 8 atm, but it could not reproduce the temperature dependence of the first stage ignition or the pressure independence of both ignition stages. The measurements are discussed in relation to data from the literature.