Gaseous nitromethane and nitromethane-oxygen mixtures: A new detonation structure

Detonation in gaseous nitromethane (NM) and mixed with O2 has been studied. Experiments were performed in a preheated steel tube at an initial temperatureT 0∼=390 K for different initial pressuresP 0 (1.7≥P 0≥5 10−2 bar). Different selfsustained detonation regimes were obtained, from multiheaded mode to spinning and galloping mode in marginal conditions. These chemical systems were characterized by a specific detonation cellular structure very different from that currently observed with classical gaseous C n H m /O2/N2 mixtures. All modes of detonation propagation in rich NM/O2 mixtures exhibit a double scale cellular structure. The pattern of this double scale structure is particularly clear in the case of spinning mode.