Etude de la détonation de mélanges pauvres H 2[sbnd]NO 2/N 2O 4

Abstract

Calculations of the detonation reaction zone of gaseous H 2 NO 2/N 2O 4 mixtures in the range of equivalence ratio Φ between 0.25 and 0.7 show that for 0.25 ⩽ Φ ⩽ 0.4 the chemical energy is released in two distinct and successive exothermic steps characterised by different chemical characteristic times. As for rich mixtures, the first exothermic step is mainly due to the reaction NO 2 + H → NO + OH, but the second one is different since it results from the exothermic decomposition of NO into N 2 and O 2. For Φ = 0.3 the measured detonation velocity in a tube of 52 mm internal diameter is very much smaller than the calculated value and the mean size of the cellular structure is very much larger than the value extrapolated from data obtained with mixtures of higher but close equivalence ratio. All these results show that the detonation, though self-sustained and steady, is ‘non-ideal’, i.e. it is supported only by a part of the available chemical energy, that provided mainly by the first exothermic step. To cite this article: D. Desbordes et al., C. R. Mecanique 332 (2004).