Sensitivity to Detonation and Detonation Cellular Structure of H₂-O₂-AIr-H₂O₂ Gas Mixtures

Today it is not known – neither qualitatively not quantitatively - how large the impact can be of the promoters on sensitivity to hydrogen-air detonation in hypothetical accidents at hydrogen-containing installations, transport or storage facilities. Report goal is to estimate theoretically an effect of hydrogen-peroxide (as representative promoter) on sensitivity to detonation of the stoichiometric hydrogen-oxygen gas mixtures. The classical H₂-O2-Ar (2:1:7) gas mixture was chosen as reference system with the well established and unambiguously interpreted experimental data. In kinetic simulations it was found that the ignition delay time is sensitive to H₂O₂addition for small initial H₂O₂concentrations and is nearly constant for the large ones. Parametric reactive CFD studies of two dimensional cellular structure of 2H₂-O₂-7Ar-H₂O₂ detonations with variable hydrogen peroxide concentration (up to 10 vol.%) were also performed. Two un-expected results were obtained. First result: detonation cell size is practically independent upon variation of initial hydrogen peroxide concentration. For practical applications it means, that presence of hydrogen-peroxide did not change drastically sensitivity of the stoichiometric hydrogen-oxygen gas mixtures. These theoretical speculations require an experimental verification. Second result: for large enough initial H₂O₂concentrations (> 1 vol.% at least), a new element of cellular structure of steady detonation wave was revealed. It is a system of multiple secondary longitudinal shock waves (SLSW), which propagates in the direction opposite to that of the leading shock wave. Detailed mechanism of SLSW formation is proposed.