Effects of ozone addition on direct detonation initiation in hydrogen/oxygen mixtures

This work computationally studies the influence of ozone addition on direct detonation initiation in stoichiometric H₂-O₂-O₃ mixtures. In addition to greatly reducing the critical initiation energy, E_c, ozone addition is also observed to qualitatively and significantly influence the detonation dynamics in both subcritical and critical regimes. In the planar configuration, an additional critical initiation energy E_c’ ≥ E_c, is identified, indicating the development of a second detonation wave when the initiation energy, E is above E_c’. Mechanistically, the second detonation is initiated through Zeldovich mechanism of reactivity gradient. Instead of artificially setting temperature or composition gradient, the propagating leading shock triggers sequential autoignition events in the unburnt pockets. This detonation evolves into a pressure/shock wave propagating behind the first detonation front, and then either gradually decays, or catches up with the leading detonation, depending on the initiation energy. However, in the spherical configuration, this second shock or pressure wave is suppressed by the curvature loss and is no longer sustainable. Furthermore, the leading shock can be greatly enhanced during the initial stage of failed initiation, which may subsequently lead to re-initiation at larger radius with less curvature loss.