Gas transport and bubble-driven ignition in slow Cookoff for a Melt-cast explosive

To investigate the effects of gas transport on heat transfer and ignition characteristics of melt-cast explosives in slow cookoff, this study develops a bubble-driven multiphase flow and ignition model. The multiphase model incorporates mechanisms such as melting, shear thinning, dissolution, pressure accelerated thermal decomposition reactions, and the rise of bubbles. The model provides accurate predictions of temperature and pressure histories of Comp-B in sealed and vented systems, as well as the mixing of the suspension, variations in flowability, and bubble distribution. The results reveal that bubble-driven local flow and the resulting convective heat transfer significantly enhance suspension mixing. Furthermore, by decoupling bubble flow and comparing results in different ullage conditions, the effect of gas products on flow and ignition is investigated. The bubble-induced convective heat transfer plays a dominant role in the thermal transport but not in the ignition delay of vented system. In the vented system, lower pressure in ullage enhances the escape of gas products, weakening pressure-dependent reactions, which in turn delays the ignition. This study could lay a solid foundation for further investigation into bubble dynamics during the slow cookoff process of melt-cast explosives.