Rapid thermochemical predictions of internal detonations using plasticised explosives

When explosives detonate in a confined space, repeated reflections of the resulting shock wave on the walls of the space result in the formation of a long-term uniform quasi-static pressure, or QSP. In fuel-rich explosives, the mixing of hot detonation products and binders with atmospheric oxygen leads to further combustion reactions, which increase the energy release and subsequent pressure rise. Predictions of these effects can currently be achieved through approximate empirical relationships or more involved CFD and thermochemical methods, but in many real-world applications the threat is not sufficiently well defined to populate these models. This paper presents the development of a fast-running thermochemical model for confined plastic explosive detonations, which takes into account afterburning of detonation products and binders. Simplifying assumptions on explosive composition and the detonation and combustion reactions allow ideal gas relationships to be used to calculate the peak QSP. Experiments performed with PE4, PE8 and PE10 in oxygenated and inert atmospheres show excellent agreement with the modelled predictions, illustrating the benefits of the method for rapid threat assessment and concept design, and the potential for use in modelling QSP mitigation solutions