Experimental measurement and thermochemical modelling of water mitigation of confined detonations

Explosive detonations in confined spaces result in a long-term quasi-static pressure (QSP), formed due to the repeated reflections of the initial shock wave from the walls of the space. In fuel-rich explosives, secondary combustion (afterburn) of the detonation products and binder ingredients contributes significantly to the total energy release and subsequent pressure change in the space. Placing water around an explosive charge has been successfully used as a method to mitigate QSP, though several potential mechanisms have been proposed on how this reduction is achieved. An understanding of this mechanism is a prerequisite for the creation of fast-running modelling tools capable of predicting mitigated explosive events.

This paper presents experimental data on the mitigation of plastic explosive detonations in an unvented chamber, where the use of air and nitrogen atmospheres is used alongside water-mitigated and unmitigated detonations to investigate the effects of mitigation on afterburn reactions, and the resulting QSP. A simplified thermochemical model of the detonation and afterburn reactions is then used to predict the peak experimental QSP using simplifying assumptions on the explosive composition and reaction products, and an assumptions of an ideal gas EOS.