Experimental and numerical studies of confined blast from detonation of plasticised high explosives in reactive and non-reactive atmospheres

We present the results of a small-scale experimental study of the temporal development of pressure following the detonation of 10-50 gram plastic explosive charges in a 275 litre sealed chamber. RDX- and PETN-based charges are used, and the tests are conducted in atmospheres of air, nitrogen and argon. The pressure-time data for repeat tests of the same explosive/atmosphere combination exhibit striking consistency, even over timescales encompassing many passes of the confined shock waves along the chamber. This suggests that both the quantity and rate of release of both the detonation energy and the energy of combustion of the partially oxidised detonation products are highly consistent and throws an interesting light on the issue of what consistency we should expect to observe in blast trials. Comparison of the pressure traces in air and non-reactive atmospheres gives strong evidence of the duration quantitative consequence of the combustion phase (commonly known as "afterburn"). This is supported by data from a purpose-built high bandwidth infra-red thermometer, which appears to be identifying the flame temperature of the afterburn reactions. Finally, the experiments are modelled using the APOLLO code, with results showing excellent correlation with the experimental data.