Detonations in Explosive Foams

Abstract

Previous work has shown that two different regimes of detonation may appear for a foam density range of 5 to 25 kg/m 3 in an aqueous foam filled with a stoichiometric propane-oxygen mixture. When the majority of the bubbles have a diameter greater than 2-3 mm, the phenomenon observed is very similar to that of a premixed gaseous detonation ; this regime is called the Normal Regime of Detonation (NRD). When the predominant diameter is less than 2 mm, the shock and the combustion fronts are clearly separated and their velocities are markedly lower than that of the detonation in the gaseous mixture alone. This regime is called the Double Front Regime (DFR). In the present work, under the same experimental conditions, the influence of the gaseous mixture composition is established.Experiments were performed with stoichiometric mixtures (2H 2 + 0 + ZN 2 , CH, +20+ ZN 2 , C 2 H, + 3 0 2 + ZN 2 and C 3 H g + 5 6 2 + ZN 2 ). At a given mean bubble diameter and foam density, a maximum dilution limit -Z.. . -is observed beyond which the NRD is not observed. The dependence of the critical predominant bubble diameter on the dilution of nitrogen (Z) at the transition from NRD to DFR was determined.