Characterization of Aerobic and Anaerobic Prompt Ignition of Explosively-Dispersed Aluminum Particles

Numerical simulations on the dispersal, ignition, and combustion of an aluminum (Al) particle shell surrounding a high-explosive (HE) charge were performed. The simulations used a compressible Eulerian granular two-fluid model that accounts for particle collisions and compaction effects. The gas-phase used the Becker-Kistiakowsky-Wilson (BKW) equation of state. Aerobic and anaerobic burning of the Al was modeled using a hybrid diffusion- and kinetic-limited approach based on empirical data. Detailed chemical reactions were used to describe afterburning of fuel-rich detonation products and aluminum sub-oxide species. The detonation of the HE is modeled in the constant-volume explosion limit and using a programmed burn approach. The model is capable of fully coupling the expansion of the detonation products, dispersal of the Al particles, and afterburning. Computed results show the expanding Al particle shell can ignite from the outside due to the shock-heated air when the layer is thin. The particle shell is also shown to ignite anaerobically in the interior due to high-pressure detonation products when a thick layer is used with a stronger HE.