Breakdown of surface burning of gas-permeable porous systems

Abstract

1. The breakdown of surface burning of porous secondary and mixed explosives has been studied at low values of the gas permeability (10−3–10−6 darcy) and porosity (0.15–0.03) of the specimens. 2. The causes of diffusion of the combustion products into the pores have been examined. 3. Relations have been obtained between critical pressure and gas permeability, porosity and initial particle size. The breakdown of surface burning is determined not only by the gas permeability but also by the nature of the pore size distribution. 4. Convective burning is initiated and develops in the individual large pores. 5. It has been shown that an increase (up to a certain limit) in the diameter of the porous charge reduces combustion stability. 6. A continuous molten layer formed at the burning surface stabilizes the combustion of gas-permeable porous systems and is a cause of the enhanced combustion stability of secondary explosives. 7. A factor facilitating penetration of combustion into the pores is the small distance from the burning surface to the high-temperature gas zone.