Transition Processes in Flame Propagation in a Closed Vessel Partially Filled with a Porous Medium

Abstract

Flame propagation in a closed vessel containing a stoichiometric propane–air mixture and partially filled with a porous medium has been experimentally studied. It has been shown that the flammability limit in the porous medium is determined by the current pressure at the time the flame approaches it and by the transition processes occurring as the wave enters the porous medium. The dynamic limit phenomenon—the flammability limit in the porous medium associated with a continuous pressure drop—has been investigated. It has been found that the range of initial pressures in which the dynamic limit is observed is determined not only by the change in the number of moles in the gas phase, as during flame propagation in vessels completely filled with a porous medium, but also by gas cooling in the free space. The dynamic limit can occur in a significantly wider range of initial pressures than that due to a change in the number of moles. This range is mainly determined by heat exchange between the gas and the walls of the vessel in the region free from the porous medium.