Transition processes during flame propagation in a closed vessel partially filled with a porous media

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 as the flame approaches it and by the transition process occurring as the wave enters the porous medium. The phenomenon of the dynamic limit – the flammability limit in a 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 initial pressure range in which the dynamic limit is possible can be significantly wider than that due to a change in the number of moles. This range is mainly determined by the heat exchange of the gas with the walls of the vessel in the region free from the porous medium.