Superadiabatic combustion of methane air mixtures under filtration in a packed bed

Filtration combustion in porous media differs substantially from combustion in a homogeneous media. The difference is the heat transfer between the filtrated gas and the porous medium under conditions of active heat transfer over a highly developed internal solid surface. The reactive transfer is characterized by a thermal wave velocity that determines the velocity of heat accumulation in a porous medium due to the filtrated flow and by a reaction wave velocity. A resonance condition can occur when both velocities nearly coincide and the heat of reaction becomes localized in a moving thermal wave. A temperature can be reached much in excess of the adiabatic reaction temperature and thus self-propagating reactions are possible even in a weakly exothermic medium. The propagation of the localized resonance wave and the superadiabatic reaction effect is confirmed by experiments and the results of a simple mathematical analysis. The model is compared with predictions for the thermal and combustion wave speeds and demonstrates good agreement.