Mechanism of upper temperature limits in a wave of filtration combustion of gases

A physical mechanism is established, responsible for the experimentally observed strong deceleration of the growth rate of the maximum skeleton temperature in a wave of filtration combustion of gases with increasing flow rate. The maximum temperatures of the gas and skeleton become commensurable, and the length of the thermal-relaxation zone becomes much shorter. A classification of regimes based on the temperature-heterogeneity criterion phi(1) is proposed. Explicit analytical solutions are obtained for the wave for phi(1) << 1 and phi(1) --> 1. A correction to reverse reactions in combustion products is considered. The effect of composition on wave behavior is studied by means of numerical calculations with a detailed kinetic scheme. The activation energy for ultrarich and ultralean methane-air mixtures is evaluated. It is concluded that the limiting efficiency of the heat-recuperation cycle in the wave is reached as phi(1) --> 1; methods for maximizing the efficiency are suggested.