A two-dimensional non-stationary model of surface combustion for gas and solid phases in a porous medium is proposed with equations for the balance of heat and matter in both phases and the gas filtration equation based on Darcy's law. At the initial time, the temperature gradient, gas velocity and reagent concentration are set. On the basis of numerical solution of the governing equations for a given heat exchange with the external environment, the structures of spirally unwinding combustion foci are obtained, which propagate along the boundary of the expanding parent foci. The structures of the thermal field are in the form of intermittent local heated and relatively cold combustion zones, which in some cases have the shape of saw teeth. Such a focal structure of thermal fields is a characteristic of combustion at the diffusion-kinetic limit of propagation of the reaction front. Namely, hot protrusions correspond to local zones of a diffusion-limited reaction, and cold protuberances correspond to local zones of a kinetically-limited reaction. The resulting spiral form of spin combustion has an analogy with the formation of fingers in the modern theory of filtration combustion.

Ключевые слова: moderate temperatures, synthesis