Modeling of premixed gas combustion in porous media composed of Coarse-Sized particles: 1-D description with discrete solid phase

Abstract

A one-dimensional non-steady-state model of gas combustion in a porous medium, treated as a discrete structure, is proposed. Each element of this regular periodic structure consists of the three elements: a solid particle, a gas flow zone, and a gas stagnation zone. Combustion occurs in the flow zones; the solid particles and stagnation zones are chemically inert. Numerical simulation of the opposing waves of premixed methane-air combustion in the discrete-modeled porous medium reveals the pulsating nature of the process. The maximal temperature and burning rate in the combustion front as well as the velocity of its propagation are low in the regions of the gas flow zone, which are adjacent to the particles, and increase in the neighborhood of the stagnation zone. At the size of elementary cells greater than some critical value d cr (1) (approximately 3 mm), the flame breaks into the high velocity regime of propagation in the neighborhood of the stagnation zone; the amplitude of pulsation of the combustion characteristics is increased considerably in this period. After crossing the threshold value d cr (1) , the high frequency oscillation (∼100 Hz) of the position of combustion front and its temperature were found in a region of the flow zone adjacent to the stagnation zone. When the diameter of particles becomes greater than the second critical value d cr (2) , the flame propagates in the high velocity regime over all the regions of the flow zone: the amplitude of pulsation of combustion characteristics is reduced. The discrete model of gas combustion in a porous medium, composed of coarse-sized particles, leads to a qualitatively new result when the process under consideration is sensitive to high-temperature reactions in the gas phase, and the final composition of the gas mixture is of main practical interest.