Discrete-continual model of flame propagation in a gas suspension of metal particles. I. One-dimensional approximation

Abstract

Experimental data on combustion of magnesium particles in oxygen-containing gas mixtures are analyzed and generalized, which allowed us to develop a semi-empirical mathematical model that takes into account the integral effect of the initial particle size, pressure, and velocity of the oxidizing flow on combustion. Flame propagation in an air suspension of fine magnesium particles is considered in a one-dimensional approximation. For this purpose, a discrete-continual model of flame propagation in a gas suspension of metal particles is developed. The flammability limits in a vessel, caused by heat losses into the ambient medium and by spatial nonuniformity of the distribution of disperse-phase particles, are numerically determined, and the influence of nonuniformity and bidispersion of a one-dimensional ensemble of particles on flame characteristics is studied.

Ignition and combustion of magnesium particles in a nonuniform thermal field

“…7); during this time, the first particle reaches the steady value of temperature T ≈ T m . Thus, the relay mechanism of ignition, which was previously observed within the framework of the pointwise approach [6,7], is also realized here.…”

Discrete-continual model of flame propagation in a gas suspension of metal particles. II. Allowance for the pre-flame oxidation reaction

“…In addition to the assumptions of the mathematical model of combustion of a chain of particles in a vessel [1], we assume that the entire heat of the heterogeneous chemical reaction of ignition is released in the disperse phase. Equations (4)-(6) from [1] are changed in accordance with the following processes: oxide-film growth…”

“…Equations (4)-(6) from [1] are changed in accordance with the following processes: oxide-film growth…”

“…A one-dimensional mathematical model of flame propagation in a gas suspension of metal particles, based on a discrete-continual approach, was developed in [1]. Based on this model, the characteristics of the combustion wave in spatially nonuniform and polydisperse mixtures of magnesium particles in air are examined.…”

“…In a certain range of the particle size, the model offers a satisfactory description of experimental data on flame velocity as a function of the particle size. In the present work, the mathematical model of [1] is supplemented by allowance for the pre-flame oxidation reaction for obtaining better predictions of local and integral characteristics of the flame.…”