Combustion of magnesium particles II—Ignition temperatures and thermal conductivities of ambient atmospheres

Combust Explos Shock Waves

Тропин

2008

A mathematical model of ignition of a magnesium particle with allowance for a heterogeneous chemical reaction is proposed. The model allows the final particle temperature after its ignition to be found and takes into account the region of the thermal influence of the particle on the gas. A stationary solution is found, which makes it possible to propose a classification of the thermal history of the particle-gas system. The mathematical model is consistent with experimental data on the dependence of the ignition delay on the gas pressure and particle radius and on the dependence of the limiting temperature on the particle radius and the ambient pressure. The mathematical model also reveals the effect of the size of the gas layer around the particle on the integral parameters of ignition.

Section: Limiting Ignition Temperaturesupporting

confidence: 89%

“…Figure 8 shows the limiting ignition temperature as a function of the sample size. The experimental dependence was borrowed from [5]. The vertical bars indicate the scatter of experimental data.…”

Section: Limiting Ignition Temperaturementioning

confidence: 99%

Mathematical model of magnesium ignition in an extended range of parameters

Combust Explos Shock Waves

Тропин

2008

“…For magnesium particles, the value of T ign depends on the initial particle size in accordance with the empirical formula obtained by processing the experimental data of [9]: (d p,0 is measured in micrometers). Part of these data are cited in Table 2. 2.…”

Section: Kinetic Functionsmentioning

confidence: 99%

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

Gosteev

Combust Explos Shock Waves

2005

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.

“…For this purpose, let us write the equations governing the pre-explosion state and apply them to two arbitrary points of the experimental curve that describes the critical ambient temperature as a function of particle radius (Cassel and Libman 1963). This yields a closed system of transcendental equations for determining the unknown quantities -the activation energy and preexponential factor (if they exist) and particle temperature at the ignition limit.…”

Section: Determination Of Kinetic Constants Comparison Of Ignition Dmentioning

confidence: 99%

On the theory of thermal explosion in moving heterogeneous media

Gosteev

2001

Shock Waves

A mathematical model for the description of the flow of a mixture of a gas and reacting metal particles is proposed in the context of a two-velocity, two-temperature approximation. As an application of this model, pointwise and one-dimensional approximations are considered. Qualitative and quantitative analyses of a catastrophe/ignition manifold for the model of magnesium particle ignition are performed taking into account metal evaporation. Then the theory of an adiabatic travelling ignition wave in a mixture of gas and magnesium particles is developed by extending Semenov's theory of thermal explosion to the case of a moving cloud of particles. A classification of possible types of flows behind the shock-wave front is given. The calculated induction period of a mixture of dispersed magnesium particles in oxygen correlates well with available experimental results. Ignition and steady propagation of a stationary ignition wave in the mixture is shown numerically.