The main aim of this research is focused on determining the velocity and particle density profiles across the flame propagation of microlycopodium dust particles. In this model, it is tried to incorporate the forces acting on the particles such as thermophoretic, gravitational, and buoyancy in the Lagrangian equation of motion. For this purpose, it is considered that the flame structure has four zones (i.e., preheat, vaporization, reaction, and postflame zones) and the temperature profile, as the unknown parameter in the thermophoretic force, is extracted from this model. Consequently, employing the Lagrangian equation with the known elements results in the velocity distribution versus the forefront of the combustion region. Satisfactory agreement is achieved between the present model and previously published experiments. It is concluded that the maximum particle concentration and velocity are gained on the flame front with the gradual decrease in the distance away from this location.
The present research deals with a hybrid combustion of aluminum/boron dust particles in a heterogeneous quiescent reaction medium with spatially discrete heat sources. A developed thermal model is employed to estimate flame propagation speed in a reaction medium. The burning velocity and minimum ignition energy are studied parametrically as a function of dust concentration and particle diameter for different percentages of boron powder in a hybrid mixture of aluminum/boron dust cloud. The model shows that the addition of boron powder as a component of the mixture decreases the burning rate and causes a higher amount of minimum ignition energy needed for ignition, owing to the role of boron as a heat sink. Comparison of the simulation results with the available experimental data shows that the model captures the flame propagation speed as a function of particle concentration, except at very low concentrations.
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