Laminar flame in fine-particle dusts

A simple conductive model of the laminar flame in fine-particle dusts, with particles burning in the diffusion mode, is presented. The model is based on the assumption about wide zones of combustion in dusts; therefore, the main contribution to the formation of the heat flux toward the pre-flame zone is made by the heat released on burning particles near the interface between the burning and pre-flame zones. The normal flame velocity is demonstrated to increase with decreasing particle size and with increasing fuel and oxidizer concentrations. The maximum velocities are reached under the condition of identical volume heat capacities of the solid and gas phases, which requires the fuel concentration to be several times higher than the stoichiometric value. The calculated results are validated by experimental data on the normal flame velocity as a function of the fuel concentration for gas suspensions of magnesium, aluminum, zirconium, iron, and boron particles.