Relationship between the dusty flame propagation velocity and the regime of combustion of fuel particles

A possibility of determining the regime of combustion of individual fuel particles on the basis of the dependence of the flame velocity on the fuel and oxidizer concentrations is considered by an example of a dusty flame of fine-grain metal particles with diameters $d_{10}<15$ $\mu$m and particle concentrations from $\approx10^{10}-10^{11}$ м$^{-3}$ $\mu$m) in a laminar dusty flame is controlled by diffusion of the oxidizer toward the particle surface, whereas combustion of iron particles of a similar size is controlled by kinetics of heterogeneous reactions. For aluminum particles with $d_{10}= 5-15$ $\mu$m, there are no clearly expressed features of either kinetic or diffusion mode of combustion. To obtain more information about the processes responsible for combustion of fine aluminum particles, the flame velocity is studied as a function of the particle size and initial temperature of the gas suspension. It is demonstrated that aluminum particles under the experimental conditions considered in this study burn in the transitional regime.