Laminar Flame Propagation in a Premixed Particle Cloud: Effect of Vaporization Rate

The propagation of a flame in a mixture of air and small solid fuel particles is analyzed. It is assumed that solid particles suffer a vaporization, after which the resulting gaseous fuel mixes with air and a premixed combustion occurs. The combustion reaction is modeled by a global reaction of Arrhenius type with large activation energy and the analysis is carried out using large activation energy asymptotics. The structure of the flow is similar to a classical premixed flame, but with some particular features due to the vaporization, whose characteristic time, through the appropriate Damkohler number, plays an important role. Lean and rich mixtures, defined from the solid fuel content, are considered, as well as the effect of Lewis numbers and heat of vaporization. The analysis shows that rich mixtures can be lean or rich in the gaseous phase depending on the value of the vaporization Damkohler number . In all regimes the structure of flow and the flame speed are obtained.