Simplified model for single aluminum particle combustion

A simplified modeling of a suspended aluminum particle burning in air is presented. The burning process consists of two stages, ignition and quasi-steady combustion (QSC), and the emphasis is laid on the effects of aluminum oxide (alumina) on the aluminum particle combustion. The film thickness is calculated using the phase diagram of Al-O and lever rule. In ignition stage, the aluminum inside of oxide film is modeled to be melting due to heterogeneous surface reaction (HSR) as well as heat transfer from ambient air until the particle temperature reaches melting point of oxide film. In quasi-steady combustion stage, 1-dimesional spherical symmetric diffusion flame is formulated with a flame sheet assumption. Extended conserved scalar formulations and modified Shvab-Zeldovich functions are used to account for the deposition of metal oxide on the surface of the molten aluminum. Oxide smoke effect is included with Brzustowski's assumption. Transport properties of materials are expressed as a function of temperature by using Chapmann- Enskog kinetic theory except for latent heat. Burning rate, combustion time, flame radius and temperature are compared with the measurements. Evolutions of particle ignition and burning of an aluminum particle is predicted.