The simulation of the combustion of micrometer-sized aluminum particles with oxygen and carbon dioxide

The Liang/Beckstead aluminum-particle combustion model has been successfully joined with a detailed chemical-kinetic mechanism. The model has been used to investigate the effect of oxidizer concentration, pressure, and particle diameter on the combustion of CO2/Ar and O2/Ar with micrometer-sized aluminum particles. The simulation results when varying the oxidizer compare well with experimental data. With CO2 as the oxidizer, the trend of each simulated diameter follows that of the experimental data, especially the simulated 7 μm particles compared to experimental data for a mass average diameter of 11 μm. For oxygen, the simulated burn times with a particle size of 11 μm has excellent agreement compared to experimental data with a mass average diameter of 11 μm. The simulation results for both CO2/Ar and O2/Ar show a transition from kinetically-controlled combustion to diffusion-controlled combustion as the pressure increases. The burn time of the particles decreases as the pressure increases, until the diffusion-controlled combustion regime is reached and then the pressure has no effect on burn time. The opposite is true for the CO2 experimental data, in that the observed burn time increases with increasing pressure. The simulations indicate that the observed experimental trend could be the result of using a distribution of particle diameters. As the pressure decreases, larger particles may not ignite and the apparent burn time does not increase. The effect of particle diameter was also investigated. The effects of particle size, oxidizer, and oxidizer concentration on the calculated surface temperatures are also shown. This is the first model to show the beginning of the transition from diffusion-limited to kinetic-limited combustion control for aluminum particles.