Numerical analysis of the effects of solid metal fuel particle characteristics on the combustion process

Combustion using aluminum particles as fuel is an attractive energy source where high energy densities are desired. Very little experimental literature or computational results are available for metal combustion in high-pressure chambers, as most experimental and computational work has been done on chamber operating at near atmospheric pressures. This paper attempts to improve our understanding of metal-fueled combustion chambers at pressures above atmospheric. A numerical model of solid Aluminum fuel particle combustion is developed to investigate the effects of radiation and fuel particle size on the combustion process. Of specific interest are particle specific burn rate, residence time, combustion efficiency, coupled radiation effects, and flame characteristics. This computational model is applied to a linear-type dump combustor. The effects of a range of particle sizes are investigated using mono-dispersed and poly-dispersed particle distributions. Combustion efficiency and characterization of the combustion process are addressed by studying particle ignition delay, surface combustion time, and particle flame radiation intensity as a function of particle diameter and mass fraction. The computational results of this detailed theoretical combustor reveal fundamental physics relating particle sizes and distributions to the variables commonly used to define the effectiveness and performance of the combustion process. The computational models include nonisotropic turbulence models, empirically derived ignition criteria and reaction rates, as well as convective and radiant heat transfer. The numerical results were compared with test data with reasonable agreement.