Abstract
Current work aimed to predict the flame velocity in aluminum dust clouds by directly solving the energy conservation equations on particles while considering the two scenarios of heat transfer: continuum regime assumption and free molecular regime assumption. Generally, the model shows that the influence of particle diameter (dp) on the velocity follows the dp-m, and the velocity is insensitive to the wide range of dust concentration 200-1000 g･m -3. For continuum regime assumption, the calculation has been compared with the reported experimental results in particle sizes range of 5.4-7.1 μm, and the velocity is comparable with the predicted size of 10 μm; however, it failed to predict the velocity as particle decreases to nano-scale resulting in the unpractical high results. These results imply that the heat transfer mechanism in nano-particle transits to free molecular regime assumption. For free molecular regime assumption, particle agglomeration has been taken into account for the flame velocity; however, due to lack of experimental flame velocity in nano dust clouds, the calculations are compared with other numerical predictions. In the last part, a particle burning time was approximated by considering the particle’s residence time in the preheat zone, and the results follow the well-known dpn-law.
