Explosion severity of micro-sized aluminum dust and its flame propagation properties in 20 L spherical vessel

Abstract

Using 20L explosion vessel, the present research work reports some experimental results which elucidate the effects of dust concentration, particle size and specific surface areas on aluminum dust explosion severity. Dust flame propagation property and explosion products were analyzed systemically. Six kinds of aluminum powders with different size distributions were selected and specially prepared for explosion tests. Results show that explosion parameters present an increasing and then decreasing trend with dust concentrations. The optimum explosion concentrations for all the selected aluminum dusts are similarly equal to 500g/m3. Maximum explosion pressures would be quadratic correlated with the decreasing of particle size. However, (dP/dt)max would be exponentially increasing with particle size decreasing. Aluminum dust flame propagation speed would be increased and the combustion mechanism would be transited from diffusion-controlled mode to kinetically controlled mode with particles diameter decreasing. For the finer dust cloud (dS less than 10μm), dust flame propagation speed would be exponential increased with dust concentration. However, there is a power function relation between flame propagation speeds and dust concentration for the coarse aluminum dust cloud (dS larger than 10μm). At the experimental condition, flame propagation speed presents an exponentially decreased trend with the increasing of particle size. Explosion products obtained at different conditions present different apparent morphology. The higher explosion pressure, the finer explosion fragments and nano-scale spherical structure would be produced. For coarse aluminum particles, explosion products present fluffy flocculent structure. Furthermore, alumina produced under lower explosion pressure conditions are mainly γ-Al2O3 components. Under high explosion pressure condition (such as 0.56MPa), there are notable bulges corresponding to α-Al2O3 are produced. Present research results may have important significance for understanding the explosion mechanism of aluminum-air dust/air cloud.