Dispersion of stratified dust layers by a moving shock wave

Abstract

Simulations of a shock passing over stratified dust layers containing two different types of particles were conducted to explore the effect of particle size and dust layer thickness on particle dispersion with application to coal mine explosion conditions. The simulations solve the Euler equations of fluid dynamics and granular flow, and accounts for different particle types using a binning approach. Test cases with a 2.7-mm layer consisting of particles with a smaller diameter (ds,2=10, 20, and 40 µm) placed on top of a 10-mm layer consisting particles with a larger diameter (ds,1=80 µm) were performed to study the effect of particle size on dust dispersion. The results indicate that larger particles from the lower layer can be lifted higher than the smaller particles from the upper layer if the two types of particles have a large size difference. In addition, dust dispersion of a shock passing over a rock-dust layer on top of a coal-dust layer were also investigated. Here the coal dust has a diameter of 30 µm and a density of 1330 kg/m3, and the rock dust has a diameter of 15 µm and a density of 2680 kg/m3. The rock-layer thickness of 1, 2, and 3 mm were considered, and the coal-dust layer underneath had a thickness of 4 mm. The results suggest that the rock particles work more effectively on suppressing the coal dust from lifting with increasing rock-layer thickness. Placing another layer of coal dust on top of the rock-coal layer shows that the rock dust underneath fails to suppress the coal particles above from being lifted, and this suggests the need to simultaneously or regularly apply rock dust during the mining operation.