292 / 2018-05-01 21:18:35

CFD simulation and experimental validation on turbulent flow and dispersion process of coal dust in a Siwek 20-L chamber

Computational fluid dynamics, Dust cloud uniformity, Dust dispersion process, Turbulent flow, Turbulence intensity

矿山职业健康与环境安全 > 防尘毒

Dust dispersion behavior plays a vital role in dust explosion hazard. In this work, to characterize the turbulent flow characteristics and dispersion process of combustible dust cloud inside a closed space, CFD simulations and experimetal validation were employed to reveal the dynamics of a transient gas–solid flow in a Siwek 20-L chamber. To achieve this purpose, a 3D CFD model on Siwek 20-L chamber was constructed and employed to simulate the turbulent flow field induced by dust feeding and dispersion as well as the associated effects on the distribution of dust concentration using Euler–Lagrange approach. Besids, a transparent Siwek 20-L chamber system was established ro realize the visualization of dispersion processes of typical carbonaceous dust and qualitative analysis with the image processing technique. Results evidenced the three consecutive stages of dust dispersion process: the fast injection stage of dust particles, the stabilization stage and the sedimentation stage of dust cloud. The motion of dust particles and the variations of dust cloud in space and time can be clearly distinguished. In the stabilization stage, the good uniformity of dust dispersion is achieved when the deviation of transmission data at different locations reaches to the minimum value. Under different nominal dust concentrations, the time periods for dust dispersion stabilization are found to be significantly different, suggesting that different dust concentrations should correspond to different ignition delay in order to accurately measure the explosion characteristics in the Siwek 20-L chamber. Moreover, it is found that the decrease trend of transmission with increasing nominal dust concentration will become gradually leveling off, different from the inversely proportional relationship according to the Bouguer's law, and this indicates that the actual dust concentration will be lower than the nominal concentration or the dust cannot be fully dispersed at the case of high dust concentration. According to the experiment, when the nominal dust concentration exceeds to 1000 g/m3, the transmission will no longer vary visibly.