Fine particles play a significant role in many industrial processes.To study the dynamic behavior of fine particle and their deposition in rock fractures,the pneumatic conveying of fine particles(approximately100 μm in diameter) through a small-scale horizontal slit(0.41 m × 0.025 m) was studied,which is useful for the sealing technology of underground gas drainage in coal mining production.The CFD-DEM method was adopted to model the gas-particle two-phase flow;the gas phase was treated as a continuum and modeled using computational fluid dynamics(CFD),particle motion and collisions were simulated using the DEM code.Then,the bulk movement of fine particles through a small-scale horizontal slit was explored numerically,and the flow patterns were further investigated by visual inspection.The simulation results indicated that stratified flow or dune flow can be observed at low gas velocities.For intermediate gas velocities,the flow patterns showed pulsation phenomena,and dune flow reappeared in the tail section.Moreover,periodic flow regimes with alternating thick and sparse stream structures were observed at a high gas velocity.The simulation results of the bulk movement of fine particles were in good agreement with the experimental findings,which were obtained by video-imaging experiments.Furthermore,the calculated pressure drop versus gas velocity profile was investigated and compared with relative experimental findings,and the results showed good agreement.Furthermore,the particle velocity vectors and voidage distribution were numerically simulated.Selected stimulation results are presented and provide a reference for the further study of fine particles.
The estimation of the blockage boundary for pneumatic conveying through a slit is of significant importance.In this paper,we investigate the characteristics for blockage of powder(48 μm average diameter)through a horizontal slit(1.6 m × 0.05 m × 0.002 m).The results show that the required critical solid mass flow rate increases as the superficial air velocity increases superficial air velocity.The solid loading ratio and superficial air velocity displayed a decreasing power law relationship.This finding agrees with existing theory and experimental results.However,a minimum inlet solid loading ratio exists.When the air velocity is greater than the corresponding air velocity of the minimum solid loading ratio,the solid loading ratio exhibits an increasing trend in power law.We also found that when the inlet conveying pressure increased,the critical solid mass flow rate required for blockage,the inlet solid loading ratio,and the minimum inlet solid loading ratio increased.
