Numerical modelling of suction filling using DEM/CFD

Suction filling is widely employed in powder compaction processes in pharmaceutical, ceramics and powder metallurgy industries, especially for cohesive powders. However, scientific understanding of suction filling is still very much in its infancy. In this study, the fundamental mechanisms of suction filling (in the presence of air) are explored using a coupled Discrete Element Method and Computational Fluid Dynamics (DEM/CFD). The effect of suction on powder flow behaviour is examined by comparing suction filling with gravity filling. It is shown that the numerical simulations can well reproduce the experimental observations obtained by Jackson et al. (2007). Moreover, from the numerical simulations, detailed information on powder flow behaviour during suction filling, such as air pressure distribution and powder flow rate, which is difficult to be obtained in the physical experiments, is easily accessible, providing deep insights to enhance our understanding of suction filling processes. According to the simulation results, It is found that the downward motion of the punch in suction filling creates a pressure gradient across the powder bed, which augments the flow of powder into a die. As a result, the mass flow rate and critical shoe velocity are significantly increased, implying that suction filling can be employed to improve the process efficiency of die filling. (C) 2012 Elsevier Ltd. All rights reserved.