Understanding the varying discharge rates of lognormal particle size distributions from a hopper using the Discrete Element Method

摘要

The focus of this study is on understanding the varying discharge rates of lognormal particle size distributions (PSDs) with the same mean particle diameter. Discrete element method (DEM) is used to simulate lognormal PSDs with the same arithmetic mean of the particle diameter of 5 mm but varying PSD widths (sigma/mu = 10% to 70%) in a 3D conical hopper. Four highlights are noted: (i) the Beverloo correlation and others modified to account for various particle properties predict the discharge rates of lognormal PSDs poorly, which underscores the need for more understanding on the influence of PSD width; (ii) the velocity vectors are less uniformly downwards in the hopper for the wider PSDs, which results in the slowing down of the discharge rate; (iii) the radial particle velocity, and both the radial and vertical particle angular velocity increase with PSD width throughout the first half of the hopper discharge; and (iv) the collision force magnitudes are greater for the wider PSDs, and the cross-sectional fluctuations of the collision forces at the cone height increases with PSD width. The increase of the magnitudes of these particle characteristics (namely, radial particle velocity, angular velocity, and collision force) with PSD width underlies the decreasing hopper discharge rate. (C) 2018 Elsevier B.V. All rights reserved.