Investigation of discharge characteristics of rod-shaped particles in a hopper: Experimental and numerical studies using polygonal/polyhedral DEM

Abstract

In this work, the discharge of numerous polygonal particles in a hopper was investigated numerically and experimentally. To this end, a polygonal/polyhedral DEM model is proposed and implemented to simulate hopper operation in 2D and 3D. The results of a conservation test show that the proposed algorithm conserves energy better than the CP algorithm owing to its straightforward contact calculation. The model then is adopted to simulate the discharge of rod-shaped particles in hopper. Lab-scale experiments were also conducted for DEM model validation. To evaluate the influence of particle shape, outlet opening, and discharge slope angle, rod-shaped particles with triangular, square, pentagonal, and hexagonal cross-sections were used in the experiments and simulation. The results show that the discharge rate of non-spherical particles was significantly affected by the shape of particles, and inter-particle packing property was found to have stronger influence than rolling-related properties, such as roundness or moment of inertia. Conditional clogging phenomena of particles were observed, and the tendency of particle clogging was enhanced by high initial loading, narrow outlet opening, and low slope angle of the hopper outlet. The criteria conditions of particle clogging from experiments were satisfactorily reproduced in the simulation. Although the discharge rate increased with increasing initial loading, the discharge rate saturated at over M = 30 kg owing to the so called Janssen’s effect. The discharge corresponding to the change in particle shape and initial loading was in good agreement between the simulation and experimental results. The comparison of 2D/3D simulation shows that the experiments and simulations successfully minimized the 3D effect.