Promote cohesive solid flow in a screw feeder with new screw designs

Abstract

Screw feeders are widely used in industries to transfer granular materials at relatively precise rates. Often, granular materials can have a certain level of cohesiveness which can significantly affect the transport among other factors. The critical mechanism that can stop granular flow is the formation of bridge or arching. In this work, novel screw designs are proposed to promote cohesive solid flows in a screw feeder. First, through a numerical model based on the discrete element method, it is demonstrated that the new designs are effective. Then, the underlying mechanism is analyzed both macroscopically in terms of particle flow pattern, velocity field and the motion of screw and microscopically in terms of temporal and spatial variations of contact force between particles. It is revealed that the new screw designs can induce a bulk perturbation to the granular material in the bin in addition to the existing local perturbation by the screw blade. Thus, the formation of bridge can be deterred, and the cohesive solid flow is promoted. It is suggested that such designs could also be effective to non-cohesive granular materials. Further study should be conducted to optimize the designs.