Modelling of Screw Feeder Performance

Executive Summary

detailed flow, and motivate further refinement in our modelling efforts.

experimental screw feeder assembly to test our model predictions, provide insight into the

constitutive model for the stress that accounts for dilatancy. We have recently built an

request of several IFPRI members at the GBM. For this, we are implementing a non-local

fluctuations in the inlet flow or spontaneous fluctuations within the screw – this was the

Our ongoing work is to model dynamical changes in the feed rate, due to

of gravity and friction at the screw surface.

volumetric discharge rate on the geometry of the feeder is not altered by the introduction

value of p/d at which the feed rate is maximum. Thus, the qualitative dependence of the

find that the discharge rate exhibits the same qualitative trend, in that there is an optimum

conditions of no friction at the screw surface and no gravity, employed in the model. We

frictionless screw in the absence of gravity. We then assess the effect of relaxing the

model to be in excellent agreement with the results of the DEM simulations for a

motion, in agreement with the assumption of the model. We find the prediction of the

simulations show that a significant fraction of the material does indeed exhibit solid body

by particle dynamics simulations using the discrete element method (DEM). Our

We then studied the detailed flow within the screw feeder for non-cohesive particles

yields a non-trivial result that could be useful in the design of screw feeders.

to a specific value. Thus, despite the assumptions that simplify the analysis, the model

discharge can be maximized by setting the ratio of the screw pitch p to barrel diameter d

the discharge rate for a given angular velocity and screw geometry. We show that the

and barrel, and neglecting the effects of gravity and friction on the screw surface, we obtain

that the granular medium moves as a rigid body that slips along the surfaces of the screw

and angular momentum on a suitably chosen continuum element. With the assumptions

We first constructed a mechanics-based model by enforcing the balances of linear

flow in a twin-screw feeder.

we have studied powder flow in a single-screw feeder, as the first step towards modelling

model. Such a model would assist in optimal design of screw feeders. In this investigation,

particulate materials, there has been no attempt to derive a detailed, mechanics-based

Despite the widespread use of screw feeders in industry for the transport of