Three-dimensional simulation of a single-screw extruder’s grooved feed section

Since the introduction of a grooved cylinder, the single screw extruder's feed section is a multifunctional zone. Currently, the mathematical approaches for the prediction of the pressure development and the output-performance are not sufficient. Most existing models consider the synthetic granules as a homogeneous compact mass with a bulk density, which is assumed to be known. Furthermore, these models do not provide a detailed insight into the transport processes and therefore complicate a systematic optimization. For these reasons, the feed section in this work will be simulated applying the discrete element method (DEM) with use of the open source software LIGGGHTS®. The DEM allows a three-dimensional treatment of the feed section and considers each single particle. Overall this work is focusing on two cases. In case of a conventional extruder with an open discharge, which conveys the plastic particles without melting them, the measured mass flows are reproduced exactly. Under real operating conditions of a grooved single screw extruder, the current modelling approaches are insufficient and the deviations from measurements are between 20 % and 40 %. In further steps LIGGGHTS® will be coupled with the computational fluid dynamics package OpenFOAM® in order to include the melting zone into the simulation approach.