Particle Simulation for the Conveying Behavior of Granules in Grooved Bushing Extruders

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The goal of the proposed research project is to reformulate the mathematical description of the conveying behavior in grooved bushing zones based on numerical simulations. This enables the possibility to detect the complex movements of the granules in the feed section in a 3D environment and thus improves the calculation accuracy. In previous research projects, it was shown that both, the conveying mechanisms and the energetic process behavior in the solids conveying area, can be well represented using the Discrete Element Method. Therefore, this method provides the basis for this application. In the simulations, process and material parameters are varied with the aid of a centrally composed design as well as geometrical parameters in the screw channel and grooves. Also axially or spiral machined grooves are taken into account by varying the groove angle. Next to verification studies supported by numerical simulations, a detection of physical boundaries will be performed. Thus, in the case of simulations with a smooth bushing zone, it can be seen that, despite a particle backlog, caused by the backpressure, the first screw flights can be partially filled. This leads to a displaced pressure profile, so that the pressure does not increase anymore over the entire feed section. Analogies are expected at sufficiently high rotational speeds on grooved systems. This also requires a new formulation of existing calculation models. The results obtained, will finally be systematically validated. Here, a test stand has been developed which will be adjusted to the desired grooved bushing system. With an existing validation, an extensive description of the conveying processes in grooved bushing zones is possible.