| Twin screw extrusion has attracted considerable attention during the last twenty years, especially the co-rotating twin screw extruder. The complexity of the flow in twin screw systems and it is difficult to optimize the extrusion conditions. It is necessary to resort to processing simulation in twin screw extruder. We try to present a global model to describe the flow of molten polymer along the realistic industrial screw profile, including different type of elements and kneading discs. Our global model will be the cutting edge in the domestic research.The flow in screw elements is classically treated in'groove model'. We principally focus on the main flow along the screw channel. The flow path along the screws follows an eight-shaped pattern, and especially C-shaped chamber. We get the longitudinal volumetric flow rate model. This model which is not based on correcting shape factors is from continuum mechanics. The simulated results are confirmed by Ludovic software.We focus on the most common device: the bilobal kneading disc. Flow in kneading discs is generally modeled using 2D approaches, such as FAN or finite volume methods. We get the geometry model by finite volume method. We compare the simulated results with the realistic industrial kneading bloc. We make the flow model of kneading bloc based on geometry model. The simulated results are similar to realistic extruder results.The global model of co-rotating twin screw extruder is based on different screw models. The isothermal simulated results are not completely similar to Ludovic software's.We analyze the mixing function of kneading bloc and add axial disperse model to simulated the global resident time distribution. The predicted value of global RTD was improved by modifying the local model. The influence of feed rate and screw speed on the residence time between new global method and experimental are compared. The shape, minimum residence time and mean residence time of simulated RTD are close to experimental results. |
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