Flow Patterns and Mixing Mechanisms in the Screw Mixing Element of a Co-Rotating Twin-Screw Extruder

摘要

Non-Newtonian and non-isothermal flow simulations based on 3-D FEM were appiled to a special and conventional elements of a twin-screw extruder. The screw mixing element (SEM), a kind of special element, was a distributive mixing promoter consisting of a standard screw profile with slots cut across the flight tip to increase leakage flow. The full flight screw (FF) and the kneading block (KB) were examined as conventional elements in order to contrast the mixing behavior with the SEM. The accuracy of numerical reuslts was verified by expeimentally measuring pressure and temperature. Additionally, marker particle mixing. Using the above analyses, the following results were obtained: The pumping capability of the SME was smaller than that of the FF and was the same as for the KB. The SME suppressed heat generation and showed the lowest temperature distribution of the three elements. For distributive mixing, the SME showed the best performance judging from the mixing coefficient G, residence time distribution, and area stretch distribution based on a laminar mixing performance. For dispersive mixing defined by stress distribution, the SME showed the second best performance next to the KB. It also showed better dispersive mixing performance with increasing rotational speed. The SME had the advantages of low heat generation and good distributive mixing.