Modeling Fully Intermeshing Co-Rotating Twin-Screw Extruder Kneading-Blocks: Part A. Conveying Characteristics
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SPE ANTEC 2021 Proceedings
Twin-screw extrusion modeling is in most cases based on analytical approaches that are build on considerable geometric simplifications. These approaches give only rough estimations of the processing behavior. More accurate predictions generally require numerical methods with less drastic simplifications. In this work, we analyzed the pressure-throughput behavior in fully-intermeshing double-flighted kneading blocks. First, we conducted a dimensional analysis based on the Buckingham ?-theorem. Second, for each staggering angle, we determined the characteristic angular position that describes the mean throughput. Based on this position, a parametric design study was carried out by varying the identified dimensionless parameters. To solve the complex flow patterns, 3D CFD simulations were conducted. For each design point we evaluated the dimensionless drag flow-rate and the dimensionless dam-up pressure. As an addition to the two established dimensionless conveying parameters A1 and A2, we propose a novel conveying parameter A3. This new parameter simultaneously enables the description of conveying and non-conveying kneading discs. Our results offer considerably deeper insight into the conveying characteristics of kneading blocks. In addition, they can serve as foundation for screw design and process modeling. For a better understanding of the process, we additionally investigated the power consumption and viscous dissipation in Part B of this publication.