啮合同向双螺杆挤出机中组合螺杆性能的数值研究(Ⅰ)瞬态流场分析

Numerical Investigation of Screw Assemblies Performance in Intermeshing Co-rotating Twin-Screw Extruders(Ⅰ) Instantaneous Flow Analysis

采用聚合物流动分析软件POLYFLOW,数值模拟了聚合物熔体在组合式啮合同向双螺杆挤出机ZSK60的组合螺杆中的三维等温流动。在计算所得速度场和压力场的基础上,全面分析并讨论了由不同厚度和不同错列角的捏合块元件组成的组合螺杆的流场分布规律;研究了组合螺杆的输送性能和挤出稳定性;并分别采用平均剪切速率、平均特征剪切应力以及平均拉伸流动指数等瞬态混合指数表征了组合螺杆的瞬态混合特性。此外还考察了两种不同流变性质的聚合物熔体在组合螺杆中的瞬态流场分布规律。所得结论可为双螺杆挤出的数值模拟研究提供一定的方法指导,并为其工程实践提供一定的理论指导。

Three-dimensional isothermal flows of polymer melt in the screw assemblies of a modular intermeshing co-rotating twin-screw extruder ZSK60 were simulated using the polymer flow analysis package POLYFLOW. Based on the velocity and pressure fields calculated, general distribution characteristics of the flow field in screw assemblies (composed of kneading blocks with different disc-widths and stagger angles) were presented; pumping capacity and extrusion stability of the screw assemblies were discussed; and instantaneous mixing capabilities were characterized in terms of average shear rate, average characteristic shear stress and average elongational flow index respectively. The conclusions could offer some methodological guidance for numerical studies of flow in twin-screw extruders, and could also be used as theoretical guidelines for engineering practices in twin-screw extrusion.