四螺杆挤出机中聚合物流动特性的计算机模拟

Computer Simulation of Polymer Melt Flow in the Metering Region of a Four-Screw Extruder

利用计算流体力学法(CFD),对聚合物熔体在四螺杆挤出机螺纹元件中的流动规律进行了数值模拟。利用计算所得的速度场和压力场,计算了四螺杆挤出特性,并和双螺杆、一字型排列和三角形排列的三螺杆挤出机进行了对比分析。结果表明,四螺杆的四个啮合区具有较大的压力和速度梯度,在中心区有明显的环流现象,延长了物料的停留时间分布,且中心区物料没有滞留现象。由于中心区的存在导致了四螺杆挤出机的建压能力较弱;但四螺杆挤出机在产量、分布性混合和分散性混合等方面好于双螺杆和三螺杆挤出机。

The flow patterns of polymer melt in new-style four-screw extruder were studied by using Computational Fluid Dynamics method. The pressure and velocity fields in the metering region of a corotating intermeshing four-screw extruder were calculated and a special study in the central area of the flow channel was employed. The extrusion characteristics of four-screw extruder, such as pumping capability, distributive mixing, dispersive mixing and productivity ratio, were calculated and compared with twin screw extruder, ‘ - ＇arrayed tri-screw extruder and triangle arrayed tri-screw extruder. The results show that the pressure and velocity gradient of the material in the four intermeshing regions is larger than that in barrel channel. Circumfluence can be observed in central region of fourscrew extruder but there is no stagnation of material in it. On the contrary, the circumfluence prolongs the residence time distribution in the central area and reduces the ability of building up pressure for four-screw extruder. By comparison, the mixing efficiency and pumping capability of four-screw extruder are better than those of twin screw and tri-screw extruder.