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

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 co-rotating 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 four-screw 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.