Extrusion Characteristic's Analysis of Multiple-Screw Reactors Based on CFD

The flow of melt polyethylene in double-screw extruder,—-shaped tri-screw extruder,triangular tri-screw extruder and four-screw extruder was analyzed by means of ANSYS/FLOTRAN.The special study focused on the central area of reactor's flow path of triangular tri-screw extruder and four-screw extruder. Extrusion characteristic of four types of reactors was compared.The results show that a large velocity gradient emerges in the intermeshing region of the screw reactors,which is helpful to mix materials sufficiently.The four reactors have different numbers of intermeshing regions.Double-screw reactor,—-shaped tri-screw extruder,triangular tri-screw extruder and four-screw extruder have one,two,three,and four intermeshing regions respectively.With the increase of the number of intermeshing regions,the mixing ability of materials is enhanced gradually.Triangular tri-screw extruder and four-screw extruder have special structure,that is,central region.Materials in the central region form circumfluence,which promotes the mixing effect and prolongs the mixing time of materials in the central region.Through calculation,the materials cannot be hold up in the central area.For double-screw extruder,—-shaped tri-screw extruder, triangular tri-screw extruder and four-screw extruder,flow rate,back flow rate,coefficient of back flow rate and average rate of shear are incremental gradually.It is verified in theory that the multiple-screw extruders have good material transportation and mixed ability.Multiple-screw extruder is fitter for polymer processing.