Abstract:

Based on the discrete element method， the solid conveying behaviors of a three?screw and a twin?screw extru?der were simulated respectively， and the particle movement trajectory， velocity distribution， and force distribution of the three?screw extruder were analyzed. The particles， filling efficiency， conveying quality and mass flow rates of the three?screw and twin?screw extruder were investigated comparatively. The results indicated that the particles located near the screw edge and barrel were greatly affected by the screw edge thrust and friction force of the barrel along with a higher speed. The filling sequence of particles in each area of the extruder was influenced by the direction of the screw rotation. The particles located in the meshing zone were affected by the spiral edge of the other side of the screw， which reduced the tendency of relative sliding between the particles and therefore improved the conveying capacity of the particles. There are more meshing areas on the three?screw extruder， so its filling efficiency is higher than that of the twin?screw extruder. As the rotation speed increases， the mass flow rates of the two extruders were improved significantly. Meanwhile， the mass flow rate of the three?screw extruder is about 25 % higher than that of the twin?screw extruder.

Key words: three?screw extruder, solid conveying section, filling efficiency, conveying quality, mass flow rate