Effects of Screw Clearance and Blend Ratio on The Flow and Mixing Characteristics of Tri-Screw Extruders In Cross Section With CFD

Abstract

A triangularly-arranged tri-screw extruder (TATSE) is a new piece of equipment for polymer processing, which has a dynamic center region. To learn about the special contributions of the dynamic center region and the circumfluence phenomenon just in cross section on the mixing mechanism of the TATSE, the 2D computational fluid dynamics (CFD) model was established to reduce the axial effect. The effects of screw clearances of the center region on mixing mechanism of the TATSE were studied. The mixing evaluations for the TATSE and twin-screw extruder (TSE) with different screw clearances were performed and compared. Moreover, the effects of different blend mass ratios of LLDPE and SBS on the mixing efficiency of the TATSE were studied. The results show that as screw clearances increase, the values of mean time-averaged and instantaneous efficiencies of the tri-screw extruder increase, but the normalized segregation scale decreases. The screw clearances even change the particle conditions from stretch to compression in the center region.