Study on fluid mixing characteristics of parallel differential three⁃screw extruder

doi:10.19491/j.issn.1001-9278.2025.05.016

Abstract

Abstract:

In this paper， a parallel differential tri⁃screw extruder with a speed ratio of 1/5/5 was designed. This tri⁃screw extruder has a geometric structure and asymmetry of rotational speed. To explore the unique flow field characteristics， the designed tri⁃screw extruder was compared with the parallel differential tri⁃screw extruder with a speed ratio of 1/1/5 and the differential twin⁃screw extruder with a speed ratio of 1/5. The results indicated that， compared to the traditional extruders， the parallel differential tri⁃screw extruder exhibited a unique complex particle trajectory along with the appearance of a phenomenon of "secondary flow" shown by a circumferential velocity field in the meshing zone appears due to the particularity of the structure and the different speeds. This makes the material in the runner reciprocate together with an increase in the residence time of the material in the runner. These results were conducive to the mixing of materials. When calculating the mixing performance parameters of three sets of parallel differential screw extruders， the parallel differential tri⁃screw extruder with a speed ratio of 1/5/5 were found to have better mixing performance.

Key words: parallel differential tri?screw, fluid mixing characteristics, dispersion mixing, distribution mixing

CLC Number:

TQ320.64

QIN Xiaoyu, ZHU Xiangzhe, CHEN Bohan, WANG Yuyu. Study on fluid mixing characteristics of parallel differential three⁃screw extruder[J]. China Plastics, 2025, 39(5): 101-106.

Figures/Tables 16

Fig.1. Differential screw end profile

Fig.2. Geometry models

五头螺杆的导程/

单头螺杆的导程/

五头螺杆的转速/

r·min^-1

单头螺杆的转速/

r·min^-1

Tab.1. Geometric dimensions

Fig.3. Screw and runner meshing

Fig.4. Vector diagrams of X⁃Y section velocity at Z=50 mm on the Z axis

Fig.5. X⁃Y cross⁃section velocity contour at Z=50 mm on the Z axis

Fig.6. X⁃Z cross⁃section velocity contour at Y=0 on the Y axis

Fig.7. Pressure distribution in the meshing zone along axial direction

Fig.8. X⁃Y cross⁃section pressure contour at Z=50 mm on the Z axis

Fig.9. Particle motion trajectory （Extrusion direction along the positive Z axis）

Fig.10. Cumulative residence time distribution

Fig.11. Residence time probability density distribution

Fig.12. Separation scale curves

Fig.13. Mixed index distribution of X⁃Y sections at Z=50 mm on the Z axis

Fig.14. Probability density function of maximum shear stress

Fig.15. Logarithmic elongation

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