Numerical Simulations of Flow and Mixing in a Baffled Single Screw Extruder
A baffled single screw structure was designed,and the geometric model of melt conveying zone was established.Based on the finite element method along with mesh superimposition technique(MST),the numerical simulations of three-dimensional flow and mixing in the extrusion process were carried out by using Bird-Carreau constitutive model of the purely viscous non-Newtonian fluid.The velocity distributions under the two conditions of static barrel and forward rotary screw,static screw and reversely rotary barrel were compared.The results show that the velocity distributions under the above assumptions are the same,proving that the flow characteristics are independent of the reference coordinate systems.Compared with the ordinary single screw,the axial velocity of the novel baffled single screw changes greatly along the axial direction.The extrusion characteristics of the two configurations are similar.Under the same pressure gradient,the output of the baffled single screw is reduced by 20%.Under the conditions of the same output and the same screw speed,for the baffled single screw,the mixing index increases and the segregation scale decreases.These results indicate that the baffled single screw further improves the distributive and dispersive mixing ability of melt conveying zone.
Baffled Single ScrewNumerical SimulationSegregation ScaleMixing IndexMixing Ability
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