Numerical Simulation Of Mixing Characteristics And Energy Consumption In Vane Extruder

The polymer vane extruder is a novel equipment for polymer extrusion molding. Itsplasticating and conveying theory is based on elongational rheology. As a result of itsunique structure and theory of plasticating and conveying，numerical simulation can be adetailed and efficient method to study the processing performance in a polymer vaneextruder.In this study, finite element CFD analysis software POLYFLOW was used to performthe numerical simulation of polymer melt flow characteristics in a vane unit. With theresults of numerical simulation，the torques acted on vanes and rotor in a vane unit werecalculated and the power of rotation in the vane unit was calculated with the relationshipformula between power and torque. Numerical simulation of the mixing characteristics ofthe vane unit was performed based on the polymer melt flow characteristics with a particletracking method applied. By using the statistical post-processor program POLYSTAT,dispersive mixing and distributive mixing characteristics were evaluated. By modifiedrelated parameters in numerical simulation model, the effects of vanes arrangement,rotational speed and eccentricity between rotor and stator on torque, power and mixingcharacteristics of the vane unit was studied.The results show that for different vanes arrangement, the vane unit with four vanesdistributed uniformly has the lowest energy consumption. With the increasing of rotationalspeed, the energy consumption in a rotation period decreased and the mount of decreasingdecreased, and the same as maximum torque and average torque acted on vanes. With theincreasing of eccentricity, the average rotational power increased, and the mount ofincreasing increased, and the same as maximum torque and average torque.In terms of vanes arrangement, the vane unit with four vanes distributed uniformly hasthe best mixing characteristics. For different rotational speed, there is a relatively balancebetween maximum tensile rate and residence time. The best mixing performance appearswhen the rotational speed is60rpm. With the increase of eccentricity, the experiencedmaximum shear rate and tensile rate increased, and the mount of increasing increased. Thissuggests that the mixing performance of vane unit is increasingly significant with eccentricity.With different vanes arrangement, rotational speed and eccentricity, themaximum experienced mixing index varied little. It suggests that the characteristics of flowfield or the proportion of shear flow and elongational flow have little to do with the aboveparameters. The numerical simulation results on mixing characteristics with differentrotational speed were compared with the experimental results and there is a good qualitativeagreement between experiments and simulations, which explained the responsibility ofnumerical simulation results. The results of the study can be used for the optimizationdesign of structure and processing parameters.