Numerical Simulation And Experiment Of Flow Field And Mixing Performance Of The Eccentric Rotor Extruder

The eccentric rotor extruder is a new type of polymer forming equipment based on the principle of volume fluctuation plasticizing transport.Its unique geometric topology and complex motion law can realize the plasticizing transport process dominated by volume tension deformation,and has good mixing ability.In view of the particularity of its processing principle,numerical simulation method is used to study the flow field and mixing performance of eccentric rotor extruder,which can intuitively display the mixing process of materials.It has important reference value for process optimization and structure design of eccentric rotor extruder.In this paper,the basic structure,working principle and the basis of numerical simulation of eccentric rotor extruder were briefly described firstly.The flow field of melt conveying section of eccentric rotor extruder was simulated by using computational fluid dynamics software POLYFLOW.The distribution characteristics of flow field were analyzed in detail.The volume efficiency of eccentric rotor extruder under different technological conditions and structural parameters was calculated to explore the influence of different factors on the melt conveying efficiency.Then the particle tracer method was used to simulate the mixing performance on the basis of the results of flow field simulation.POLYSTAT which is a post-processing module was used to calculate the mixing characteristic parameters.By changing the rotational speed,rotor radius,eccentricity,rotor pitch and clearance,the influence on the mixing performance of the eccentric rotor extruder is studied.Finally,the simulation results are verified by experiments.The results show that the volume efficiency and melt leakage degree of the eccentric rotor extruder do not change obviously with the increase of rotational speed,but when the radius and clearance of the rotor increase,the volume efficiency decreases and the leakage degree increases.On the contrary,when the pitch and eccentricity of the rotor increase,the volume efficiency increases and the melt leakage degree decreases.By analyzing the probability distribution function,probability density function and percentile of the mixing characteristic parameters in one rotating cycle,the mixing effect of materials in eccentric rotor extruder is better and better with the increase of volume stretching deformation time.By analyzing the variation trend of mixing characteristic parameters under different technological conditions and structural parameters,found that the residence time distribution of particles in eccentric rotor extruder is hardly affected by structural parameters,but is greatly affected by rotational speed.When the rotational speed increases,the residence time of particles decreases,but the flow field strength increases.When the rotational speed is 45r/min the mixing effect is the best,because the maximum shear rate and tensile rate of particles increase the fastest,the maximum time-average mixing efficiency and mixing index are the maximum value.When the radius and eccentricity increased,the mixing characteristic parameters at different percentiles increased gradually.Increasing the rotor radius and eccentricity was beneficial to improve the mixing performance of eccentric rotor extruder.The mixing characteristic parameters decrease when the rotor pitch and clearance increase,which indicates that the mixing performance of eccentric rotor extruder will be weakened if the rotor pitch and clearance are too large.The experimental results are in agreement with the numerical simulation conclusions by comparing the mixing performance of eccentric rotor extruder at different rotational speeds,which proves the reliability of the numerical simulation in this paper.