Fluid-structure Interaction Calculation And Experimental Verification Of Eccentric Rotor Extruder

The eccentric rotor extruder is a type of polymer material plasticizing and transporting equipment based on the principle of tensile rheology,realizing the melt plasticizing and transportation with the normal stress as the main role.In view of its unique spatial topology and complex motion law,the flow field and structural force field of the eccentric rotor extruder can be studied by numerical simulation based on unidirectional fluid-structure interaction method,which can intuitively display the flow characteristics of polymer melt and the law of stress and deformation of the rotor.It has important reference value for the selection of process conditions and structural optimization of the eccentric rotor extruder.In this paper,the basic structure,transport mechanism and rotor motion law of eccentric rotor extruder were briefly introduced firstly,and reasonable assumptions were made for the complexity of melt flow.On this basis,a numerical model of melt flow field was constructed.The transient simulation of flow field of eccentric rotor extruder was realized by the fluid dynamics software FLUENT and dynamic mesh technology,and the distribution characteristics of melt pressure and velocity were analyzed in detail.Based on the simulation results of flow field,the stress and deformation of eccentric rotor were calculated by the structural analysis module Static Structure and the effect of different speed,clearance between stator and rotor,eccentricity and rotor radius on flow field distribution and structural deformation were studied.Finally,under the same conditions,the experimental and simulated melt pressures were compared,and the melt pressure changes at different positions of the flow field are consistent,which verifies the reliability of the numerical simulation results.The results show that the distribution of flow field is basically the same at different times in a rotor motion cycle.Along the extrusion direction,the melt pressure increases first and then decreases.The closed cavity presents the alternate distribution of high-pressure cavity and low-pressure cavity,and the pressure extreme area appears on the spiral surface of the stator and rotor that is biased toward the shaft.The flow direction of the melt in the stator cavity is consistent with the direction of revolution,while the melt on the spiral surface of the rotor rotates with the rotor under the action of drag.When the rotor is in the middle of the stator cavity,the equivalent stress and total deformation of the rotor are the largest.On the helical surface of the rotor,the equivalent stress is mainly distributed at the rotor part located in diffusion area of the closed cavity,while the total deformation is mainly distributed at the rotor part located in the meshing area of the closed cavity.Under certain operating conditions,the melt pressure load of flow field is the main factor affecting the rotor stress and deformation.Through the analysis of the flow field and rotor stress and deformation field under different process conditions and structural parameters,it is found that the change of different variables has basically no effect on the distribution of the flow field and the rotor force field,and the research components only change in value.The melt pressure and flow velocity of the flow field will increase with the increase of rotating speed,eccentricity and radius of rotor,while increasing the clearance of stator and rotor will reduce the melt pressure and flow velocity;the increase of rotor speed will also increase the equivalent stress and total deformation of eccentric rotor,but the growth rate gradually slows down,while increasing the meshing clearance,eccentricity and rotor radius will reduce the total deformation of the eccentric rotor,and the reduction amplitude gradually tends to be gentle,in which the change of the rotor radius has a greater influence on the total deformation of the rotor.