Study On The Mixing Characteristics Of A Variable-gap Six-row Rotor Internal Mixer

Internal mixers are widely used in the mixing and processing of polymers and occupy an important position in the rubber industry.The mixing process mainly includes distributed mixing and dispersive mixing.The rotor,as a key component inside the internal mixer,determines the final effect of the two mixing.The rationality of the rotor configuration determines the production capacity of the equipment and the quality of the product.Therefore,it is necessary to optimize the design of the internal mixer rotor to make the mixing effect better.This paper uses a variable-gap 6WI rotor internal mixer as the calculation model.The rotor gaps are 1mm,2mm,and 3mm respectively.During the mixing process,attention should be paid to the effect of the change of the rotor gap on the mixing performance.By establishing the three-dimensional model of the polymer flow field and the finite element model of the rotor,the finite element method is used to clarify the internal mixing mechanism of the internal mixer from multiple angles.Under the conditions of isothermal,fully filled,non-Newtonian fluid calculation,the influence of different length and short edge ratios,different speeds,and rotor structure dimensions on the mixing effect is explored.First,analyze the influence of the ratio of length to short edge of the variable gap 6WI rotor on the mixing effect.The initial phase angles of the rotors are the same.The comparison and analysis of the rotors with different cross-sections and the ratio of length to short at different moments are 3:1 and 2:1 respectively.Including average velocity field,pressure field,shear rate field and mixing exponential field,etc.,and get the fluid flow law between them.The speed vector diagram compares the complex flow state of the same rotor and the opposite rotor in the central area of the flow field of the mixing chamber.The results show that the average velocity field and mixing index field of the rotor with the ratio of length to short edge of 3:1 are higher than that of the rotor with ratio of length to short edge of 2:1,and its feed capacity is stronger,and the axial distribution ability is better than that of the 2:1 type;And the long-short-edge ratio of 2:1 rotor in the pressure field,shear rate field is higher than the long-short-edge ratio of 3:1 rotor,the pressure resistance requirements of the internal mixer equipment is higher.Secondly,analyze the variable gap 6WI length and short edge ratio of3:1,2:1 and 1.15:1 rotors,and compare the mixing characteristics of the three rotors with long and short edge ratios.Use particle tracing technology to visualize the particles released from different locations.By obtaining mixing parameters such as particle stretch index,instantaneous and time average mixing efficiency,separation scale and residence time,the mixing characteristics of the three rotors were compared.The results show that the mixing parameters of most particles of the rotor with a length ratio of 3:1are better and the mixing effect is stronger,but the particle residence time of the 2:1 rotor is longer.Finally,the influence of the increase of the variable-clearance rotor speed on the mixing performance of the flow field is analyzed.The three speeds are 10 rpm,20rpm,and 30 rpm respectively,and the changes of the rotor speed on the changes of the parameters of the flow field and the structure field are analyzed.The results show that as the rotor speed increases,the mixing efficiency and maximum shear stress increase correspondingly,but the separation scale decreases and the residence time of the particles decreases.