Numerical Simulation Of The Mixing Performance Of Polymer Melts In Spiral And Ball Socket Mixers

Before functional fibers are processed for melt spinning,functional substances need to be added to the polymer melt to give the fiber products better functional properties to meet the demand for functional textiles in daily life.However,since the particles tend to agglomerate during the in-line addition process,a mixer is required to improve the mixing of the particles to enhance the functional properties of the fibers.For the differences of mixers in the structure of mixing elements,this paper selects spiral and ball-and-socket mixers as the research objects,and further evaluates their mixing effects by improving the structural parameters such as the length-to-diameter ratio and the number of ball-and-socket,and calculates the mixing performance indexes of the mixers under different structures and process parameters using finite element numerical simulation methods.The results of this study can provide some reference value for the online addition process of functional particulate matter.Firstly,this paper uses POLYFLOW software to solve the flow and mixing process inside the spiral static mixer,and derives the influence mechanism of the mixing effect of the static mixer under the influence of different parameters such as length-to-diameter ratio and inlet flow.The research results show that with the increase of blade rotation angle,the pressure drop and shear rate increase significantly.From the variation law of rotation angle and mixing performance,we know that the segregation scale of 120°static mixer is reduced to 1 mm,and the parameters such as stretch length also increased to 4.The mixing performance is better than other static mixers of rotation angle.It is confirmed that the static mixer with a rotation angle of120°has a better distribution mixing and axial mixing effect.Secondly,in the actual production process due to the static mixer blade structure for the dispersion of the mixing effect is weak,so this paper uses the ball socket structure of the dynamic mixer to analyze the flow and mixing characteristics to improve the mixing effect.The results show that the mixing effect of the mixer is more obviously affected by the structural parameters,with the increase of the number of ball nests,the residence time,mixing index,and stretching length are increased,the segregation scale rapidly decreases to near 2.5 mm within 5s,and the distribution and dispersion mixing effect is significantly improved.Rotational speed and inlet flow rate of the mixer has a greater impact on the distribution of mixing,the speed increases or the inlet flow rate decreases,its residence time becomes longer,the stretch length increases exponentially,and the mixing performance of the dynamic mixer is enhanced.The values of mixing efficiency are essentially greater than zero and oscillate upward,indicating the presence of a strong orientation inside the dynamic mixer,which promotes distributed mixing.When changing several process parameters and using the mixing index as the main objective of evaluation,the significance ranking of the process parameters is:number of radial spheres>clearance>rotational speed>inlet flow rate>number of axial spheres,and the optimal solution is:number of axial spheres 6,number of radial spheres 6,clearance 7 mm,rotational speed 60 rpm,and inlet flow rate 2×10^-6 m³/s.This solution increases the size of the mixing index while guaranteeing the distribution and dispersion mixing effect,thus allowing a better dispersion of the functional particles inside the ball socket type dynamic mixer in the polymer melt,thus effectively compensating for the weak dispersion effect of the static mixer.