双螺杆挤出机模具过渡和稳流段流场的数值模拟

Simulation of flow field in die transition and steady-flow zone of twin screw extruder

采用Carreau模型描述熔体的黏度特征,使用POLYFLOW软件数值模拟了异向旋转双螺杆挤出机模具过渡和稳流段的三维等温流场。在不同的工艺参数下,分析比较了模具过渡和稳流段内的速度场、压强场、剪切速率场、剪切应力场以及黏度场。结果表明在模具过渡和稳流段内,螺杆的旋转是该聚合物熔体流变性能的最大影响因素,螺杆头对高黏度熔体的影响范围不大,只限于螺杆头的周围；进入稳流段后,在稳流段作用下熔体的流动逐渐变得稳定均匀；在本文讨论的转速和流量范围内,转速和流量的增加,分别会在不同的区域使熔体受到的剪切速率和剪切应力明显地增大。研究结果为某企业设计双螺杆模具和优化工艺条件提供理论依据。

Three-dimensional isothermal flow field of die transition and steady-flow zone of twin screw extruder are simulated by Carreau model and using POLYFLOW software. The fields of velocity, pressure, shear rate, shear stress and viscosity with different technical parameters are analyzed and described in this paper. Results show that rotation of screws play the most important role of melting polymer rheological property in the die transition and steady-flow zone. The influence area of screw heads just limits to the ambient of screw heads. Melting Polymer entry into the steady-flow zone and gradually becomes stable and uniform. In the range of rotary speed and flux discussed in this paper, with the augmentation of rotary speed and flux, shear rate and shear stress obtained by melting polymer increase in a great extent respectively in different zones. These researches have proved the mechanism theory of design die and optimization of technical parameters.