塑化过程螺槽中三维流场的数值模拟

采用CROSS模型表示聚氯乙烯(PVC)的黏度特征,使用POLYFLOW软件数值模拟了塑料注射成型机螺杆计量段螺槽中熔体在塑化过程的三维等温流场,求解和分析了3条参考直线、yz截面和xy截面上不同时刻螺槽中的压强场、速度场、剪切速率场和黏度场,数值计算的结果表明:在螺棱附近区域物料的剪切速率大,物料剪切稀化作用增强,物料黏度减小。并采用粒子运动轨迹示踪的方法研究了塑化过程中注塑机粒子运动轨迹。得知塑化过程中注塑机粒子运动轨迹比挤出机复杂得多,有三种典型的运动方式:一部分粒子边旋转边向负Z方向运动、另一部分粒子在旋转的同时先向负Z方向运动后向正Z方向运动,还有一部分粒子和边旋转边向正Z方向运动。

Simulations of 3-D flow in the screw channel during plastication process

Three-dimensional isothermal material flows of a cross law fluid in the channel of metering section of injection molder during plasticizing process are simulated by using POLYFLOW software.The velocity fields,pressure fields,shear rate fields and viscosity fields in the three reference lines and the yz section and the xy section at different time are respectively analyzed in details.It is shown that because the velocity gradient near the screw increased,the particles stress near the screw region increased whereas the particles viscosity decreased.The shear effect around the screw thread is strengthened.The particle trajectories in the injection molder are stud- ied too.It is shown that the moving styles of the particles in the molder are more complex than those in the extruders.There are three typical moving styles of the particles.The one of particles revolve around the screw and move backward in the axis direction,the one of particles revolve around the screw and move backward then forward in the axis direction,and the other revolve around the screw and move forward in the axis direction.