滑移边界条件对同向啮合三螺杆挤出机混合性能的影响

Numeral Simulation of the Effects of Wall Slip on an Intermeshing Co-Rotating Tri-Screw Extruder in the Cross-Section

利用计算流体力学软件Polyflow,考虑了螺杆表面的剪切应力与熔融体的滑移速度满足纳维线性定律,对不同滑移系数条件下二维正三角形排列的啮合同向三螺杆挤出机的混合性能参数进行了数值模拟。对比分析了不同滑移系数条件下中心区和螺槽区的混合指数及用探针技术分析了中心点的混合指数变化。并基于流场计算进行混合运算,研究了不同滑移系数对分离尺度、对数长度拉伸、瞬时和平均时间混合效率的影响。结果表明,螺杆表面的滑移边界条件对于三螺杆挤出机的分散性和分布性混合的计算结果具有较大的影响,为了提高计算精度,应采用适当的滑移边界条件和滑移系数。

Mixing performance in an intermeshing co-rotating triangle arrayed tri-screw extruder in the cross-section was investigated under different slip coefficients using computational fluid mechanics software packaged Polyflow.The relationship between the shear stress at the screw surface and the slip velocity of the flowing melt obeys Navier’s linear law.The mixing index in the central region and screw region were studied under different slip coefficients by comparison,as well as the mixing index at the mid-point with probe technology.Mixing simulation was conducted based on the flow field.The scale of segregation,logarithm of the length stretch,instantaneous and time averaged efficiencies were studied using the statistics module Polystat.The results show that the proper smooth wall of the screw is of benefit to improving mixing performance.