Abstract: The new concept of dissymmetry modeling of cross-section geometries for fully wiped co-rotating screws was proposed.The corresponding mathematical model was established with the fluid concerned obeying the Carreau flow model.Based on the mesh superposition technique，the two-dimensional periodical flow and mixing in co-rotating screws with two kinds of cross-section geometries were simulated with finite element package Polyflow.The distributive mixing was investigated in terms of particle tracking visualization combined with segregation scales.In contrast，the dispersive mixing was characterized by the mixing index together with the shear rate distribution in the flow field.When the sum of rotations of the left screw and the right screw was kept as constant，the group with speed ratio 2∶3 was better in the ability of mixing than the group with speed ratio 2∶1.

Key words: co-rotating non-twin screws, mixing, mixing index, segregation scale

摘要： 提出了同向自洁型双螺杆挤出机端面非对称造型的新概念。以符合Carreau定律的纯黏性流体为加工对象，建立相应的数学模型。采用Polyflow软件，基于叠加网格技术，对两种螺杆造型端面内的周期性流动和混合情况进行数值模拟。将粒子示踪技术及分离尺度相结合，研究了流场内分布混合能力；将分散准数与剪切速率相结合，表征了流场的分散混合能力。当两组螺杆单位时间转过的总圈数一致时，螺杆转速比为2∶3的组合混合能力稍优于转速比为2∶1的组合。

关键词: 非对称同向双螺杆, 混合, 分散准数, 分离尺度