Abstract The mixing performance in a miniature conical counter-rotating twin-screw extruder was investigated by means of experimental technique and computational fluid dynamics (CFD) simulation. An on-line experimental device based on the fluorescence detection was built to study the residence time distribution (RTD). Polypropylene was selected as the flow material and the blend of Polypropylene and anthracene was used as the tracer. This on-line detection device has good reproducibility. The hydrodynamics in the extruder was simulated by the finite element method (FEM) combined with the mesh superposition technique (MST). The particle tracking technique was carried out to evaluate the RTD and mixing efficiency. The effect of screw speed and feed rate on the hydrodynamics and mixing performance was investigated. The velocity magnitude and local shear rate tend to become smaller from inlet to outlet due to the decreasing diameters of screws. The mean length of stretch increases exponentially from inlet to outlet and the mean value of time averaged mixing efficiency remains positive along the axial direction.

中文翻译：

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连续微型锥形反向旋转双螺杆挤出机的流体动力学和混合性能

摘要 采用实验技术和计算流体动力学（CFD）模拟研究了微型锥形反向旋转双螺杆挤出机的混合性能。搭建了基于荧光检测的在线实验装置，研究停留时间分布（RTD）。选择聚丙烯作为流动材料，聚丙烯和蒽的混合物作为示踪剂。该在线检测装置重现性好。挤出机的流体动力学采用有限元法（FEM）结合网格叠加技术（MST）进行模拟。采用粒子跟踪技术来评估 RTD 和混合效率。研究了螺杆转速和进料速率对流体动力学和混合性能的影响。由于螺杆直径的减小，从入口到出口的速度大小和局部剪切速率趋于变小。平均拉伸长度从入口到出口呈指数增长，时间平均混合效率的平均值沿轴向保持为正。