新型偏心双螺杆挤出机流域混合特性
Mixing Characteristics in Conveying Section of New Eccentric Twin-Screw Extruder
林格非 1朱向哲1
作者信息
- 1. 辽宁石油化工大学,机械工程学院,辽宁,抚顺 113001
- 折叠
摘要
基于非对称流场的混沌混合理论,设计了一种新型的偏心双螺杆挤出机.通过对比传统普通螺杆元件与新型偏心螺杆元件,偏心距不仅决定了螺杆的端面形状,也改变了螺槽形状,使同一导程内的2个独立的C型室螺槽形成一个ω型室螺槽.利用Polyflow软件分别对传统双螺杆挤出机与3种不同偏心距螺杆元件的新型双螺杆挤出机进行模拟仿真,分析了压力场、速度场与混合指数分布规律,计算了4种双螺杆挤出机流场的停留时间分布、分离尺度、最大剪切应力等混合表征系数.结果表明,与传统双螺杆挤出机相比,偏心双螺杆挤出机压力分布不均匀,正负压压力值增大,因此,压力差增大,使熔体回流速度增大,混合效果更佳;拉伸流区域增大,混合能力增强;熔体在流体域内的总体停留时间缩短,混合效果更佳;分离尺度数值下降较快,混合效率较高;偏心螺杆元件对流体的剪切应力增大,分散混合能力增强.
Abstract
A new type of eccentric twin-screw extruder was designed based on the chaotic mixing theory of asymmetric flow field.Comparing the conventional common screw element with the new eccentric screw element,the eccentric pitch not only determines the end face shape of the screw but also changes the shape of the screw groove so that two independent C-chamber screw grooves in the same lead became one ω-chamber screw groove.Polyflow software was used to simulate the conventional twin-screw extruder and the new twin-screw extruder with three different eccentric pitch screw elements,respectively,to give the distribution laws of the pressure field,velocity field,and mixing index and to calculate the mixing characterization coefficients such as residence time distribution,separation scale and maximum shear stress for the flow field of the four twin-screw extruders.The results showed that compared with the conventional twin-screw extruder,the eccentric twin-screw extruder had uneven pressure distribution,increased positive and negative pressure values,and increased pressure difference to improve the melt reflux velocity and better mixing effect.The tensile flow region was more extensive,and the mixing ability was more substantial.The overall residence time of the melt in the fluid domain was shorter,and the mixing effect was better.Separation scale values fall quickly,and mixing efficiency was high—greater shear stress on the fluid from the eccentric screw element,better dispersion,and mixing ability.
关键词
新型偏心双螺杆挤出机/偏心距/螺杆端面/ω型室螺槽/仿真模拟Key words
new type eccentric twin screw extruder/eccentricity/screw end face/ω type chamber screw groove/simulation引用本文复制引用
出版年
2024
NETL
NSTL
万方数据