不同角度内模填充衣架型机头的数值模拟

利用Polyflow软件对填充了不同角度内模的衣架型机头流道进行了模拟。研究了不同内模夹角对流道压力分布、出口压力、出口速度以及流道内流体停留时间的影响。结果表明:不同角度内模填充机头流道后,流道压力分布、出口压力和出口速度无明显改变;流道内物料主要停留在歧管端部;通过改变内模夹角,可以改变物料最大停留时间及停留面积,内模夹角为40°时,流道内最大停留时间短,物料停留少。     

片材机头内聚合物熔体流动的模拟分析

利用ANSYS和MATLAB软件,对缩放型片材机头中熔体的速度、压力和剪切应力的分布进行三维有限元模拟和分析。通过对机头流道不同截面处熔体场量分布的模拟,探知了熔体在流道内的运动规律及特点。     

扁平机头设计基础

平膜机头与片材机头基本上相同。片材与薄膜之间的差异主要在于制品厚度。厚度大于0.5mm的通常称为片材,小于0.5mm的则称为薄膜。按分配流道的形状,可把片材机头分成T型机头,鱼尾型机头及衣架型机头三种。片材机头分配流道的设计应保证离开机头的塑料熔体在机头整个宽度上具有均匀的     

衣架机头三维数值模拟

利用美国FLUENT公司研究开发的Polyflow软件，以衣架型机头为基本的几何模型。对其流道内的聚合物熔体流动进行了数值模拟分析，建立控制方程，找出相关边界条件，以1组机头基本尺寸数据为例，计算得到了整个衣架机头流道内部的压力、速度分布图，最后通过分析幂律流体压力和速度分布图，对出口处料流的均匀性进行了讨论。     

衣架机头的优化计算及压力分布模拟

阐述了泪滴型歧管衣架机头流道优化计算原理和压力分布模拟计算的方法,编制了CAE软件包。讨论了流道主要参数对挤出压力分布均匀性的影响,并将本计算模块应用于工业实践。从使用效果来看,这种计算方法对于机头的设计和故障诊断具有实际的指导意义,具有一定的应用前景。     

衣架式机头

<正> 衣架式机头是介于T型机头和鱼尾式机头之间的一种挤出机头。如图1所示,衣架式机头与T型机头相比,都有一根岐管,但衣架式机头的岐管比T型机头的岐管小,熔体在机头内的停留时间短,对热稳定性较差的聚氯乙烯之类的树脂来说,采用衣架式机头进行板、膜的挤出生产,其物理力学性     

共挤出机头中的聚合物熔体流动分析

采用Hele-Shaw模型对共挤出机头流道内的聚合物熔体流动进行了数值模拟分析，计算得到了衣架型机头出口处各层料流分界面的位置，并讨论了物料特性、进口处流率比对机头出口处分界面位置的影响。     

板型机头流道的有限元计算辅助设计

在板型机头中聚合物流动的有限元分析基础上,建立了一种利用有限元计算设计板型机头流道的方法,建立了流道设计原则,编制了设计计算程序,井用该方法对φ65挤出机平板机头流道进行了校验和再设计。实践表明:该机头流道经重新设计后,其内的胶料速度分布与停留时间分布有明显改善,这说明了本文所提出的板型机头流道设计方法的可行性。     

挤出机缝口模头流道系统的计算机辅助设计

本文概述了几种典型的挤出单一熔体的缝口模头的分配流道系统结构，并在流变学理论分析和对衣架型分配流道系统进行实际假设的基础上，采用特征数据法，对挤出单一熔体的衣架型缝口模头的分配流道（歧管）系统实现了计算机辅助设计，以生成最优化的衣架型缝口模头的分配流道系统。     

直圆锥形衣架机头非等温三维流场的数值模拟

选用Carreau和近似Arrhenius二种数学模型，提出假设条件，利用Polyflow软件对直圆锥型衣架机头内的流场进行三维非等温有限元模拟和分析，得到不同截面上不同层面的速度、压力和温度分布曲线图。根据分布曲线图进行分析处理，总结得出熔体在机头内的运动规律及特点。     

The flow distribution of molten polymers in slit dies and coathanger dies through three-dimensional finite element analysis

The isothermal flow of power-law fluids in slit dies and coathanger dies is studied. A general three-dimensional finite element code is developed for the purpose of flow analysis. The pressure distribution, the velocity distribution, and the transverse flow rate distribution are obtained. The effect of the die geometry on the flow distribution is critically discussed. It is found that a die channel with cross section of dog bone profile produces a flatter transverse flow rate distribution.     

A personal computer software program for coathanger die simulation

A good extrusion die must distribute the polymer melt in the flow channel such that the material exits from the die with a uniform velocity and temperature. Coathanger dies are commonly used for the extrusion of plastic sheets and films. The die is usually provided with a straining bar allowing a regulation of the flowrate in the case of a poor design. But this, in turn, can affect temperature uniformity. Therefore, the design of coathanger die is a complex task which is mainly accomplished by trial and error in industry. Analyses of the flow in coathanger dies have been reported in the literature. Analytical and numerical approaches are used to solve this problem. The first one involves many simplifying assumptions: the most important ones being the unidirectional and isothermal flow of the polymer. Most numerical methods deal with a 2-D geometry, but only a few of them have considered the non-isothermal flow. A new model has been developed using a modified FAN method (Flow Analysis Network introduced by Tadmor) for the calculation of the 2-D flow, coupled with a finite-difference scheme for the calculation of temperature. The overall model can run on a PC with only a few minutes of calculation. Good agreement was obtained between experimental data and simulations.     

衣架式口模设计计算的一种改进

采用表征值方法，根据等压线平行于模唇的流动模式，并考虑歧管斜率的影响，对衣架式口模圆形截面歧管系统的设计公式进行了改进，不但使口模结构设计与材料的性能与流率无关，而且修正了以前文献中对歧管斜率影响的忽略而造成的流率分配的误差，从而使流动均匀性指数提高到１，并对两种流动模式的等效性给予了证明     

衣架式机头口模设计公式的修正探讨

基于表征值方法和熔体等压线平行于模唇这一流动模型,对衣架式机头口模进行了流动分析,并发现了文献[1]提出的口模设计公式中的一个缺陷,即计算的扇形狭缝区域与歧管发生了分离,针对该缺陷给出了修正公式。     

衣架式板材与片材挤出机头优化设计软件的研制

在建立合理的分配流道数学模型基础上，开发了衣架式板材与片材挤出机头优化设计软件，能方便而合理地指导设计者正确处理各影响参数，达到优化设计的目的。     

衣架型模头内流道参数的确定和优化

根据聚合物加工流变学理论 ,采用衣架型单流道模头计算公式确定了模头的流道参数并加以优化 ,然后设计出适用于HDPE平膜的衣架型宽幅模模头尺寸。     

塑料板材挤出口模流道系统的一种设计

根据聚合物加工流变学理论，采用表征值方法，在对衣架式口模缝型截面的流道分配系统进行分析基础上，提出了缝型截面歧管结构的设计计算公式，使之适用于岐管截面具有恒定宽度和宽高比为常量这两类口模的设计计算     

The influence of power‐law rheology on flow distribution in coathanger manifolds

Coathanger dies are effective in delivering uniform flow if a polymer melt; however, when the fluid flow index varies from the design values, the flow is not uniform. Although mechanisms such as die lip adjustments have been effective tools for adjusting flow profiles, the issue of a variable flow index has not been fully addressed at the design stage. An analytical solution, based on the assumptions present in the 1‐D design equation, has been developed for the flow distribution in a coathanger manifold. This solution determines the flow distribution for a power‐law fluid with a flow index n* in a manifold designed for a separate flow index n*. From this solution, a uniformity index and a critical design angle are defined. The critical design angle is the angle at which the local derivative of the uniformity index with respect to n* approaches a maximum (for n* < n) or a minimum (for n* > n) as a function of the design angle. The critical design angle is independent of n and is presented as a function of the manifold aspect ratio.     

Optimization of the coathanger manifold via computer simulation and an orthogonal array method

A well-designed coathanger die may deliver a polymer melt through the die more uniformly. However, it is difficult to optimize the manifold profile because of the complexity of flow distribution with regard to problems of die geometry, temperature, shear, and viscoelastic effects. The empirical methods have been widely used to design the manifold of a flat slit die. But this approach is time consuming and causes die material waste due to the iterative design process. With computer simulation, die designers can repeat modifications to obtain the optimal manifold shape easily. In this research, the Taguchi method was used to investigate the influences of the materials, die geometry, and processing conditions on optimizing the manifold profile. The comparison of the thickness distributions with and without modified manifold showed that the modified manifold improves the thickness uniformity significantly.