L型挤出机头中物料温度分布的研究

对挤出机L型机头中流动物料的温度场分布进行了研究 ,提出了计算L型机头内物料温度分布的数学模型 ,并据此编制了CAE软件包。利用此软件包对两种不同的挤出物料进行了计算分析。通过分析计算结果 ,讨论了物料性能和机头温度对L型机头内物料温度分布的影响     

L型宽幅挤出机头挤出稳定性研究

通过ANSYS软件对L型宽幅挤出机头流道三维非等温流场进行数值模拟,分析高分子物料在非等温挤出过程中的流场规律,探讨机头流道壁面温度、进料口压力、阻尼宽度和阻尼高度等参数对机头流道内物料流动的影响规律。结果表明:阻尼宽度对物料具有明显的调压作用;机头流道参数对物料挤出压力和挤出均匀性的影响趋势不同,当壁面温度为338～343 K、进料口压力为15.0～19.6 MPa、阻尼宽度为8 mm、阻尼高度为3 mm时,物料挤出均匀性和稳定性较好,可实现高分子片材挤出质量和挤出产量的平衡。     

两端进料式宽幅片材挤出机头流道流场分析

建立两端进料式宽幅片材挤出机头流道三维几何模型,并对物料在流道内的流动进行数值模拟.模拟结果表明,流道内部压力在沿挤出方向递减的同时逐渐趋于横向均匀.高度分别为5和8 mm的阻尼部分对比分析表明,适当调整阻尼部分高度,可影响出口区域挤出速度横向分布,使横向挤出压力和速度更均匀.     

L型宽幅片材挤出机头优化设计及流场模拟

构建L型宽幅片材机头的三维物理模型,利用ANSYS WORKBEM、H和POLYFLOW软件对机头内部幂牢流体的压力场和速度场进行模拟。分析结果表明,当口模高度为4 mm、阻尼高度为3.5mm、主流道首末端直径比为1.2：l-l：1时,L型机头具有较好的挤出效果。     

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。     

计算机Pro/E软件设计鱼尾式片材模具

本文利用计算机Pro/E设计软件进行鱼尾式片材挤出模具的设计,利用软件中的塑料顾问,对物料在鱼尾式机头流道内的流场进行模拟:并通过改变扇形区阻流块高度与长度,对物料在模具中熔体流动时机头内熔体压力和出口速度均匀性的影响进行了分析和讨论;这对实际挤出模具的设计具有一定的指导意义。     

基于响应面法的轮胎胎面挤出机机头流道结构参数优化

建立轮胎胎面挤出机机头流道几何模型,运用数值仿真方法对胶料在机头流道内的流场进行仿真分析;流道出口截面胶料流动速度方差为流动速度均匀性的评价指标,通过Plackett Burman(PB)试验方法从8个流道结构参数中筛选出3个关键结构参数(夹角A和B及出口宽度D);采用中心复合设计(CCD)方法对3个关键结构参数对胶料挤出质量的影响规律进行分析,并经响应面法分析获得优化结构参数。结果表明:机头流道的3个关键结构参数A,B和D是影响胶料挤出质量的关键因素;优化流道结构能显著改善挤出胶料流动速度均匀性,提高胶料挤出质量。     

基于Pro／E的鱼尾式片材模具设计

本文利用Pro／E设计软件进行鱼尾式片材挤出摸具的设计．利用软件中的塑料顾问,对物料在鱼尾式机头流道内的流场进行模拟;并通过改变扇形区阻流块高度与长度,对物料往模具中熔体流动时机头内熔体压力和出口速度均匀性的影响进行了分析和讨论;对实际挤出模具的设计具行一定的指导意义。     

橡胶护舷挤出过程中机头内的流场分析

在橡胶护舷挤出过程中,机头结构影响胶料的流动,而胶料的流动对胶料所产生的剪切和拉伸作用是影响护舷规则成型的重要因素。利用ADINA对橡胶护舷挤出机头内的流场进行模拟分析,对判断机头结构的合理性,并优化机头结构,缩短机头的研发周期,具有重要的意义。模拟分析主要包括压力场、速度场、黏度场等。     

挤出提速产生质量问题原因分析及改进措施

我厂轮胎胎面挤出采用两台ＸＪ 2 0 0型挤出机。随着产量不断增加 ,挤出速度不断提高 ,挤出速度提高后 ,挤出生热、变形增大 ,随之产生胎面熟芯、气孔和尺寸不稳定等质量问题 ,对轮胎内、外质量影响较大。本文针对这些质量问题进行原因分析 ,并提出相应的改进措施。1　原因分析(1 )胎面熟芯大规格汽车轮胎胎面胶料挤出时 ,机头内部压力较大 ,生热高。挤出提速后 ,胶料在机头内部的生热进一步增大 ,如果降温效果不好 ,则会产生熟芯现象。(2 )胎面气孔大规格拖拉机轮胎胎面断面尺寸较大 ,要求挤出机吃胶量较大且机头内部压力较小。挤出提速后 …     

发射药药料离模膨胀和流动均匀性模拟及在模具设计中的应用

为了分析挤出成型过程中模具结构参数对七孔硝基胍发射药离模膨胀率及流动均匀性的影响规律,采用计算流体力学方法,对挤出成型过程进行模拟计算,讨论了模具各结构参数重要性的主次关系;对七孔发射药制备模具进行了结构优化,并进行了实验验证。结果表明,模具收缩角对膨胀率和药料出口速度均匀性的影响最大,压缩段高度次之,成型段长度的影响最小。模具优化后流道出口端速度分布均匀性提高36.53%,表明该模拟计算的可靠性与实用性。     

Three‐dimensional nonisothermal simulation of a coat hanger die

We studied the nonisothermal flow of Carreau fluid in a coat hanger die. A general three‐dimensional finite volume code was developed for the purpose of flow analysis. The pressure distribution and velocity distribution were obtained in addition to the temperature distribution. The results illustrated that the highest temperature occurred more by the center of manifold than by the die‐lip region. In the regions where the die gap was small relatively, the wall temperature played a key role in the determination of the temperature distribution in the melt. However, in the manifold, the viscous dissipation was the key factor that determined the temperature distribution in the melt where the heat conduction was relatively poor because of the thicker gap. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101:2911–2918, 2006     

Simulation of particle migration in free‐surface flows

The migration of particles in free surface flows using the diffusive flux model was investigated. As the free‐surface flows, a planar jet flow and a slot coating flow were chosen. The suspension was assumed to be a Newtonian fluid with a particle concentration dependent viscosity. The governing equations were solved numerically by the finite volume method, and the free‐surface problem was handled by the volume of the fraction model. The result shows that even though the velocity profile is fully developed and becomes flat, the particle distribution never reaches the uniform distribution for both of the cases. It is also shown that the die swell of the free jet is reduced compared to the Newtonian fluid and when the particle loading is 0.5, die contraction is observed. The change in die swell characteristics is purely due to particle migration since the suspension model does not show normal stress differences. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Optimization‐based design of polymer sheeting dies using generalized Newtonian fluid models

A polymer sheeting die design methodology is presented, which integrates finite element flow simulations, numerical optimization, and design sensitivity analyses to compute die cavity geometries capable of giving a near‐uniform exit velocity. This work extends earlier die design methods to include generalized Newtonian fluid (GNF) models that represent the shear‐thinning behavior of polymer melt. Melt flow computations and design sensitivity analyses are provided using the generalized Hele‐Shaw flow approximation with isothermal power‐law, Carreau‐Yasuda, Cross, Ellis, and Bingham fluid models. The nonlinear equations for die cavity pressure are solved using the Newton‐Raphson iteration method and design sensitivities are derived with the adjoint variable method. The die design method is applied to an industrial coat hanger die, in which a design parameterization is defined that allows for an arbitrary gap height distribution in the manifold of the die. In addition, die performance is assessed and compared for power‐law and Carreau‐Yasuda fluid flow over a range of die operating conditions. Pareto optimal die designs are also considered in this study. POLYM. ENG. SCI., 45:953–965, 2005. © 2005 Society of Plastics Engineers     

小截面精密异型管材挤出模拟与实验研究

对异型管材挤出机头流动进行了模拟,讨论了边界对流场速度分布的影响。依据流动平衡原则,根据流场速度分布探讨了部分关键尺寸的确定。针对热塑性聚氨酯材料进行了异型管材机头的设计。经实验验证,模拟与实验相结合设计口模的方法可以使小截面精密型材口模设计更加合理,缩短口模设计周期。     

衣架式模头设计理论及其流道数值模拟验证

按照微元法进行数学建模,以非牛顿流体在歧路管中的全展流动模型和在狭缝流道中的全展流动模型为理论基础,应用所有流径上压力降相等和歧路管内外壁剪切速率相等的设计准则,实现沿模头幅宽方向的流量分布均匀设计目标,并用Pro/E进行参数化建模和几何模型网格划分,最后采用Polyflow有限元软件对理论设计进行数值模拟验证,得到压力分布、速度场和壁面剪切速率.模拟结果表明:压力降符合较好,均匀性在宽幅方向上基本一致,剪切速率与设计准则相符.     

多腔精密医用导管机头结构及口模设计研究

介绍了较佳的多腔精密医用导管机头结构,并对两类典型多腔精密医用导管的机头定型段流场进行了数值模拟分析,获得了出口截面上的速度分布图。同时研究了截面上沿最大壁厚路径及最小壁厚路径上的速度分布,提出了整个截面速度均匀性的定义。此外,综合实际挤出过程中注气这一特征,给出了修正后的口模截面形状,同时进行了定型段流场的模拟。结果表明:修正后口模截面的速度均匀性和壁厚均匀性都有了很大的提高,这对同类机头的结构设计及口模截面的确定具有较强的参考价值。     

Investigating the process of liquid-liquid extraction by means of computational fluid dynamics

Liquid-liquid two-phase flow in extraction columns of the rotating disc contactor type is analysed using the multi-dimensional computational fluid dynamics (CFD) technique. Euler-Euler and Euler-Lagrange models are employed to give insight into the global flow structure and to analyse the turbulence related dispersion processes. Laser-Doppler velocity measurements are used to check the Euler-Euler results while a measured residence time distribution allows the assessment of the Euler-Lagrange approach. The results give rise to the expectation that CFD will become an accepted design tool in chemical engineering.     

Nonisothermal comprehensive 3D analysis of polymer melt flow in a coat‐hanger die

The nonisothermal flow of Carreau fluid in a coat‐hanger die is studied. A general three‐dimensional finite volume code is developed for the purpose of flow analysis. The isobars, the isotherms, and the velocity distribution are obtained. Simulation results illustrated that the highest temperature occurred by the center of manifold, rather than the die‐lip region because of the combined effects of high shear rate and poor heat conduction, which is important for processing those heat‐sensitive materials. In the regions where die gap is relatively small, the wall temperature plays a key role in deciding temperature distribution in the melt. The validity of simulation results is verified experimentally. POLYM. ENG. SCI., 46:406–415, 2006. © 2006 Society of Plastics Engineers.     

Three-Dimensional Finite Element Simulation and Analysis of Half-Club Coextrusion Processes

The three-dimensional flow of non-Newtonian polymer melts in coextrusion dies was analyzed based on finite element simulations. Simulation results, especially the interface predictions were discussed. The effects of flow rate ratio and the roughness of die wall on the interface were examined farther. It is found that the flow rate affects the shape and location of the interface notably. The velocity of fluid flow mainly controls the shape and location of the interface. Increasing that the higher slipperiness of the fluid path can make the velocity field more uniform and the interfacial offset less.