挤出机螺杆加料段的优化设计

讨论了挤出机螺杆加料段的优化设计问题。以单位产量的能耗最小为优化目标,建立简化的挤出机加料段螺杆优化设计的数字模型,应用约束坐标轮换法求解,螺槽深度和螺纹升角的最佳值均位于或接近献中所建议的最佳取值范围。     

挤出机螺杆计量段的优化设计

讨论了挤出机螺杆计量段的优化设计问题。应用粘性流体动力学基本方程，分析了聚合物物料在螺槽中的流动。以单位产量能耗最小为优化目标，建立简化的挤出机计量段螺杆优化设计的数学模型，应用约束随机方向法求解。结果表明，螺槽深度、螺纹棱顶宽度、螺纹棱顶与机筒间隙和螺纹升角均位于或接近于献中所建议的最佳取值范围。     

挤出机螺杆的计算机辅助优化设计

讨论了挤出机螺杆的计算机辅助优化设计问题。以单位产量能耗最小为优化目标，建立简化的挤出机螺杆优化设计的数学模型，应用复合形法求解。结果表明，螺杆的主要几何参数螺槽深度、螺纹顶宽度和螺纹升角均位于或接近文献中所建议的最佳取值范围。     

双螺杆挤出机物料熔融因素的研究

通过对PP粉料在双螺杆挤出机中的熔融实验，研究了不同螺纹组合和螺杆转速对物料的熔融能力。研究结果表明，物料的熔融热能来自于转动的剪切组合；螺纹组合的剪切能力越强，所产生的热量也越大；不同的物料需选用不同的螺纹组合，并配以不同的工艺条件；双螺杆挤出机的产能与螺杆的组合及转速存在线性关系。     

NE62型双螺杆挤出机螺杆组合的模拟优化分析

使用Ludovic软件模拟不同螺杆组合的NE62型双螺杆挤出机性能。以平均停留时间和功率为指标,在保证物料混合性能的同时降低其能耗,进而优化NE62型双螺杆挤出机螺杆组合结构。结果表明,熔融段存在两个正向螺纹元件,正向螺纹元件在熔融区的位置靠后,并保持一定的间隔,此时的停留时间最长,所耗功率小;混合段存在两个以上的混合元件,混合元件的位置相邻并处于混合区的初始位置时,平均停留时间较长,所耗功率较小。最终优化后的螺杆组合在保证不减少平均停留时间的基础上,降低了所耗功率。     

机筒沟槽和螺杆螺槽耦合作用下的熔融理论研究

对固体输送段和熔融段机筒开设螺旋沟槽的单螺杆挤出机,构建了基于反压缩比分离型螺杆和正压缩比沟槽机筒的耦合双槽熔融模型,并通过液压剖分式单螺杆挤出机实验平台对耦合双槽熔融模型进行了验证。结果表明:对于沟槽机筒单螺杆挤出机,利用熔融段沟槽固体塞和螺杆螺槽固体塞在机筒沟槽和螺杆螺槽界面处发生层间剪切产生的大量内摩擦热来实现物料的高效熔融是可行的;实验结果和理论模型相一致;螺杆转速对熔融长度影响不大,而螺杆结构参数则对其影响较大。     

沟槽机筒单螺杆挤出机塑化特性的实验研究

采用剖分式机筒单螺杆挤出机实验平台,对熔融段沟槽机筒单螺杆挤出机塑化过程中熔融起始点、熔融长度、熔体温度/压力等塑化性能及产量进行了实验研究,比较了不同物料在不同工艺条件下对沟槽机筒单螺杆挤出机塑化特性的影响。结果表明,增大螺杆转速或提高机筒温度,塑化过程实际所需熔融长度增加,但对熔融起始点影响不大;熔融段机筒沟槽内熔体温度和熔体压力随螺杆转速增大无明显变化;随螺杆转速增大,沟槽机筒单螺杆挤出机挤出产量呈线性增加,表现出良好的挤出特性。     

新型螺杆的研究与设计——第一讲

<正> 近年来,国外合成纤维熔融纺丝的挤出机已装备了各种新型螺杆。所谓新型螺杆是具有某种特殊结构,而与普通单螺纹(突变或短区渐变)螺杆相区别的螺杆总称。国内有些化纤机械厂已开始生产装有新型螺杆的纺丝挤出机;一些进口的高速纺设备也配有新     

沟槽机筒单螺杆挤出机耦合双槽熔融理论研究

利用自制的液压剖分式沟槽机筒单螺杆挤出机实验平台,研究了沟槽机筒单螺杆挤出机的熔融长度和螺杆转速的关系,实验验证了单螺杆挤出机固体输送段和熔融段机筒均开设沟槽的耦合双槽熔融理论。结果表明,与传统光滑机筒单螺杆挤出机和IKV单螺杆挤出机相比,在熔融段机筒开设沟槽的单螺杆挤出机的熔融长度较短且熔融过程比较稳定,熔融效率得到较大提高。     

锥形单螺杆挤出机产量模型分析

锥形螺杆挤出机容易加料,轴向具有压缩效应,可加工粉体或热敏性材料。参考普通单螺杆挤出机经典理论,建立了考虑锥度影响的固体和熔体产量模型及压缩段的熔融模型。分析模型发现,比普通平直螺杆挤出机,固体输送率和熔体输送率有所增加;熔融段长度减小;挤出段产量有波动。     

Melting performance of single screw extruders with a grooved melting zone

A novel melting model for single screw extruders with a grooved melting zone was established. The whole solid plug, which came from the grooved feed zone, was ruptured and melted mainly by continuously changing the volume of the barrel grooves and the screw channel in the grooved melting zone. A new single screw extruder platform with hydraulic clamshell barrels was constructed to investigate the melting of solid polymer with different combinations of barrels and screws. The melting model was verified by experiments. The results showed that the melting started earlier and finished in a shorter length for single screw extruders with a grooved melting zone than that for conventional single screw extruders and the melting efficiency was improved by introducing a grooved melting zone to a single screw extruder. The theoretical values are consistent with experimental results. The novel single screw extruder with grooved melting zone can dramatically increase the plasticizing efficiency and the throughput.     

Contribution of the melting stage to the evolution of the morphology and chemical conversion of immiscible polyamide/polyethylene blends in twin‐screw extruders

This study investigates the effects of processing conditions (the screw speed, throughput, barrel temperature, and screw configuration) on the chemical conversion and morphology evolution of polyamide/polyolefin blends along a twin‐screw extruder. Polymer samples were collected rapidly at specific barrel locations with a special sampling device for subsequent chemical and morphological characterization. Increasing the screw speed or using more restrictive screw modules at the beginning of the melting zone promoted a faster reaction and better dispersion along the extruder. Increasing the throughput or decreasing the barrel temperature slowed the evolution of the morphology and chemical conversion along the extruder because of the lower melting rate. As soon as melting started, the chemical reaction took place. However, high chemical conversion rates required extensive melting, that is, significant interface generation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Plastification or melting: A critical process for free radical grafting in screw extruders

This paper shows for the first time that when a monomer is to be grafted onto a polymer backbone by a free radical mechanism in a twin screw extruder, the grafting process occurs mainly, if not exclusively, in the plastification (melting) zone. For this purpose, the free radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) and polyethylene (PE) was chosen as model systems. A co-rotating self-wiping twin screw extruder of type Werner Pfleiderer ZSK-30 (L = 42D) was used to process the grafting. Owing to its modular character in terms of barrel arrangement, screw element combination and barrel temperature, the position and length of the plastification zone can be adjusted virtually at will. This allowed us to follow up the grafting not only at the die exit, but also in the plastification zone under different grafting conditions. Our results clearly show that it is in the plastification (melting) zone that the entire grafting process occurs. This length is usually very short in a co-rotating twin screw extruder like ours. Under the grafting conditions, it varied from 1D to 5D. Thus, any relevant analysis or model of a free radical grafting process carried out in a screw extruder must be based on detailed information generated not only at the die exit, but also and most importantly in the plastification zone. Otherwise, it may lead to incomplete and/or wrong conclusions.     

普通螺杆和屏障螺杆挤出机的计算机模拟

提出了普通螺杆和屏障螺杆的计算机模拟方法，所用模拟包括：喂料区、固体输送区、熔融区和熔体输送区。在屏障型螺杆中，其固体熔融速率是按Ｔａｄｍｏｒ模型计算出来的，而Ｔａｄｍｏｒ模型的固体床速率是以固体床厚度和宽度的变化为基础的。模拟的数据同试验数据相比，可精确合理以预测出普通型和屏障型螺杆的挤出特性。     

Numerical simulation of fluid flow and heat transfer in a single-screw extruder with different dies

In a plasticating screw extruder, a polymer melt forms in the melting zone of the extruder. Pressurization of the molten polymer takes place in the melting and the metering sections so that the melt can flow through the restricted passage of the die and assume a desired shape. In a melt fed extruder, the throughput is governed by the pressure rise over the entire length of the extruder. The pressure developed in the screw channel may also be employed in rapid filling of molds, such as those in injection molding. When the geometry of the screw, the barrel temperature, and the die are selected, a unique set of operating parameters arise for a particular flow rate or screw speed. In the present study, numerical and analytical methods are used to calculate the transport in the extruder and the pressure drop in the die. An iterative numerical method based on solving the equations of motion and energy in the screw channel and a correction scheme to couple the die with the screw channel is discussed. The numerical algorithm is capable of handling an arbitrary variation of the viscosity of the polymeric fluid with the shear rate and temperature. The results obtained by simulating the fluid flow in the screw channel are compared with available numerical and experimental results in the literature, indicating good agreement. The performance characteristics of the extruder, for chosen thermal boundary conditions and screw geometry, are presented for different die geometries and different fluids. The important considerations that arise in the numerical simulation of the extrusion process are also discussed.     

Numerical simulation of a single-screw plasticating extruder

A fully-predictive steady-state computer model has been developed for a single-screw plasticating extruder. Included in the model are a model for solids flow in the feed hopper; a variation of the Darnell and Mol model for the solids conveying zone; a variation of Tadmor's melting model for the melting zone; an implicit finite difference solution of the mass, momentum, and energy conservation equations for the melt-conveying zone of the extruder and die; and a predictive correlation for the extrudate swell at the die exit. A temperature- and shear-rate-dependent viscosity equation is used to describe the melt-flow behavior in the model. The parameters in the viscosity equation are obtained by applying regression analysis to Instron capillary rheometer data. Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions, the following are predicted: flow rate of the polymer, pressure and temperature profiles along the extruder screw channel and in the die, and extrudate swell at the die exit. The predictions have been confirmed with experimental results from a 11/2 in. (38 mm) diameter, 24:1 L/D single-screw extruder with a 3/16 in. (4.76 mm) diameter cylindrical red die. High- and low-density polyethylene resins were used.     

振动诱导单螺杆挤出机熔融过程实验研究

利用剖分式料筒振动诱导单螺杆挤出机以及透明料筒振动诱导单螺杆挤出机对振动力场作用下的熔融过程进行了可视化实验研究，获得了熔融过程的固体床宽度分布曲线；对比了不同振动参数条件下的熔融长度与无振动条件下的熔融长度。实验结果表明，振动的引入可加快熔融进程，缩短熔融长度。对应不同的材料，不同的螺杆转速、料筒温度设置等工艺条件存在一个振动强度范围，在此范围内随着振动强度的增加，熔融速度进一步加快。