普通螺杆和屏障螺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,所用模型包括喟料区、固体输送区、熔融区和熔体输送区。在屏障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。模拟的数据同实验数据相比较,可精确合理的预测出普通型和屏障型螺杆挤出特性。     

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 ,所用模型包括喂料区、固体输送区、熔融区和熔体输送区。在屏障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。模拟的数据同实验数据相比较 ,可精确合理的预测出普通型和屏障型螺杆挤出特性。     

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。     

双锥型螺杆挤出机固体输送离散元分析

利用EDEM软件对一种普通锥形和两种双锥型螺杆挤出机固体输送段进行模拟.分析了高密度聚乙烯(PE-HD)颗粒在锥形双螺杆挤出机内的运动状态和分布规律.对比分析了3种锥形螺杆挤出的质量流速率、填充率、平均速度、平均压力、平均剪切应力和力矩等参数,给出了普通型和双锥型螺杆挤出机固体输送机理以及主要影响因素.结果表明,相比于...     

螺杆冷却时的单螺杆挤出熔融理论研究

利用可视化挤出实验对螺杆冷却情况下的单螺杆挤出熔融机理进行了研究。实验表明，挤出过程中固体床始终保持连续而不会出现固体床破碎现象，螺槽表面会出现聚合物的亚稳态相转变行为。通过建立螺杆冷却时熔融理论的数学模型，用数值方法获得了熔融段聚合物流场的数值解，结果表明，理论预测的固体床宽度和机筒压力与实验结果基本吻合。     

沟槽机简单螺杆挤出机塑化性能的模拟研究

对传统光滑机筒单螺杆挤出机、固体输送段沟槽机筒单螺杆挤出机和熔融段沟槽机筒单螺杆挤出机的结构特点、输送机理、熔融热源以及熔融模型进行了对比分析,并对其熔融过程中熔融速率、熔融长度和熔融起始点进行了数值模拟,根据模拟结果分析了机筒结构形式对单螺杆挤出机熔融性能的影响。结果表明,机筒内壁开设沟槽的单螺杆挤出机在结构、机理和性能等方面均优于传统光滑机筒单螺杆挤出机,且将机筒沟槽由固体输送段延伸至熔融段对单螺杆挤出机的熔融性能有显著的提高。     

戴维斯公司推出新型挤出螺杆

戴维斯公司最近推出两款新型挤出螺杆：DSB-V型和DSB-VI型。DSB-V型的特点是：变螺距螺旋行程类似DSB-I型螺杆，同时含有一台独特的熔融装置。在DSB-V型挤出螺杆上，固体料的重复变形，形成一个流动重排的驱动力，促使物料在螺杆螺旋区早期混合。经过试验后确认，在一个很宽的螺杆速度范围内，均具有极好的均匀的熔融温度，这是其它类型的螺杆无法达到的；同时提高了添加剂及颜料的分散性，使树脂混合更理想化。DSB-VI型包括一个具有变螺距引导的双螺旋设计．其基本原理是：在凹槽喂料机中，提供平衡径向力，以减少磨损，与普通…     

三螺杆挤出机固体输送理论的实验研究

首先研究了啮合区固体输送,得到了啮合区的固体输送率,再通过建立非啮合区的非塞流固体输送物理模型,运用虚功原理得到了固体输送的数学模型。以三层模型为例对非塞流固体输送模型进行了求解,求得螺槽中物料层的平均速度,进而得到非啮合区的固体输送率。通过引入转化系数,将啮合区转化为非啮合区,从而将啮合区和非啮合区的固体输送统一为非塞流输送,并得到了转化后的等效螺槽充满度和固体输送率,建立了三螺杆挤出机的固体输送理论,采用粒料(LDPE)和粉料(PP)进行实验验证所建立的固体输送理论,并对固体输送的影响因素进行了研究。     

屏障型螺杆与混炼型螺杆的试验对比

<正> 目前,薄膜生产厂家面临着选择什么类型的螺杆才能满足产品质量要求的问题。螺杆的类型从普通型到带有各种不同屏障段的屏障型,多种多样。最近几年,在吹膜法和铸膜法生产LDPE和LLDPE薄膜的应用中,屏障型螺杆的使用多于普通型混炼螺杆。实践证明:在稳定的加工条件下,屏障型螺杆的加工性能优于普通型混炼螺杆,其生产效率高,熔融温度低.     

基于离散单元法一字排列三螺杆挤出机固体输送段输送机理分析

利用离散单元法对计量加料下一字排列三螺杆挤出机固体输送段进行模拟。分析了聚合物颗粒在一字排列三螺杆挤出机正位移输送和摩擦拖曳输送2种输送机理下的输送情况,计算出一字排列三螺杆挤出机的输送特性参数,并与双螺杆挤出机进行对比分析。结果表明,由于三螺杆挤出机啮合区的增加,提高了颗粒在挤出机螺槽内的填充率。一字排列三螺杆挤出机在填充程度、质量流速率等方面均优于双螺杆挤出机,并且输送产量大约为双螺杆挤出机的1.3倍,在聚合物加工行业具有较好的工程应用前景。     

Melting mechanism in single screw extrusion

Flow visualization experiments of polycarbonate and polystyrene resin extrusion were performed to observe the melting mechanism and the flow kinematics around the solid-bed in the melting zone of a single screw extruder. The axial solids content and pressure profile calculations of the Tadmor melting model were modified as a result of variable solid-bed velocity and solid-bed temperature observations.     

Melting mechanism of a starved‐fed single‐screw extruder for calcium carbonate filled polyethylene

A study of starved‐fed single screw extrusion was initiated to understand the relation between its distinctive melting mechanism and the improved mixing capabilities attained during compounding of a calcium carbonate filler into HDPE. Experiments were carried out in a 63.5 mm single screw extruder, examining the effect of degree of starvation on a conventional and barrier feed screw. Interest was focused on the mixing/melting mechanism of starved‐fed solids‐conveying as it affects the size and number of filler agglomerates observed in the extrudate. The melting performance of both feed screws was examined using pressure and temperature measurements down the screw length as well as direct inspection of the polymer in the screw channel via rapid screw cooling. Both screws showed improved mixing quality with increased starvation.     

A plasticating model for single-screw extruders

By measuring the solid-bed transfer velocity, width and thickness under various conditions, die following results are obtained. As the result of melting, the solid bed decreases in width and thickness almost with the same rate, and the solid-bed transfer velocity is constant, while a melt layer exists between the solid bed and the screw root; also, when the phenomenon of dam-up occurs, caused by the combined effect of decreasing depth of the screw channel with tin insufficient decrease of solid-bed thickness, the transfer velocity increases proportional to the rate of decrease of channel depth. Consequently, the solid bed is considered to behave us loosely packed particles. A new plasticating model is developed by making the above results an assumption and adopting finite differential calculus with the Newton-Raphson method to obtain accurately the melting velocity, melt profile, and solid-bed temperature. Calculated values are in remarkably good agreement with the experimental values Solid-bed softening point, pressure, and screw torque are also successfully estimated.     

注射成型塑化过程的可视化实验研究

利用自行开发的可视化实验装置对注射成型的塑化过程进行了系统的观察,着重讨论了不同的工艺条件对塑化性能的影响,同时借助示踪粒子对塑化过程的重要参数——固相速度进行了测量。实验所取得的数据为注射成型熔融模型的建立和对模型的验证提供了依据,同时也是注射螺杆优化设计的基础数据。     

单螺杆挤出过程中固体粒子的变形、取向与熔融Ⅰ.固体粒子的变形分析

在带有在线取样和在线显微观察系统的全程透明视窗单螺杆挤出机上 ,采用普通三段式螺杆和分离型螺杆 ,对LDPE和LLDPE等物料进行了挤出实验。对实验过程中的固体床结构与变形、固体粒子的变形现象和变形机理进行了描述和分析 ,针对固体粒子的粒间运动与变形现象 ,提出了固体粒子粒间变形三个阶段的概念。     

The Plasticating Sequence in Barrier Extrusion Screws Part II: Experimental Assessment

A modular laboratorial single screw extruder was used to perform screw pulling experiments and generate data on the development of plasticating of two polymers along the axis of a Maillefer barrier screw. The effects of the presence of the barrier (by comparison with an equivalent conventional 3-zone screw), of its geometrical parameters and of operating conditions were investigated and compared to the predictions provided by a previously developed computational model. Although the small size of the extruder influenced solids conveying and induced premature and quick melting, the two sets of data were generally in satisfactory agreement.     

Performance study of barrier screws in the transition zone

This paper defines through a mathematical model the advantages and disadvantages of barrier screws as far as their melting and mixing performances in the transition zone are concerned. The melting analysis is based on the Tadmor's original model, and the flow in the melt channel is considered to be non-Newtonian and nonisothermal. The performance of these barrier screws is investigated for the solids channel in terms of melting rate/interface a I contact area; melting efficiency; melting length; solid bed velocity profile; and power consumption in the melt film at barrel surface. For the melt channel, their performance is investigated in terms of pressure buildup; average bulk temperature; power consumption in the melt channel and in the main flight clearance at barrel surface; and average bulk mixing. The present study confirms that the increased-pitch multichannel screw (Ingen Housz screw) outperforms clearly the other barrier screws investigated, since it gives the highest melting rate with reasonable pressure buildup in the melt channel. When compared with conventional screws, all the barrier screws examined give better melting performance.     

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。