立式循环撞击流反应器中桨叶垂直交错排布条件下的混合性能

立式循环撞击流反应器(VCISR)桨叶的倾角及其布置形式,是影响混合性能的重要因素.本文采用数值方法对VCISR桨叶不同角度垂直交错排布条件下的混合性能进行了研究.上下两对桨叶倾角θ均设置为45°,上下两对桨叶错位角分别设置为15°、30°、45°、60°,结果表明:上下两对桨叶错位角在45°时,VCISR特征撞击面上...     

双螺杆捏合机理及其捏合段设计

定性分析了捏合段的混合及输送机理，讨论了捏合块错列角、螺棱间隙、捏合块头数、螺杆转速等因素对混合质量及输送能力的影响，并由此提出了一些捏合段设计时应注意的问题。     

新型捏合盘元件不同螺杆构型混合性能的数值模拟

采用POLYFLOW模拟软件分析了啮合同向双螺杆挤出机中新型捏合盘元件下物料的流动模式。考察了新型捏合盘元件的斜棱旋向、捏合块组合的错列角对物料在流道中的剪切速率、出入口压差以及回流量的影响。数值模拟分析结果表明:4种新型捏合块构型的输送特性和混合性能均有所不同。在正向输送能力方面,右旋正向捏合块更佳,在分布、分散混合性能方面,左旋反向捏合块更佳,并且捏合块的正反向比单片捏合块的螺旋方向在输送能力、混合性能上影响更大。     

啮合同向双螺杆3种构型的模拟分析和实验研究

通过数值模拟方法对3种含捏合盘元件螺杆构型的剪切速率、停留时间和回流量等指标进行了分析,通过实验对3种螺杆构型的混合性能进行了对比。结果表明,90°捏合盘元件与反向捏合盘元件组合可以达到较好的分布混合效果,45°捏合盘元件与反向捏合盘元件的组合可以达到较好的分散混合能力,捏合段加入反向螺纹元件并不能提高分布混合能力,但可以延长停留时间。     

反向旋转卧式双轴捏合反应器混合特性的数值模拟

以差速反向旋转卧式双轴捏合反应器为研究对象,选用高黏牛顿流体糖浆为模拟物料,通过三维有限元数值模拟方法研究了高黏糖浆在捏合反应器中的流动过程,获取了流速和剪切速率的空间分布,进一步结合粒子示踪技术探究了分布混合过程与混合效率,并且考察了搅拌结构对流动与混合过程的影响规律。研究表明,捏合反应器中几乎不存在流动死区,桨叶末端和重叠区域的流速和剪切速率较高,且高流速和高剪切区域均随着捏合杆数目和捏合杆长度的增加而增大。捏合杆可以推动物料在圆周方向上的运动,在重叠区域存在周期性交互作用,进而可以强化分布混合过程。拉伸率随着混合时间以指数形式增加,且随着捏合杆数目和捏合杆长度的增加而增加。时均混合效率大于零,随着捏合杆数目的增大而增大,随着捏合杆长度的增加呈现先增大后减小的趋势。     

POM捏合机桨叶排列对聚合反应的影响研究

研究了聚甲醛(POM)聚合用捏合机的桨叶排列方式对POM聚合效果的影响.通过对捏合机桨叶排列方式的调整,提高了POM生产的转化率,降低了150μm粒径以下聚合物的含量,稳定了HO曲线,从而改善了POM的聚合效果.     

高效捏合机在火炸药高粘性混合物工艺上的应用

捏合机一般用于必须搅拌高粘性流体的工艺上。一方面人们因长期使用卧式捏合机有了丰富的经验,所以乐于选用卧式捏合机;另一方面就捏合机来看却有某些趋于“新产品”的偏向。我们这里谈的是立式捏合机,就操作和搅拌效率而言,立式捏合机决不次于卧式,西德Staufen 的 Janke 和 Kunkel 收集了立式捏合机方面二十年来的经验,已发现这种新系列的 PLANETRON 捏合机易于销售,现拟订了一个包括有效容积为2.5～800升的各种立式捏合机的规划。     

高效捏合机在火炸药高粘性混合物工艺上的应用

捏合机一般用于必须搅拌高粘性流体的工艺上。一方面人们因长期使用卧式捏合机有了丰富的经验,所以乐于选用卧式捏合机;另一方面就捏合机来看却有某些趋于“新产品”的偏向。我们这里谈的是立式捏合机,就操作和搅拌效率而言,立式捏合机决不次于卧式,西德Staufen的Janke和Kunkel收集了立式捏合机方面二十年来的经验,已发现这种新系列的PLANETRON捏合机易于销售,现拟订了一个包括有效容积为2.5～800升的各种立式捏合机的规划。     

三层桨叶搅拌器内桨叶位置的优化分析研究

利用CFD技术 ,对搅拌器内 12个桨叶位置情况下的流场、混合特性、功率消耗进行了模拟分析研究。结果表明 :桨叶的空间位置对搅拌性能的影响是非常明显的 ,位置即使发生较小的变化 ,也会在功率消耗、混合时间上产生较大的差异。桨叶之间的间距在一定范围内相对加大有利于混合 ;底层桨叶的位置高度对混合性能影响最大。     

布斯大容量捏合机面世

瑞士著名塑料机械企业布斯公司最近推出BussOuanter EV新型捏合机。与以前标准型号捏合机比,这种型号捏合机机简外径不变,内衬厚度减薄,因而机筒容量约增大20％,使配混时物料分散更均匀,因此应用范围比标准型捏合机广。该机主要用于PVC材料的配混,用于医疗和食品软管用透明PVC的捏合时,由于停留时间长,捏合温度可下调10℃,使温度控制在不超过130℃的限定水平。而对于磨损性大的材料,如填充含量高的硬PVC挤出牌号,     

炭素制品的混捏工艺改进研究

在炭素制品生产中,混捏是制备优质糊料的关键工艺,对制品的理化指标具有重要的影响。本文以铝用炭阳极制备为例,对传统混捏工艺进行了改进。结果表明,与传统混捏工艺相比,在配方固定的前提下,将适量的粉料预先添加到熔化沥青中,然后再与干料混捏,能有效改善炭阳极的常规物理性能。     

啮合异向双螺杆挤出机中捏合块元件对PE-HD/PS不相容体系混合效果的研究

在常规啮合异向双螺杆上引入不同错列角和不同捏合盘厚度的捏合块元件,将其用于高密度聚乙烯/聚苯乙烯（PE-HD/PS）不相容体系的混合,观察混合体系的相态并分析分散相的粒径。结果表明,增加捏合块元件后啮合异向双螺杆挤出机的分散混合能力得到了提高;捏合块的错列角和捏合盘的厚度对PE-HD/PS不相容体系分散相PS的重均粒径和粒径分布指数有较大影响。     

Melt-mixing by novel pitched-tip kneading disks in a co-rotating twin-screw extruder

Melt-mixing in twin-screw extruders is a key process in the development of polymer composites. Quantifying the mixing performance of kneading elements based on their internal physical processes is a challenging problem. We discuss melt-mixing by novel kneading elements called “pitched-tip kneading disk (ptKD)”. The disk-stagger angle and tip angle are the main geometric parameters of the ptKDs. We investigated four typical arrangements of the ptKDs, which are forward and backward disk-staggers combined with forward and backward tips. Numerical simulations under a certain feed rate and screw revolution speed were performed, and the mixing process was investigated using Lagrangian statistics. It was found that the four types had different mixing characteristics, and their mixing processes were explained by the coupling effect of drag flow with the disk staggering and pitched-tip and pressure flows, which are controlled by operational conditions. The use of a pitched-tip effectively controls the balance of the pressurization and mixing ability.     

The effects of kneading block design and operating conditions on distributive mixing in twin screw extruders

A mixing limited interfacial reaction between polymer tracers was used to directly measure the distributive mixing performance of a co‐rotating twin screw extruder during melt‐melt blending of polypropylene. The reaction between the polymer tracers, which are low molecular weight succinic anhydride and primary amine terminally functionalized polymer chains, was followed using Fourier‐Transform Infrared Spectroscopy (FT‐IR). Experiments were completed to determine the effects of flow rate, screw speed, and kneading block design on the distributive mixing performance and the residence time distribution (RTD). The only RTD variable that was significantly affected by the experimental factors was the average residence time. Distributive mixing with neutral and reverse kneading blocks was controlled by the average residence time, the fully filled volume, and the shear rate. Conversely, the mixing performance of a forward kneading block did not follow the same trends.     

Mixing mechanism of three‐tip kneading block in twin screw extruders

In recent years, twin screw extruders have been applied to various kinds of polymer processing. It has been important to find their optimum geometrical configurations and operational processing conditions for the best performance of extrusions and products. Many engineers have been evolving numerical and the experimental methods to characterize the mixing performance for twin screw extruders. We have carried out three‐dimensional flow simulations of kneading blocks in intermeshing co‐rotating twin screw extruders by using the finite element method to quantify their ability in distributive and dispersive mixing. We discuss their performance in distributive mixing for three different type of kneading blocks in terms of the residence time distribution and the nearest distance between markers at various periods of time, by using the marker tracking method. Those numerical techniques and applications of mixing indices have enabled us to quantify and evaluate their abilities in distributive mixing of kneading blocks in twin screw extruders.     

Study of mixing efficiency in kneading discs of co-rotating twin-screw extruders

Co-rotating twin-screw extruders are widely used for compounding and blending in polymer processing. In a modular machine, the dominant elements determining dispersive mixing efficiency are the kneading discs. A fluid dynamics analysis package - FIDAP, using the finite element method was implemented to simulate the 3-D isothermal flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK-53 co-rotating twin-screw extruder. The kneading discs simulated are three-lobe discs. The flow field characteristics relevant for dispersive mixing are shear stresses generated and elongational flow components. We compare these flow characteristics for the three-lobe kneading discs of the ZSK-53 with the two-lobe discs of a ZSK-30 machine. We also discuss the influence of processing parameters on the flow field mixing efficiency.     

Analytical and Experimental Evaluation of Dispersive Mixing Performance of Special Rotor Segments in a Corotating Twin-Screw Extruder

An intermeshing corotating twin-screw extruder is often used for producing polymer composites. In this study, we discussed mixing performance of special rotor segments in molten zone. These rotor segments have several tip clearances for achievement of self-cleaning and effective mixing, and these are named various clearance mixing technology. We studied about dispersive mixing performance of configuration, which consists of various clearance mixing technologys (various clearance mixing technology configuration) using numerical analyses and experiments. For the analytical evaluation of mixing performance, we have adopted a particle tracking method. As evaluation indices of dispersive mixing performance, we focused on following three values (1) maximum value in a history of first principal stress of each particle, (2) time-integrated shear rate of each particle, and (3) time-integrated first principal stress of each particle. And we made the probability distributions of the indices. We adopted weighted probability as approximation of volume probability in each region. The results were compared with those of kneading disk segments configuration (kneading disk configuration). Furthermore, we validated the accuracy of the analytical evaluation by performing experiments under same conditions as those of numerical analyses. For the experimental evaluation of mixing performance, we used twin-screw extruder. Polypropylene was selected as suspending media. And CaCO₃ was selected as filler. To compare just the mixing performance of various clearance mixing technology configuration with that of kneading disk configuration, side feeding and screw configuration which had third mixing segments zone were adopted. From the experimental result, it is found that various clearance mixing technology configuration dispersed better than kneading disk configuration. And from the comparison between the experimental evaluation and the analytical evaluation, it is found that the first principal stress is more appropriate for evaluation index of dispersive mixing. Finally, it can be mentioned that various clearance mixing technology configuration has better mixing performance than kneading disk configuration, and large stress is important for dispersive mixing.     

转子间隙对调距式密炼机的影响

通过2种调距式密炼机（剪切型调距式密炼机和啮合型调距式密炼机）的对比实验，对实验结果进行了分析，讨论了转子间隙的变化对密炼机各性能参数和胶料性能指标的影响。     

Computational study of chaotic mixing in co-rotating two-tipped kneading paddles: Two-dimensional approach

This study attempts to investigate the kinematics of the mixing occurring in the lenticular kneading disc section of the co-rotating twin screw extruder, employing the tools of dynamics. The Eulerian velocity field distributions, generated by a two-dimensional isothermal and creeping flow of Newtonian fluid under the periodic co-rotation of the kneading discs, were obtained by Finite Element Method. A simple and novel particle tracking technique based on the FEM solution of the velocity field was employed to follow individual particles, and to produce the Poincare section mapping. Furthermore, fingerprints of chaotic motion were revealed essentially through the Lyapunov exponents, which were positive. The results suggest that the dynamics in the two-dimensional kneading disc section of the twin screw extruder can be characterized as capable of imparting chaotic motion. The tools developed in this study should facilitate a better understanding of the mixing capabilities of the twin screw extrusion process.