销钉机筒挤出机内物料流动与混合效果的数值模拟

在单螺杆挤出简化模型的基础上 ,采用滑移网格技术 ,考虑销钉与螺杆相对运动的条件 ,分别研究销钉数量、销钉排间距、螺槽宽度、拖曳速度对螺杆圆周展开面内物料流动与混合效果的影响。结果表明 :销钉及螺棱切槽对物料具有明显的强化混合作用 ,减小销钉排间距及螺槽宽度、增大销钉数量和提高拖曳速度都会改善混合效果。对于Φ90销钉挤出机 ,每排 68枚销钉、销钉排间距为 60 72mm、螺槽宽度为 5 4mm左右、转速为 2 5 5 0r·min- 1 时可达到较好的混合效果     

新型带孔销钉混合段及其分布混合性能

介绍了一种国外开发的用于改善单螺杆挤出机混合性能的新型带孔（或带槽）销钉混合段,与常规销钉混合段相比,其混合能力强,熔体温度 低,当销钉间的轴向距离在11－14mm之间时,有效地加强了熔体的周向汉动,极大地改善了单螺杆挤出机的分布混合性能。     

注塑机螺杆混炼元件混炼性能对比研究

根据生产实际设计销钉型、屏障型及菠萝型三种螺杆混炼元件,并借助于计算流体动力学软件POLYFLOW分别对位于计量段末端的三种类型混炼段进行数值仿真,对比分析其混炼性能和塑化质量。结果表明,三种构型混炼元件中,屏障型混炼元件出入口压力降最小,销钉型压力降最大,菠萝型压力降介于两者之间;菠萝型混炼元件拉伸速率最大,销钉型与屏障型相似;菠萝型混炼元件混合指数最大,销钉型次之,屏障型最小。     

往复式挤出机螺杆往复运动及销钉排布对混炼性能的影响

应用黏性流体有限元数值模拟计算的方法,研究了Buss机内物料流场分布特征,分析了螺杆往复运动特征参数及销钉排数等对Buss机螺杆几何构型的影响,以及由此所造成物料微元所经历的最大拉伸长度分布和最大剪切应力分布的变化,从而揭示了往复式单螺杆销钉挤出机往复运动特征参数及销钉排数对高聚物熔体分布和分散混合性能的影响规律。     

往复式混炼挤出机市场看好

螺杆往复式混炼挤出机作为一种新型的加工设备,在高填充、高分散、热敏性材料的加工方面有其独特的优势。这种挤出机在螺杆芯轴上设有独特的积木式螺块,螺块在一个螺距内断开三次,称为混炼螺块,对应这些空隙,在机筒内衬套上,排列有三排混炼销钉。同时,螺杆在转动过程中作往复式运动,每转动一周,轴向往复运动一次。由于这种独特的运动方式,以及混炼螺块和销钉的作用,使物料不但在混炼销钉和不规则梯形混炼螺块之间被剪切,而且被往复输送,增强了混炼效果,保证了最佳的分散性和分配性混合。另外,混炼销钉和螺块的相互啮合,也提高了机筒的自我清     

X(S)M-50D销钉混炼室密炼机测试数据分析

本文以生产机台现场测试所获得的参数为依据,介绍销钉混炼室密炼机的功率、排胶温度、能耗、生产能力与混炼加工性能,并采用新老机台的对比方法,反映销钉混炼室密炼机的一系列优点。     

基于拉格朗日的单螺杆销钉挤出机混沌混合分析

从拉格朗日理论的新视角,分析了高分子聚合物熔体在单螺杆销钉挤出机内的流型结构以及流动行为,揭示了销钉强化聚合物熔体输运和混沌混合的机理。使用有限元软件Polyflow计算了流场的速度分布和混合指数;借助Matlab数学软件进行自主编程对速度场进行积分得到了三种不同销钉挤出机模型的有限时间李雅普诺夫指数。结果显示,在加入销钉之后,单螺杆销钉挤出机流域中出现了圆柱绕流现象,绕流产生的尾迹将撞击螺棱,销钉和螺棱的这种相互作用将加剧聚合物熔体的拉伸作用。每个销钉都将产生尾迹,随着销钉数量的增加,导致流域中产生了更多的尾迹。尾迹与销钉相互作用得到了增强,导致流域中产生了更多的涡结构,说明流域中的大部分熔体处于混沌混合的状态。混沌混合使销钉挤出机内的流体拉伸作用得到了增强,流体的混合指数得到增加,混合效率也逐渐增大。     

往复式单螺杆混炼挤出机应用良好

经过实践检验，中国首台终炼胶混炼挤出机连续生产线在德国哈默市MDS公司应用取得成功，产品质量符合德国行业标准。设备主机往复式单螺杆混炼挤出机由江苏新达科技有限公司生产，弥补了普通单螺杆及双螺杆挤出机只能对一薄层物料进行剪切的缺陷。采用独特的运转方式，物料在螺块与销钉之间被剪切，并且被往复输送。     

销钉机筒单螺杆挤出机功耗的模拟研究

采用流体力学计算软件Fluent，在对销钉机筒冷喂料挤出机熔融段和计量段的胶料进行三维流动数值模拟的基础上，考察螺杆转速、反向压差、销钉数量、销钉排间距和螺槽深度对挤出量和螺杆转矩的影响。结果表明，螺杆转速是影响挤出机功耗的首要因素，随着转速增大，挤出量增大，功耗和功耗比（螺杆转矩与挤出量之比）下降；反向压差对挤出量、螺杆转矩和功耗比有一定影响，反向压差越大，功耗比越大；每排销钉数量对对功耗比影响不大；销钉排间距对挤出机功耗比有较为明显的影响，若只考虑产量和功耗，则销钉排间距越大越好。     

销钉式混炼室密炼机的试验研究

本文报道了销钉混炼室密炼机与普通混炼室密炼机对比试验情况。如实介绍了功率消耗、单位能耗、排胶温度和混炼胶性能的试验结果。同时对两种混炼室密炼机的工作原理作了简单分析。     

Mixing in curved tubes

The mixing efficiency in a curved tube is a complex function of the Reynolds number, Schmidt number, curvature ratio and tube pitch, therefore, the relative effectiveness of a helical tube is quite complicated and challenging over a straight tube. A state of art review on mixing of two miscible liquids in curved tubes revealed that the mixing in coils of circular cross section has not been reported in the literature. In the present work a computational fluid dynamics study is performed in curved tubes of circular cross-section of finite pitch under laminar flow conditions to examine the scalar mixing of two miscible fluids using scalar transport technique. In the present study the phenomenon of mixing by convection and diffusion of two flow streams with inlet scalar concentrations of zero and unity in the two halves of a tube perpendicular to the plane of curvature has been reported. The mixing efficiency has been quantified with concentration distributions and unmixedness coefficient at different cross-sections and process conditions (Reynolds number, Schmidt number and curvature ratio) in the straight and curved tube of circular cross-section. The result shows that, in curved tube, for higher Schmidt number fluids, mixing is considerably improved at moderately low Reynolds numbers (Re∼10), but is not affected for Reynolds number of the order of 0.1. It is also reported that mixing in the curved tube is higher at low values of curvature ratio as compared to the higher curvature ratio.     

销钉机筒挤出机螺槽横截面内流体流动与混合的研究

在一定简化条件下，对销钉机筒挤出机螺槽横截面内的流场及混合均化效果以及销钉位置对流场和混合均化效果的影响进行了数值与实验研究。提出了流场中某点混合均化效果、整个流场平均混合均化效果以及混合均化效果统计分布的数值计算与评价方法。数值分析结果与实验结果具有较好的一致性。结果表明，销钉对物料具有明显的强化流动与混合均化的作用：销钉愈接近于螺棱，强化混合均化的效果愈显著：有销钉结构较无销钉结构的平均混合均化效果提高2．5％-5．6％；有销钉结构随着挤出时间的增加，混合均化效果不断提高，无销钉结构随着挤出时间的增加，当混合均化效果达到一定值后则不再提高。     

Mixing efficiency in a pin mixing section for single‐screw extruders

Non‐Newtonian, non‐isothermal, 3D finite‐element simulation of mixing performance in a pin mixing section with different axial gaps in the pins has been carried out according to their realistic configurations. The quantitative evaluation of mixing ability was based on the theory of kinematics of fluid mixing. To learn and to compare the local mixing performance in a standard screw and a pin mixing section, the local mixing efficiency distribution proposed by Ottino was calculated. Also, the RTDs of these mixers were calculated in an attemt to measure mixing. The integration of the two, namely, the integrating local mixing efficiency along a number of particle pathlines from entrance to exit, together with statistical treatment, which was referred as integral mixing efficiency, then gives a quantitative judgment of the total mixing ability of a continuous mixer. The calculated results showed a nonlinear dependence of the mixing ability of a pin mixing section on the axial gap of the pins. Finally, the calculation results were compared with the experimental ones obtained in our previous study.     

往复式单螺杆销钉挤出机典型螺纹元件混合性能研究

使用Polyflow有限元软件对往复式单螺杆销钉挤出机（简称Buss机）的三类典型螺纹元件内物料流动和混合过程进行了数值模拟。流场分析中使用了网格重叠技术。在得到流场速度分布后,基于粒子轨迹跟踪技术计算了物料微元在螺纹元件内的流动轨迹,并分析了Buss机螺纹元件内物料的动态混合过程。以分布混合指数和分隔比例为指标定量地对比了螺纹元件的分布和分散混合性能,在此基础上分析了加工条件、物料特性及销钉布置对Buss机混合性能的影响。数值模拟结果与前人研究有较好的吻合性。     

振动力场对销钉螺杆挤出机混炼过程的影响

利用流体动力学软件POLYFLOW对销钉螺杆挤出机的混炼段进行三维等温数值模拟.通过引入振动力场,采用粒子示踪分析方法对比分析不同振动力场参数对销钉螺杆挤出机混炼过程的影响.结果表明,振动力场对销钉的混炼性能有着明显的改善作用,但存在最佳的振动频率和振幅范围.该结论为寻求最优振动力场参数从而提高塑料混炼质量提供了参考.     

Transitional Mixing of Shear‐Thinning Fluids in Vessels with Multiple Impellers

The mixing efficiency of shear‐thinning fluids was evaluated using carboxymethylcellulose sodium salt (Na‐CMC) aqueous solutions of varying mass concentrations and three types of impellers (Rushton turbine (RT), six‐flat‐blade turbine (FBT), six‐pitched‐down‐blade turbine (PBT)) which were mounted on a common shaft in combinations of three, four, and five impellers. The mixing time proved to be dependent on the number of impellers as well as on the distance between. The Reynolds number has a significant influence on the mixing time for all studied systems. The results of power consumption allowed to choose the impeller system with the best efficiency.     

螺带式混凝土搅拌机混合特性及DEM模拟

采用离散单元法模拟新拌混凝土于搅拌机中的混合过程,研究了双筒螺带式混凝土搅拌机的混合效率。 用Hertz-Mindlin with JKR接触方法建立新拌混凝土离散元模型,模拟了坍落度实验、L箱实验和流变仪实验,将模拟结果与实验结果进行对比,校准模型参数,采用混合系数定量研究了不同初始装填方式下搅拌机的混合效率。结果表明,采用上下装填方式时搅拌机混合效率较高;对任一初始装填方式,左部区域与右部区域、前部区域与后部区域间混合效率无明显差别,而上部区域混合效率比底部区域高,底部出料口处存在搅拌盲区,采用舍弃初始出料的方法可提高新拌混凝土性能。转速较高时混合效率较高,相同旋转圈数时,混合效率基本相同。     

混沌混合中流体指数拉伸与混合效率的数值研究

The stretching and folding of fluid element during chaotic mixing field is studied using numerical method. The chaotic mixing process is caused by periodic secondary flow in a twisted curved pipe. Using the nonlinear discrete velocity field as the dynamical system, the present study connects the fluid particle‘s stretching along its trajectory in one period to a linearized time-varying variational equation. After numerical approximation of the variational equation, fluid stretching is calculated on the whole cross section. The stretching distribution shows an exponential fluid stretching and folding, which indicates an excellent mixing performance.     

基于香农熵的超细粉体填料混合均匀度的评价研究

以香农熵理论为基础,提出了一种量化表征超细粉体填料在基体中混合均匀度的方法。以高密度聚乙烯/碳酸钙(PE-HD/CaCO3)复合材料为研究对象,首先用Photoshop和Image-pro-plus对样品扫描电子显微镜照片中的颗粒和团聚体尺寸进行统计,计算出了相对香农熵和团聚系数,分别表征超细铝粉的分布混合和分散混合,然后引入混合系数对混合均匀性进行综合评价。结果表明,添加了分散剂的PE-HD/CaCO3,CaCO3混合系数较高,拉伸强度和弯曲强度较大,验证了此方法对超细粉体填料混合均匀度评价的适用性。