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。     

螺杆轴向移动对塑化流场均匀性影响的三维仿真研究

采用Polyflow软件对相同工艺条件下螺杆挤出机和往复式螺杆注塑机塑化时计量段流道内熔体进行了三维非等温流动模拟。比较两者中温度场、黏度场、速度场及压力场分布。结果表明,挤出螺杆塑化时的温度和黏度分布更加均匀;注射螺杆后退有利于提高熔体输送能力,但挤出螺杆塑化更稳定。     

木塑复合材料单螺杆挤出机螺杆计量段的优化设计

从单螺杆挤出机的挤出过程及挤出理论出发,分析螺杆结构及其几何参数对螺杆塑化性能的影响,提出衡量螺杆塑化性能优劣的标准,并以此为优化目标,以竹粉/PP为例,对螺杆的相关几何参数进行优化。优化结果表明:木塑复合材料专用螺杆较普通塑料用螺杆更利于木塑复合材料熔体的输送,避免了因为木塑复合材料熔体黏度增加而出现的一系列问题。     

挤出机计量段螺杆的优化设计

通过有限元与正交设计相结合的方法,对单螺杆挤出机计量段内物料的流动过程进行数值模拟,通过多目标优化计算得到的结果探讨螺杆的几何参数对计量段挤出过程的单耗,熔体输送速率及螺杆所受轴向力的影响,得出最优的螺杆参数因子水平组合.用此方法对螺杆的优化设计有一定指导意义,不但可缩短产品设计周期.而且减少设计成本.     

三螺杆挤出机中剪切-拉伸交变流场对PP/PE-HD体系增韧效果的影响

利用倒三角形排列三螺杆挤出机与传统双螺杆挤出机对不同黏度比的聚丙烯/高密度聚乙烯(PP/PE-HD)体系进行混炼加工,研究了三螺杆挤出机中剪切拉伸交变流场对于高黏度比聚合物两相体系的分散混合及分布混合效果的影响;并通过高黏度比体系的混合效果证明三螺杆挤出机中剪切拉伸交变流场的作用效果及机理。结果表明,在高黏度比体系的加工中,倒三角形排列三螺杆挤出机分散与分布混合效果明显优于双螺杆挤出机,且三螺杆挤出机的增韧效果随着体系黏度比的增大而提升。     

同向双螺杆熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响

对啮合同向双螺杆挤出机,将捏合盘置于熔体输送段,通过改变捏合盘错列角,研究双螺杆挤出过程熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响。应用差示扫描量热仪对两相共混体系HDPE/PS的热性能进行了实验研究,结果表明:螺杆构型对共混物的相容性影响不大。同时采用扫描电子显微镜考察了HDPE/PS共混物在熔体输送段末端位置和机头末端所取试样的相态结构,研究表明:置于熔体输送段捏合盘元件错列角对共混物分散相的相畴尺寸有一定影响。     

Sc-CO_2辅助聚合物挤出中螺杆结构对熔体压力的影响

采用Polyflow软件对双螺杆挤出机内不同螺杆元件所形成流道中的熔体流动进行了模拟,分析了不同螺杆元件的建压能力。结合超临界二氧化碳(Sc-CO2)辅助挤出的螺杆组合原则,对不同螺杆元件组合的螺杆结构进行了挤出实验;并通过对熔体压力的模拟值与实际测量值的比较,分析了不同螺杆结构对熔体压力的影响;另外还针对不同材料的挤出加工确定了相应的螺杆结构。     

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。     

啮合同向双螺杆挤出机单／双头螺纹元件熔体输送与混合特性的研究

采用数值模拟和实验的方法,对啮合同向双螺杆挤出机中单／双头螺纹元件的熔体输送与混合特性进行对比。结果表明,在计量输送段放置一段单头螺纹元件时,回流量小,正向输送能力强;螺杆所受扭矩小,消耗能量少;挤出物料的耐冲击性能较高。     

"一字"型排列三螺杆挤出机三维流场分析

利用ANSYS软件包分析了聚乙烯在“一字”型排列三螺杆挤出机常规螺纹元件中的流动情况,讨论了整个流道的速度分布、压力分布、粘度分布,并和双螺杆挤出机常规螺纹元件的挤出特性进行了比较。结果表明,三螺杆挤出机的物料输运能力、分散性混合能力以及分布性混合能力都好于双螺杆挤出机。     

Analysis and experimental evaluation of twin screw extruders

Twin screw extruders can he classified according to their geometrical configuration. The main distinction is made between intermeshing and nonintermeshing extruders. Another distinguishing characteristic is the sense of rotation. The most important characteristics of the various twin screw extruders are examined, with particular emphasis on the effect of screw geometry on the conveying characteristics. A brief review is given of the state of the art in theoretical analysis of twin screw extruders. Experiments with two lab scale, intermeshing twin screw extruders are described, one co- and one counterrotating. Results are presented on power consumption, residence time distribution, and mixing characteristics of the two extruders. The counterrotating extruder exhibits a narrower residence time distribution and better dispersive mixing capability. The corotating extruder showed a better distributive mixing capability. These results can be explained in terms of the conveying and mixing mechanisms in both extruders. The overall extruder performance seems to be dominated by the effect of the intenneshing region. Any realistic, theoretical analysis of twin screw extruders should be centered around the flow behavior and mixing characteristics of the intermeshing region. The corotating extruder appears to be best suited for melt blending operations, while the counterrotating extruder seems to be preferred in operations where solid fillers have to be dispersed in a polymer matrix.     

Theoretical analysis of residence time distribution functions and strain distribution functions in plasticating screw extruders

The residence time distribution (RTD) function in a single screw plasticating extruder was theoretically calculated. The calculation is based on the solids conveying, melting, and melt conveying models in extruders. The screw channel is divided into small axial increments and the path of each exiting fluid particle is followed from hopper to die. In addition to the residence times the total shear deformation or strain imposed on the fluid particles was also calculated. This together with the RTD function has led to the definition and calculation of the strain distribution function (SDF). This function is proposed for quantitative characterization of the mixing performance of screw extruders as well as other laminar mixers. Some simple idealized batch and continuous laminar mixers are analyzed in terms of the SDF. Finally, the effect of extruder operating conditions and screw design on the RTD and SDF were investigated by computer simulations.     

三螺杆挤出机与双螺杆挤出机混合性能的比较

利用聚合物流体分析软件Polyflow,对倒三角形排列的三螺杆挤出机和等规格的双螺杆挤出机的混合性能进行了深入分析。通过计算不同角度的拟稳态流场,采用示踪粒子法对聚合物熔体在流场中的动态混合情况进行三维等温数值模拟,在此基础上对粒子轨迹进行统计后处理,并分别采用混合指数、面积伸展率和停留时间分布表征流场的分散混合能力、分布混合能力和轴向混合能力,进而比较两种挤出机的混合性能。另外,在实验条件与模拟条件相同的情况下,进行了实验验证。模拟结果表明,三螺杆挤出机各方面的混合性能均优于双螺杆挤出机。实验结果表明,实验数据与模拟结果基本一致。     

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...     

Study on Extrusion Characteristics of the Tri-Screw Extruder

A novel kind of extruding machinery is proposed—a tri-screw extruder (TRISE), in which three intermeshed screws are arranged in the three corners of a triangle; three meshing regions and a center zone also comprise the special construction. The flow rate and the pressure-generating ability of the melt in the thread-zone flow field of the tri-screw extruder, especially the pumping formed by the action of taking in and sending out melt in the unique center zone, are also described. The results of simulation and experiments clearly show that the tri-screw extruder has stronger conveying capacity. The shear frequency of material in the tri-screw extruder is higher than that in the twin-screw extruder, which means that filler could be loaded to a much higher point in the TRISE than in the twin-screw. Results from the TRISE also show that energy consumption of the TRISE is lower than that of the twin-screw extruder.     

塑料电磁动态塑化挤出机的挤出功率研究与模拟

本文采用自行修正的Tanner本构方程研究了塑料电磁动态塑化挤出机中熔体输送挤出功率对振动力场的响应。建立了振动力场作用下熔体输送挤出功率的理论模型,以此为基础模拟塑料电磁动态塑化挤出机的挤出功率,并进行了实验研究,结果表明理论模拟能够在一定范围内反映实际情况,为塑料电磁动态塑化挤出设备的设计和生产应用提供重要的理论指导依据。     

Characteristics Study of Polymer Melt Conveying Capacity in Vane Plasticization Extruder

A vane extruder is novel equipment for polymer processing. The materials were conveyed and plasticized by a group of vane plasticization units and the materials suffered normal stress during processing. An analytic model was developed to analyze the conveying capacity of melt in the vane plasticization unit of which the melt can be conveyed positively. The analysis of conveying capacity of melt in the vane plasticization unit shows that the conveying capacity increased with the rotate speed, eccentricity distance, vane width, inner-diameter of stator. And the leakage flow model was developed to show that the leakage flow is increased with the width of leakage gaps but decreased with the apparent viscosity of melt. The experiment results show a linear variation of production with rotating speed, and small dependence effect of production with die pressure variation.     

同向旋转三螺杆挤出机固体输送段输送特性研究

基于离散元法分别对同向旋转的三螺杆以及双螺杆挤出机固体输送行为进行仿真模拟,对三螺杆挤出机颗粒速度分布以及受力分布进行分析,将三螺杆和双螺杆挤出机颗粒填充效率、输送质量以及质量流率进行对比分析.结果表明,位于螺棱和机筒附近位置的颗粒受到螺棱推力及机筒摩擦力影响较大,具有较高的速度;挤出机内部各区域颗粒填充顺序受螺杆旋转...     

耦合双槽单螺杆挤出机停留时间研究

提供了一种全新的分析挤出机停留时间的方法。在相同螺杆转速下,耦合双槽单螺杆挤出机物料的停留时间低于传统光滑机筒单螺杆挤出机和螺旋沟槽IKV单螺杆挤出机;耦合双槽单螺杆挤出机可以有效提高挤出机的熔融效率,实现高固体输送产量下的熔融效率与固体输送效率的匹配。     

Qualitative analysis of twin-screw extruder performance in stabilization pelletizing of HDPE resins

Two twin-screw extruders of different size and centerline distance C_L were compared. To understand better the performance of the extruders, the operation points were optimized for an HDPE (high-density polyethylene) film product, and the performance of screw configuration was qualitatively analyzed with some numerical methods at the operation points. The machinery with narrower C_L was found to have lower average shear rate, higher conveying capacity, and more channeling in the conveying flow. That means also a need for severe processing in the kneading zone. The extruder with narrow C_L had a narrow operation window, and that made it more difficult to combine homogenization and degradation of the product.