共查询到18条相似文献,搜索用时 656 毫秒
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提出了全新的同向自洁双螺杆非对称造型新概念。给出了转速比为2∶1的2根螺杆的端面造型和运动关系并建立了数学模型。以符合Carreav定律的流体为加工对象,采用Polyflow软件的叠加网格技术,分别对新型非对称双螺杆和传统双螺杆端面内的周期性二维流动和混合进行数值模拟研究。采用粒子追踪技术,对混合过程进行了动力学行为表征,证实了新型非对称螺杆内混沌混合的存在。通过统计学分析,得出累积分散准数和拉伸长度,分析了新型非对称双螺杆和传统双螺杆的混合行为差异。 相似文献
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设计了非对称差速三螺杆挤出机端面造型,并且,对比其与常规三螺杆、非对称双螺杆挤出机内流体混合行为。对流场中速度矢量场和压力场进行分析,同时,比较分布混合性能中停留时间、分离尺度和混合效率,分散混合性能中最大剪切应力、对数拉伸率和混合指数。结果表明,与常规三螺杆相比,非对称差速三螺杆能有效地避免常规三螺杆中心区回流较大的问题,正向输送能力更强,并且,啮合区两侧压差更大,有利于物料压延。流域内粒子停留时间分布区间集中,分离尺度显著降低,有利于物料分布混合。同时,能提供较强的拉伸作用,使流域内粒子受到更好的拉伸和折叠,从而使其具有较好的混沌混合能力,有利于物料分散混合。 相似文献
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研究了在同向双螺杆挤出机不同混合段螺杆组合下制备玻璃纤维(GF)增强聚酰胺66(PA66)复合材料时的纤维破坏情况,并通过沿螺杆轴向取样分析纤维长度沿挤出方向的变化规律,研究了不同螺杆组合对制品力学性能的影响,设计出适合于PA66/马来酸酐接枝乙烯辛烯共聚物(POE-g-MAH)/GF体系的螺杆组合。结果表明,合理设计纤维加入后的螺杆组合可以有效提高剩余纤维长度及制品的力学性能,同捏合块相比,使用反向齿形盘能够在提供较强混合能力的同时保证较低的剪切强度,从而有利于保持纤维长度,并有助于纤维的分散及物料的混合;将混合元件分开布置,并用输送元件将其分隔开,有助于提高输送能力,保持纤维长度。 相似文献
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啮合同向双螺杆挤出机中组合螺杆性能的数值研究(Ⅱ)混合特性分析 总被引:7,自引:0,他引:7
采用有限元软件POLYFLOW,对组合式啮合同向双螺杆挤出机ZSK60中不同构型的组合螺杆进行了混合分析。通过计算螺杆转过不同角度时的拟稳态流场,采用粒子示踪分析(PTA)方法,对组合螺杆中聚合物熔体的动态混合过程进行了可视化模拟;在此基础上通过对大量粒子运动轨迹的统计处理,分别采用停留时间分布、分布混合指数、分离尺度等累积混合指数表征了组合螺杆的轴向混合性能、分布混合性能以及分散混合性能。此外还研究了不同工艺条件下组合螺杆的混合特性。并将部分数值模拟结果与前人实验研究进行了对比。 相似文献
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应用FEM模拟计算了啮合员向双螺杆挤出机正反向螺纹组合的新型螺杆元件S型元件与捏合块元件的流场,考查了两种元件流场的特性,对比了两种元件流场的挤出特性、分散和分布混合能力。得出在相同有操作条件下,相同外径的S型元件和捏合盘元件相比具有相当的分散混合能力、更加优异的分布混合能力和更加优异的生产能力的结论。 相似文献
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基于非对称流场的混沌混合理论,设计了一种新型的偏心双螺杆挤出机。通过对比传统普通螺杆元件与新型偏心螺杆元件,偏心距不仅决定了螺杆的端面形状,也改变了螺槽形状,使同一导程内的2个独立的C型室螺槽形成一个ω型室螺槽。利用Polyflow软件分别对传统双螺杆挤出机与3种不同偏心距螺杆元件的新型双螺杆挤出机进行模拟仿真,分析了压力场、速度场与混合指数分布规律,计算了4种双螺杆挤出机流场的停留时间分布、分离尺度、最大剪切应力等混合表征系数。结果表明,与传统双螺杆挤出机相比,偏心双螺杆挤出机压力分布不均匀,正负压压力值增大,因此,压力差增大,使熔体回流速度增大,混合效果更佳;拉伸流区域增大,混合能力增强;熔体在流体域内的总体停留时间缩短,混合效果更佳;分离尺度数值下降较快,混合效率较高;偏心螺杆元件对流体的剪切应力增大,分散混合能力增强。 相似文献
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R. M. Secor 《Polymer Engineering and Science》1986,26(9):647-652
A mass transfer model was developed to represent the desorption of a volatile species from a molten polymer in an extruder consisting of co-rotating twin screws in a figure-eight bore. The melt undergoes a series of alternating exposure and mixing processes while being transported axially through the device. The model relates the ratio of entrance to exit concentrations of the volatile species to the dimensions of the screws, the rate of their rotation, the rate of polymer flow, and the diffusion coefficient of the volatile species in the polymer. Experimental data, obtained with a halocarbon-polybutene system in a twin-screw extruder, were compared with predictions of the model. For the observed performance, the model predicts a process screw length about 14 percent below the actual screw length in the experimental extruder. 相似文献
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黄凤春;马秀清;周炳斌;梁文虎 《中国塑料》2011,25(10):90-94
根据啮合同向双螺杆挤出机的啮合原理,设计了一种高分散混合双螺杆元件。运用Polyflow有限元分析软件对该双螺杆元件的3种螺杆构型的流场进行了模拟分析,并且对这3种螺杆构型进行了实验研究。研究表明,错列角为150°的元件的分散混合性能最好,其次是错列角为30°的元件,错列角为90°的元件的分散混合性能最差。 相似文献
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The morphology of high‐density polyethylene (HDPE)/polyamide‐6 (PA‐6) blends with different melt‐shear‐viscosity ratios (VRs), prepared by combining a single‐screw extruder with a convergent die was studied. Two different screw geometries, metering and mixing screws, and three screw speeds, 20, 40 and 60 rpm, were evaluated to investigate their effects on the morphology of extruded ribbons. Two mixing screws with low and high shear intensity, respectively, were used. Both the geometry and speed of screw were found to have an important role in the morphological changes of the blends. In contrast to previous studies, the results shown in this work reveal that it is possible to develop a laminar structure of PA‐6 in an HDPE matrix with a VR larger than one by controlling the flow fields, through appropriately combining the type and shear intensity of the screw with its speed. A well‐developed laminar PA‐6 phase with an aspect ratio of about 100 was obtained under the optimum combination. Copyright © 2004 Society of Chemical Industry 相似文献
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Toshihisa Kajiwara Yuki Nagashima Yoshio Nakano Kazumori Funatsu 《Polymer Engineering and Science》1996,36(16):2142-2152
We have developed a method for predicting the three-dimensional flow field in the melt conveying zone in counter-rotating and co-rotating twin-screw extruders. We applied this technique to the full flight screws with thin flight width and open C-shaped channels in both rotating type extruders having the same screw configurations. We compared the details of velocity and stress fields, the flow rates of transportation, and various kinds of leakage flows for both rotating type extruders. Also, we obtained the spatial distribution of tracer particles and residence time distribution using a numerical tracer experiment. The flow rate in the transport direction in the co-rotating twin-screw was larger than that in the counter-rotating twin-screw, and this suggested that the latter has higher transport performance when the screws have thin flight width and open C-shaped channels as used in this study. As for the distributive mixing, it was found that the co-rotating twin-screw excels in the area of fluid rearrangement between the two screws and distribution in the rotational direction, while the counter-rotating twin-screw has the desirable characteristic of wide distribution in the axial direction. With regard to dispersive mixing, there was no considerable difference between calculated stress fields in both rotating type extruders. 相似文献
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基于同心双轴搅拌器的结构与运行特点,建立了兼顾其流动、混合过程的三维数学模型,并以过程工业应用较多的两种不同尺寸双层组合桨作为内桨、框式桨作为外桨构成的同心双轴搅拌器为研究对象,数值模拟了其在中高黏牛顿流体中同向及反向转动模式的功率特性、流场特性及混合特性。模拟结果表明,同向转动模式下,整个系统的搅拌功耗更小、混合效率更高;外桨功耗受内桨影响较大,一般随内桨转速的增大,恒速外桨的功耗同向转动时会减小、反向转动时会增大;对由桨式搅拌器构成的组合式内桨而言,当内桨直径与釜体直径之比为0.35左右时,相同Reynolds数下的单位体积混合能更小;中高黏牛顿流体中,同心双轴搅拌器的内桨采用上层六斜叶桨+下层六直叶桨的组合形式时更高效节能,仅在体系Reynolds数小于36时,上层二斜叶桨+下层二直叶桨的内桨组合形式才具有相对优势。 相似文献
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Co-rotating, intermeshing twin screw extruders are widely used in polymer compounding and blending. Among the different modules of the co-rotating twin screw extruder, the kneading discs are the dominant ones in determining mixing efficiency. The major difficulty in solving the flow problem in the kneading disc region arises from the complex geometry and the time-dependent flow boundaries as the discs rotate. In this work, a fluid dynamics analysis package—FIDAP—using the finite element method was employed to simulate the flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK-30 co-rotating twin screw extruder. The problem of time dependent flow boundaries was solved by selecting a number of sequential geometries to represent a complete mixing cycle. The flow field was characterized in terms of velocity profiles, pressure distributions, shear stresses generated and a parameter λ quantifying the elongational flow components. The last two parameters are the most important ones in analyzing mixing efficiency. The influence of design variables (stagger angle, right or left handed configuration) and processing conditions (rpm, axial pressure gradient) on the flow characteristics was analyzed. 相似文献