共查询到20条相似文献,搜索用时 218 毫秒
1.
2.
《工程塑料应用》2020,(3)
在双螺杆挤出机中引入偏心圆啮合盘元件,分析了新型啮合盘元件偏心圆啮合盘元件的压力场、速度矢量场、剪切速率场和混合指数场。同时比较了其在不同错列角和偏心距下的对数拉伸率、最大剪切速率、停留时间分布、分布指数和分离尺度。结果表明,偏心圆啮合盘元件轴向和周向压力梯度较大,两转子棱峰之间区域流动性较好。偏心圆啮合盘元件的轴向间隙和螺棱顶隙为其提供了良好的剪切能力。偏心搅拌提供了较强的拉伸作用,增强了其拉伸折叠效果,从而使其具有较好的混沌混合能力。对比不同的几何参数发现错列角为60°和偏心距为5 mm的啮合盘元件拥有较好的分散混合性能和分布混合性能。通过粒子可视化及其混合特性曲线分析,为深入了解偏心搅拌提供了理论依据。 相似文献
3.
利用ANSYS有限元分析软件对带有混合块的新型锥形双螺杆的混合段流场进行了三维模拟分析,通过速度场求出流量,并求出剪切速率,剪切应力及回流量来衡量混合效果,找出了混合块几何条件(间隙,错列角)及操作条件(转速,压差等)对挤出机混合效果的影响。 相似文献
4.
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
5.
以装有玻璃视窗的可视化双螺杆挤出机为手段,在不同操作条件下对高密度聚乙烯(HDPE)粒料在不同错列角、不同轴向长度的反向捏合块的熔融过程进行了实验研究。以实验为基础,讨论了加料量、螺杆转速以及反向捏合块厚度与错列角对聚合物颗粒熔融过程的影响。研究表明,反向捏合块的阻力大小对聚合物的熔融过程十分重要,捏合块中物料的充满度与物料的停留时间是聚合物颗粒熔融的决定因素。 相似文献
6.
7.
8.
9.
啮合同向双螺杆挤出机中组合螺杆性能的数值研究(Ⅰ)瞬态流场分析 总被引:7,自引:1,他引:7
采用聚合物流动分析软件POLYFLOW,数值模拟了聚合物熔体在组合式啮合同向双螺杆挤出机ZSK60的组合螺杆中的三维等温流动。在计算所得速度场和压力场的基础上,全面分析并讨论了由不同厚度和不同错列角的捏合块元件组成的组合螺杆的流场分布规律;研究了组合螺杆的输送性能和挤出稳定性;并分别采用平均剪切速率、平均特征剪切应力以及平均拉伸流动指数等瞬态混合指数表征了组合螺杆的瞬态混合特性。此外还考察了两种不同流变性质的聚合物熔体在组合螺杆中的瞬态流场分布规律。所得结论可为双螺杆挤出的数值模拟研究提供一定的方法指导,并为其工程实践提供一定的理论指导。 相似文献
10.
采用同向啮合双螺杆挤出机的不同螺杆组合形式,研究了捏合错列角对双螺杆挤出聚合物共混物表层和内层分散相粒子粒径及其分布的影响。发现螺杆后段采用不同错列角的捏合盘,对于分散相粒子尺寸和分布状态都有明显影响。在塑化区多段式组合的后段采用剪切强、停留时间长的捏合盘(K45°、K60°),可有效地减小分散相粒子尺寸但分布状态不理想;使用 K30°的捏合盘时,分散相粒子分布状态最佳;整体两段式螺杆的前段混合段中设置 K45°捏合盘,有利于分散相含量较少情况下粒子的尺寸及分布的均匀性的提高。 相似文献
11.
Yu He Xiaobin Zhan Baojun Shen Zhibin Sun Jiecai Long Yili Yang Xiwen Li 《American Institute of Chemical Engineers》2022,68(2):e17492
A twin cam mixer (TCM) system equipped with two triangular cams is built in this study. The effect of operating conditions on chaotic advection in TCM is investigated. Particle Image Velocimetry (PIV) is employed to investigate the flow characteristics under co- and counter-rotating modes. Based on the good agreement between simulation and experimental results, chaotic advection under various operating conditions is investigated numerically. To evaluate the chaotic advection, time series Poincaré section, recording point density, and combined mixing index are proposed. The results show that counter-rotating mode is superior to co-rotating mode regarding chaotic advection. A more global chaotic advection can be obtained with the cams in TCM rotating at a higher average angular velocity, higher disturbance quantity, and lower disturbance frequency. The chaotic advection in TCM under different waveform protocols has no significant difference, but it is all better than that under constant protocol. 相似文献
12.
Mubashshir Ahmad Ansari 《Chemical engineering science》2007,62(23):6687-6695
Shape optimization of a staggered herringbone groove micromixer using three-dimensional Navier-Stokes analysis has been carried out. The analysis of the degree of mixing is performed by the calculation of spatial data statistics. The calculation of the variance of the mass fraction at various nodes on a plane in the channel is used to quantify mixing. A numerical optimization technique is applied to optimize the shape of the grooves on a single wall of the channel. Two design variables, namely, the ratio of the groove depth to channel height ratio and the angle of the groove, are selected for optimization. A mixing index is used as the objective function. The results of the optimization show that the mixing is very sensitive to the shape of the groove which can be used in controlling the mixing in microdevices. The mixing is affected by the depth of the groove much more than the angle of the groove. 相似文献
13.
微混合器是常见的用于流体混合的设备,由于特斯拉阀结构简单稳定,流动方式特殊,具有开发微混合器的潜质。本文通过数值模拟的方法,在特斯拉阀结构以及前期研究的基础上,改进并优化了一种特斯拉型的微混合器,利用流体力学软件(Fluent)研究了不同θ角度以及不同雷诺数下的混合程度,并对该结构的混合效果进行了流场分析以及试验验证。结果表明,该新型微混合器的最佳几何参数为θ=30°。两股流体在Re=52.5、混合长度为50mm时,混合程度η=0.9647,体系压降为330.45Pa。该微混合器的操作压降较低,相对于先前结构,混合性能更好,混合长度更短。 相似文献
14.
The radial basis neural network (RBNN) method has been applied to shape optimization of a staggered herringbone groove micromixer using three‐dimensional Navier‐Stokes analysis. The calculation of the variance of the mass fraction at various nodes on a plane in the channel is used to quantify the mixing. Optimization techniques based on the RBNN method are used to optimize the shape of the grooves on a single wall of the channel. Three design variables, i.e., the ratio of the groove depth to channel height, the ratio of the groove width to groove pitch, and the angle of the groove, are selected for optimization. The mixing index at the end of the patterned groove is employed as the objective function. The dependence of the objective function on the design variables is analyzed. The RBNN method is successfully applied to improve the degree of mixing with modification of the groove shape. 相似文献
15.
16.
17.
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
18.
Yoji Akao Hisakazu Shindo Nobuo Yagi L.T. Fan R.H. Wang F.S. Lai 《Powder Technology》1976,15(2):207-214
Most of the available definitions of the mixing index, which specifies homogeneity or distribution of the composition in a solids mixture, are based on the variance of the concentration of a certain component among spot samples. However, for a solid—solid chemical reaction or any process involving contact between different solid phases, its rate is proportional to the contact points or area among particles of the different phases. Thus a definition of a microscopic and geometric mixing index based on the number of contact points appears to be of practical significance.The contact number is the number of contact points between two different types of particles for one key particles, a particle species which is selected as a reference. In this paper, the estimation of the mean contact number from spot samples is considered. An expression for estimating the contact number from spot samples is derived. Expressions for the expected value (population mean contact number) and the variance of this mean contact number are also derived. To verify these expression, random numbers with a uniform distribution are generated to simulate a binary component mixture in the completely mixed state. Results of the simulation are in reasonably good agreement with the derived expressions. The mixing index based on the mean contact number is able to indicate the homogeneity of a mixture with regular packing arrangement. In such a mixture, particles are packed either cubically or hexagonally in each layer, and therefore it is difficult to estimate the homogeneity of the mixture from the sample variance. 相似文献
19.
Hongjun Song Xie-Zhen Yin Dawn J. Bennett 《Chemical Engineering Research and Design》2008,86(8):883-891
In this paper the mixing effect of the staggered herringbone micromixer (SHM) was investigated by using the slip-driven method. This method simplified the 3D flow in the staggered herringbone micromixer into a 2D cavity flow with an axial Poiseuille flow. The solution of the 2D cavity flow was obtained by solving the biharmonic equation. An improved design with a cosine asymmetric factor P(z) was proposed, and its mixing effect was demonstrated by comparing the effect with the original design [Stroock, A.D., Dertinger, S.K.W., Ajdari, A., Mezic, I., Stone, H.A. and Whitesides, G.M., 2002, Chaotic mixer for microchannels, Science, 295: 647–651; Stroock, A.D., Dertinger, S.K.W., Whitesides, G.M. and Ajdari, A., 2002, Patterning flows using grooved surfaces, Anal Chem, 74: 5306–5312]. Four methods evaluating the mixing effect were used: (1) mixing images at different cycles; (2) Poincaré Sections; (3) segregation intensity and (4) stretching computation. Finally, an optimized value of P0 = 1/6 was obtained, and the mixing effect of the improved design for different P0 is discussed. 相似文献
20.
提出了采用副螺棱轴向往复运动提高单螺杆挤出机混合的结构并建立了相应的数学模型。对挤出机内牛顿流体三维周期性流动和混合过程进行了数值模拟。采用有限体积方法,变量分布采用交错网格,副螺棱的周期性运动边界通过叠加网格方式实现。采用4阶Runge-Kutta方法实现流体追踪计算,得到了示踪剂界面增长及累积停留时间分布。采用Poincaré 截面揭示混沌混合存在的区域,证实了副螺棱往复运动能够产生混沌混合效应提高螺槽内的混合效果,与其位置固定时相比,缩短了平均停留时间,停留时间分布变窄。作为对比,同时分析了常规的副螺棱位置固定的单螺杆挤出机内的相应混合行为。 相似文献