共查询到19条相似文献,搜索用时 628 毫秒
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利用POLYFLOW软件,对聚合物熔体在双转子连续混炼机混炼段的拟稳态流场进行数值模拟,采用粒子示踪分析方法对物料所经历的流场特性进行统计学分析。得到了平均剪切应力、停留时间分布、累积最大拉伸速率等参数,通过其分析了转子结构和工艺参数对双转子连续混炼机混合性能的影响。结果表明,转子转速的提高使得物料所经受的剪切和拉伸作用增强;喂料速率的提高,使比剪切速率减小,物料在混炼段的停留时间变短;螺棱交汇区长度减小,流场中的剪切作用增强,螺棱交汇区长度和螺棱包角对停留时间分布的影响不大。最后对数值模拟的结果进行试验验证,结果基本一致。 相似文献
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双转子连续混炼机是一种具有优异分散与分布混合特性的连续混炼设备。本文运用混沌流动理论,对双转子连续混炼机混炼流场的混沌流动特性进行了分析研究,提出了采用以物料停留时间为基准的修正Lyapunov指数来描述混合过程中发生的拉伸应变,并借助于有限元计算,得出流场绝大部分区域的修正Lyapunov指数大于零,并发现混炼流场中存在非常有利于拉伸、折叠流动的涡旋流动,赋予了双转子连续混炼机优异的分散与分布混合特性。 相似文献
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双转子连续混炼机新型多棱榫状转子结构与混炼工艺特性研究 总被引:1,自引:0,他引:1
研究了新型多棱榫状转子的结构、混炼原理和工艺特性。结果表明,多棱榫状转子混炼能力强、分散混合效果好、混炼能耗低。其混炼功率随转速、加料量加大而增加,随卸料门开启度增大而减小。混炼时加料量与物料停留时间成反比,转速对物料停留时间影响不大。 相似文献
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AndreasLimper 《塑料挤出》2003,(1):26-28
行星齿轮挤出机混炼效率高,物料停留时间区间短,温度控制精确,可满足塑料混炼中的高质量要求。行星芯轴构型对混合料质量有着极大影响。 相似文献
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双转子连续混炼机混合工艺特点及影响因素 总被引:1,自引:1,他引:0
讨论了双转子连续混炼机的混合工艺特点及转子结构尺寸,转子螺杆顶部线速度,物料卸料门开启度大小对混合过程的影响,提出了以物料在混炼机中的转向混合循环次数,转子螺棱顶部线速度为基本参数控制混炼机的混合过程。 相似文献
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使用Polyflow软件对往复式单螺杆销钉挤出机(Buss机)三类典型螺纹元件的停留时间分布(RTD)进行了三维动态模拟,分析了工艺条件和物料特性对RTD的影响。根据Buss机的螺杆组合构型,应用卷积技术求得了物料沿整根螺杆的RTD曲线,探讨了物料在Buss机内的RTD规律与工艺条件变化的相关性。 相似文献
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该文介绍了一种聚合物和纳米复合材料共混的新型微型混炼机。这种混炼机配备了一个独特的不对称转子,它可以在一个圆筒型的空间内旋转,从而实现对物料的拉伸和高剪切混合。文中通过与密炼机和MiniMAX模型机的比较,评价了这种混炼机的工作性能。即,用这几种混炼机分别对不混溶高分子共混物和用蒸馏法获得的纳米碳纤维进行了共混,研究它们在形态上的差异。结果表明,这种新型的微型混炼机较之其它类型混炼机,具有更优良的分散和分布效果。 相似文献
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采用有限元分析软件POLYFLOW对非牛顿聚合物熔体在ECM30双转子连续混炼机转子混炼段的三维等温流动进行了数值模拟,得到了转子混炼段流场的压力、各速度分量、剪切速率的分布。通过对这些流场参数分布的分析。发现在该类混炼机的轴向存在着一定的反向流动。使得该设备具有较强的轴向分布混合特性;另一方面,转子螺棱顶部与机筒内壁的问隙处存在较大的剪切速率,保证了对物料进行有效的分散。 相似文献
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J. Wei X.L. Liang D.B. Chen Y.L. Yang D.M. Zhou 《Polymer Engineering and Science》2014,54(10):2407-2419
In this article, a novel continuous twin‐screw kneader was proposed. The end‐cross section of the screw rotor consists of convex arcs and cycloidal curves and the rotors profiles were presented. The mixing performance of the novel twin screw kneader was simulated using finite element method (FEM) combined with mesh superimposition technique (MST). Statistical analysis was carried out for flow field using particle tracking technique to research the effect of geometry parameters and working parameters on the mixing performance. To study the dispersive mixing performance, specifically the maximum shear rate, maximum shear stress, maximum mixing index, residence time distribution (RTD) and RTD density function of tracer particles, and dispersive mixing is evaluated using the mixing index in combination with the shear stress. The results show that the changes of centre distance between female and male rotor have little influence on dispersive mixing performance, the lead of rotor has little effect on maximum shear stress and maximum shear rate, while it has an obvious effect on mixing index, cumulative RTD, and RTD density function. The rotor speed has obvious influence on mixing performance, and average residence time of material decreases greatly and the mixing ability is weakened, while the self‐cleaning performance of rotor improved obviously with the increasing of rotor speed. POLYM. ENG. SCI., 54:2407–2419, 2014. © 2013 Society of Plastics Engineers 相似文献
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Measuring the residence time distribution in a twin screw extruder with the use of NIR‐spectroscopy 下载免费PDF全文
The mean residence time (MRT) and the residence time distribution (RTD) of polypropylene in a twin‐screw extruder was determined directly in‐line with the help of near infrared (NIR) spectroscopy and the use of an UV‐absorber as tracer. Different experiment alignments such as screw speed, mass throughput, back pressure as well as tracer content and their influence on MRT and RTD have been investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39919. 相似文献
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Clémence Nikitine Elisabeth Rodier Martial Sauceau Jacques Fages 《Chemical Engineering Research and Design》2009,87(6):809-816
The residence time distribution (RTD) of a flowing polymer through a single screw extruder was studied. This extruder allows injecting supercritical carbon dioxide (scCO2) used as physical foaming agent. The tested material is Eudragit E100, a pharmaceutical polymer. RTD was measured at various operating conditions and a model describing RTD has been developed. High screw speed or high temperature implies short residence time, but these parameters do not have the same effect on polymer flow. In the flow rate range studied, scCO2 has no significant influence. A mathematical model consisting of a plug flow reactor in series with a continuous stirred tank reactor (CSTR) cross-flowing with a dead volume fitted well the experimental data. 相似文献
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齿形盘元件的局部停留时间分布 总被引:2,自引:0,他引:2
采用自制荧光检测装置在线测量含齿形盘元件(TME)的双螺杆挤出机的部分停留时间分布(PRTD),利用去卷积方法计算TME的局部停留时间分布(LRTD),并将PRTD转换成停留体积分布(RVD)和停留转数分布(RRD)。研究表明,直齿的LRTD曲线形状比斜齿更宽,其混合能力更强;喂料速率(Q)和螺杆转速(N)的提高均使LRTD曲线向短时间方向移动。等流量转速比(Q/N)的RRD和RVD曲线重合;提高Q/N,使RRD向低转数的方向移动,而RVD向高体积方向移动。对于特定螺杆构型,不同螺杆转速和喂料速率下的RVD曲线仅是体积坐标方向的平移,RVD曲线形状主要取决于螺杆构型。 相似文献
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This paper reports measurements of the influence of riser exit geometry upon the particle residence time distribution in the riser of a square cross section, cold model, circulating fluidised bed. The bed is operated within the fast fluidisation regime. The fast response particle RTD technique developed by Harris et al. (Chem. Eng. J. 89 (2002) 127-142) was used to measure the residence time distribution.The geometry of the riser exit is shown to have a modest but consistent influence upon the particle RTD; the influence of operating conditions, i.e. superficial gas velocity and solids flux is more significant.Increasing the refluxing effect of the riser exit increases the mean, variance and breakthrough time and decreases the coefficient of variation of the residence time distribution. Changes in reflux do not have a systematic effect upon the skewness of the RTD. 相似文献
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The residence time distribution (RTD) of heterogeneous citrus waste particles was determined in a semi-pilot-scale rotary dryer with concurrent flow under several operational conditions. The experimental methodology was based on the stimulus-response technique, which consisted of injecting pulse-like tracers in the dryer feed stream. Measurements of RTD were performed to build up experimental curves that were numerically integrated to provide the mean residence time. A perfectly-stirred-tank in series model and a neural network model were derived. In addition, empirical and semi-empirical correlations from the literature were used to estimate residence time and the influence of operating conditions on this variable was investigated. 相似文献