基于ANSYS/CFX渐加速双螺杆设计及三维流场分析

目的:提高双螺杆挤出机的混合效率和工作性能。方法:设计了一种内嵌行星轮系和安装捏合块的新型双螺杆挤出机，并用SolidWorks建立三维模型，以有限体积法为基础，用ANSYS/CFS有限元分析软件对其流道进行分析。获得其宏观压力图、速度矢量图、速度流线图并与传统双螺杆挤出机三维流场进行对比。结果:在行星轮系和捏合块的渐加速作用下，渐加速双螺杆挤出机的混合性能和工作效率要明显优于传统双螺杆，经计算渐加速型双螺杆比普通双螺杆提高20%～25%。结论:渐加速双螺杆在不断加速的过程中使得物料在机筒内停留的时间变短，从而提高产量且减少耗能，捏合块的加入更使得物料可以得到更好的剪切。     

基于ANSYS的带行星轮同轴变速单螺杆挤出机三维流场分析

运用ANSYS/CFX软件对带行星轮同轴变速单螺杆挤出机流道进行分析,并与普通单螺杆进行对比。结果表明：相较于普通单螺杆,新型同轴变速单螺杆挤出机的建压能力更好,物料在螺杆中的停留时间更长,有利于物料更好地混合,表明带行星轮同轴变速单螺杆可局部降低物料运输速度,增加物料混合能力以及螺杆建压能力。     

基于CFX的同轴变速双螺杆挤出机三维流场分析

目的：分析物料在改良后的同轴变速优化双螺杆挤出机流道中的工作状态。方法：运用ANSYS/CFX模拟分析双螺杆挤出机流道数值,得到物料的运动情况,并与传统双螺杆进行对比,通过宏观压力场、宏观速度场、速度流线图、速度矢量图对比分析两种螺杆的性能。结果：同轴变速优化双螺杆的建压能力、混合性能明显优于传统双螺杆,通过中段的减速输送可有效延长物料运输时间。结论：新型优化双螺杆在保留传统双螺杆优势的情况下,额外提升了建压能力和混合性能。     

基于ANSYS的新组合型单螺杆挤出机特性研究

针对普通单螺杆挤出机剪切混合模式单一、工作性能差等问题，研究设计一种新组合型单螺杆。采用SolidWorks建模，ANSYS/CFX有限元分析和对比试验的方法；形成新组合型单螺杆流道整体压力差高于传统单螺杆1.22 MPa左右，物料在进出强剪切段过程中有回流产生，强剪切段物料输送速度较传统单螺杆加快0.012 m/s左右的结果；得出新组合型单螺杆挤出机在80?160 r/min的转速下，物料停留时间较传统单螺杆挤出机缩短5%?12%的试验结论。研究为高性能单螺杆挤出机的优化创新提供理论依据。     

同向全啮合双螺杆植物蛋白挤出机不同螺杆元件的仿真分析

为了明确和量化同向全啮合双螺杆挤出机各螺杆元件的功能,增加配置用于生产植物基肉双螺杆挤出机螺杆的合理性,以低温脱脂花生蛋白粉的物性参数为条件,对SLZ36型挤出机的3种元件长度为32 mm的螺杆元件双头螺旋元件、5啮合盘啮合元件及3齿形盘齿形元件的剪切速率、混合指数、物料停留时间、最大剪切应力分布进行仿真分析。采用Solidworks软件建立元件的几何模型,应用Gambit软件进行模型的网格划分及网格质量分析,在Polyflow软件中进行数值模拟,通过Fieldview软件对仿真结果进行后处理分析。结果表明：通过混合指数分析得到3种螺杆元件对物料的混合性能大小为齿形元件>啮合元件>螺旋元件;通过物料停留时间分析得到3种螺杆元件的轴向混合性能大小为齿形元件>螺旋元件>啮合元件;通过剪切速率及平均最大剪切应力分析得到对物料的剪切性能大小为啮合元件>螺旋元件>齿形元件。进行植物基肉双螺杆挤出机螺杆组合时,针对目前整个螺杆配置螺旋元件最多的情况,在进行物料更换时可以合理地配置啮合元件以增加螺杆剪切能力,配置齿形元件以增加螺杆的混合能力。     

螺棱间隙对单螺杆食品挤压膨化机熔体输送影响数值模拟

采用POLYFLOW软件对单螺杆挤压膨化机中食品熔体的三维等温流场进行数值模拟,结合粒子示踪技术,探索不同螺棱间隙(0.4,0.8,1.2mm)对食品熔体流场和混合性能的影响。研究表明:随着螺棱间隙的减小,螺棱顶端的剪切速率增大,食品熔体平均黏度变小,螺杆的轴向输送能力变差;随着螺棱间隙的增大,食品熔体的停留时间先增后减,分散混合能力变差。当螺棱间隙增至1.2mm时,物料停留时间反而比间隙值为0.4 mm时长,说明螺棱间隙过大,食品物料的停留时间将难以控制,同时对各物料组分的混合效果也较差。螺棱间隙对熔体流场和混合特性均有一定的影响,螺棱间隙为0.8mm时,既能保证对熔体的输送能力,又能保证良好的流场分布和混合效果,为比较理想的螺棱间隙。     

基于CFX的谐波减速优化双螺杆挤出机特性研究

为提高双螺杆挤出机挤出性能，结合谐波减速器，研究设计了一种内含谐波减速器的同轴异速优化双螺杆；用SolidWorks建模，导入ANSYS/CFX有限元分析模块，模拟物料在机筒内的流动状态，围绕宏观压力场、速度场分析，与普通双螺杆对比，并进行实验验证。结果表明：新型双螺杆的物料停留时间较之普通双螺杆提升15%左右；物料在输送过程中有物料交换现象；流道整体压力差几乎不受影响；实现了双螺杆挤出机混合性能的进一步优化。     

单螺杆挤压破裂植物细胞力学模型的研究

单螺杆挤压可以破裂植物细胞,用于辅助植物有效成分的提取.通过选取单螺杆中物料运动方向上的一段微元进行受力分析,分别求得螺杆、机筒、背压对物料的作用力和物料由于自身形变而产生的作用力,得到单螺杆中压力分布的数学模型;并针对截面为正六边形的柱状植物细胞模型,得到植物细胞受力的数学模型.模型表明细胞的受力情况和螺杆自身的结构参数、螺杆转速和挤出速率有关系,在螺杆结构参数确定的前提下,可以通过调整螺杆的转速和挤出速率来改变物料的受力情况,从而达到理想的破壁效果.     

三螺棱周期性扰动混炼单元混炼性能模拟

通过Solidworks软件建立三螺棱周期性扰动混炼单元模型,利于Polyflow的流体分析功能对新型混炼单元与普通螺杆单元进行模拟分析。通过统计停留时间、分离尺度、最大剪切应力三个参数来表征混炼单元的混炼性能,模拟表明:新型混炼单元使物料的分布混合性能和分散混合性能均优于普通螺杆单元;新型混炼单元的流道内物料粒子受到小于2500Pa最大剪切应力的粒子数多于普通螺杆单元的,降低了物料因摩擦过热而导致降解的风险;新型混炼单元的混炼性能优于普通螺杆单元,主要是使物料受到的拉伸作用强于普通螺杆单元。     

单螺杆挤压机工作性能探讨

单螺杆挤压机由于结构简单、价格低而得到广泛的应用。本文从单螺杆挤压机的喂料、输送、挤压的全过程进行分析，探讨改善其输送性能和提高对物料的混合作用的方法。     

Analysis of the dispersive mixing efficiency in a twin-screw extrusion processing of starch based matrix

The flow of plasticized maize starch in a co-rotating twin screw extruder was simulated by using computational fluid dynamics (CFD). Sensitivity of the simulation to the selected viscosity model was analyzed. The results suggest that about 16 times increase in zero shear viscosity has no influence on the flow, whereas a slight change in viscosity at the shear thinning region leads to significant increase in pressure drop along the mixing zone of extruder. Simulation results were validated quantitatively by experimental data. Furthermore, the flow type and profile in the extruder were discussed by using the influence of screw speed and screw configuration as exemplary process parameters. To evaluate the dispersive mixing efficiency, material specific critical capillary number was implemented into particle tracking simulations. Maximum shear stress generated at the tip of the screws was used to calculate the maximum capillary ratio, and therefore to determine the dispersive mixing efficiency. The results show that increase in screw speed led to better dispersive mixing, although the generated shear stresses decreased. To investigate the influence of screw geometry, two different screw configurations were simulated. The results show that the dispersive mixing efficiency can be improved by using reverse kneading blocks at which more particles are exposed to high shear stresses.     

正向螺纹元件组合对反向螺纹元件熔体输送特性的影响

目的：探究熔体输送段正向螺纹元件间的不同组合对反向螺纹元件的熔体输送特性的影响。方法：通过改变导程构建两种不同模型,使用SolidWorks软件建立三维模型,使用Polyflow软件对两种模型在熔体输送段的挤出过程进行数值模拟,分析不同导程下螺纹元件的螺槽宽度及螺棱厚度对流场的影响及不同转速下流场的变化,通过实验验证转速对物料混合效果的影响。结果：所构建的模型均可使熔体通过反向螺纹元件;在相同螺杆转速下,由大导程螺纹元件构建的模型一建压能力和输送能力强于由小导程构建的模型二;模型一在分散混合能力上优于模型二,在分布混合能力上弱于模型二;在两端压差相同的情况下,增加转速可以提高物料的分散混合效果。结论：在聚乳酸改进加工过程中采用模型一且提高螺杆转速可进一步破碎物料,提高挤出物的质量。     

啮合同向双螺杆挤出机不同螺杆构型对其流场的影响

目的：探究啮合同向双螺杆挤出机不同螺杆构型对流场的影响,改善聚乳酸的材料性能。方法：应用Solidworks软件建立双头螺纹元件的几何模型,在Polyflow中进行数值模拟,借助Fieldview软件对仿真结果进行后处理分析,并对比剪切速率场、压力场、速度场、黏度场以及停留时间分布曲线RTD,得出螺槽深度对流场的影响。结果：在中心距相同的情况下,通过改变螺纹元件的外径和内径之比改变螺槽深度,在相同的工艺条件下,同向双螺杆流道内各物理场以及混合性能均存在较大差异;与构型二相比,构型一的剪切作用更强,但构型二的建压能力更好;挤出过程中,构型二轴向混合能力较好但自清洁能力较差,而构型一轴向混合能力较差、自清洁能力较好。结论：螺槽深度的改变对流道混合性能有着一定影响且存在规律性,可有效指导双螺杆挤出机螺纹元件的设计。     

Distribution of the residence time in a single-screw extruder with differing numbers of mixing elements

Starch was extruded with sodium trimetaphosphate and sodium hydroxide in a single‐screw extruder at 40% moisture content and screw speeds of 90 and 140 r.p.m. The effect of screw configurations, which included one and two mixing elements, on mean residence time, spread of residence time distribution (RTD), and flow pattern were determined. Increasing the screw speed and reducing the number of mixing elements reduced mean residence time. Higher RTD spread values were obtained at a screw speed of 90 r.p.m. when compared with 140 r.p.m. and increasing the number of mixing elements in the screw increased the RTD spread. The flow pattern was between plug and mixed flow, and increasing the number of a mixing element in the screw did not significantly affect the flow pattern in the single‐screw extruder.     

EFFECT of SCREW CONFIGURATION and SPEED ON RTD and EXPANSION of RICE EXTRUDATE

The influence of screw configuration and screw speed on the residence time distribution and product expansion was determined for rice meal processed in a corotating twin screw extruder. Screw speed had strong effect on the E(t)- and F(t)-diagrams, with the mean residence time varying inversely with screw speed from 206 s to 256 s. the F-diagram was modeled by the combination of perfect mixing and plug flow. the P estimates, which express the fraction of material in plug flow, varied inversely with screw speed from 0.41 to 0.55 for the operating conditions in this study. Both screw configuration and screw speed were statistically significant to the expansion ratios of rice extrudate, with the expansion in the height ranging from 2.98 to 4.13.     

PROPERTIES of CROSS-LINKED STARCH PRODUCED IN A SINGLE SCREW EXTRUDER WITH and WITHOUT A MIXING ELEMENT

Starch was extruded with sodium hydroxide and sodium trimetaphosphate in order to cross‐link it in a single‐screw extruder with and without a mixing element at constant screw speed of 90 rpm in the first set of experiments and at similar mean residence time controlled by screw speed in the second set of experiments. For the screw without mixing element in the second set of experiments, screw speed was adjusted to give the similar residence time as the single‐screw extruder with mixing element at 220 rpm. Phosphorus content and pasting curves of extrudates showed that starch was cross‐linked during extrusion. Replacing the screw without mixing element by the screw with mixing