啮合同向差速双螺杆挤出机挤出聚乳酸流场分析

目的：探究不同差速比的螺杆组在流道性能上的差异,明确差速对聚乳酸材料挤出性能的影响。方法：应用Solidworks软件建立4组差速双螺杆组,通过Fluent软件进行网格划分和有限元数值模拟,使用CFD-post软件分析计算结果,并对其性能进行验证。结果：当进出口压力分别为0.2,0.5 MPa,单头基准转速为30 r/min时,差速比为1∶2和1∶3的螺杆在不同性能下各有优劣,螺杆的产量和机筒内压力在差速比为1∶2时具有优势,螺杆的混合能力在差速比为1∶3时具有优势。结论：对比传统双螺杆挤出机,差速双螺杆挤出机对聚乳酸材料的挤出性能为正向影响,可作为全新的聚乳酸改性设备。     

啮合异向双螺杆挤出机中螺杆端面结构参数对聚乳酸流场的影响

目的:探究啮合异向双螺杆挤出机中螺杆构型的改变对聚乳酸流场的影响。方法:通过Solidworks软件建立异向双头螺纹元件的理论模型和经两种不同方式调整结构参数后的螺纹元件几何模型,将建立的三维模型导入Gambit软件进行网格划分,再应用Polyflow软件进行流场模拟计算,最终借助Fieldview软件提取流场分布结果,对比分析修正时螺纹元件端面上结构参数的调整对剪切速率场、黏度场和速度场的影响。结果:修正时螺纹元件的结构参数经两种方式调整后均会对聚乳酸流场造成影响;两种对结构参数的调整方式均在不同程度上减小了流道内的剪切速率梯度,方式一还造成了流道内聚乳酸的黏度降低。结论:从对剪切速率场、黏度场和速度场的影响上看,经方式一调整后的螺纹元件更有利于挤出,而经方式二调整后的螺纹元件实体构型更贴近螺纹元件理论构型。     

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。     

聚乳酸在啮合同向双螺杆挤出机机头过渡体的流场研究

采用PALYFLOW软件数值模拟聚乳酸(PLA)在长径比为441的试验用小型啮合同向双螺杆挤出机机头过渡体的三维等温流场。在不同的工艺参数下,分析比较了过渡体内的速度场、压力场、剪切速率场和黏度场。结果表明:在适当温度下,增加螺杆转速与增加流量都可以提高流场效果,但与螺杆速度的增加相比,熔体流量的增加更有益于提高整个机头过渡体流场的混合与塑化效果,增加PLA成品的质量。     

PP熔体在非啮合双螺杆挤出机中流动的数值模拟

利用ANSYS有限元分析软件对PP熔体在双螺杆挤出机非啮合并列型螺纹元件中的流动进行了三维非等温非牛顿流场分析,求出了速度场、压力场、温度场的基本规律以及螺杆特性曲线的分布。计算结果对实际生产具有一定的指导意义。     

不同螺杆接触状态下异向双螺杆挤出机的流道分布规律

目的:探索聚乳酸在异向双螺杆挤出机不同螺杆接触状态下的流道分布规律。方法:用Solidworks软件建立啮合螺杆、部分啮合螺杆和非啮合螺杆3种几何模型;运用POLYFLOW流体仿真软件进行数值模拟;对3种螺杆不同接触状态下聚乳酸流体的压力场、剪切速率场与黏度场进行对比研究。结果:部分啮合状态下的异向双螺杆挤出机对聚乳酸有较好的建压能力与分散混合能力。结论:聚乳酸在部分啮合状态下的挤出效果优于其他2种螺杆接触状态。     

同向啮合型双螺杆挤压机挤压过程分析

对同向啮合型双螺杆挤压机内挤压过程进行了研究,并分析不同双螺杆挤压机之间的关系和影响因素,从公式中推出挤压机内物料完全充满段对挤压机生产和设计的影响。     

滑移条件对啮合同向双螺杆挤出过程的影响

［目的］探讨物料在机筒内壁面和螺杆表面发生的滑移现象及对同向双螺杆挤出过程的影响。［方法］利用相对运动法设计三维模型,设定不同的滑移边界条件并进行有限元模拟,通过仿真分析得到相关物理场数据,并计算其体积流率。［结果］与无滑移时相比,螺杆滑移条件下流道内压力减小,剪切速率减小,黏度增加;壁面滑移条件下,在螺杆与机筒间隙处压力减小,剪切速率减小,黏度增加,在螺杆啮合处则相反,即压力增加,剪切速率增加,黏度减小。螺杆滑移条件下的产量提升了 28%,壁面滑移条件下的产量下降了 62.5%。［结论］壁面滑移现象的发生有助于提升螺杆在螺杆啮合处的剪切能力,而螺杆滑移现象的发生则有利于提高同向双螺杆的挤出产量。     

螺距变化对异向双螺杆挤出机流场影响的仿真分析

目的：以聚乳酸（PLA）为例,研究螺距变化下的异向双螺杆挤出流道的分布规律。方法：在Solidworks中根据理论端面曲线方程并修正,绘制变螺距与不变螺距两种三维模型,使用Workbench软件对两种螺杆构型使用扫略网格方法生成所需要的分析模型,再使用Polyflow流体仿真软件进行实际情况的模拟得到后处理结果,使用FieldView软件进行最终结果分析;研究聚乳酸流体在模拟条件下的压力、剪切速率以及黏度。同时使用Polystat统计模块对停留时间分布曲线RTD进行分析。结果：在其他条件相同的情况下,相比于不变螺杆,变螺距螺杆的压力变大,剪切速率和黏度波动增加,轴向混合性能提高,但自清洁能力降低。结论：螺距变化对聚乳酸来说存在一定的影响,但过大的螺距变化往往产生不利的影响,因此,需要结合实际情况具体设计合适的变螺距螺杆以提高产量和质量。     

同向旋转双螺杆挤压机螺杆的计算机辅助设计

通过ＭＤＴ计算机软件对同向旋转双螺杆挤压机双螺杆进行设计和分析,为探讨不同螺杆结构形式对挤压过程所产生的影响不同螺杆结构形式对挤压过程所产生的影响提供依据。     

Velocity field in a twin-screw extruder

Velocity measurements inside the screw channels of a co-rotating, self-wiping, twin-screw extruder were carried out. A laser Doppler anemometer (LDA) system was used to measure tangential and axial velocity components in the translational region of one of the screws of a twin-screw extruder. The velocity measurements were carried out using heavy corn syrup at different screw speeds and for two forwards conveying elements differing in their pitch. It was found that velocity profiles in the translational region were substantially affected by the pitch of the screw element, however, screw speed (30–90 r.p.m.) did not have a significant effect on the shape of the velocity profiles. The range of velocity values in a 14 mm pitch screw element was wider than that in a 28 mm pitch screw element. Experimentally measured velocity profiles were compared with predictions of a one-dimensional model, which showed that the model underpredicted the velocity values, for the 14 mm pitch element.     

The influence of a barrel-valve on the degree of fill in a co-rotating twin-screw extruder

The influence of a barrel-valve on the degree of fill of a co-rotating, twin-screw extruder (MPF-50) built by APV Baker was measured by opening the barrel and by residence time distribution (RTD) measurements. The RTDs, which were measured by a radio tracer technique, were characterised by their minimum and average residence times and curve widths. Measurements were made at a ‘low’ and a ‘high’ barrel temperature profile, two mass flows and three screw speeds. The degree of fill and the minimum and average residence time increased when the valve in the barrel was closed. When the rotational speed of the screw decreased the hold-up in the extruder increased. The degree of fill during the measurements ranged from 30% to 56%, depending on the temperature, barrel-valve position, rotational speed of the screws and the feed rate. With a ‘low’ temperature profile the width of the curve was independent of the barrel valve position. When the barrel-valve was closed at ‘high’ temperatures, only a minor increase in the curve width, of the order of twice the measurement accuracy, was found.     

同向旋转双螺杆挤压机产量和膨化效果的实验研究

采用向应面法研究同向旋转双螺杆挤压机操作变量对产量的影响 ,实验研究表明喂料速度和螺杆转速对常量有著影响 ,并在获得最大产量和良好膨化效果状态下对喂料速度和螺杆转速进行了优化 ,拟合的二阶统计模型适用于生产和挤压控制设计。     

Effect of screw profile on extrusion-cooking of wheat flour by a twin-screw extruder

The effects of forward-, reverse-, and no-flight screw elements on the residence time distribution, dispersion number, and product properties were investigated in extrusion cooking of wheat flours in a twin-screw extruder. Mean residence times of 46.5s with a forward element increased to 59.6s with a reverse flight and 67.6s with a no-flight element. Dispersion numbers were 0.051, 0.056, and 0.075 respectively. The no-flight element reduced cooking loss and increased the degree of gelatinization of products.     

双螺杆挤压设备的特征及应用

针对如何选择一台适合于食品企业自身的双螺杆挤压机,从双螺杆挤压设备的特征与应用等方面进行了探讨.     

双螺杆挤压机的性能分析及应用

介绍了食品挤压加工的原理，对双螺杆挤压机的工作性能进行了分析。通过试验，论述了螺杆转速、原料含水量、加热温度等参数对膨化产品质量的影响、确立了玉米膨化食品的生产数据。     

Properties of gluten-based sheet produced by twin-screw extruder

Wheat gluten sheet plasticized with glycerol was successfully produced using a twin-screw extruder and the formation of the translucent sheet was found to occur when temperature of the melt was around 137 °C. Water sorption, thermal, mechanical and gas permeability properties of the extruded gluten sheet were studied at various relative humidities. The water sorption isotherms obtained were typical for a plasticized high protein content material and could be described by the Guggenheim-Anderson-de Boer (GAB) and Brunauer-Emmett-Teller (BET) equations. The glass transition temperatures (T_g) of extruded gluten sheet at various water contents were measured by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and dielectric analysis (DEA). T_g of anhydrous sheet was markedly below room temperature and was found to decrease with increasing water content. A decrease in Young's modulus, tensile strength at break and elongation at break was observed with increasing relative humidity. Water vapor permeability of the sheet increased with increasing relative humidity. The water vapor permeabilities obtained were high as compared to the permeabilities of synthetic polymers but comparable to those reported for cast wheat gluten films. Oxygen permeability of the extruded gluten sheet was low and comparable to those reported for cast wheat gluten films.     

人参粉挤压制品膨化特性的研究

探讨双螺杆挤压条件对人参挤压制品膨化品质的影响,以人参粉末为原料,利用双螺杆挤压机制备产品,分析不同物料含水量和机筒温度对制品的径向膨化率、水溶性指数、吸水性指数以及显微结构的影响.结果表明,人参挤压制品的径向膨化率在物料含水量30%、机筒温度100℃时最高(1.32),气孔细小而均匀.水溶性指数随物料含水量的增加而减少,随温度升高而增加,在20%、140℃时水溶性指数最高(44.77%).人参经双螺杆挤压不仅发生膨化,而且其制品质地疏松、均匀,有望开发膨化类人参保健休闲食品.