Simulation of the process of the filling of planar channels with viscoplastic fluid

Simulation of the flow of a non-Newtonian fluid with the free surface that is realized on the filling of planar channels in the gravity field has been carried out. Mathematical statement of the problem with the use of the Shwedow-Bingham rheological model has been formulated. A numerical algorithm for solving the problem on the basis of finite difference methods has been constructed. Parametric investigations of major features of the process in relation to values of governing parameters have been made. Flows have been studied, and various filling regimes for two different orientations of the flow direction relative to action of gravitational forces have been identified. Evolution of quasi-solid nuclei for various values of yield stress has been demonstrated.     

Variations in surface gloss on parts made by gas assisted injection moulding

Abstract

Gas assisted injection moulding has proved to be a breakthrough in moulding technology for thermoplastic materials. However, there are still unsolved problems that limit the overall success of this technique. The aim of this work was to study the phenomenon of gloss variations occurring across the surfaces of gas assisted injection moulded parts. Experiments were carried out on an 80 t injection moulding machine equipped with a high pressure, nitrogen gas injection unit. The materials used were pigmented acrylonitrile/butadiene/ styrene and polypropylene. A plate cavity with a gas channel across its centre was used to mould the parts. Various processing parameters were varied: melt temperature; mould temperature; melt filling speed; short shot size; gas pressure; and gas injection delay time. After moulding, a glossmeter was used to determine the effects of these processing parameters on the surface gloss profiles of the parts. A roughness meter and scanning electronic microscope were also employed to characterise the surface quality of moulded parts. In addition, a numerical analysis of the filling process was carried out to help better understand the mechanisms responsible for the phenomenon of surface gloss variations. It was found that the surface gloss difference occurs mainly in the transition area between channel and plate in the moulded parts, which might be the result of the shear stress gradient in the polymer melt during the filling process. Surface roughness of moulded parts might also be another factor resulting in the gloss difference problem. PRC/1720     

不锈钢三角螺旋高效填料在水-氢交换工艺中的性能研究

对液相水-氢交换工艺中的小型高效三角螺旋填料进行脱脂除油、亲水等进行了表面处理;通过总有机碳方法 TOC分析,处理工艺对填料的脱油效果明显,扫描电子显微镜SEM分析表明该处理工艺明显改善了填料比表面积。在典型的水-氢交换工艺条件下,处理过后的小型高效填料与Pt-SDB催化剂分层填装,该处理方式显著提高了水-氢交换性能,等板高度HETP降低至13.46 cm;进一步实验测定水-氢交换柱流体力学性能:床层持液量为0.03 m3/m3、床层压降为20 Pa/m,与理论计算一致。     

连续液柱流表面真空蒸发模型

真空条件下连续液柱流表面蒸发现象及模型表达是低能耗汽-液分离过程设计的重要基础。研究了重力作用下通过孔口的连续液柱流条件,获得了液柱断裂的判据。研究了该体系表面蒸发的机理并建立了数学模型。数值模拟与实验数据较为吻合,结果表明：绝热闪蒸条件下,汽液相界面附近液相侧温度梯度显著,过程阻力主要在液相;增加孔口流速、增加液体过热度、减小孔径均可提高蒸发速率,但必须满足液柱断裂判据的限制。     

界面致稳型柔性胆甾相液晶显示器件的制备与性能

以镀有氧化锡铟的聚对苯二甲酸乙二酯（ITO-PET）薄膜为柔性电极,对电极导电表面进行处理,以间隔子控制器件厚度,采用灌注法制备了界面致稳型可挠性双稳态胆甾相液晶显示器件。利用接触角测试仪、显微镜和紫外-可见分光光度等分析胆甾相液晶显示器件的微观结构及光电特性。结果表明,表面处理涂层可与液晶分子作用并产生界面致稳效应;采用大小为6 μm的间隔子,当改性层溶液中间隔子质量分数为3%时,制备了有效面积为10×15 cm²的柔性双稳态液晶显示器件,测得饱和驱动电压为40 V,在550 nm的透过率为90%;最后通过刻蚀技术处理器件电极制备了字符显示器件。     

液氯充装系统技术改造

为了减少电解精制盐水中产生的物质NCl3在液氯充装过程中聚集而发生爆炸的危害,满足安全生产和节能的要求,对液氯充装的隐患及危害进行了分析,提出了采用新的工艺方式,利用液氯屏蔽泵充装液氯钢瓶和物料输送改造方案;同时,为保证液氯屏蔽泵的安全运行,对其进行相关的安全自控方面的设置,应用于实践操作中取得了效果。     

甲基乙烯基硅橡胶聚合新工艺的研究

通过对现有甲基乙烯基硅橡胶生产工艺、过程和设备的分析研究,针对高粘度流体传热难度大的问题,进行了热流体混合速度及反应速度的试验,设计了一种生产甲基乙烯基硅橡胶的新工艺。     

J-190聚合物补偿填充料耐油性能试验研究

完成了J-190聚合物补偿填充料与HM109-1密封剂相容性试验、J-190聚合物补偿填充料与阳极化铝合金相容性试验、J-190聚合物补偿填充料与S06-0215底漆的相容性试验、J-190填充料耐燃油-盐水双层液(即燃油和盐水混合液)试验、J-190聚合物补偿填充料自身的耐油性能试验.试验结果均满足设计要求.     

液氯充装系统技术改造

介绍原液氯充装工艺流程.分析原液氯充装系统存在的问题.针对原液氯充装工艺存在安全隐患的缺点,将充装泵由屏蔽泵改为磁力泵.针对原充装秤管路造成瓶装液氯质量降低的缺点,改造充装管道和抽负管道,确保产品质量稳定.针对原抽负装置不稳定也不经济的缺点,将抽负装置由纳氏泵改为水力喷射泵.给出改造后液氯充装工艺流程.     

Fiber mat deformation in liquid composite molding. I: Experimental analysis

When a resin in injected into the mold in liquid composite molding, the preplaced fiber mat may deform near the inlet gate because of the high momentum carried by the injected fluid. A fiber free region near the gate followed by the fiber mat deformation may emerge. This phenomenon is most likely to occur when the stacked fiber mats have low permeability and the resin has high viscosity. A set of mold filling experiments were carried out using an instrumented metal mold and a small transparent mold to investigate the fiber mat deformation during mold filling. Experimental results showed that the fiber mat deformation was limited to a small region near the gate and that deformation greatly reduced the molding pressure. A forced fiber mat deformation employing a modified gate design was proposed to facilitate mold filling in liquid composite molding.     

汽车自动定量高效充装硫酸技术研究与应用

金川集团股份有限公司镍冶炼厂硫酸产品主要通过汽车装运销往外地,通过深入观察、分析硫酸充装问题,从提高汽车充装硫酸的合规合法性、充装效率、精度和安全性考虑,进行了汽车定量自动充装计量、高效兑车、液位防溢保护及声光报警等方面技术创新,保证了定量自动充装的同时,兑车效率大幅提高,降低了操作人员劳动强度,确保了硫酸充装的安全性...     

传热管外液体流动数值模拟研究

采用计算流体力学方法(CFD),对传热管外液体流动过程进行了模拟研究.建立了传热管三维网格模型,考察了不同布液密度下液体在传热管表面铺展形态、流型、液膜厚度以及绕管停留时间的变化规律.该研究结果对于加深理解降膜流动过程,指导蒸发器优化设计和工艺条件优化有一定的借鉴意义.     

组装式铝合金内浮顶结构的设计分析

内浮顶是漂浮在油罐液面上随油品上下升降的浮动顶盖。采用这种内浮顶盖覆盖在液面上是目前公认的最理想的降低油品蒸发损耗的方法。由于内浮顶在工作过程中要始终保持漂浮于液面上的状态,因此在设计时一定要保证其有足够的浮力,同时要保证各个部位的连接强度及稳定性。就内浮顶进行了强度、稳定性、浮力等相关方面的计算。     

Injection Molding Nanoscale Features with the Aid of Induction Heating

During injection molding of micron or submicron scale features, incomplete filling frequently occurs, resulting from premature freezing of the polymer melt in contact with a cold mold. In order to overcome the filling difficulty without increasing the total cycle time, the mold surface temperature was raised rapidly by induction heating. A prototype mold insert with cooling channels was fabricated and integrated with a nickel stamp having nanoscale-grating structures. The nickel stamp surface was successfully heated from 25 to 258°C in 2.7 sec. Four different mold surface temperatures, 100, 150, 200 and 250°C, were tested to determine if the nanograting structures can be replicated with an optical quality cyclic olefin copolymer. Experimental results indicate that the nanocavities were successfully filled when the surface temperature reached 250°C, but mold release caused drag damages on the nanogratings. Further, coupled thermoelectromagnetic analyses were carried out to simulate the induction heating process of the nanostructured mold insert. The predicted surface temperature responses in general agree with the experimental ones and the simulation model can be used in the further development of process control and mold design in micro/nano molding.     

硅灰石/环氧树脂增强体系性能研究

通过对针状硅灰石粉进行干法表面化学改性,制成不同粒径的增强填料。并填充于环氧树脂中进行十字交叉法试验,探讨了硅灰石／环氧树脂体系的增强机理。力学性能测试结果表明：环氧树脂经硅灰石填充后．可显著提高机械强度和硬度;改性硅灰石与未改性硅灰石相比,改性后填充量增大,增强效果明显。同一粒径的硅灰石,随填充量的增加,环氧树脂的机械强度增大。硅灰石粒径越小。比表面积越大。与环氧树脂的结合力越强,强度越大。     

干铺丝预制体的液体成型工艺研究

为解决RTM类成型工艺中的预制体制备及定型问题,在国内率先开展对干铺丝-液体成型工艺的研究,主要研究内容为液体成型过程工艺参数影响机制及制件的力学性能。采用单因素法确定液体成型时预制体粘结剂含量、注胶温度、充模时间的影响机制,再通过正交法确定了最佳工艺组合,最后就层间剪切与弯曲性能与模压工艺进行比较。实验结果表明,液体成型过程中,树脂的流动充模会受到工艺参数不同程度的影响,注胶温度的影响最大,充模时间影响甚微,通过正确的工艺组合可以减少孔隙等缺陷,保证复合材料的内部质量。力学性能测试表明,干铺丝-液体成型工艺的力学性能水准与模压工艺持平,其中弯曲强度略有降低。     

Simulation of the mold-filling process

The transport equations for a power law fluid are used to solve the transient and non-isothermal problem of filling a disk-shaped cavity. Using the results obtained it is possible to predict gate pressures, fill times and short shots. Furthermore, the velocity and temperature fields can be obtained throughout the filling process. This information specifies the formation of a frozen surface layer during filling. Rigid PVC was primarily used in the simulations, but some results are also given for linear polyethylene, nylon 6–6, ABS and polystyrene.     

The occurrence of surface roughness in gas assist injection molded nylon composites

Gas assist injection molding has increasingly become an important industrial process because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that limit the overall success of this technique. The purpose of this report was to study the surface roughness phenomenon occurring in gas assist injection molded thermoplastic composities. The materials used were 15 % and 35% glass‐fiber filled nylon‐6 composites. Experiments were carried out on an 80‐ton injection molding machine equipped with a high‐pressure nitrogen‐gas injection unit. Two “float‐shape” axisymmetric cavities were used. After molding, the surface quality of molded parts was measured by a roughness meter. Various processing variables were studied in terms of their influence on formation of surface roughness: melt temperature, mold temperature, melt filling speed, short‐shot size, gas pressure, and gas injection delay time. Scanning electronic microscopy was also employed to characterize the composites. It was found that the surface roughness results mainly from the exposure of glass fiber in the matrix. The jetting and irregular flows of the polymer melt during the filling process might be factors causing the fiber exposure.     

Heat transfer to a helical cooling coil in mechanically agitated gas—liquid dispersions

An experimental investigation of the heat transfer, from mechanically agitated gas—liquid dispersions to a helical cooling coil has been carried out. Air was sparged into six different Newtonian liquids and agitation was provided by a four-bladed paddle impeller. An equation, which is of the forced convection type used in single-phase heat transfer experiments, was developed from over 520 measurements correlating the influence of important process parameters such as the superficial gas velocity and indirectly the power consumption of the stirrer. The surface tension of the liquid was shown to be a beat transfer process variable.     

液氯充装工艺的改造

将液氯气化充装工艺改为液下泵充装工艺后,运行安全、可靠,节省能量,操作方便,解决了污染问题。