CFD技术在油气分离器选型和设计中的应用

利用CFD数值模拟方法,气相采用RNGκ-ε湍流模型,油滴相采用随机轨道模型,对油气两相流在一次油份内的流动分布进行研究,分析油滴在分离器内的运动轨迹及分离机理。计算结果表明:油气分离器的长径比越大其分离效果越好;当入口速度较大时,增大分离器容积可提高分离效率;当入口速度较慢时,即使增大容积其分离效果也不会得到明显的改善;分离器入口速度越大分离效果越理想。在工程应用中,利用以上分析结论进行选型和尺寸设计的油气分离器可以满足实际要求,并取得理想的分离效果,同时验证了采用的方法切实可行。     

高工程化颜料的基本概念与工程化问题

传统的颜料颗粒粒径分布较宽,大多数颗粒的尺度一般在5～50μm之间。经过研磨加工的颜料制备物（俗称颜料色浆）其粒径分布要窄得多,大多数颗粒的尺度一般在0．5～5μm之间,高工程化颜料的颗粒粒径分布更窄,在0．1～0．15μm之间。高工程化颜料的饱和值和透明性都接近它的最佳状态,因此可以用于液晶显示屏等高技术领域,但加工到这么小的尺度是有困难的。该文从粒径分布和加工方式以及应用领域诸方面讨论了高工程化颜料与颜料色浆的区别。同时结合理论分析,指出了制造高工程化颜料的技术瓶颈。     

Recent advances in polymer reaction engineering: Modeling and control of polymer properties

Complex reaction kinetics and mechanisms, physical changes and transport effects, non-ideal mixing, and strong process nonlinearity characterize polymerization processes. Polymer reaction engineering is a discipline that deals with various problems concerning the fundamental nature of chemical and physical phenomena in polymerization processes. Mathematical modeling is a powerful tool for the development of process understanding and advanced reactor technology in the polymer industry. This review discusses recent developments in modeling techniques for the calculation of polymer properties including molecular weight distribution, copolymer composition distribution, sequence length distribution and long chain branching. The application of process models to the design of model-based reactor optimizations and controls is also discussed with some examples. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

棉秆皮纤维的长度分布

用单根纤维长度测量法测棉秆皮纤维的长度,测试结果表明棉秆皮纤维的长度范围是20～206 mm。采用分组测量分析法研究棉秆皮纤维的长度―根数分布、长度―质量分布及长度―线密度分布等,计算出棉秆皮纤维的线密度范围是5.185～9.677 tex,实验测试纤维的平均线密度为7.62 tex。     

基于细观模型的纤维增强树脂基复合材料的裂纹与强度关系研究

纤维增强树脂基复合材料是一类高比强度、高比刚度的结构材料。开展该材料的裂纹与强度关系研究具有重要的科学意义和工程价值。采用细观力学模型和有限元方法,分析Ⅰ型裂纹长度和裂尖位置对复合材料应力状态和应力强度因子的影响,进而获得启裂载荷与裂纹长度和裂尖位置的关系。     

Bivariate Lognormal Distribution for Characterizing Asbestos Fiber Aerosols

The width and length distributions of fiber aerosols were successfully correlated using a lognormal distribution, and the joint distribution could be described by a bivariate lognormal distribution. Means and variances of the length and width for the joint distribution were the same as those for individual marginal distributions, and the correlation between the width and length was between 0.1 and 0.5. Based on the bivariate lognormal distribution, other physical properties of fiber aerosols of the form Q = aW^bL^c such as aspect ratio, surface area, volume, and aerodynamic diameter were also shown to be lognormally distributed. The mean and variance of In Q can be estimated from parameters in the bivariate analysis. The result shows the usefulness of this analysis in deriving aspect ratio, volume, and aerodynamic diameter from the basic length-width distribution. It also provides a simple way to convert the number concentration to surface area and mass concentration.     

Modeling of network degradation in mixed step-chain growth polymerizations

The ability to form degradable hydrogels having controlled network structure is important for applications related to both drug delivery and tissue engineering. Although significant advances have occurred, these applications cannot reach full potential without the availability of materials with tunable degradation behavior. Here, we present novel thiol-acrylate degradable networks, which provide a simple method for forming degradable networks having specific degradation profiles. Degradable thiol-acrylate networks are formed from copolymerizing a thiol monomer with PLA-b-PEG-b-PLA based diacrylate macromers. A theoretical model has been developed to describe the kinetic chain length distribution, the bulk degradation behavior, and the reverse gelation point of these thiol-acrylate hydrogels. Varying the thiol functionality, as well as the relative stoichiometries of the thiol and acrylate functional groups, provides a facile means to control the kinetic chain length distribution and the concomitant degradation behavior of these systems. The extent of percentage mass loss of the network at the reverse gelation point is controlled from as low as 30% to as high as 95%, thereby giving the unique ability to dictate the material properties of the hydrogel before the network becomes completely soluble.     

A method for determination of length distributions of multiwalled carbon nanotubes before and after melt processing

A relatively simple method to determine the length distribution of carbon nanotubes (CNTs) before and after melt processing was developed. This involves the selection of a suitable solvent for dispersing pristine CNTs as well as to dissolve the matrix of melt mixed composites and the choice of an appropriate nanotube concentration. The length of suitably individualized CNTs was visualized using transmission electron microscopy and length distributions were measured using image analysis. Examples are shown for Baytubes® C150HP and Nanocyl™ NC7000 and their melt mixed composites with polycarbonate where the same procedure was applied to both, measuring the initial length distribution and the distribution after recovering from the composites. These results indicated a significant shortening after melt processing up to 30% of the initial length.     

Engineering plastics from lignin. XVI. Starlike macromers with propylene oxide

Starlike macromers were prepared from hydroxypropyl organosolv lignin by reaction with propylene oxide, and they were analyzed by a combination of conventional analysis techniques. The average number of arms per macromer was controlled by partial capping with an alkoxy group; and the average length of arms by the degree of chain extension with propylene oxide. Analysis methods included treatment with hydriodic acid followed by gas chromatographic separation of alkyl iodides (HI/GC), UV spectroscopy, H-NMR spectroscopy, and thermal analysis. The results were consistent with a hypothetical pentameric model structure having between two and six radiating arms, each with a length of between 1 and 4 propylene oxide units. The UV method was best qualified to determine degree of chain extension, while HI/GC was best suited for analyzing average number of arms per macromer fragment. The synthesis and analysis of starlike macromers from lignin is viewed as an important stepping stone for the formulation of lignin-based engineering plastics and multiphase materials.     

涡流分级机转笼结构改进及内部流场数值模拟

引言 随着科技的进步,各行各业对粉体粒径和粒径分布的要求向细而窄的方向发展,因此对分级设备提出了高效、高精度的性能要求.涡流空气分级机是20世纪70年代末日本发明的,属于第三代动态干式分级机,具有能耗低、流场稳定等特点,广泛应用于建材、精细化工、食品、医药以及矿物加工等领域.     

基于一维数值分析的FRP筋基本锚固长度研究

采用一维数值分析程序,对12组拉拔模型试验数据进行模拟计算,得到FRP筋的基本锚固长度,分析基本锚固长度以内界面粘结强度分布情况随拉拔应力增加时的演化,表明基本锚固长度受残余界面强度的影响很大。建立考虑极限粘结强度、残余粘结强度、直径、屈服强度等影响因素的新的FRP筋基本锚固长度的计算公式,新公式简化了计算程序,对计算结果拟合精度良好。     

过滤粉尘层净化氟化氢的优化分析

针对国内布袋除尘器（主要用于铝电解烟气净化）设计中的不足，分析了对该类布袋除尘器进行基础理论研究的必要性，提出包括流场优化、布袋长度对粉尘层影响、工艺参数对粉尘层厚度分布的影响及研究粉尘层吸附氟化氢性能4点研究思路，并在有些方面进行了初步实验研究，为工程设计和工艺操作提供理论参考依据。     

基于双剪强度理论的弯管塑性极限载荷计算与有限元分析

根据对弯管在受内压作用下的应力分布特点,应用双剪强度理论推导出求解弯管极限载荷的一般公式,并用基于Mises和Tresca这两种准则的有限元方法以及Goodall公式法计算的结果进行了比较,得到了弯管系数m和包辛格系数a对极限载荷的影响规律,为双剪强度理论在工程中计算弯管的极限载荷的应用提供理论上的参考.     

Oligo Pools as an Affordable Source of Synthetic DNA for Cost-Effective Library Construction in Protein- and Metabolic Pathway Engineering

The construction of custom libraries is critical for rational protein engineering and directed evolution. Array-synthesized oligo pools of thousands of user-defined sequences (up to ∼350 bases in length) have emerged as a low-cost commercially available source of DNA. These pools cost ≤10 % (depending on error rate and length) of other commercial sources of custom DNA, and this significant cost difference can determine whether an enzyme engineering project can be realized on a given research budget. However, while being cheap, oligo pools do suffer from a low concentration of individual oligos and relatively high error rates. Several powerful techniques that specifically make use of oligo pools have been developed and proven valuable or even essential for next-generation protein and pathway engineering strategies, such as sequence-function mapping, enzyme minimization, or de-novo design. Here we consolidate the knowledge on these techniques and their applications to facilitate the use of oligo pools within the protein engineering community.     

Three-dimensional path line tracking and residence time distribution in fishtail dies

The flow kinematics of power-law fluids in fishtail dies is studied. A general isothermal three-dimensional finite element code developed by the authors is used for the flow analysis purpose. The basic geometry of the fishtail die is defined by simple super-elliptical curves, which allows a smooth transition from a circle to a slit. The three-dimensional path line and the residence time distribution (RTD) are calculated from the velocity field obtained from the finite element solution of the conservation equations. The effects of the rheological properties and the die geometry on the path line pattern and the residence time distribution are investigated. The results indicate that as both the length of the transition zone and the fishtail angle increases, the residence time distribution becomes more uniform. However, the power-law index does not affect the residence time distribution significantly.     

线性锥形衣架机头流率分布数值模拟

给出了预测线性锥形歧管衣架机头出口流率分布的计算程序,研究了影响出口流率分布的相关因素。模拟结果表明:衣架机头的出口流率分布与机头的几何参数和材料的物性参数都有关系,其中调节块区的缝隙高对出口流率分布的影响最大;基于流动指数n为常数而设计的衣架机头,如果没有调节块的调节作用是很难满足实际生产需要的。     

轮胎花纹噪声仿真与优化系统软件设计

从软件实现的角度阐述了构建轮胎化纹噪声仿真与优化系统（ＴＰＮ－ＯＤＳ）的整体思路,分析了系统的结构及其功能分布,并分别从轮胎花纹噪声仿真分析、噪声评判、缺陷诊断和低噪声优化４个方面阐述了四个方面的具体实现。表明ＴＰＮ－ＯＤＳ可成为轮胎花纹低噪声圾和开发轮胎新产品的有力辅助工具。该系统已达到工程实用水平。     

Compounding of glass fiber-reinforced polypropylene and investigation of its mechanical properties under simple and complex loading

Polypropylene is one of the important thermoplastics that has been reinforced with glass fibers to give a reasonably good engineering plastic. Because of its inert nature, it does not easily adhere to the glass surface and hence some improvement in mechanical properties. In the present study a vinyltriethoxysilane coupling agent in polymeric form has been tried and seen to improve the properties. Tests have been carried out at (a) constant strain rate (in the Instron testing machine), and (b)constant stress rate (water loading on a biaxial testing machine). Under constant strain rate only tensile properties have been studied while under constant stress rate, the tensile, torsional and combined tensile-torsional tests have been carried out. In each of the above cases, a considerable improvement in elastic modulus has been observed. The Tensile strength is improved to the extent of about 25 percent. There is only a slight improvement in torsional strength. Different fiber volume contents were used and their effect studied on modulus and strength. The mechanical data for reinforced-polypropylene samples have been discussed in terms of the fiber-length distribution in the composite. Detailed analysis of tensile data suggests that at low strains, when the critical length is relatively low, the fibers contribute to a high modulus. With increasing strain the critical length increases and the load carrying capacity of the fibers is reduced. Consequently the gain in strength is relatively less. The effect of fiber length distribution in torsion and combined tension-torsion tests would be expected to be similar and the results seem to confirm this.     

漂移流模型用于毛细管两相流数值计算

毛细管作为家用空调器、电冰箱的节流元件，因为不能随制冷系统负荷变化而调节流量，所以设计毛细管合理参数至关重要。今将整个毛细管内的流动分为过冷液体区和气液两相区两个过程，建立了毛细管内制冷剂两相流动的漂移流模型；这一模型考虑了各相平均速度之间的差异，克服了以往均相流动模型的缺点。进一步考虑两相间相对运动和空隙率及流速沿截面的分布规律，对毛细管长度进行了数值计算。编制了毛细管长度计算的应用程序，并将数值计算结果与文献中的实验数据进行了分析比较，其误差在工程设计的允许范围之内。     

FRP与混凝土界面粘结性能的试验研究

纤维(FRP)与混凝土的粘结性能是外贴纤维增强聚合物加固钢筋混凝土结构技术的关键问题。采用修正梁模型,对9个外贴FRP条带加固混凝土受弯构件的粘结性能进行了试验研究。分析了FRP应变、局部粘结剪应力发展规律以及沿粘结长度在各级荷载下的分布规律。考察了混凝土强度和FRP粘结长度对粘结强度等粘结性能的影响。验证了FRP有效粘结长度,探讨了有效粘结长度的影响因素,计算得到了局部粘结剪应力滑移关系曲线。通过对试验结果的统计回归分析,提出了局部粘结剪应力滑移本构关系模型以及有效粘结长度计算公式,分析结果与试验结果都吻合较好,可供实际加固改造工程应用及完善相应规范的编制参考。