机械密封静环温度场的有限元分析

分析了机械密封的几何形状,讨论了影响密封温度的各个参数,利用有限元分析软件ANSYS7.0计算了在特定工况下密封静环的温度场,可作为合理评估机械密封静环的温度的理论依据.     

高压容器双锥环密封性能的研究

针对高压容器双锥密封结构实际应用中泄漏事故,从高压容器双锥密封结构密封机理,关注双锥密封结构密封比压,提出了拐点压力和最小密封比压的概念。分析了操作工况主螺栓载荷计算、主螺栓预紧力计算,进而推导了双锥密封结构操作工况回弹量和密封比压公式,求出了双锥环与端盖支撑面刚产生、尚未产生径向间隙的拐点压力和此时的最小密封比压,并与有限元分析结果进行比较,两者结果相当一致,并建议GB150对最小密封比压进行校核。     

高PV值的气体润滑轴向滑动环密封

本文报道了气体润滑辆向环密封的新计算理论，并用大量实验验证了计算结果，对三种密封结构（试验压力直至１００ｂａｒ，滑动速度直至１１０ｍ／ｓ）进行的试验表明：正确选择密封环材料和密封面的几何参数，能保证一个稳定且无磨损折工况。     

无油涡旋压缩机涡旋齿齿顶密封结构的研究

本文对无油涡旋压缩机涡旋齿齿顶密封结构进行优化,提出一种新型径向组合密封结构,利用几何和工程流体力学的方法,推导出基圆渐开线无油涡旋压缩机齿顶光滑间隙密封、齿顶迷宫密封、齿顶组合密封泄漏量的算法,建立了无油涡旋压缩机相邻压缩腔实验台,分别测量了3种密封结构在相同压差条件下的气体泄漏量,并研究了无油涡旋压缩机动涡旋盘转速对泄漏量的影响。对比实验与理论计算结果可得：理论计算结果与实验结果基本相近,光滑密封与迷宫密封泄漏量随压差的增大而增大,而组合密封泄漏量与压差成反比,但密封条磨损量增加。迷宫密封泄漏量实测值约为光滑密封实测值的80%,组合密封泄漏量实测值约为光滑密封实测值的63%,且3种密封结构的径向泄漏量随动涡旋盘转速的提高而降低,当动涡旋盘转速超过4 000 m/s时趋于平稳。     

轴类机械密封失效的原因与对策

机械密封在石油、化工企业的运转设备上广泛使用,具有密封性好、性能稳定、泄漏量少、摩擦功耗低、使用周期长等优点而被广泛使用,尤其适用于较高转速且对泄漏要求较高的轴类机件密封,同时也存在结构复杂,使用条件苛刻、价格昂贵及不易维修等弊端,特别是机械密封工艺条件温度,压力等工艺参数的影响直接关系到设备机械密封的性能和使用寿命。因此,找出机械密封失效原因及检修对策是保证企业安全生产、提高设备使用寿命的重要任务。     

单金属密封的结构优化及其密封性能研究

针对油气田勘探中,复杂的钻井工况导致动密封工作性能极不稳定的问题,结合单金属密封结构和井底高压环境,利用有限元方法对单金属密封受压情况下的接触压力进行分析。用雷诺方程计算单金属动密封的泄漏率,以减小最大接触压力和泄漏率为优化目标,利用正交试验和F评价方法对单金属密封结构参数进行优化,得到密封结构参数对密封面接触压力和泄漏率的影响情况,并将每个水平数对应的优化目标计算结果分别取平均值,得到不同水平影响下接触压力和泄露率平均值的变化趋势,从而确定密封结构的最优水平值,并借助有限元仿真对优化前后的密封性能进行对比。最后根据优化前后的密封结构参数加工2套密封试件,进行密封实验。仿真分析和实验结果表明：高压工况下优化前的密封面内侧磨损严重,钻井液颗粒容易侵入密封面;而优化后密封面的最大接触压力有所降低,动密封面的最高温度和泄漏率明显降低。研究结果对改进单金属密封的工作性能、提高井下动密封的可靠性有重要的现实意义。     

偏心率和转速对迷宫密封力和动力学参数影响分析研究

通过数值方法和商用CFD(计算流体动力学)软件对密封-转子系统进行建模和求解,研究了5种偏心率和5种转速下的计算机求解时间、流场压力分布、密封力的变化情况,并对泄漏量影响分析和迷宫密封动力学参数影响进行分析研究。研究结果表明:该方法能较好地模拟计算迷宫密封泄漏量和动力学参数,得到腔室压力随着偏心率增大而增大,密封切向力随着偏心率、转速的增大而增大,密封径向力随着偏心率、转速的增大而负向增大;通过密封长度、密封间隙、密封压差对泄漏量影响计算,三者变化率分别为6.62%,65.21%和69.97%,表明密封间隙和压差变化是影响泄漏量变化的重要影响因素;通过密封压差和密封长度对动力学参数影响分析,得出增大密封压差和密封长度不利于系统稳定、增大密封间隙会使得系统趋于稳定。     

逆滞流迷宫密封气流激振特性研究

密封是透平机械减小泄漏的关键部件,其气流激振特性对转子系统稳定性具有重要影响。该研究基于计算流体力学与多频涡动密封动力特性系数识别方法研究逆滞流迷宫密封气流激振特性,计算分析逆滞流喷嘴结构参数及位置对迷宫密封动静特性的影响,揭示其抗气流激振机理。结果表明:逆滞流喷嘴能有效抑制周向流动,改善密封腔压力分布,提高系统稳定性;与传统迷宫密封相比,逆滞流迷宫密封具有更小交叉刚度k、更大直接阻尼C与有效阻尼C_(eff),特别在低涡动频率下,效果更显著;相同结构参数逆滞流喷嘴的径向位置存在最佳值,当型心高度h_c=1.65 mm(径向中心)时密封有效阻尼C_(eff)最大;增大喷嘴进口高度h_(in)、减小进出口高度比例h_(out)/h_(in)均有利于提高系统稳定性;喷嘴进口高度h_(in)=1.00 mm、进出口比例h_(out)/h_(in)=0.25、型心高度h_c=1.65 mm为计算工况下最优结构,但泄漏量略有上升。     

乏燃料运输容器事故工况密封分析研究

目的 为防止放射性物质泄漏,要求乏燃料运输容器在事故工况下保证容器的密封。通过对乏燃料运输容器比例容器事故工况密封分析研究,为乏燃料运输容器密封分析提供依据。方法 为验证假想事故工况乏燃料运输容器的密封性,采用LS-DYNA分析软件,开展乏燃料运输容器比例容器9 m跌落分析,提取密封螺栓跌落过程中的载荷时程和密封面分离量,并在比例容器跌落试验后开展气密性能试验。结果 跌落分析结果表明,比例容器内、外盖在跌落过程中,密封螺栓应力满足限值要求;内、外盖密封面最大分离量小于密封结构有效回弹量。同时跌落后容器的气密性检查试验结果表明其密封性能良好。结论 乏燃料运输容器比例容器的跌落密封分析和气密性试验结果表明,在事故工况下乏燃料运输容器货包能够保证密封要求,该分析方法可用于乏燃料运输容器事故工况的密封分析。     

载人航天器中橡胶密封结构低温性能研究

载人航天器对密封性能要求极为严苛,密封结构的泄漏特性与温度相关。本文研究了一种典型的硅橡胶密封结构的泄漏方式,通过对低温下橡胶材料的透气性能的测试,结果表明:从50℃下降到5℃时、气体通过材料的渗透量降低约一个数量级。本文还通过实测材料在低温下的应力-应变关系、低温下材料的收缩特性,借助ABAQUS分析软件建立了该结构的压缩状态的有限元模型,得到了低温下密封应力变化情况,并据此计算了界面泄漏结果:低温下,密封结构的界面泄漏量略有所增大。本文研究的某典型橡胶密封结构在低温下的气体渗透泄漏和界面泄漏的量化数据,为产品在低温下的使用可靠性评估打下基础,也为类似结构设计提供参考。     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.