煤粉燃烧过程中矿物质气化影响因素的模拟研究

鉴于目前国内的实验设备和测量手段，精确测量煤燃烧过程中各种矿物质的气化率还存在很大困难。该文通过建立煤中矿物质气化的数学模型，针对煤中SiO2和FeO两种成分，来探讨相关因素对它们气化率的影响，最后应用CFD软件来研究它们在600MW锅炉内的气化行为。计算结果表明：温度是煤中SiO2和FeO气化的主要影响因素，煤粒粒径和CO2浓度也会对它们有一定影响。通过与实验结果的比较，表明计算结果比较合理。     

在气蚀和闪蒸场合下调节阀选用的研究

对气蚀和闪蒸的定义、产生的条件进行了详细论述,以规范不同版本书籍在概念上的模糊不清,以及 由此造成的调节闯流量系数计算的复杂性和对调节阀的损害,以便采取相应措施,在实际工况条件下加以避免.     

利用转炉汽化冷却系统蒸汽保障真空精炼装置用汽的工程应用

介绍了南京钢铁联合有限公司RH真空精炼工程中利用转炉汽化冷却系统蒸汽保障真空精炼装置用汽的工程实例。重点阐述了转炉汽化冷却蒸汽用于真空精炼炉的技术方案特点、采取的有效措施、采用的专利技术、技术经济比较、推广前景及意义。     

真空汽化法产生块状纳米锌的试验研究

介绍了真空汽化冷凝技术制备纳米级材料实验的原理和过程，用真空汽化冷凝技术制备纳米块状锌，并用扫描电镜观察纳米锌的形貌、晶粒度，用X射线衍射测定真空汽化冷凝钠米锌的生长方式及择优取向，用显微硬度计测定了合金锌、粉状锌以及纳米锌的显微硬度，并对此进行了分析。     

Mechanism of Material Removal from Silicon Carbide by Carbon Dioxide Laser Heating

The mechanism of material removal from SiC by CO₂ laser heating was studied using sintered and single-crystal α-SiC. Removal rate and width of the groove showed maxima when plotted as a function of translation speeds. Groove depth decreased as the translation speed of samples increased. Similar results were obtained if argon or air was used as gas assist, which indicated that the material removal mechanism is induced dissociation of SiC. Microstructure of the material deposited in and outside of the groove was studied by SEM. At low scanning speeds, columnar grains 10 to 50 μm long appeared. As the scanning speed increased, columnar grains became smaller and finally only irregular polycrystalline particles were observed. By using Raman spectroscopy, Auger analysis, and X-ray diffraction, phases inside and outside the groove were identified as Si, β-SiC, C, and SiO₂. Columnar grains were identified as β-SiC covered with thin layers of C, Si, and SiO₂. Slow scanning speeds enhanced the growth of β-SiC. At slow scanning speed, free silicon was always found in the grooves of lased single crystals but not in the grooves of lased sintered SiC. It can be concluded that the mechanism of material removal from silicon carbide by CO₂ laser heating is a vaporization process, and material found in the groove and on the surface near the groove is formed by condensation from the vapor.     

Molar enthalpy of vaporization of ethanol-gasoline mixtures and their colloid state

Vapour pressure measurements are used to evaluate the enthalpy of vaporization of ethanol-gasoline mixtures. Partial molar values are also derived. The dispersed structure of ethanol-gasoline fuel is studied for the first time using the method of correlation spectroscopy of scattered light. A large range of dispersed particle sizes in different alcohol-gasoline systems is found. The dependence of the mean radius of drops on ethanol content is determined. It is found that coalescence phenomenon occurs in the systems when extra ethanol is added.     

Low temperature flash vaporization for desalination

The feasibility of desalination by low pressure vaporization of seawater at temperatures between 26°C and 32°C was demonstrated in a pilot plant. The plant operated at vacuum pressures between 1.3 KPa and 2.3 KPa. The saline water was sprayed into the vaporizer as fine droplets using a swirl nozzle and evaporated at the low pressure. The maximum flow rate was 1,000 1/h. Condensation of the vapor so formed, was carried out in a shell and tube heat exchanger. The yield of fresh water was up to 4% as predicted by theory. The quality of the condensed water was excellent. The investigation demonstrated a novel concept of devising a desalination system by using warm water from the upper strata of the ocean for flash vaporization at low pressures and condensing the vapors using cold water from the lower strata of the ocean. The performance of the pilot plant was determined for different feed water temperatures, vacuum and water injection pressures.     

Importance of thermophysical data in process simulation

The need for thermophysical properties of components and their mixtures has grown as computer simulation of processes has developed and expanded. Although equations of state require fewer input data, they are not yet generally applicable to all types of systems. Accordingly, in many cases, the liquid activity models are still very much required. A long-time disadvantage of the liquid activity method, for systems containing supercritical components, is overcome if the Henry constant is utilized. A van Laar-type interpolative equation provides the Henry constant in liquid mixtures from the values in the pure liquid components. The addition of a ternary interaction in addition to the usual binary ones provides improved MVL prediction of phase equilibria, espcially VLLE involving three phases. Examination of the consistency of thermal properties is made feasible with the aid of a generalized reduced Frost-Kalkwarf vapor pressure equation. It is useful also for extending and supplementing sparse data and for predicting properties from the structure and boiling point. Possible trends in properties needed and their availability to simulators are discussed in view of available computer facilities.Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

槽参数对高温密封汽液固流动特性及性能的影响

以高温动压型机械密封为研究对象,基于Eulerian多相流模型和蒸发冷凝模型,建立涉及高温汽化、固体颗粒、黏温效应及牛顿流体内摩擦效应的动压型机械密封润滑膜汽液固三相流动模型,模拟研究槽深、槽宽比、螺旋角及槽径比对润滑膜汽化、固体颗粒分布规律及密封性能的影响关系。研究表明：润滑膜固体颗粒体积分数随槽深、槽径比的增大而增大,且在槽宽比为0.5时出现最大值,而固体颗粒体积分数随螺旋角的变化规律与转速有关;润滑膜平均汽相体积分数随槽深的增大而减小,随螺旋角的增大而增大,槽宽比为0.7时平均汽相体积分数出现最大值,槽径比在0.3以上时平均汽相体积分数随槽径比的增大而增大;槽深8 μm时润滑膜汽相、固体颗粒相出现突变,槽深低于8 μm时处于气相较高、固体颗粒相较小状态,槽深高于8 μm时则相反;基于汽液固流动的密封性能分析表明,选用9 μm左右的槽深、0.6左右的槽径比、16°～20°的螺旋角、0.3~0.4的槽宽比时对密封性能有利,采用8 μm以上的槽深及小于0.5的槽宽比时,转速较高时选用较小槽径比、转速较低时选用较大槽径比时有利于抑制汽化。