应力和侵蚀性溶液渗透耦合作用下碳酸盐岩渗透特性试验研究

为研究不同应力及溶液组合下碳酸盐岩渗流特性演化规律,选择H2SO4溶液、蒸馏水作为渗透流体,使用岩石耦合渗透试验装置对碳酸盐岩试样分别进行较长时间的渗透试验,得到三种不同工况下岩石试样渗透率和渗出液中矿物离子浓度随时间变化的曲线,分析了试验中围岩、渗透压、溶液等影响因素与渗透率、岩石内部矿物质溶解规律之间的内在联系。结果表明,试验初期阶段,围压对岩样渗透率有较大影响,恒定围压施加后使得岩样孔隙受到压缩从而影响渗透率。试验过程中,渗透压的增大会导致岩样渗透率产生短时间的上升,随后岩样渗透率逐渐回落。不同渗透溶液则有不同的影响,H2SO4溶液对岩样内部的侵蚀性较强,在岩样上游段产生较强溶解,当溶解的矿物离子浓度达到过饱和后,可能在下游段产生沉淀,使得岩样整体渗透率不断降低;而蒸馏水对岩样的侵蚀作用较弱,沿程产生均匀溶解,不能对孔隙结构造成较大改变,整体渗透率保持稳定。岩样整体渗透率的变化是应力、渗透溶液的溶蚀作用和矿物沉淀共同作用的结果。研究成果可用于指导工程实践。     

氢气非预混燃烧的流场输运特性分析

采用高精度直接数值模拟的方法对氢气非预混燃烧流场进行了精细的预测.模拟所求解的控制方程为三维可压缩的无量纲形式的Navier-Stokes方程,采用六阶精度紧致差分格式,结合基于详细化学反应和输运过程的FGM化学反应机制,利用768个处理器核、共近4.53亿网格点进行了基于CPU的大规模高效并行计算,分析氢气非预混燃烧特性,并进一步探讨了浮力对氢气燃烧流场输运特性的影响.研究发现,由于氢气燃烧过程中产生不同扩散性质的化学组分,使燃烧过程中遵循优势扩散的行为.这将影响流场的输运特性和火焰不稳定性的形成.在浮力驱动的氢气优势扩散燃烧流场中,对流是质量、动量及热量输运行为的主要影响因素,而无浮力火焰中优势扩散主导着流场的输运特性.平均统计结果表明,有浮力和无浮力的燃烧流场中都可以捕捉到逆梯度输运现象,且浮力会促进逆梯度输运行为的发生.     

Effect of microstructure inhomogeneity on hydrogen embrittlement susceptibility of X80 welding HAZ under pressurized gaseous hydrogen

Hydrogen embrittlement (HE) of high-grade pipeline welded joint is a threat to hydrogen gas transport. In this research, slow strain rate tension (SSRT) tests in high-pressure hydrogen gas, combined with hydrogen permeation tests and microstructure analysis were conducted on X80 steel, intercritical heated-affected zone (ICHAZ), fine-grained heat-affected zone (FGHAZ) and coarse-grained heat-affected zone (CGHAZ). The change of HE susceptibility from high to low was CGHAZ, FGHAZ, ICHAZ, and base metal. Microstructure was the important factor influencing hydrogen permeation and susceptibility to HE. Susceptibility to HE was increased in the order of “fine-grained massive ferrite (MF) and acicular ferrite (AF)”, “fine-grained granular bainite (GB) and MF”, “coarse-grained GB and bainite ferrite (BF) embedded with martensite-austenite (M-A) constitute”. The fine-grained MF and AF in base metal with lower hydrogen diffusivity can impede the embrittlement behaviour, while the coarse-grained GB and BF with higher hydrogen diffusivity in CGHAZ increased its susceptibility to HE.     

海洋风电机组防腐蚀技术研究进展

海上风电作为一种绿色能源,已经成为风电开发的热点领域,但是,由于所处的海洋环境复杂,海上风电机组防腐工作面临着巨大挑战。介绍了我国东南沿海地区海洋腐蚀环境的特点,针对海上风电机组所处的腐蚀环境情况,把风机结构进行了区域的划分,沿垂直方向可将所处的海洋环境分为5个腐蚀区域,即大气区、飞溅区、潮差区、全浸区及海泥区。通过电化学及相关理论,阐述了多种环境状态下的风机不同结构间的腐蚀机理,并归纳了常规的防腐蚀技术,包括涂层防腐、阴极保护防腐、复层包覆防腐等方法。为确保海上风电机组的安全平稳运行,对设备的防腐措施提出了建议,以期对海上风电机组的大规模发展提供参考。     

水平管道细粉高浓度分层流动阻力特性的试验研究

高浓度粉体输送由于人们对其优越性认识的深入而得到了广泛的研究。水平管内分层流动是高浓度粉体输送流型中最重要的形式 ,研究其阻力特性有着重要的意义。本文通过对近 5 0年来在这一领域内工作的回顾 ,分析了不同学者所获得的经验公式的利弊。在一高浓度气力输送试验台上的试验 ,获得了水平管道细粉高浓度分层流动的阻力公式 ,误差分析认为 ,该公式能够满足一般工程设计要求。     

BaCe0.85Tb0.05Co0.1O3−δ perovskite hollow fibre membranes for hydrogen/oxygen permeation

Co-doped BaCe_0.85Tb_0.05Co_0.1O_3−δ (BCTCo) nanopowder was synthesized via a sol–gel method using ethylenediaminetetraacetic acid (EDTA) and citric acid as the chelating agents. Using the resultant powder, BCTCo perovskite hollow fibre membranes were then fabricated by the combined phase inversion and sintering technique. Properties of the BCTCo powder and the hollow fibre membranes in terms of crystalline phase, morphology, electrical conductivity, porosity, mechanical strength and hydrogen/oxygen permeation were investigated by a variety of characterization methods. The results indicated that doping of cobalt in the BCTb oxide led to a higher electrical conductivity and lower calcination temperature for the powder precursor to a perovskite structure as well as sintering temperature for the hollow fibre precursors to gastight membranes. In order to obtain gastight and robust hollow fibre membranes, the sintering temperature should be controlled between 1300 and 1450 °C. The maximum hydrogen flux through the BCTCo hollow fibre membranes reached up to 0.385 mL cm⁻² min⁻¹ at 1000 °C under 50% H₂–He/N₂ gradient, which is higher than that of the un-doped BCTb hollow fibre membranes with the same effective thickness, and especially much higher than that obtained from other proton conductors due to the asymmetric structure of the membrane designed. Moreover, the BCTCo hollow fibre membrane also exhibited noticeable oxygen permeation fluxes, i.e. 0.122 mL cm⁻² min⁻¹ at 1000 °C under the air/He gradient. However, doping of cobalt might damage the mechanical stability of the perovskite membranes in the hydrogen-containing atmosphere.     

煤粉高浓度输送阻力特性的试验研究

本文在东南大学磁流体发电ＭＨＤ燃烧室供粉系统上对煤粉高浓度气力输送阻力特性进行了试验研究,运用相似理论对试验数据进行关联,得到了用以计算煤粉高浓度的输送水平阻力系数的准则式,该准则与试验数据吻合良好,同时给出了计算任意管长压降的程序流程图。     

加压气固喷射器内静压分布特性的试验研究

在增压气力输送系统试验装置上,对影响收缩型气固喷射器内静压分布特性的关键因素作了较深入地研究。试验研究结果表明,静压在气固喷射器收缩段入口处明显急剧上升。气固喷射器内静压随气体喷嘴位置S的增大而减小,而随收缩角α的增大而有所提高。提高气体喷嘴出口速度,气固喷射器内的最大静压值由喷射器收缩段入口处附近迁移至喷射器收缩段出口处附近。此外,气体喷嘴位置、收缩段的收缩角和输送风对收缩型气固喷射器内的静压分布的影响还与系统背压相关联。     

Analysis of electrochemical hydrogen permeation through X-65 pipeline steel and its implications on pipeline stress corrosion cracking

Electrochemical hydrogen permeation tests were performed to measure the hydrogen permeation current through the X-65 pipeline steel in the electrolytes simulating the soil conditions to initiate near-neutral pH stress corrosion cracking (SCC) in pipelines. The hydrogen permeation current was analyzed following the constant concentration model. It is shown that, AQDS, simulating the organic compound in the soil, inhibits hydrogen permeation by decreasing the sub-surface hydrogen concentration, while sulfide promotes hydrogen permeation by inhibiting the hydrogen recombination and thus increasing the sub-surface hydrogen concentration. The steel specimen is more susceptible to stress corrosion cracking in the soil solution with a higher sub-surface hydrogen concentration, indicating that hydrogen is involved in near-neutral pH SCC in pipelines. It is suggested that hydrogen promotes the cracking of the steel, accompanying with the anodic dissolution on the crack sides and at the crack tip.     

Hydrogen permeation behavior and mechanism of Cr2O3/Al2O3 bipolar oxide film under plasma discharging environment

To improve the thermal stability between aluminide and stainless steel substrate and obtain thermodynamically stable phase of alpha-Al₂O₃, a new Cr₂O₃/Al₂O₃ bipolar oxide barrier was proposed, in which metallic Al was sputtered on the preoxidation coating of electroplated chromium and then oxidizing by oxygen plasma. It was found that Cr₂O₃ film exhibits P-type semiconducting properties while Al₂O₃ acts as N-type. Hydrogen discharging plasma was used to simulate the in-pile hydrogen permeation. Raman spectra and atomic force microscopy (AFM) were employed to analyze phase structure and surface morphology. Electrochemical impedance spectroscopy and Mott–Schottky were utilized to qualitatively evaluate effective thickness and the integrity for the oxide film. The depth profile and surface chemical states of involving elements were analyzed by auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), respectively. The result shows that Cr₂O₃/Al₂O₃ bipolar oxides have improved hydrogen permeation resistance and would be a potential candidate for barrier application.     

Hydrogen permeation barrier - Recognition of defective barrier film from transient permeation rate

Hydrogen permeation barrier films often exhibit lower efficiency than anticipated. The cause could be defects in the barrier film, high permeability of the defect-free (dense) barrier film, or a combination of both. It is very difficult to point at and quantify the responsible mechanism since the defects can be of submicrometer dimensions and very sparsely populated. This study addresses the recognition of the defects in the hydrogen permeation barrier films using the hydrogen permeation rate transient evolution analysis. For this purpose a mathematical model of the steady-state and transient hydrogen permeation through the membrane coated either with a defective or a defect-free barrier film was developed for the diffusion limited permeation regime. Analysis shows that a defective barrier film might be recognized only in a transient permeation experiment. The effective diffusion coefficient of the membrane with the defect-free barrier film is variable and depends mainly on the ratio of diffusion coefficients in the film and the substrate. Contrary to this, the transient permeation only through pinholes has a constant value of the effective diffusion coefficient. Result of the study is an experimentally useful criterion when and how the permeation through the defects in the barrier layer can be recognized and its extent determined.     

Deep Potential Molecular Dynamics Systematic Study of Microstructure and Thermophysical Properties of NaCl-CaCl2 Molten Salt System across Phase Transition Temperature

Understanding the microscopic ionic structure and thermal properties of the NaCl-CaCl2 mixture is of great importance for improving its photothermal energy conversion efficiency.However,the measured values of thermophysical parameters are affected by the processes near the phase transition temperature,and the measured values often change abruptly.Classical and first-principles molecular dynamics studies have recently been performed to determine the thermal properties of molten salts,but such simulations for binary molten salts including NaCl-CaCl2 are still rare and limited to a range above the phase transition temperature(786.0 K),and the deviations from the measurements are still large.In this study,the molecular dynamics method based on the trained deep potential is used to systematically predict the variations of the ionic structure,phonon density of state,density and thermophysical properties including heat capacity,thermal conductivity,and diffusivity,and Prandtl number of the binary chloride system of NaCl-CaCl2 in a wide temperature range(600-1000 K)above the phase transition temperature.The variations and correlations of the properties(especially thermal diffusivity and Prandtl number)with temperature are deduced.It is found that an increase in temperature enhances ionic vibration,thus increasing the specific heat capacity.An increase in temperature weakens the interaction and vibrational transfer between ions,and hence the thermal conductivity tends to decrease.As the temperature increases,the heat capacity increases,while the density,thermal conductivity,thermal diffusion coefficient,and Prandtl number of the system all decrease.In general,the properties obtained by applying the deep potential trained in this work reflect the experimental values more accurately than the classical and first-principles molecular dynamics simulations.     

雅克拉凝析气田单井集输管道腐蚀因素分析及治理对策

雅克拉凝析气田于2005年投入开发,生产层系为白垩系。该气田井流物复杂,呈高CO2(含量为2.34%～3.1%),高Cl-(含量约为7×104mg/L),低H2S(含量为13.33～43.59mg/m3),低pH值等特点,凝析油含水率为0.76%～12.37%,地层水矿化度约为14×104mg/L。在气、水、烃、固共存的多相流腐蚀介质中,H2S、CO2、Cl-和水是主要的腐蚀物质,在温度为40～60℃、压力为8.5MPa工况条件下,单井集输管道(尤其是出井口150m范围内)出现多次腐蚀暴管、穿孔事件,且不同区域内的管道均有结垢发生。腐蚀因素主要包括介质组分和含量、介质流速和流态、管道材质等。通过对单井集输管道各种腐蚀影响因素进行分析,并对常用防护措施进行比选,综合应用缓蚀剂加注技术、阴极保护技术,以及管道材质优选、材料表面改性和弯头改型技术等防护措施,有效解决了单井集输管线腐蚀穿孔、刺漏问题,为治理高含CO2、Cl-及高流速的"甜性"腐蚀环境下的集输管道腐蚀提供借鉴。     

The optimized composition and strong sustainability of hydrogen permeation of Nb30Ti35Co35 eutectic alloy membrane after 5 at%Fe substitution

The microstructure of Nb₃₀Ti₃₅Co₃₀Fe₅ eutectic alloy was investigated by using scanning electron microscope (SEM) and transmission electron microscope (TEM). The alloy exhibits typically lamellar eutectic structures which are composed of uniformly arranged nano-scale bcc-(Nb) phases and B2–Ti(Co, Fe) phases. 5 at% Fe partially substituting Co induced the composition modification of bcc-(Nb) phase such as the increasing Ti/Nb ratio and existing Fe solutes, which contributes to the enhanced hydrogen permeability. Nb₃₀Ti₃₅Co₃₀Fe₅ eutectic alloy shows strong sustainability during hydrogen permeation under continuous hydrogen pressure and thermal cycles, and the hydrogen permeation flux can restore when the hydrogen pressure or temperature recovered again. No hydrogen induced fractures were found during hydrogen permeation. The present work demonstrates that Nb₃₀Ti₃₅Co₃₀Fe₅ eutectic alloy exhibits excellent sustainability under the conditions of changing temperature and feed hydrogen pressure, which is very promising to be an alternative for Pd used for hydrogen separation and purification.     

_Y_型送灰器的试验研究

本文介绍了一种新型的循环流化床（ＣＦＢ）飞灰回送装置－“Ｙ”型送灰器的试验研究及其结构特点,探讨了“Ｙ”型送灰器输送特性和调节特性以及主要结构尺寸对其性能的影响,对“Ｙ”型送灰器在ＣＦＢ中的应用前景作了展望。     

Effects of supplied gas humidity change on PEFC transient power generation

Polymer electrolyte fuel cells (PEFCs, PEMFCs) are gaining increasingly more attention as clean and efficient energy‐conversion devices. Vapor and liquid transport has a strong impact on the power generation characteristics and efficiency of PEFCs, and so proper water management is needed for efficiency and durability. However, water transport factors are not well understood, particularly during unsteady operation—often the case in vehicles and distributed stationary power generators. In this study, to understand and generalize the effects of local water transport on PEFC performance, transient mass transport characteristics inside a PEFC were investigated experimentally and numerically. For this purpose, we developed an unsteady two‐dimensional numerical model based on mass‐ and charge‐conservation equations in the channel, gas diffusion layer (GDL), and membrane electrode assembly (MEA). As necessary parameters for model development, we measured the water content of the MEA, the membrane resistivity, the activation overvoltage, overall mass transfer coefficient, and so on. The membrane resistivity greatly increases as the relative humidity decreases. The activation overvoltage is also affected by the relative humidity, and not only by the current density and oxygen activity. Current load and voltage changes are frequently used as PEFC transient inputs, but lead to very complicated and intractable phenomena such as changes in the amount of generated water and electro‐osmosis, state of the electrical double layer, and so on. Hence, stepwise changes in the relative humidity of the supplied gas were adopted in this study. The experimental and numerical transient responses were in good agreement under most operating conditions, and the reliability of our measurement methods for the water transport properties and our numerical model were confirmed. Here we discuss the dominant factor in the transient responses, and conclude that the transport resistance at the PEM–GDL interface is the largest and most dominant factor in a relatively dry state under unsteady operating conditions. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20371     

一台110t/h高温高压秸秆锅炉受热面的结构设计

针对秸秆燃料的易结焦、易积灰和易腐蚀性等特性,主要介绍了一台110 t/h高温高压秸秆直燃锅炉在炉膛、过热器、省煤器和空气预热器等各个受热面从参数选取、材料选择、结构设计等各方面所采取的防治措施。