Influence of CO2 inleakage on the slight-alkalization of generator internal cooling water

The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO₂ inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO₂ inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO₂-NaOH-H₂O system, CO₂ inleakage saturation was derived to quantify the amount of the dissolved CO₂ in GICW. This parameter can be directly calculated with the measured conductivity and the [Na⁺] of GICW. The influence of CO₂ inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO₂ inleakage and the NaOH dosage. This study provides insights into the influence of CO₂ inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO₂ inleakage occurs.     

Effect of residual surface stress on the fatigue behavior of a low-alloy powder metallurgy steel

In this study we have characterized the fatigue behavior of a low-alloy powder metallurgy (P/M) sintered steel, composed mainly of martensite and bainite with 10.4% porosity. After each processing step, the residual axial surface stress was measured by X-ray diffraction. Significant compressive surface stresses were generated during the machining of the fatigue specimens. A heat-treatment at 175 °C after machining had no effect on these residual stresses, but polishing the surface resulted in a 20% reduction in compressive stresses. The residual surface stresses had no apparent effect on the fatigue behavior of the sintered steel. Rather, the fatigue behavior was controlled by sub-surface defects consisting of weakly bonded particles located in regions of high porosity.     

抽真空对独立外缸低压模块端汽封间隙的影响分析

以某独立外缸结构汽轮机低压模块为研究对象,对低压内缸及汽封体等部件在抽真空阶段的变形进行了分析和计算。为了理清抽真空阶段所受的重力、真空力、热影响等因素对低压端汽封间隙的影响,分步骤施加以上3种载荷进行有限元分析。结果表明:在重力作用下,低压内缸产生整体下沉两头上翘的变形;在真空力作用下,端汽封随汽缸进一步下沉,底部间隙变大;在投低压缸喷水情况下,高温轴封蒸汽对端汽封及低压内缸加热,端汽封随汽缸整体抬升,底部间隙减小;在真空力、热影响联合作用下,端汽封底部间隙减小0.061~0.105 mm;在投入喷水情况下,整个抽真空阶段对低压端汽封间隙的影响并不大。     

基于红外感应技术的风扇摇头装置设计

为了使风扇摇头装置实现对人体的跟踪送风,该文提出将人体红外感应技术应用于送风装置上。该摇头装置采用一种基于多光谱识别技术的红外模块。对应区域的红外模块感应到人体方位后,立即发出信号,通过角度控制系统算法分析后,控制摇头机构做出相应的动作。在此基础上,利用matlab对摇头机构的运动规律进行仿真,进一步验证设计方案的可行性。     

拱坝混凝土施工机械系统配置优化模型及其模拟

施工机械配置及其协同作业效率直接影响拱坝混凝土施工的质量和进度.系统分析拱坝混凝土施工机械系统的构成以及混凝土生产、运输和浇筑的施工机械子系统前后衔接、循环封闭的相互联系特性,构建混凝土施工机械的有限源多级服务系统和施工作业过程中机械设备运行的统计参数方法,提出基于机械设备效率与混凝土的浇筑时间、施工进度的机械配置方案优选及其系统模拟的实现方法.针对锦屏一级水电站拱坝混凝土施工,采用Monte Carlo模拟、优选典型坝段的混凝土施工机械配置,实证分析方法的可行性和有效性.     

大口径环喷式流量调节阀数值模拟优化

针对南水北调天津段对水流控制的特殊要求,考虑了大口径环喷式流量调节阀的不规则几何形状和各结构尺寸对其性能的影响,采用基于非结构、交错网格的有限体积法求解用k-ε两方程模型封闭的雷诺平均N-S方程组,对其进行了二维数值模拟,得到了阀内流场的分布,并以此为基础,从减小过阀损失、减小涡量、预防汽蚀的角度,对其结构进行优化.     

CN<em>x/TiN多层复合涂层抗水蚀性能的研究

采用多弧-磁控溅射镀膜机在不锈钢2Cr13衬底上沉积CN_<em>x/TiN多层复合涂层。利用光电子能谱仪(XPS)和透射电子衍射(TED)对涂层的组成和结构进行分析。利用自行研制的高压水蚀试验装置对不锈钢、高铬铸铁、司太立合金以及CN_<em>x/TiN多层复合涂层的抗水蚀性能进行对比试验,最后对涂层的水蚀失效机理进行了探讨。试验结果表明:CN_<em>x/TiN多层复合涂层具有较高的硬度、附着力、抗热冲击性能以及优异的抗水蚀性能,是一种优良的汽轮机末级叶片抗水蚀用涂层。     

Ammonia decomposition kinetics over LiOH-promoted, α-Al2O3-supported Ru catalyst

A LiOH-promoted Ru-based catalyst was recently reported to have a high TOF of 17.7 s⁻¹ at 623 K, compared to 2.7 s⁻¹ for an un-promoted Ru-based catalyst, and has been reproduced for this study to develop further understanding of the catalyst activity under a range of conditions. The kinetic values were calculated using a Temkin-Pyzhev-like power law rate expression model. Reaction orders, pre-exponential factors (A) and activation energies (E) were calculated for two temperature ranges, 623–748 K, and 748–873 K. The TOF of this catalyst at 623 K is not similar to that previously reported, being only 1.6 s⁻¹ in this study. A follow-up CFD analysis supports the fact that the kinetic model effectively describes performance of the catalyst at a range of temperatures and pressures, and can be used in the future on similar catalysts. H₂ partial pressure has an inhibitory effect on the rate of decomposition of NH₃ at all temperatures, not just near or below 673 K as previously proposed in the literature, however equilibrium decomposition is still possible with sufficient catalyst loading.