三维非轴对称薄壁管件旋压成形机床液压系统的研究

在分析三维非轴对称薄壁管件旋压成形机床工作过程的基础上,利用MATLAB软件中SIMULINK模块对该机床的液压系统进行了建模与仿真。仿真结果与实验结果相吻合,结果表明,由比例流量阀、位移传感器和放大器共同构成的闭环控制系统能较好地满足三维非轴对称零件旋压成形工艺要求,从而为进一步进行系统的液压和机械系统的协同仿真,提供了客观可靠的理论基础。     

PRAKLA气枪压缩机的故障诊断与分析

本文针对德国JUNKER公司生产的4FK115K20自由活塞式压缩机在使用中出现的故障进行了较为系统的分析,指出了故障产生的原因、诊断的一般步骤及排除故障的方法。     

火电厂空冷平台换热的数值模拟

本文利用计算流体力学软件对火电厂中直接空气冷凝器的换热情况进行数值模拟。并根据计算结果提出增加空冷平台最外一圈风机功率及在空冷平台下方修建挡风建筑以提高空冷平台换热效率的可行性建议。     

采用高温氮气氛直流电弧放电法制备大直径碳管

在高温氮气氛以及铁、钴、镍的氧化物混合催化剂作用下,采用直流电弧放电法制备了具有不同形貌特征的外径超过100 nm的大直径碳管(LDCTs).透射电子显微镜(TEM)表征结果表明,LDCTs的外径为90~160 nm,内径为70~150 nm,管壁厚度为9~24 nm.高分辨透射电子显微镜(HRTEM)表征结果表明,LDCT的管壁内层为石墨层结构(平均厚度约为4~7 nm),外层为无定形碳结构(平均厚度约为4 nm),管壁间的隔层亦为石墨层结构.能量色散X射线(EDX)谱图和选区电子衍射(SAED)表征结果表明,LDCTs中掺杂有氮和过渡金属元素.初步探讨了LDCTs的生长机理.     

Behavior of biaxially-loaded rectangular concrete-filled steel tubular slender beam-columns with preload effects

In composite construction, rectangular hollow steel tubular slender beam-columns are subjected to preloads arising from construction loads and permanent loads of the upper floors before infilling of the wet concrete. The behavior of biaxially loaded thin-walled rectangular concrete-filled steel tubular (CFST) slender beam-columns with preloads on the steel tubes has not been studied experimentally and numerically. In this paper, a fiber element model developed for CFST slender beam-columns with preload effects is briefly described and verified by existing experimental results of uniaxially loaded CFST columns with preload effects. The fiber element model is used to investigate the behavior of biaxially loaded rectangular CFST slender beam-columns accounting for the effects of preloads and local buckling. Parameters examined include local buckling, preload ratio, loading angle, depth-to-thickness ratio, column slenderness, loading eccentricity and steel yield strength. The results obtained indicate that the preloads on the steel tubes significantly reduce the stiffness and strength of CFST slender beam-columns with a maximum strength reduction of more than 15.8%. Based on the parametric studies, a design model is proposed for axially loaded rectangular CFST columns with preload effects. The fiber element and design models proposed allow for the structural designer to efficiently analyze and design CFST slender beam-columns subjected to preloads from the upper floors of a high-rise composite building during construction.     

高纯碳酸丙烯酯的精馏工艺研究

以工业级碳酸丙烯酯为原料,重点研究再沸器、二丙二醇含量、真空度及回流比对高纯碳酸丙烯酯的品质及收率的影响,总结出最佳的精馏工艺条件.     

西夏热电2×200MW机组凝汽器真空低的原因分析

对西夏热电2×200 MW机组凝汽器真空降低的现象进行分析,并结合现场实际制订了相应措施,针对实施后的效果,提出了进一步治理的方法和建议,以保证机组在合理的真空下运行,达到提高机组运行的安全性、可靠性、稳定性和经济性的目的。     

TA18钛合金导管的内径滚压连接工艺

针对TA18钛合金导管开展了内径滚压连接工艺研究,研制了基于扭矩控制的滚压连接专用设备,实现了难变形钛合金导管的内径滚压连接成形;同时掌握了成形扭矩与连接件管端伸出量和连接件内径的关系,指出管端伸出量和连接件内径与成形扭矩呈线性递增关系,确定了最佳成形扭矩;采用痕迹法作为连接组件配合面密接度的检测试验方法,检测结果表明,管套与堵头之间的密封面沿圆周无间断,密接度达到100%。所研制的钛合金导管内径滚压连接件通过了配合面密接度检测和28 MPa液压系统性能验证,达到了28 MPa液压系统的性能要求。     

Means of improving the operating efficiency of air condensers at the Verkhne-Mutnovskaya Geothermal Power Plant in Kamchatka

Operation of the Verkhne-Mutnovskaya Geothermal Power Plant (VMGPP) has revealed ineffective summer-time performance of air condensers (AC), which is caused by an insufficient heat reserve. Four alternate schemes are examined for improvement of the operational efficiency of the AC: replacement of the four-by five-tier heat-exchange modules; installation of high-output fans; a combination of the first two schemes; and, installation of additional sections in each power-generating set. Based on thermodynamic analysis that we have adapted for conditions at the VMGPP, it is established that the last alternate scheme is optimal, andwill have a payback period of six years, and a heat reserve of more than 40%, a figure approaching requirements now in force. __________ Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 40–43.     

丹江口左岸土石坝测压管水位异常原因分析

2000年6月以来,丹江口水利枢纽左岸土石坝“1140-1上”测压管水位出现异常。通过对测压管灵敏度检测,结合多年监测资料,采用多种分析手段,对异常现象进行了分析研究,得到以下结论：在坝体加高过程中,测压管受碾压损伤,经多年使用,导致降雨引起的渗流水进入测压管内,致使水位发生异常,而土石坝坝体的防渗结构工作是正常的。