具有特殊地形条件的长距离供水工程水锤防护

在长距离供水工程中输水管道一般按地形走势布置。针对一些地形条件特殊的供水工程,本文提出了一种空气罐与出口溢流池联合设置的水锤防护方案,并建立了出口溢流池的数学模型。在空气罐体型一定时,给出了出口溢流池截面积的理论计算公式,有效地减小了在溢流池体型初期选取过程中的盲目性和工作量。结合某长距离输水工程,对比分析了空气罐和出口溢流池联合防护与单纯的空气罐防护对水锤的影响。结果表明空气罐与出口溢流池联合防护方案在前陡后缓的长距离供水工程中能够取得良好的水锤防护效果,且溢流池的溢流水位越高,其对负压的防护效果越好。     

长距离输水系统停泵水锤防护多目标优化研究北大核心CSCD

长距离有压输水系统中的水锤现象会导致管道系统振动或破裂,通常需增设水锤防护措施。为保障安全的同时降低水锤防护成本,针对长距离输水系统泵站停泵水锤过程中的水锤防护措施优化问题,提出基于随机森林(RF)算法与快速非支配排序遗传算法(NSGA-Ⅱ)协同的多目标优化方法。采用特征线法建立水力瞬变模型,构造期望样本集,利用RF算法拟合优化变量与优化目标间的映射关联。以最大水锤压力值、最大无量纲反转转速和水锤防护成本最小作为构建多目标优化模型目标函数,迭代搜索最优参数集。研究表明,该方法能在短时间内获得各目标均匀分布的停泵水锤防护优化方案集,所得方案满足规范中水锤防护要求,可为长距离输水系统停泵水锤的优化设计提供参考。     

火力发电厂循环供水系统的水锤现象及防护

在循环供水系统及长距离供水系统中,管道内的水流速度由于某种原因发生急剧变化或运行中的水泵动力突然中断,将引起水流量的急剧变化,常常导致水柱分离现象的出现,分离的水柱弥合时往往造成巨大的冲击波,从而使管道中的水流产生一个相应的冲量,冲量变化速率越大,这一冲量产生的冲击力也越大,该力作用在水泵部件以及管道及其附件上有如锤击,这就是水锤现象.火力发电厂冷却水系统一般采用直流供水系统和二次循环供水系统.2种供水系统都存在着在停泵、事故断电停泵及出口阀门事故情况下的水锤现象.如果在管道系统及泵出口不采取有效的防护措施,往往会对水泵及系统设备产生损坏,造成供水系统故障、影响电厂的安全可靠运行.     

长距离输水升压级数比选

通过正蓝电厂工程实例对长距离输水升压方案进行了经济比较,认为长距离输永管道宜采用强度较高的16Mn钢,并应采用少的升压级数和较高的输水压力。     

考虑蒸汽密度变化的长距离供热蒸汽管道的优化设计

对较长的加热蒸汽管道，若蒸汽流速过高，则压降过大，蒸汽饱和温度会下降过多，较难满足生产工艺的加热要求。该文在考虑蒸汽密度变化的基础上、建立了确定最优蒸汽流速和保温层厚度的模型，其目标函数为管道的年度总费用，它考虑了摩擦压降、散热温降、管道和保温材料折旧和维修等费用。实例计算表明，低压蒸汽的最优蒸汽流速在公称直径为0．10—0．20m时仅为15-25m/s，在公称直径大于0．20m时为25-35m/s。设计和计算时需考虑蒸汽密度的变化。     

长距离低扬程输水系统爆原因分析及预防措施

通过对长距离低扬程输水系统水锤事故的调查和总结,发现某些发生爆管事故的输水工程在系统布置及爆管规律上有显著的相似之处。运用水锤理论对典型的爆管事故进行分析比较,结合数值仿真计算,评价这些工程的系统布后委生的人出预防非常水的工程措施,旨在总结经验才识为工程设计提供借鉴和参考,以提高设计水平。     

"非常水锤"的发生条件及预防措施

在对输水系统水锤事故的调查中发现有大量事故属于“非常水锤”，由于这类事故的发生条件较特别，很容易被忽略，所以这类事故频频发生而又令人困惑不解。在电力工业中有不少输水系统都有发生非常水锤的条件，在对系统布置和调压设施的处理上稍有不慎即可能在运行时引发事故而造成重大损失。本文的目的在于总结产生非常水锤的条件并提出预防措施。     

长距离低扬程输水系统爆管原因分析及预防措施

通过对长距离低扬程输水系统水锤事故的调查和总结,发现某些发生爆管事故的输水工程在系统布置及爆管规律上有显著的相似之处。运用水锤理论对典型的爆管事故进行分析比较,结合数值仿真计算,评价这些工程的系统布置,分析事故发生的原因,给出预防非常水锤的工程措施,旨在总结经验教训,为工程设计提供借鉴和参考,以提高设计水平。     

电站锅炉管道飞灰磨损及防护研究动态

1飞灰磨损对于一个450MW燃煤量为200t/h的锅炉，煤中含有约15％的矿物质，燃烧后70％左右成为飞灰。飞灰的粒度在0．075－500μm范围。一般来说，飞灰冲击管道的速度为9～15m／s，然而在管束之间，管与炉壁之间的局部区域其速度可达40m／s。图1和表1分别为640MW直流锅炉各...     

滨海电厂钢质海水管道的选材及防护

通过对目前滨海电厂钢质海水管道常用材料耐海水腐蚀性能的比较，结合当前防腐蚀技术的发展及在电厂中的应用情况，提出在采用涂层与阴极保护的前提下，选用普通碳钢作为管道材料，完全可以达到其正常的使用寿命要求。     

管道水击的防治

对管道产生水击的原因进行分析,介绍在管道设计应注意的问题。     

简单管水击随机分析

水击发生的条件及影响水击的各种因素的随机性决定了水击现象的随机性。本文从水击极值近似解析式出发推导了由水库、管道及阀门组成的简单管的水击最大升压解析概率分布，随后引入了随机数值模拟方法。算例表明数值模拟法和解析法结果吻合很好，而水击随机分析与传统的定量计算方法存在相当大的差距。文中还初步讨论了简单管水击概率的分布规律。     

非棱柱体管道的一维水击计算及分析

在水电站输水系统水力过渡过程的一维计算中,对非棱柱体管道的处理,一般采用等价管方法。为了分析等价管方法带来的计算误差,本文给出了非棱柱体管道的一维水击计算方程,建立了相应的特征线解法。本文通过计算某一电站的水力过渡过程,分析了本文的计算方法和等价管计算方法对计算结果的影响,得出了一些有价值的结论。     

Flow-Accelerated Corrosion Wear of Power-Generating Equipment: Investigations,Prediction and Prevention: Part 3. Managing the Flow-Accelerated Corrosion of Pipelines and Equipment

The third part of this review1 discusses matters concerned with managing the flow-accelerated corrosion of power-generating equipment’s and pipelines' components. The importance of these matters tends to increase with increasing the capacity of power plant units and the time for which they have been in operation. The article considers the capabilities of object-oriented software packages aimed at providing information support to the personnel (PSSPs) in regard to scheduling in-service inspections for timely revealing cases of close-to-inadmissible flow-accelerated corrosion-induced thinning. The prospects of using PSSPs for minimizing the carryover of iron-containing products of general flow-accelerated corrosion into the process circuit of NPP units are shown. The list of parameters and characteristics necessary for numerically estimating the thinning rates and residual life of pipelines and equipment susceptible to flow-accelerated corrosion is determined. The possibility of using some PSSPs to predict the thinning of process circuit component walls taking into account the effect of cavitation and droplet impingement erosion on the metal is pointed out. The need to optimize the scheduling of in-service inspections of near-seam zones of welded connections used in the pipelines of the condensate–feedwater and wet steam paths of power units is substantiated. It is pointed out that work is underway for fitting the Russian NPP units with PSSPs able to define— based on calculation results, data of in-service inspections, and other information—a priority list of components to be subjected to first-priority or next scheduled in-service inspection and to schedule repair (or replacement) of components susceptible to intense thinning. It is shown that the use of stainless steels for making the components of pipelines and equipment operating in the secondary circuit of NPP power units is often an excessive measure for preventing the occurrence of inadmissible local flow-accelerated corrosioninduced thinning and for minimizing the concentration of iron in feed water. The prospects for comprehensively solving the flow-accelerated corrosion problems by implementing appropriate measures at the designing, construction, and operation stages are considered. The main topical practical objectives for coping with the problem of flow-accelerated corrosion in power engineering are formulated.     

锥管水击计算的特征线法

本文从管道非恒定流基本微分方程出发，导出了锥管水击计算的特征线法，并通过算例证实了该法的有效性。     

简单管水击随机分析再探

水击大小的不确定性取决于水电站水击的发生条件及其影响因素的随机性。在文献（１）的研究基础上,本文考虑更多的随机影响因素,从简单管水击极值近似解析表达式出发,推导了年最在耒击压力的解析概率分布。算例表明,与概率分布的０．９５分位点值相比,总内水压力和第一相水击升压的确定性分析结果在数值上尚接近,但极限水击升压的确定性分析结果偏小,这值得引起工程界注意。     

Flow-Accelerated Corrosion Wear of Power-Generating Equipment: Investigations,Prediction, and Prevention: 2. Prediction and Prevention of General and Local Flow-Accelerated Corrosion

The second part of this review considers physicochemical models and computer codes used for predicting flow-accelerated corrosion wear of power generating equipment. Approaches used to prevent the occurrence of general and local flow-accelerated corrosion that are based on selecting metals resistant to flow-accelerated corrosion and adjusting the water chemistry of power units are also discussed. The existing computer codes use physicochemical models of flow-accelerated corrosion and statistical data on damages inflicted to power units due to flow-accelerated corrosion processes. Advantages and drawbacks of different analytical physicochemical models describing the flow-accelerated corrosion process are pointed out together with the specific features of using them in elaborating flow-accelerated corrosion computing codes. It is shown that the processes lying at the heart of the flow-accelerated corrosion mechanism include, on the one hand, the occurrence of a protective oxide layer on the metal surface and, on the other hand, the dissolution of this layer and carryover of dissolution products in the flow. Differences between the processes through which metal undergoes flow-accelerated corrosion in a single-phase water flow and in a two-phase wet steam flow are analyzed. Thus, the redistribution of admixtures and gases between the phases that takes place in two-phase media may cause a change in the pH values, thereby significantly influencing the flow-accelerated corrosion rate. In addition, the rate with which flow-accelerated corrosion products are carried over into a two-phase stream depends on the liquid film flow mode on the streamlined surface. The flow-accelerated corrosion rate computing codes most widely known around the world, including the COMSY code (Germany), CHECWORKS SFA code (United States), BRT-CICERO^TM code (France), and RAMEK code (Russia) are considered. Their specific features and application limits are pointed out. Information on the effect the content of chromium, molybdenum, and copper has on the flow-accelerated corrosion rate is given. It is shown that the choice of metals resistant to flow-accelerated corrosion is a combined technical and economic problem, and the way in which it is solved has an effect on the safety and reliability of power unit operation. It is pointed out that the liquid phase pH value is essentially affected by the steam wetness degree if the latter exceeds 20%.     

交流长线的开断过程

介绍了长线发布参数的情形、及对输电线路参数的影响。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity are increased, and the costs are decreased. The process parameters of relay production lines are studied based on the long-and-short-term memory network. Then, the Keras deep learning framework is utilized to build up a short-term relay quality prediction algorithm for the semi-finished product. A simulation model is used to study prediction algorithm. The simulation results show that the average prediction absolute error of the fraction is less than 5%. This work displays great application potential in the relay production lines.     

特高压交流试验线段的无线电干扰特性研究及长线路预测

为了准确评估特高压交流(UHV AC)输电线路的无线电干扰(RI)水平,利用模态分析法对多导体试验导线进行理论分析。推导得出试验导线终端接3种典型的阻抗网络时,导线正下方的无线电干扰电场强度分布特性,并对两端开路情况下的驻波进行了实际测量。再根据武汉特高压交流试验基地中线路的布置情况,结合短线路的无线电干扰特性,对试验导线所测得的大雨条件下0.5 MHz的无线电干扰值进行数学反推,得到其激发函数值。利用该激发函数值对实际已运行的晋东南—南阳—荆门特高压输电线路的无线电干扰特性进行预测分析和实测对比。实验结果表明:当施加1 050 k V电压时,8×LGJ–500/35导线的激发函数值为39.3 d B;当测试点与中相导线的距离60 m时,无线电干扰电场强度实测值与激发函数预测值之间的误差基本2 d B。因此,可以利用数学反推来计算试验线段的激发函数值。