轴流转桨式水轮机特性神经网络三维建模

针对轴流转桨式水轮机复杂的非线性特性以及水力机组过渡过程仿真计算所需的水轮机流量与力矩特性难以准确描述的情况,介绍了基于BP神经网络的轴流转桨式水轮机特性建模方法：利用BP神经网络强大的非线性数值逼近功能,由已知的综合特性曲线、定桨特性曲线、飞逸特性曲线得到离散数据以及边界约束条件,建立轴流转桨式水轮机流量和力矩特性模型,对导叶小开度区、低转速区和高转速区等未知区域进行三维曲面延拓。建立导叶桨叶三维协联特性模型,以提高水轮机特性曲线数据处理的精度。     

大型轴流转桨式机组导叶和桨叶协联关系探讨

轴流转桨式水轮机存在的导叶和桨叶的协联关系,对机组出力效率、摆动、振动等数据至关重要。本文从机组在不同工况下、不同水头下,导叶和桨叶两者的配合关系入手,说明了导叶和桨叶协联关系的实现方法及其配合关系的要点,总结了多个大型轴流转桨机组调试和控制改进的实际经验,提出了该类型机组在运行、维护、优化等方面的改进方法和意见。希望能为今后大型轴流转桨式机组在协联关系优化、调速器控制方式改进、防抬机措施等方面提供借鉴。     

纪村水电站机组效率试验与效率在线监测系统建立

纪村水电站水轮机组是运行超过30a的轴流转桨式机组,为提高机组性能,对2台机组进行绝对效率试验。文中重点介绍了效率试验的方法和成果,求解了轴流转桨式水轮机导叶开度与桨叶转角的最优协联关系,以提高机组运行效益。采用多声路超声波流量计建立了机组效率在线监测系统,以加强机组实时状态监视,充分挖掘旧机组潜力,为指导水电厂经济优化运行提供了可靠的技术资料。     

轴流式水轮机转轮内三维紊流场预测

转轮是水轮机中影响机组特性的一个重要部件．研究水轮机转轮内三维素流场的流动特性对于提高水轮机组的特性及效率具有重要的意义．本文基于N-S方程和标准的κ-ε紊流模型，采用SIMPLEC算法，数值模拟了轴流式水轮机转轮内的三维紊流场，同时讨论了其收效性和准确性．轴流式水轮机转轮内的三维紊流场数值模拟结果有助于提高轴流式水轮机的水力设计、性能分析和优化设计的水平．     

纪村电站机组效率试验与效率在线监测系统建立

大唐陈村水力发电厂纪村站2×17 MW机组系运行超过30年的轴流转桨式机组,为了提升机组性能,特对2台机组进行绝对效率测试工作。介绍效率测试试验方法和成果,寻求轴流转桨水轮机导叶开度、桨叶转角的合理最优协联关系,提高机组运行效益;以及介绍采用多声路超声波流量计建立机组效率在线监测系统,加强机组实时状态监视,充分挖掘机组潜力,为指导电厂开展经济优化运行提供可靠的基础技术资料。     

灯泡贯流式机组协联优化试验分析

灯泡贯流式机组具有低水头、大流量的特点,运行中导桨叶协联关系对机组的运行效率及稳定性影响较大。本文针对某灯泡贯流式机组开展了真机协联优化试验分析,通过真机试验对机组的协联曲线进行了优化,提高了水轮机出力及效率,改善了机组的运行稳定性。     

挂治水电厂调速器水头采集及控制功能的实现

在轴流转桨式机组运行过程中,桨叶与导叶的协联关系决定着水轮机的运转效率,而水头的变化则决定着桨—导协联曲线值的选取,从而决定了调速器是否拥有良好的调节性能,故水头信号的实时性与准确性就显得尤其重要。文中介绍了挂治水电厂调速器自动水头的实现方式,对其他类似水电厂实现调速器自动水头功能具有一定的借鉴意义。     

灯泡贯流式水轮机桨叶操作机构故障分析处理

介绍了长洲水利枢纽电站灯泡贯流式水轮机桨叶操作机构故障的原因及处理。经处理,机组转轮已检修完成,试验操作桨叶无异常,协联正常,机组恢复正常运行。     

应用MATLAB求取转桨式水轮机的最优协联关系

转桨式水轮机的协联关系直接影响到机组的运行性能,因此实测并准确计算转桨式水轮机的最优协联关系是一项重要工作。通过将MATLAB强大的数值计算和图形显示功能应用在最优协联试验的数据处理中,可以取得很好的效果。     

灯泡贯流式水轮机导叶与桨叶协联关系探讨

探讨了灯泡贯流式水轮机导叶开度与桨叶开度的协联关系的含义、协联关系曲线中水头的正确理解及设置方法、现场协联调试及优化方法、调速器自动水头输入及自动协联可行性、同一电站不同机组协联关系中水头损失设置差异、机组各运行水头下功率限制的严格控制、机组负荷周期性波动原因分析、机组异常振动噪音分析及改善等。灯泡贯流式水轮机实际运行时应尽可能接近协联工况,并能充分发挥其最佳水力性能。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.