引水式水电站水轮机额定水头的选择

(一) 前言水轮机的额定水头(水轮发电机组发出额定功率时的最小水头)如选择不当,将直接影响水电站的建设投资与发电经济效益。因此,对水轮机的额定水头应根据水电站的水能特性进行多方案比较,选择最优的额定水头。中小型水电站多数为径流引水式,以往对这这种径流引水式水电站的水轮机额定水头有不少是选择不适当的,因而使选用的水轮机型号、转轮直径、额定转速等与水电站的运行特征不符,造成水轮     

大中型水电站额定水头选择探讨

水电站额定水头是水轮机组发额定容量时相应的最小水头,其选择是一个技术、经济等综合性问题.最佳的额定水头必须在满足稳定的前提下,通过经济技术综合比较,分析水轮机预想出力降低对电力系统平衡的影响等综合分析确定.文章重点介绍了大中型水电站额定水头的选择方式、方法.     

对水电站额定水头选择的研究

水电站额定水头是水轮机组发额定容量时相应的最小水头,对其进行选择是一个技术、经济等综合性问题。最佳的额定水头必须在满足机组稳定的前提下,通过经济、技术综合比较,综合分析出水轮机预想出力以降低对电力系统平衡的影响等进行确定。介绍了大中型水电站额定水头的选择方式、方法,提出了从参数选择、水头范围、吸出高度控制、避振运行、补气方式等提高机组运行稳定性的措施。     

几内亚苏阿皮蒂水电站机组额定水头选择

水电站额定水头的选择是一个技术、经济等综合性问题。针对几内亚苏阿皮蒂水电站额定水头的确定,若额定水头较高,当机组长时间低于额定水头运行时,会造成较大的受阻容量;若额定水头较低,机组存在运行稳定问题,且在额定容量不变时,需加大水轮机直径或相应降低机组转速,从而增加投资。结合国内相同水头段已建水电站的设计、运行资料综合分析,确定苏阿皮蒂水电站额定水头为87 m。     

立洲水电站水轮机额定水头的优选方法

确定一个合适的水轮机额定工作水头,对于保障水轮发电机组的稳定运行和提高水电站运行的经济效益是至关重要的。以立州水电站水轮机选型设计为例,通过对不同额定水头方案水轮机的加权平均效率、投资、运行可靠性等的分析和比较,阐述了确定水轮机额定水头时应考虑的主要因素和优选方法。     

黄花寨水电站额定水头选取及稳定性分析

在水电站的设计中,额定水头的选取是关系水电站稳定运行的重要因素。黄花寨水电站最高水头90.47 m,最低水头59.48 m,针对水头变幅大这一特点,对水轮机的额定水头选取进行综合的技术经济比较,对水头出现频率分析后,得出适合电站运行的额定水头。并提出了从参数选择、水头范围、吸出高度控制、避振运行、补气方式等提高机组运行稳定性的措施。     

混流式水轮机电站运行稳定性与装机容量选择的探讨

当前电力系统希望水电站能以较高的保证率发足装机容量，也就是要求较低的额定水头；但从混流式水轮机稳定的要求出发，希望额定水头、设计水头都不能低于Hmax/1.1，怎样才能既满足电力系统的要求又能使水轮机稳定运行呢。建议采取提高额定水头，增加机组台数或加大单机容量的方式来协调解决。     

双江口水电站水轮机额定水头的选择

额定水头既是水轮机的重要参数,也是电站的重要动能参数。从水轮机运行特性、动能经济指标、统计成果及机组制造可行性等方面出发,介绍了双江口水电站额定水头的选择成果,并论述了发电机不设最大容量的可行性。     

低水头水电站水轮机机型比选分析

雷公滩水电站属于低水头水电站,其水库仅具有日调节性能,因此,机组型式的选择及额定水头的确定将会直接影响到整个工程的投资规模和后期的经济效益。综合考虑该水电站处于交界水头的实际情况,通过对不同机型的投资、能量特性等方面展开分析,对不同额定水头方案下水轮机的运行稳定性、经济效益等方面的参数进行比较,最后确定雷公滩水电站采用灯泡贯流式机组,额定水头选取为14.53 m。     

惠州抽水蓄能电站水泵水轮机水轮机工况额定水头选择

抽水蓄能电站水泵水轮机水轮机工况额定水头的确定直接关系到电站运行的稳定性和经济性，而它的选择与常规电站水轮机额定水头的确定既有相似之处、又有不同之处，本文通过对惠州抽水蓄能电站水轮机工况额定水头的选择，介绍抽水蓄能电站水轮机工况额定水头的选择应考虑的问题，为今后抽水蓄能电站水轮机工况额定水头的选择提供参考。     

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。     

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.     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。