惯性密封及其在离心泵上应用的探讨

惯性密封是指利用密封腔内旋转的液体在牵连惯性力的作用下处于相对平衡状态这一流体静力学特性,使液体的自由面高度和密封腔保持相对静止,或在一定范围波动,但不从密封腔流出造成泄漏的密封。惯性密封属于流体动力密封的范畴,是无接触密封。因此这种密封最大的特点是具有相当长的使用寿命,在泵的使用过程中,可不对密封进行更换和修理,这是机械密封、填料密     

土贤庄水电站水轮机主轴密封运行与改造措施

土贤庄水电站水轮机主轴密封原为双平板密封,原密封随着机组运行时间的增加、机组主轴摆度及窜动的加大,密封效果也越来越差,主轴漏水量也随之加大,直接影响到水机轴承的安全。通过采取将原双层平板密封主轴密封改造为活塞式主轴密封的方案,对水轮机主轴密封进行更新改造,改造后的新主轴密封为橡胶活塞密封。主轴密封改造不破坏原机组结构,能够解决主轴密封漏水问题,具有安装、维修方便、工作性能稳定可靠的优点,彻底解决了原主轴密封在运行中存在的问题,提高了电站整体的安全系数,达到了预期的改造效果。     

几种泵用密封失效原因简析

水泵轴封采用的密封方法最常用的填料密封外通常有机械密封,动力密封,迷宫密封。这些密封方法都是成熟的,可靠的,但在实际应用中却并不是十分令人满意,原因何在？让我们作一简析。填料密封在此不再赘述。     

金属非接触水轮机主轴密封在九甸峡水电站的应用

主要介绍了水轮机主轴密封的几种形式,并分析了各种密封形式的优缺点。九甸峡水电站水轮机主轴密封采用金属非接触密封,密封效果良好,可在其他混流式机组水轮机主轴密封改造时推广。     

碧口水电厂水轮机主轴密封结构形式的分析与实践

碧口水电站3台水轮机主轴密封历年来采用过尼龙端面密封、液压端面橡胶密封、端面水压密封,均属于端面密封形式。文章就3种密封的结构特点、工作原理、使用情况、优点不足等进行了简要分析介绍,为水轮机主轴密封的改造和使用提供一定的参考。     

SGB6—10型灌浆泵柱塞密封的改进

注意到柱塞密封的泄漏问题；结合生产和应用实际，分析了密封泄漏的原因。介绍了通过改进柱塞密封中柱塞表面加工工艺及密封材质，提高密封效果。     

卧轴强制式砼搅拌机轴端密封装置新结构的探讨

针对卧轴强制式砼搅拌机轴端密封装置目前存在的密封性能差的问题，提出了两种新型的密封装置，即油浸石棉填料密封与箱形截面骨架环或角形截面金属环唇形密封相结合的两种轴端密封装置。新型装置具有结构较简单、密封可靠、成本低、维修方便以及适应性强等特点。     

高水头混流式水轮机主轴密封的改造研究

国内高水头混流式水轮机主轴密封一般采用端面式结构，实践证明在许多电站这咎结构达不到安全可靠运行的要求，螺旋动力泵式主轴密封为一种非接触的动力密封，能使机组主轴密封处于不接触，无漏泄的运行状态，南桠河和耿达水电站机组主轴密封履行为螺旋动力泵式主轴密封后，解决了多年存在的运行缺陷。这种主轴密封结构可以广泛应用于高水头混流式水轮机主轴密封中。     

水泵水轮机主轴密封及烧损故障处理

大容量、高转速水泵水轮机主轴密封相对常规水轮机主轴密封更容易发生故障。分析3种典型水泵水轮机主轴密封即平衡式流体静压径向双端面机械密封、非平衡水压自调整轴向式分瓣机械型平面密封、弹簧复位式浮动型双端面机械密封的结构、工作原理和故障发生原因,提出了这3种水泵水轮机主轴密封的故障处理方法。     

高水头水泵水轮机组通流部件密封运行特点及改进

天荒坪抽水蓄能电站投产以来,导叶轴端"O"形密封、球阀工作密封投退腔"O"形密封和球阀枢轴"U"形密封等多次发生漏水。作者认为水泵水轮机组通流部件密封失效的原因是密封形状、材质和密封座的材质等不能满足现场高水压力、导叶和球阀频繁动作的运行条件,经过多年改进,漏水现象已明显改善。总结了天荒坪抽水蓄能电站水泵水轮机组通流部件密封多年改进实践经验,希望能够为水力机械通流部件密封设计和改善水力机械漏水现象有参考作用。     

聊城市城区排涝存在的问题及对策

通过系统分析山东省聊城市及城区多年涝灾变化情况,总结了城区涝灾形成的原因,提出了防洪排涝减灾的几项措施:建设高标准城区防洪排涝工程,利用生态功能集蓄、滞缓、调蓄雨洪,科学规划城区防洪排涝体系,提高政府应对能力,实现城区防汛自动化、现代化。     

广西钦江流域水沙年际变化规律分析

为了探究河流水沙的变化规律及影响因素,利用钦江陆屋流域1957—2016年的长时序年降水量、年径流量和年输沙率数据,采用5年滑动平均法、R/S检验法、Mann-Kendall突变检验法、累积距平法及复Morlet小波分析法分析以上序列的趋势性、突变性和周期性;运用双累积曲线法分析降水和径流输沙关系的变化;最后结合流域森林转型特征来进行分析。结果表明:(1)降水量弱上升、径流量减少、输沙率显著减少,在α=0.05和β=0.01的显著水平下,降水量和径流量无变异,输沙率弱变异。降水量在1962年、1971年、1989年和2013年发生突变,径流量在1963年、1971年、1989年和2007年发生突变,输沙率在1967年、1971年、1981年和2001年发生突变。降水量存在4类时间尺度,23 a、13 a分别为第一、二主周期;径流量序列存在3类时间尺度,14 a、9 a分别为第一、二主周期;输沙率序列存在4类时间尺度,22 a、5 a分别为第一、二主周期。(2)降水量-径流量累积关系分为两个阶段,即1957—1988年和1989—2016年,斜率分别为0.006 8、0.005 8;降水量-输沙量累积关系分为四个阶段:1957—1962年、1963—1988年、1989—1998年和1999—2016年,斜率分别为0.014、0.019 4、0.016 4、0.009,造成水沙关系变化的原因是人类活动的影响。(3)广西林业建设和森林转型的发展过程是径流量和输沙量不断发生变化的原因。     

地下水资源可持续水价模式研究

面对当前地下水资源低价或无偿使用的局面,首先探讨了地下水资源价值及价格构成,指出现行地下水资源费必须全面反映资源的价值以及水管单位、用户和环境的承受能力,然后在全成本水价理论基础上建立了地下水资源可持续水价模式。考虑了地下水资源开采成本及利润、水资源价值及地下水资源开采潜力等方面的可持续水价既能满足区域经济、社会可持续发展的要求,又能实现地下水资源的合理开发利用与保护。     

保护水环境与合理开发利用水资源

水是人类必须且不可替代的资源,我国北方大部分地区严重缺水,工农业生产损失巨大,生态环境日趋恶化;南方各流域交替发生洪涝灾害损失惨重,年年防洪、防汛抗旱消耗大量资源;保护水环境、节水与合理开发利用水资源、建立稳定和谐的人水关系是我国经济社会长期健康发展的根本,藏水北调是合理配置水资源的重大举措,建立全国联通水库网,仅限汛期调水、重复利用,治污后再输往沙化地区植被改善生态,是唯一能趋利避害、争取更大效益的方案,建议“藏水和南水”北调应以恢复生态为主要功能目标并与防洪协调。     

Groundwater Protection and Management Strategy in Jordan

Groundwater resources are essential in Jordan that require careful planning and management in order to sustain human socio-economic development and various ecosystems. However these vital resources are under the threat of degradation by both mismanagement and over-exploitation that leads to contamination and decline of water levels. A new by-law, which specifically addresses pollution prevention and protection of water resources used for domestic purposes through appropriate land use restriction and zoning, is currently under preparation in Jordan. This law (i.e., Groundwater Management Policy) addresses the management of groundwater resources including development, protection, management, and reducing abstraction for each renewable aquifer to the sustainable rate (i.e., safe yield). Groundwater vulnerability mapping and delineation of groundwater protection zones were implemented in different areas in Jordan in cooperation between the German Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) company and Ministry of Water and Irrigation. This paper presents the status of groundwater resources in Jordan and their major issues. It attempts to discuss the groundwater vulnerability and protection strategy and the impacts of over-exploitation on the groundwater aquifers in an integrated water resources management perspective.     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

The making and re-making of places along the St. Louis River in Duluth: From paintings to projects

Studies of the effectiveness of Remedial Action Plans (RAPs) call for the prioritization of placemaking and broadening of the definition of stakeholders. This paper argues that such stakeholder groups should include local historians, archivists, and art-or-architectural historians whose knowledge of local, place-based initiatives and familiarity with the built and visual landscape offer invaluable insights. In addition, instead of making new places as part of revitalization and remediation initiatives, such work should focus on the re-making of human-scaled spaces and places with unique histories to which residents are already attached. Several recent-and-ongoing projects in the St. Louis River AOC demonstrate the effectiveness of work that re-imagines places with clear and established identities and which does not turn away from problematic and complicated histories. An exploration of these initiatives in the St. Louis River AOC is combined with further consideration of placemaking and place attachment and an examination of industrial portraits created by Art Fleming for the Kom-on-Inn Bar in West Duluth in the 1950s, which are testament to the pride in place and the importance of the river and industries in the making and then breaking of the neighborhoods and the larger ecosystems of which they are a part.     

全级配混凝土干缩变形性能研究

混凝土裂缝会对结构的稳定产生不利因素,为此进行了全级配和湿筛混凝土的干缩变形试验。通过分析混凝土的干缩机理,在弹性力学理论基础上建立了考虑骨料粒径和含量的混凝土干缩模型,分析了混凝土的干缩变形与骨料及水泥浆体弹性模量之间的关系。同时通过分析试件尺寸对混凝土干缩性能的影响,对比研究了全级配与湿筛混凝土干缩变形随龄期的变化规律,结果显示模型计算数据与试验数据吻合良好。研究表明,全级配与湿筛混凝土干缩变形比值随龄期增加而逐渐增大,180d龄期时的比值约为0.29左右。     

The Design of an International Real Time Data Collection System: SADC-HYCOS

It is increasingly clear that there is a need to assist National Hydrological Agencies in Africa to improve their hydrometric data collection capabilities and at the same time to halt the decline in hydrometric standards. This has to be achieved in a cost-effective and sustainable way and, at the same time reinforce existing systems with new technology and equipment and strengthen the institution capacity of these agencies. The Southern African Development Community-Hydrological Cycle Observation System (SADC-HYCOS) will provide the framework, methodologies and tools to achieve this goal. This paper provides the first opportunity to inform the global hydrological community of the aims and activities of the SADC-HYCOS project. Significant advances will be made in the installation of real time data collection platforms and transmission system, the development and implementation of a regional database, the improvement and/or development of data exchange and dissemination systems using a regional electronic network and Internet links, the development of hydrometeorological products from the database and establishing a large scale training programme relating to activities during the life-time of the project. SADC-HYCOS will promote the collection, processing and exchange of hydrological data and information within the region and raise the profile of the regional hydrological issues, hydrological research, operational hydrology, availability of data and information to a global audience.     

Hydraulic Resistance Determination in Marsh Wetlands

Restoration of degraded and creation of constructed wetlands require proper hydraulic design. Of particular importance is the accurate determination of flow resistancefactors and the proper use of resistance equations, somethingessential for computing basic hydraulic parameters, such as depth and velocity, and for modeling the hydrodynamics of the system. In this study, selected previous theoretical, laboratoryand field studies on wetlands and vegetated-channel hydraulics are reviewed, and existing data from these studies are extractedand compiled in a common database. Resistance determining parameters are discussed, and results are summarized and presented, aiming at obtaining laws governing the flow, and deriving values for frictional factors under various flow scenarios. Graphs of Darcy-Weisbach f or Manning's n versus appropriate hydraulic parameters are presented.A modified n-VR graph is also presented, appropriate for marsh preliminary hydraulic analyses and design. These graphs also indicate missing information and can guide in future research.