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超滤系统的物理清洗是通过阀门频密开启和关闭、水泵的交替起动和停机来实现的,这使液体流速产生急剧变化;并引起很高的水锤压力,造成管道及膜元件损坏.分析了超滤系统出现关阀水锤及停泵水锤的成因,提出相应的防护措施. 相似文献
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本文结合超高层建筑工程中给水系统管道水锤现象,通过对高区传输水泵产生水锤现象与其他设备层管线分析对比,采取不同方案进行整改,最终发现产生水锤现象的原因与现场管线走向有密切关系,通过增加水锤消除器,彻底缓解了水击现象造成的管道抖动,经施工实践总结的技术措施对今后高层建筑给水系统安装及调试有借鉴作用。 相似文献
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水锤现象在有压管道输水工程中不可避免,气囊式空气罐在高扬程中小流量输水工程中相比其他水锤防护措施体现出较好的可靠性和经济性。基于实际工程,应用商用软件Bentley Hammer对输水管道进行水力过渡过程分析,研究气囊式空气罐与多功能水泵控制阀和空气阀联合使用时的水锤防护效果及罐体的体积和气囊预设压力对水锤防护效果的影响。通过Bentley Hammer软件对无防护措施,加装多功能水泵控制阀和空气阀,多功能水泵控制阀、空气阀与气囊式空气罐联合使用3种情况建立数值模拟模型,在3台水泵同时停机时进行水力过渡过程分析。研究结果表明,在高扬程中小流量输水工程中加装气囊式空气罐能起到良好的水锤防护效果。对输水管道系统整体而言,气囊式空气罐的水锤防护能力随罐体体积和预设压力的增大而增强。合理选择气囊式空气罐的体积与预设压力,能使管道内水锤最大正压和负压得到有效控制,并取得最佳的社会经济效益。 相似文献
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《振动与冲击》2018,(24)
为研究充液容器内液体介质类型对液压水锤效应的影响,利用ANSYS/LS-DYNA分析了水、柴油和航空煤油对水锤效应的影响,并进行试验验证。结果表明:破片以1 000 m/s的速度撞击分别装满水、柴油和航空煤油容器的过程中,破片在水中消耗的能量最大,约占破片总动能的40. 28%,柴油次之,航空煤油中消耗的能量最少。破片在水中速度衰减系数约为航空煤油中衰减系数的1. 29倍,三种介质中的阻力系数相差不大,说明液体密度为影响破片在液体中运动规律的主要影响因素。装有水介质的容器后壁面的最大变形量最大,为装有航空煤油容器后壁面变形量的1. 22倍,说明破片撞击装有水介质的容器时形成的水锤效应对容器的破坏更严重。 相似文献
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本文通过管道破坏的成因分析,指出了给水管道破坏的主要原因是管材及其接口方法温度变化应力以及水锤等的影响,并提出了解决办法 相似文献
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水力瞬变也称为水锤,是由于管道内压力瞬间升高,压力波在管道内以声速传递的现象。紧随着压力波,管壁上产生动态应力,进而导致管道失效。基于ALE流固耦合方法模拟由于阀门突然关闭导致的管道中流体冲击波,并与一维水锤冲击波理论值进行了对比。在此基础上分析了不同约束条件下,距离管道末端一定距离,由于管壁变形和振动而产生的三维动态应力。发现在水锤波传播过该位置一段时间之后,管壁应力才达到最大值,此外管壁周向应力在动态应力中影响是最主要的。 相似文献
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差值法与比值法对不同测量系统的误差修正效果不一样.本文将两种方法的比较用一个比值来描述,并用推得的公式进行量化表示.在进一步的应用研究中,理论分析与实验数据相互印证,同时得到许多有益的结论,有助于全面掌握测量系统的误差来源,从而灵活选择各种修正方法以获得更加准确的测量结果. 相似文献
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本文提出了一种采用测量接收机HP8902A测量射频信号源谐波的方法,对该方法的特点及应用范围进行了分析与说明,并通过与常规的频谱分析仪测量谐波的方法进行比较,确定了该测量方法的可行性,可以用于没有频谱分析仪的情况下射频信源谐波的检定。 相似文献
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三峡工程水电站压力管道和蜗壳技术结构型式的选择及论证 总被引:2,自引:0,他引:2
长江三峡水利枢纽工程建设中重大技术问题的决策是建立在大量科学试验和专家论证的基础上,三峡工程水电站压力管道和蜗壳技术结构型式的选择不仅是重大的技术经济问题,也是关系水电站长期运行问题,文章介绍了三峡工程水电站压力管道和蜗壳技术型式选择及决策。 相似文献
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I J Yu Y H Chung S H Maeng K S Song Y M Lee H K Chung H J Kim J I Park S K Lee Y H Lee J S Chang 《Quality Assurance: Good Practice, Regulation, and Law》1999,7(1):57-62
The Korean Society of Good Laboratory Practice (KSGLP) was established Dec. 10, 1998. The objectives of the KSGLP are to enhance the quality of domestic studies and the level of GLP compliance, in safety testing, and to promote information exchange among its members. The activities of KSGLP include: offering workshops and symposiums, linking with related governmental organizations, collecting GLP related information and providing the information to the related organizations, building international networks to collect information and to establish relationship, developing training materials and publishing periodicals, and other business necessary to achieve the objectives of the KSGLP. The KSGLP achieved its goals within a short period of time by offering workshops and symposia, and by providing important GLP related information in newspapers or via the KSGLP's internet homepage (www.ksglp.or.kr). The main role of the KSGLP will be to disseminate GLP technology nationwide. The KSGLP would like to help many labs that are preparing their facilities for GLP compliance. Further, the KSGLP is hoping to share GLP experiences with other members. 相似文献
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This summary article resulted from an informal discussion period held during the International Conference on Precision Electromagnetic Measurements, August 14-17, 1962. This session was presided over by Prof. Norman Ramsey of Harvard University. The Radio Standards Laboratory of the National Bureau of Standards in Boulder, Colorado, sponsored the meeting along with the IRE Professional Group on Instrumentation and the AIEE Instrumentation Division. Partial support for the conference came from a grant from the National Science Foundation. 相似文献
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Jesper Lützen 《Centaurus; international magazine of the history of science and medicine》2010,52(1):4-37
Today we credit Pierre Wantzel with the first proof (1837) of the impossibility of doubling a cube and trisecting an arbitrary angle by ruler and compass. However two centuries earlier Descartes had put forward what probably counts as the first proof of these impossibilities. In this paper I analyze this proof, as well as the later related proof given by Montucla (1754) and the brief version of this proof published by Condorcet (1775) . I discuss the many novelties of these early arguments and highlight the problematic points addressed by Gauss (1801) and Wantzel. In particular I show that although Descartes developed many of the algebraic techniques used in later proofs he failed to provide an algebraic impossibility proof and resorted to a geometric argument. Montucla and Condorcet turned this proof into an algebraic one. I situate the analysis of the early proof of the impossibility of the two classical problems in the general context of early modern mathematics where mathematics was primarily viewed as a problem solving activity. Within such a paradigm of mathematics impossibility results arguably do not play the role of proper mathematical results, but rather the role of meta-results limiting the problem solving activity. 相似文献