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1、给水泵最小流量控制装置是给水泵的自动保护装置.由水泵的性能可知给水泵的有效气蚀余量只取决于倒罐儿何高度和吸水管的阻力•在运行电厂屮，儿何高度已成定值，吸水管的阻力随水泵流量的减少而减少,因此有效气蚀余量随流量的减少反而增大•但是，给水泵总的必需气蚀余量，却随着流量的减少，先减后增•这是因为轴功率对流经水泵的给水儿乎在绝热下压缩，除了给水在泵屮获得一定能量外，其余耗功都转化为热能•当出水不能完全把它带走时，就会导致泵水的温升.同时由于第一及叶轮密封环的泄出水和末及后的平衡装置泄放水返回水泵入口，引起进水温度的升高,提高了相应的汽化压头，从而加大了总的气蚀余量，这个现象随着流量的减少，水泵效率
2、的降低，耗功转化为热能的愈增多而愈甚，直到总的必需气蚀余量等于有效的气蚀余量时为止,该流量叫做最小允许流量.关键词：给水泵，最小流量控制,流量阀AbstractThecontroldeviceofminimumflowofthefeedwaterpumpistheautomaticprotectorofthefeedwaterpump.Rkthesurplusofeffectivecavitationerosionwaterpumpistheautomaticprotectorofthefeedwaterpump.Inoperatingthepowerplant,thegeometirch
3、eighthasalreadybecomedefinitevalue,theresistanceofsuckingthewaterpipeisreducedwithreductionoftheflowofthewaterpump,socavitateeffectivelythesurplusincreasewiththereductionoftheflowinstead・Butfeedwaterpumpmustcavitatesurpluswhilebeingtotal,withthereductionoftheflow,increaseafterreducing.Thisisbecaus
4、etheaxlepower,toflowingthroughthenearlywatersupplilycompressingunderheatinsulationofthewaterpump,exceptsupplyingwaterandobtainingcertainenergyinthepump,otherwastedworkareturnedintoheatenergy.WillcauseWenShengofpumpwaterwhensurfacingcan'ttotallytakeitawaying.Itbecauseandnotlastsurfacingandtheendati
5、mpellerringssealedfirstandafterequilibriumdeviceletoutifturningonthewater，lastwaterpumpentry,causeintotherisingofwatertemperature,presstheheadafterimprovingthecorrespondingvaporization,thusstrengthenedthetotalsurplusofcavitationerosion,thisphenomenon,withthereductionoftheflow,thereducingofthewater
6、pumpefficiency,thewastedworkistransformedforincreaseofhealingofheatenergy,untilthefactthatatotalonemustcavitatesurplusequaltoeffectivecavitationerosionatthesurplus,thisflowisnamedallowingtheflowminimumly[18]Keyword:feedwaterpump,theminimumflowiscontrolled,theflowvalve摘要IABSTRACTII1弓I言31.1课题苗景及选题意义
7、31.2国内外发展状况31.3本课题研究的主要内容42火电厂主要工艺52.1火电厂基本生产过程53火电厂三大系统简介73.［燃烧系统73.2汽水系统73.3电气系统74给水控制系统84.1汽包锅炉的控制任务84.1.1主要控制任务84.1.2工要控制系统84.2给水控制手段及特点94.2.1电动定速泵+调节阀94.2.2电动调速泵+调节阀94.2.3汽动泵+电动调速泵+调节阀94.3给水控制系统的基本结构114.3.1单
