《水处理技术（双语）》课件-离心泵

Centrifugalpumps(I)离心泵（上）离心泵的工作原理Theworkingprincipleofcentrifugalpump离心泵是根据离心力原理设计的，通过高速旋转的叶轮叶片带动液体转动，将液体甩出，从而将液体延管路进行输送的机械。Centrifugalpumpisdesignedaccordingtotheprincipleofcentrifugalforce,throughthehigh-speedrotationoftheimpellerbladesdrivetherotationoftheliquid,theliquidwillbethrownout,sothattheliquidextendedpipelinefortransportmachinery.离心泵的工作原理Theworkingprincipleofcentrifugalpump离心泵的工作过程分为吸液过程和排液过程，其工作原理如下：Theworkingprocessofcentrifugalpumpisdividedintosuctionprocessanddischargeprocess,anditsworkingprincipleisasfollows.离心泵的工作原理Theworkingprincipleofcentrifugalpump排液过程：在泵启动前，先用被输送的液体把泵灌满。启动后，高速旋转的叶轮带动叶片间的液体作旋转运动。

Drainageprocess:Beforethepumpisstarted,thepumpisfilledwiththeliquidbeingconveyed.Afterstarting,thehigh-speedrotatingimpellerdrivestheliquidbetweenthevanesforrotationalmovement.在离心力的作用下，液体便从叶轮中心被抛向叶轮外缘。

Undertheactionofcentrifugalforce,theliquidisthrownfromthecenteroftheimpellertotheouteredgeoftheimpeller.在这个过程中，叶片间的液体获得了机械能，液体的静压力提高了，同时其动能也增加了。Inthisprocess,theliquidbetweenthebladesacquiresmechanicalenergy,thestaticpressureoftheliquidisincreased,whileitskineticenergyisalsoincreased离心泵的工作原理Theworkingprincipleofcentrifugalpump液体离开叶轮进入泵壳后，由于泵壳中流道逐渐增大，液体流速逐渐降低，部分动能转变为静压能，至泵出口处，液体的静压力进一步提高，最后进入排出管。Aftertheliquidleavestheimpellerandentersthepumpcasing,astheflowchannelinthepumpcasinggraduallyincreases,theliquidflowrategraduallydecreases,andpartofthekineticenergyistransformedintostaticpressureenergytothepumpoutlet,thestaticpressureoftheliquidfurtherincreases,andfinallyentersthedischargepipe.因离心泵的排液是由于离心力的作用，故称为离心泵。

Becausethedischargeofacentrifugalpumpisduetocentrifugalforce,itiscalledacentrifugalpump.离心泵的工作原理Theworkingprincipleofcentrifugalpump吸液过程：当泵内液体从叶轮中心被抛向叶轮外缘时，在叶轮中心处形成低压区。Suctionprocess:Whentheliquidinthepumpisthrownfromthecenteroftheimpellertotheouteredgeoftheimpeller,alowpressureareaisformedatthecenteroftheimpeller.这样，造成了吸入管贮槽液面与叶轮中心处的压力差,贮槽内的水被吸入叶轮中心，以补充被排出的液体，这就是离心泵的吸液过程。Thus,thepressuredifferencebetweentheliquidlevelofthesuctiontubereservoirandthecenteroftheimpelleriscaused,andthewaterinthereservoirissuckedintothecenteroftheimpellertoreplenishthedischargedliquid,whichisthesuctionprocessofthecentrifugalpump.图为整台离心泵Completecentrifugalpumps离心泵的工作原理Theworkingprincipleofcentrifugalpump若在启动前泵内未充满液体，则泵内存在空气。Ifthepumpisnotfilledwithliquidbeforestarting,thereisairinthepump.由于空气的密度比液体小得多，泵内产生的离心力就很小，因而在吸入口处的真空度很低,贮槽液面与泵入口处的压力差很小，不足以将贮槽内的液体吸入泵内。Becausethedensityofairismuchsmallerthantheliquid,thecentrifugalforcegeneratedinthepumpisverysmall,sothevacuumatthesuctioninletisverylow,andthepressuredifferencebetweenthereservoirlevelandthepumpinletisverysmall,whichisnotenoughtosucktheliquidinthereservoirintothepump.离心泵的工作原理Theworkingprincipleofcentrifugalpump由于泵内存在空气,启动离心泵而不能输送液体的现象，称为“气缚”。Duetothepresenceofairinsidethepump,thepumpcannotstarttheliquidtransferphenomenon,called"airbinding".在吸入管末端安装底阀的目的也是为了在灌泵时，防止水泄漏，使泵内容易充满液体。Thepurposeofinstallingthebottomvalveattheendofthesuctionpipeisalsotopreventwaterleakagewhenfillingthepump,sothatthepumpcanbeeasilyfilledwithliquid.离心泵的结构Structureofcentrifugalpump离心泵主要由泵壳、叶轮和轴封装置三部分构成。离心泵的主要零件可参考图1-2。Centrifugalpumpismainlycomposedofthreeparts:pumpcasing,impellerandshaftsealdevice.ThemainpartsofthecentrifugalpumpcanbereferredtoFigure1-2.离心泵主要有泵体、泵盖、叶轮、泵轴、轴承及支架、密封装置等组成离心泵的结构Structureofcentrifugalpump1、泵壳PumpCasing离心泵的泵壳通常制成如同蜗壳状的渐开线形，如图所示。Thepumpcasingofacentrifugalpumpisusuallymadeintoaninvoluteshapelikeawormshell,asthepictureshows.叶轮在泵壳内沿着蜗形逐渐扩大的通道方向旋转，愈接近液体的岀口，流道截面积愈大。Impellerinthepumpcasingalongtheworm-shapedgraduallyexpandingthedirectionofthechannelrotation,theclosertotheoutflowofliquid,thelargerthecross-sectionalareaoftheflowchannel.图为泵体及泵内液体液动情况Pumpbodyandliquidmovementinthepump液体从叶轮边缘高速流出后，在泵壳中的蜗形通道作惯性运动时流速将逐渐降低，动能逐渐减小，在忽略位能改变的前提下，根据机械能守恒原理，减少的动能转化为静压能，从而使液体获得高压，并因流速的下降减少了流动能量损失。Aftertheliquidflowsoutfromtheimpelleredgeathighspeed,theflowvelocitywillgraduallydecreasewhentheworm-shapedchannelinthepumpcasingmakesinertialmovement,andthekineticenergygraduallydecreases,underthepremiseofignoringthechangeofpotentialenergy,accordingtotheprincipleofmechanicalenergyconservation,thereducedkineticenergyisconvertedintostaticpressureenergy,sothattheliquidcanobtainhighpressureandreducetheflowenergylossduetothedecreaseofflowvelocity.所以泵壳不仅是收集由叶轮甩出液体的部件，还是一个能量转换部件。Therefore,thepumpcasingisnotonlyaparttocollecttheliquidthrownoutbytheimpeller,butalsoanenergyconversionpart.离心泵的结构Structureofcentrifugalpump离心泵的结构Structureofcentrifugalpump2、叶轮（impeller）叶轮是离心泵的关键部件，一般有6~12片弯曲的叶片。Impelleristhekeycomponentofcentrifugalpump,generallyhas6~12curvedblades.按其机械结构可分为闭式、半闭式和敞开式三种，如图所示。Accordingtoitsmechanicalstructure,itcanbedividedintothreetypes:closed,semi-closedandopen,asthepictureshows.叶片两侧带有前、后盖板的称为闭式叶轮，它适用于输送清洁液体，多数离心泵均采用这种叶轮。Bothsidesofthebladewiththefrontandbackcoveriscalledclosedimpeller,itissuitablefortransportingcleanliquid,mostcentrifugalpumpsareusingthisimpeller.没有前、后盖板，仅由叶片和轮毂组成的称为敞开式叶轮。只有后盖板的称为半闭式叶轮。Thereisnofrontandrearcoverplate,onlythebladeandhubiscalledopenimpeller.Thosewithonlytherearcoverplatearecalledsemi-closedimpellers.(a)闭式(b)半闭式(c)敞开式图为叶轮impeller离心泵的结构Structureofcentrifugalpump3、轴封装置（Shaftsealingdevice）Shaftsealingdevice

泵轴与泵壳之间的密封称为轴封，其作用是防止高压液体沿轴外漏，同时也防止外界空气吸入泵的低压区，对泵轴与泵壳之间的间隙采用密封装置，称为轴封装置。Thesealbetweenthepumpshaftandpumpcasingiscalledshaftseal.Itsfunctionistopreventthehighpressureliquidfromleakingoutalongtheshaft,andalsotopreventtheoutsideairfrominhalingintothelowpressureareaofthepump,andthesealdeviceisusedforthegapbetweenthepumpshaftandthepumpcasing,whichiscalledshaftsealdevice.常用的轴封装置有填料密封和机械密封两种。Therearetwotypesofshaftsealingdevicescommonlyused:packingsealandmechanicalseal.离心泵的结构Structureofcentrifugalpump

填料密封Packingseal如图所示。asthepictureshows.它主要由填料函壳、软填料和填料压盖组成。Itismainlycomposedofpackinglettershell,softpackingandpackinggland.软填料可选用浸油及涂石墨的方形石棉绳缠绕在泵轴上，或直接釆用橡胶密封圈密封，然后将压盖均匀压紧，使填料紧压在填料函壳和转轴之间，达到密封的目的。Softpackingcanbeselectedfromoil-impregnatedandgraphite-coatedsquareasbestosropewrappedaroundthepumpshaft,ordirectlysealedwitharubberseal,andthentheglandisevenlypressed,sothatthepackingistightlypressedbetweenthepackinglettershellandtheshafttoachievethepurposeofsealing.图为填料函packingbox1-填料函壳；2—软填料；3—液封圈；1-stuffingboxshell;2-softpacking;3-liquidsealring.4一填料压盖；5—内衬套4apackinggland;5-innerbushing离心泵的结构Structureofcentrifugalpump机械密封MechanicalSeals对于输送易燃、易爆或有毒、有腐蚀性液体时，轴封要求严格，一般采用机械密封装置，如图所示。Forconveyingflammable,explosiveortoxic,corrosiveliquids,theshaftsealrequirementsarestrict,andmechanicalsealingdevicesaregenerallyused,asthepictureshows.图为密封圈Seals离心泵的结构Structureofcentrifugalpump主要的密封元件是装在轴上随轴转动的动环和固定在泵体上的静环组成的密封面(一般动环用硬质耐腐蚀金属材料、静环用浸渍石墨或耐腐蚀塑料制作以便更换)，两个环的环形端面由弹簧使之平行贴紧，当泵运转时，两个环端面发生相对运动但保持贴紧而起到密封作用，因此机械密封又称为端面密封。Themainsealingelementisinstalledontheshaftwiththeshaftrotationofthedynamicringandfixedinthepumpbodyofthestaticringsealingsurface(generallydynamicringwithhardcorrosion-resistantmetalmaterials,staticringimpregnatedwithgraphiteorcorrosion-resistantplasticforreplacement),theringendfaceofthetworingsbythespringtomaketheparalleltight,whenthepumpisrunning,thetworingsendfacerelativemovementbutkeeptightandplayasealingrole,Therefore,themechanicalsealisalsocalledendfaceseal.图为密封装置示意图Diagramofthesealingdevice1—螺钉；2—传动座；3—弹簧；4—推环；1-screw;2-driveseat;3-spring;4-pushring.5—动环密封圈；6—动环；7—静环；5-dynamicringseal;6-dynamicring;7-staticring.8-静环密封圈；9一防转销8-Staticringseal;9-Anti-rotationpin离心泵的结构Structureofcentrifugalpump与填料密封相比，机械密封的密封性能好，结构紧凑，使用寿命长，功率消耗少，现已较广泛地应用于各种类型的离心泵中.Comparedwithpackingseal,mechanicalsealhasgoodsealingperformance,compactstructure,longservicelifeandlowpowerconsumption,andisnowmorewidelyusedinvarioustypesofcentrifugalpumps.但其加工精度要求高，安装技术要求严，价格较高，维修也较麻烦。However,itrequireshighprocessingaccuracy,strictinstallationtechnology,higherpriceandmoretroublesomemaintenance.离心泵的性能Performanceofcentrifugalpumps（一）主要性能参数Mainperformanceparameters要正确选择和使用离心泵，必须了解其性能，离心泵的主要性能有流量、扬程、轴功率、效率和允许汽蚀余量等，常标注在泵的铭牌上。

Tocorrectlyselectandusecentrifugalpumps,itisnecessarytounderstandtheirperformance.Themainpropertiesofcentrifugalpumpsareflowrate,head,shaftpower,efficiencyandallowablecavitationmargin,whichareoftenmarkedonthepumpnameplate.离心泵的性能Performanceofcentrifugalpumps1、流量（flow）离心泵的流量Q是指离心泵在单位时间内输送到管路系统中的液体体积，单位m3/h。离心泵的流量与泵的结构、规格(主要为叶轮直径和宽度)及转速等有关。TheflowrateQofcentrifugalpumpisthevolumeofliquiddeliveredtothepipelinesystemperunittime,inm3/h.Theflowrateofcentrifugalpumpisrelatedtothepumpstructure,specifications(mainlytheimpellerdiameterandwidth)andspeed.

应予指出，离心泵总是和特定的管路连接的，因此离心泵的实际流量还与管路特性有关。

Itshouldbenotedthatthecentrifugalpumpisalwaysconnectedtoaspecificpipeline,sotheactualflowrateofthecentrifugalpumpisalsorelatedtothecharacteristicsofthepipeline.离心泵的性能Performanceofcentrifugalpumps2、扬程(压头)（Lift）离心泵的扬程H是指离心泵对单位重量(1N)的液体所提供的有效机械能，单位为J/N或m。其大小取决于泵的结构形式、规格(叶轮直径、叶片的弯曲程度)、转速、流量以及液体的密度和黏度。

TheheadHofacentrifugalpumpistheeffectivemechanicalenergyprovidedbythecentrifugalpumpperunitweight(1N)ofliquidinJ/Norm.Itssizedependsonthepump'sstructuralform,specifications(impellerdiameter,degreeofbendingofthevanes),speed,flowrate,andthedensityandviscosityoftheliquid.

离心泵的扬程与柏努利方程中的外加压头是有区别的，外加压头是系统在流量一定的条件下对输送设备提岀的做功要求，而扬程是输送设备在流量一定的条件下对流体实际做功能力。

ThereisadifferencebetweentheheadofacentrifugalpumpandtheexternalpressureheadinBernoulli'sequation.Theexternalpressureheadistheworkrequirementoftheconveyingequipmentundercertainflowconditions,whiletheheadistheactualworkcapacityofthefluidundercertainflowconditions.离心泵的性能Performanceofcentrifugalpumps3、轴功率（Shaftpower）离心泵的轴功率N是指泵轴所需的功率。当泵直接由电动机带动时，即为电机传给泵轴的功率，单位为J/s或W。离心泵的轴功率与设备的尺寸、流体的黏度、流量等有关，其值可用功率表进行测量。TheshaftpowerNofacentrifugalpumpreferstothepowerrequiredbythepumpshaft.Whenthepumpisdrivendirectlybythemotor,thatis,thepowertransmittedtothepumpshaftbythemotor,theunitisJ/sorW.Theshaftpowerofthecentrifugalpumpisrelatedtothesizeoftheequipment,theviscosityofthefluid,theflowrate,etc.,anditsvaluecanbemeasuredbyapowermeter.离心泵的性能Performanceofcentrifugalpumps4、效率Efficiency

离心泵在输送液体的过程中，当外界能量通过叶轮传给液体时，不可避免地会有能量损失，即电机传递给泵轴的能量不能全部由液体获得，致使泵的有效扬程和流量都较理论值为低，通常可用泵的效率η来反映设备能量损失的大小。

Centrifugalpumpintheprocessoftransportingliquid,whentheexternalenergythroughtheimpellertotheliquid,therewillinevitablybeenergyloss,thatis,themotortransfertothepumpshaftcannotbealltheenergyobtainedbytheliquid,resultingintheeffectiveheadandflowofthepumparelowerthanthetheoreticalvalue,usuallyavailablepumpefficiencyηtoreflectthesizeoftheenergylossofequipment.

离心泵的性能Performanceofcentrifugalpumps5、离心泵的能量损失Energylossofcentrifugalpumps主要包括以下几项。（1）容积损失。（2）机械损失。（3）水力损失。Itmainlyincludesthefollowingitems.(1)Volumeloss.(2)Mechanicallosses.(3)Hydraulicloss.图为

离心泵特性曲线图离心泵的性能Performanceofcentrifugalpumps（二）特性曲线CharacteristicCurve实验表明，离心泵在工作时的扬程、功率和效率等性能参数并不是固定的，而是随流量的变化而变化。

Experimentshaveshownthattheperformanceparameterssuchashead,powerandefficiencyofcentrifugalpumpsinoperationarenotfixed,butvarywiththeflowrate.离心泵的性能Performanceofcentrifugalpumps将实验测得的离心泵的流量Q与扬程H、轴功率N和效率η间的关系，绘制在一张图上（图1-13），称为离心泵的特性曲线或工作性能曲线。

TherelationshipbetweentheexperimentallymeasuredflowrateQandheadH,shaftpowerNandefficiencyηofthecentrifugalpumpisplottedonagraph(Figure1-13),whichiscalledthecharacteristiccurveoroperatingperformancecurveofthecentrifugalpump.此曲线通常由泵的制造厂提供并附于离心泵样本或说明书中，供用户选择和操作离心泵时参考。Thiscurveisusuallyprovidedbythepumpmanufacturerandattachedtothecentrifugalpumpsampleormanualfortheuser'sreferencewhenselectingandoperatingthecentrifugalpump.离心泵的安装Installationofcentrifugalpumps（一）安装位置InstallationLocation离心泵的安装位置可高于液面，也可低于液面，必须在允许安装高度之内。Theinstallationpositionofthecentrifugalpumpcanbehigherthantheliquidlevelorlowerthantheliquidlevelandmustbewithintheallowableinstallationheight.图为位置和汽蚀现象离心泵吸入液体是依靠叶轮的高速旋转，在吸入口（叶轮中心处）形成负压。Thecentrifugalpumpdrawsinliquidbyrelyingonthehigh-speedrotationoftheimpeller,whichcreatesanegativepressureatthesuctionport(atthecenteroftheimpeller).

如果离心泵离地面太高，引起液体有效气蚀余量减少，液体进入泵的低压区时，其压力小于液体输送温度下的饱和蒸汽压力，液体沸腾而汽化，从而引起气蚀，对泵本身造成损失。

Ifthecentrifugalpumpistoohighfromtheground,causingareductionintheeffectivecavitationmarginoftheliquid,theliquidentersthelowpressurezoneofthepump,itspressureislessthanthesaturatedvaporpressureatthetemperatureoftheliquiddelivery,theliquidboilsandvaporizes,thuscausingcavitation,causinglossestothepumpitself.离心泵的安装Installationofcentrifugalpumps离心泵的安装Installationofcentrifugalpumps

离心泵汽蚀现象:当贮槽液面上的压力一定时，吸上高度越高，则压力越小。Centrifugalpumpcavitationphenomenon:Whenthepressureontheliquidsurfaceofthereservoiriscertain,thehigherthesuctionheight,thelowerthepressure.若吸上高度高至某一限度，压力降至等于输送温度下液体的饱和蒸气压时，在泵进口处，液体就会沸腾，大量汽化。Ifthesuctionheightishightoacertainlimit,thepressuredropstoequaltothesaturationvaporpressureoftheliquidattheconveyingtemperature,atthepumpinlet,theliquidwillboilandvaporizealot.液体汽化产生的大量气泡随液体进入高压区时，又被周围的液体压碎，气泡所在空间形成真空，周围的液体质点以极大的速度冲向气泡中心。Liquidvaporizationproducesalargenumberofbubbleswiththeliquidintothehigh-pressurearea,andthencrushedbythesurroundingliquid,wherethebubblespacetoformavacuum,thesurroundingliquidmassatgreatspeedtothecenterofthebubble.由于液体质点互相冲击，造成很高的瞬间局部冲击压力。Thehighinstantaneouslocalshockpressureiscausedbytheliquidmassesimpactingeachother.Thisgreatimpactcanmaketheimpellerorpumpcasingsurfacemetalparticlesoff,thesurfacegraduallyformedspots,smallcracks,andevenmaketheimpellerintoaspongeorthewholeoff,thisphenomenoniscalled"cavitation".这种极大的冲击力可使叶轮或泵壳表面的金属粒子脱落，表面逐渐形成斑点、小裂缝，甚至使叶轮变成海绵状或整块脱落，这种现象称为“汽蚀”。离心泵的安装Installationofcentrifugalpumps离心泵的安装Installationofcentrifugalpumps汽蚀会引起以下后果：Cavitationcancausethefollowingconsequences.（1）产生振动和噪声；Generationofvibrationandnoise.（2）产生大量气泡，使泵的流量、扬程、效率均明显下降；

Generatealargenumberofairbubbles,sothattheflow,headandefficiencyofthepumparesignificantlyreduced（3）在叶片入口附近金属疲劳剥蚀。

Fatiguespallingofmetalnearthebladeinlet.图为离心泵发生气蚀时性能曲线的变化离心泵的安装Installationofcentrifugalpumps（二）安装基础InstallationBasics

离心泵的安装工作必须根据设计图纸进行。对于安装位置、安装高度等都必须符合设计要求。

Theinstallationofthecentrifugalpumpmustbecarriedoutaccordingtothedesigndrawings.Fortheinstallationposition,installationheight,etc.mustmeetthedesignrequirements.但如果安装时发现设计存在问题，要在现场及时解决。基础的作用是支承并固定机组，使它运行平稳，不致发生剧烈振动，更不允许产生基础沉陷。However,ifproblemswiththedesignarefoundduringinstallation,theyshouldbesolvedonsiteintime.Theroleofthefoundationistosupportandfixtheunitsothatitrunssmoothlyanddoesnotvibrateviolently,nottomentionthatfoundationsubsidenceisnotallowedtooccur.离心泵的安装Installationofcentrifugalpumps（三）水管的布置

ayoutofwaterpipes进出水管的布置，对泵站安全运行和工程投资有较大影响，应通过方案比较后确定，应考虑管线的选择，其布置原则是：Thearrangementoftheinletandoutletpipeshasagreaterimpactonthesafeoperationofthepumpingstationandengineeringinvestment,shouldbedeterminedthroughprogramcomparison,thechoiceofpipelineshouldbeconsidered,anditsarrangementprinciplesare.合理选择管道直径，管道直径大，在相同流量下，液流速度小，阻力损失小；管道直径小，会导致阻力损失急剧增大，使所选泵的扬程增加，功率增加，成本和运行费用都增加。Reasonablechoiceofpipediameter,pipediameterpipediameterislarge,inthesameflowrate,liquidflowvelocityissmall,resistancelossissmall;pipediameterissmall,willleadtoasharpincreaseinresistanceloss,sothattheselectedpumpheadincreases,powerincreases,thecostandoperatingcostsareincreased.

泵的出口侧必须装设阀门（球阀或截止阀）和止逆阀。阀门用来调节泵的工况点，止逆阀在液体倒流时可防止泵反转，并使泵避免水锤的打击。

Theoutletsideofthepumpmustbeequippedwithavalve(ballvalveorglobevalve)andacheckvalve.Thevalveisusedtoregulatetheworkingpointofthepump,andthecheckvalvecanpreventthepumpfromreversingwhentheliquidflowsbackwards,andmakethepumpavoidwaterhammerblow.离心泵的安装Installationofcentrifugalpumps离心泵的安装Installationofcentrifugalpumps（四）振动、噪音的防治Vibration,noisepreventionandcontrol离心泵使用时发现泵振动及噪音异常，应立即停机作检查。Whenthecentrifugalpumpisusedandabnormalpumpvibrationandnoisearefound,itshouldbestoppedimmediatelyforinspection.（1）泵基础是否牢靠whetherthePumpfoundationissecure当发生振动时，Whenvibrationoccurs,首先应检查离心泵的地脚螺栓是否紧固。若未紧固会造成离心泵震动。

Firstofall,youshouldcheckwhetherthegroundboltsofthecentrifugalpumparetightened.Ifnottightened,itwillcausethecentrifugalpumptovibrate.还要考虑地脚基础强度是否够用，有时由于设计原因，基础偏软也能引起震动。

Alsoconsiderwhetherthefootingfoundationstrengthissufficient,sometimesduetodesignreasons,thefoundationissoftcanalsocausevibration.离心泵的安装Installationofcentrifugalpumps（2）联轴器找正

Couplingalignment