毕业设计水利水电工程英文文献翻译

外文文献：hydraulicturbinesandhydro-electricpowerAbstractPowermaybedevelopedfromwaterbythreefundamentalprocesses:byactionofitsweight,ofitspressure,orofitsvelocity,orbyacombinationofanyorallthree.InmodernpracticethePeltonorimpulsewheelistheonlytypewhichobtainspowerbyasingleprocesstheactionofoneormorehigh-velocityjets.Thistypeofwheelisusuallyfoundinhigh-headdevelopments.Faradayhadshownthatwhenacoilisrotatedinamagneticfieldelectricityisgenerated.Thus,inordertoproduceelectricalenergy,itisnecessarythatweshouldproducemechanicalenergy,whichcanbeusedtorotatethe‘coil’.Themechanicalenergyisproducedbyrunningaprimemover(knownasturbine)bytheenergyoffuelsorflowingwater.Thismechanicalpowerisconvertedintoelectricalpowerbyelectricgeneratorwhichisdirectlycoupledtotheshaftofturbineandisthusrunbyturbine.Theelectricalpower,whichisconsequentlyobtainedattheterminalsofthegenerator,isthentransitedtotheareawhereitistobeusedfordoingwork.heplantormachinerywhichisrequiredtoproduceelectricity(i.e.primemover+electricgenerator)iscollectivelyknownaspowerplant.Thebuilding,inwhichtheentiremachineryalongwithotherauxiliaryunitsisinstalled,isknownaspowerhouse.Keywordshydraulicturbineshydro-electricpowerclassificationofhydelplantsheadschemeTherehasbeenpracticallynoincreaseintheefficiencyofhydraulicturbinessinceabout1925,whenmaximumefficienciesreached93%ormore.Asfarasmaximumefficiencyisconcerned,thehydraulicturbinehasaboutreachedthepracticablelimitofdevelopment.Nevertheless,inrecentyears,therehasbeenarapidandmarkedincreaseinthephysicalsizeandhorsepowercapacityofindividualunits.Inaddition,therehasbeenconsiderableresearchintothecauseandpreventionofcavitation,whichallowstheadvantagesofhigherspecificspeedstobeobtainedathigherheadsthanformerlywereconsideredadvisable.Theneteffectofthisprogresswithlargerunits,higherspecificspeed,andsimplificationandimprovementsindesignhasbeentoretainforthehydraulicturbinetheimportantplacewhichithaslongheldatoneofthemostimportantprimemovers.1.typesofhydraulicturbinesHydraulicturbinesmaybegroupedintwogeneralclasses:theimpulsetypewhichutilizesthekineticenergyofahigh-velocityjetwhichactsupononlyasmallpartofthecircumferenceatanyinstant,andthereactiontypewhichdevelopspowerfromthecombinedactionofpressureandvelocityofthewaterthatcompletelyfillstherunnerandwaterpassages.Thereactiongroupisdividedintotwogeneraltypes:theFrancis,sometimescalledthereactiontype,andthepropellertype.Thepropellerclassisalsofurthersubdividedintothefixed-bladepropellertype,andtheadjustable-bladetypeofwhichtheKaplanisrepresentative.1.1impulsewheelsWiththeimpulsewheelthepotentialenergyofthewaterinthepenstockistransformedintokineticenergyinajetissuingfromtheorificeofanozzle.Thisjetdischargefreelyintotheatmosphereinsidethewheelhousingandstrikesagainstthebowl-shapedbucketsoftherunner.Ateachrevolutionthebucketenters,passesthrough,andpassesoutofthejet,duringwhichtimeitreceivesthefullimpactforceofthejet.Thisproducesarapidhammerblowuponthebucket.Atthesametimethebucketissubjectedtothecentrifugalforcetendingtoseparatethebucketfromitsdisk.Onaccountofthestressessoproducedandalsothescouringeffectsofthewaterflowingovertheworkingsurfaceofthebowl,materialofhighqualityofresistanceagainsthydraulicwearandfatigueisrequired.Onlyforverylowheadscancastironbeemployed.Bronzeandannealedcaststeelarenormallyused.1.2FrancisrunnersWiththeFrancistypethewaterentersfromacasingorflumewitharelativelylowvelocity,passesthroughguidevanesorgateslocatedaroundthecircumstance,andflowsthroughtherunner,fromwhichitdischargesintoadrafttubesealedbelowthetail-waterlevel.Alltherunnerpassagesarecompletelyfilledwithwater,whichactsuponthewholecircumferenceoftherunner.Onlyaportionofthepowerisderivedfromthedynamicactionduetothevelocityofthewater,alargepartofthepowerbeingobtainedfromthedifferenceinpressureactingonthefrontandbackoftherunnerbuckets.Thedrafttubeallowsmaximumutilizationoftheavailablehead,bothbecauseofthesuctioncreatedbelowtherunnerbytheverticalcolumnofwaterandbecausetheoutletofhedrafttubeislargerthanthethroatjustbelowtherunner,thusutilizingapartofthekineticenergyofthewaterleavingtherunnerblades.1.3propellerrunnersnherentlysuitableforlow-headdevelopments,thepropeller-typeunithaseffectedmarkedeconomicswithintherangeofheadtowhichitisadapted.Thehigherspeedofthistypeofturbineresultsinalower-costgeneratorandsomewhatsmallerpowerhousesubstructureandsuperstructure.Propeller-typerunnersforlowheadsandsmalloutputsaresometimesconstructedofcastiron.Forheadsabove20ft,theyaremadeofcaststeel,amuchmorereliablematerial.Large-diameterpropellersmayhaveindividualbladesfastenedtothehub.1.4adjustable-bladerunnersTheadjustable-bladepropellertypeisadevelopmentfromthefixed-bladepropellerwheel.Oneofthebest-knownunitsofthistypeistheKaplanunit,inwhichthebladesmayberotatedtothemostefficientanglebyahydraulicservomotor.Acamonthegovernorisusedtocausethebladeangletochangewiththegatepositionsothathighefficiencyisalwaysobtainedatalmostanypercentageoffullload.Byreasonofitshighefficiencyatallgateopenings,theadjustable-bladepropeller-typeunitisparticularlyapplicabletolow-headdevelopmentswhereconditionsaresuchthattheunitsmustbeoperatedatvaryingloadandvaryinghead.Capitalcostandmaintenanceforsuchunitsarenecessarilyhigherthanforfixed-bladepropeller-typeunitsoperatedatthepointofmaximumefficiency.2.thermalandhydropowerAsstatedearlier,theturbinebladescanbemadetorunbytheenergyoffuelsorflowingwater.Whenfuelisusedtoproducesteamforrunningthesteamturbine,thenthepowergeneratedisknownasthermalpower.Thefuelwhichistobeusedforgeneratingsteammayeitherbeanordinaryfuelsuchascoal,fueloil,etc.,oratomicfuelornuclearfuel.Coalissimplyburnttoproducesteamfromwaterandisthesimplestandoldesttypeoffuel.Dieseloil,etc.mayalsobeusedasfuelsforproducingsteam.Atomicfuelssuchasuraniumorthoriummayalsobeusedtoproducesteam.Whenconventionaltypeoffuelssuchscoal,oil,etc.(calledfossils)isusedtoproducesteamforrunningtheturbines,thepowerhouseisgenerallycalledanOrdinarythermalpowerstationorThermalpowerstation.Butwhenatomicfuelisusedtoproducesteam,thepowerstation,whichisessentiallyathermalpowerstation,iscalledanatomicpowerstationornuclearpowerstation.Inanordinarythermalpowerstation,steamisproducedinawaterboiler,whileintheatomicpowerstation;theboilerisreplacedyanuclearreactorandsteamgeneratorforraisingsteam.Theelectricpowergeneratedinboththesecasesisknownasthermalpowerandtheschemeiscalledthermalpowerscheme.But,whentheenergyoftheflowingwaterisusedtoruntheturbines,thentheelectricitygeneratediscalledhydroelectricpower.Thisschemeisknownashydroscheme,andthepowerhouseisknownashydelpowerstationorhydroelectricpowerstation.Inahydroscheme,acertainquantityofwateratacertainpotentialheadisessentiallymadetoflowthroughtheturbines.Theheadcausingflowrunstheturbineblades,andthusproducingelectricityfromthegeneratorcoupledtoturbine.Inthischapter,weareconcernedwithhydelschemeonly.3.classificationofhydelplantsHydro-plantsmaybeclassifiedonthebasisofhydrauliccharacteristicsasfollow:①run-offriverplants.②storageplants.③pumpedstorageplants.④tidalplants.theyaredescribedbelow.Run-offriverplants.Theseplantsarethosewhichutilizetheminimumflowinariverhavingnoappreciablepondageonitsupstreamside.Aweirorabarrageissometimesconstructedacrossariversimplytoraiseandmaintainthewaterlevelatapre-determinedlevelwithinnarrowlimitsoffluctuations,eithersolelyforthepowerplantsorforsomeotherpurposewherethepowerplantmaybeincidental.Suchaschemeisessentiallyalowheadschemeandmaybesuitableonlyonaperennialriverhavingsufficientdryweatherflowofsuchamagnitudeastomakethedevelopmentworthwhile.Run-offriverplantsgenerallyhaveaverylimitedstoragecapacity,andcanusewateronlywhenitcomes.Thissmallstoragecapacityisprovidedformeetingthehourlyfluctuationsofload.Whentheavailabledischargeatsiteismorethanthedemand(duringoff-peakhours)theexcesswateristemporarilystoredinthepondontheupstreamsideofthebarrage,whichisthenutilizedduringthepeakhours.hevariousexamplesofrun-offtheriverpantare:GanguwalandKoltapowerhouseslocatedonNangalHydelChannel,MohammadPurandPathripowerhousesonGangaCanalandSardapowerhouseonSardaCanal.Thevariousstationsconstructedonirrigationchannelsatthesitesoffalls,alsofallunderthiscategoryofplants.(2)StorageplantsAstorageplantisessentiallyhavinganupstreamstoragereservoirofsufficientsizesoastopermit,sufficientcarryoverstoragefromthemonsoonseasontothedrysummerseason,andthustodevelopafirmflowsubstantiallymorethanminimumnaturalflow.Inthisscheme,adamisconstructedacrosstheriverandthepowerhousemaybelocatedatthefootofthedamsuchasinBhakra,Hirakud,Rihandprojectsetc.thepowerhousemaysometimesbelocatedmuchawayfromthedam(onthedownstreamside).Insuchacase,thepowerhouseislocatedattheendoftunnelswhichcarrywaterfromthereservoir.Thetunnelsareconnectedtothepowerhousemachinesbymeansofpressurepen-stockswhichmayeitherbeunderground(asinMainthonandKoynaprojects)ormaybekeptexposed(asinKundahproject).Whenthepowerhouseislocatednearthedam,asisgenerallydoneinthelowheadinstallations;itisknownasconcentratedfallhydroelectricdevelopment.Butwhenthewateriscarriedtothepowerhouseataconsiderabledistancefromthedamthroughacanal,tunnel,orpen-stock;itisknownasadividedfalldevelopment.(3)Pumpedstorageplants.Apumpedstorageplantgeneratespowerduringpeakhours,butduringtheoff-peakhours,waterispumpedbackfromthetailwaterpooltotheheadwaterpoolforfutureuse.Thepumpsarerunbysomesecondarypowerfromsomeotherplantinthesystem.Theplantisthusprimarilymeantforassistinganexistingthermalplantorsomeotherhydelplant.Duringpeakhours,thewaterflowsfromthereservoirtotheturbineandelectricityisgenerated.Duringoff-peakhours,theexcesspowerisavailablefromsomeotherplant,andisutilizedforpumpingwaterfromthetailpooltotheheadpool,thisminorplantthussupplementsthepowerofanothermajorplant.Insuchascheme,thesamewaterisutilizedagainandagainandnowateriswasted.Forheadsvaryingbetween15mto90m,reservoirpumpturbineshavebeendevised,whichcanfunctionbothasaturbineaswellasapump.Suchreversibleturbinescanworkatrelativelyhighefficienciesandcanhelpinreducingthecostofsuchaplant.Similarly,thesameelectricalmachinecanbeusedbothasageneratoraswellasamotorbyreversingthepoles.Theprovisionofsuchaschemehelpsconsiderablyinimprovingtheloadfactorofthepowersystem.(4)TidalplantsTidalplantsforgenerationofelectricpoweraretherecentandmodernadvancements,andessentiallyworkontheprinciplethatthereisariseinseawaterduringhightideperiodandafallduringthelowebbperiod.Thewaterrisesandfallstwiceaday;eachfallcycleoccupyingabout12hoursand25minutes.Theadvantageofthisriseandfallofwateristakeninatidalplant.Inotherwords,thetidalrange,i.e.thedifferencebetweenhighandlowtidelevelsisutilizedtogeneratepower.Thisisaccomplishedbyconstructingabasinseparatedfromtheoceanbyapartitionwallandinstallingturbinesinopeningthroughthiswall.Waterpassesfromtheoceantothebasinduringhightides,andthusrunningtheturbinesandgeneratingelectricpower.Duringlowtide，thewaterfromthebasinrunsbacktoocean,whichcanalsobeutilizedtogenerateelectricpower,providedspecialturbineswhichcangeneratepowerforeitherdirectionofflowareinstalled.Suchplantsareusefulatplaceswheretidalrangeishigh.RancepowerstationinFranceisanexampleofthistypeofpowerstation.Thetidalrangeatthisplaceisoftheorderof11meters.Thispowerhousecontains9unitsof38,000kW.4.Hydro-plantsorhydroelectricschemesmaybeclassifiedonthebasisofoperatingheadonturbinesasfollows:①lowheadscheme(head<15m),②mediumheadscheme(headvariesbetween15mto60m),③highheadscheme(head>60m).Theyaredescribedbelow:(1)Lowheadscheme.Alowheadschemeisonewhichuseswaterheadoflessthan15metersorso.Arunoffriverplantisessentiallyalowheadscheme,aweirorabarrageisconstructedtoraisethewaterlevel,andthepowerhouseisconstructedeitherincontinuationwiththebarrageoratsomedistancedownstreamofthebarrage,wherewateristakentothepowerhousethroughanintakecanal.(2)MediumheadschemeAmediumheadschemeisonewhichusedwaterheadvaryingbetween15to60metersorso.Thisschemeisthusessentiallyadamreservoirscheme,althoughthedamheightismediocre.Thisschemeishavingfeaturessomewherebetweenlowhadschemeandhighheadscheme.(3)Highheadscheme.水轮机和水力发电摘要水的能量可以通过三种基本方法来获得：利用水的重力作用、水的压力作用或水的流速作用，或者其中任意两种或全部三种作用的组合。在如今的实际应用中，佩尔顿式水轮机或冲击式水轮机是唯一只利用其中一种方法来获取水能的，即利用一束或者好几束高速的水流的作用获得能量的一种水轮机。这种类型的水轮机通常应用在高水头电站上。法拉第曾经指出：线圈在磁场中旋转，就产生了电。因此，为了获得电能，我们必须产生使“线圈”旋转的机械能。用燃料或流水的能量带动原动机（称为涡轮机）就产生了机械能。这种机械能转换成电能是通过电动机来实现的，电动机直接连接在涡轮机轴上，由涡轮机驱动。因此，就在发电机的出线端获得电能，然后输送到需要它做功的地区。发电需要的装置或机械（即原动机+发电机）统称为动力设备。安置所有机械和其他辅助设施的建筑称为发电厂。关键词水轮机水力发电水电站种类水头系统从1925年开始，水轮机的最高效率达到93%或稍微高一点就没有再提高了。就最大效率而言，水轮机的对水能的利用率已经达到了实际发展的极限了。然而，在最近几年里，水轮机的大小和单机容量却增长的很快。另外，人们还对引起空蚀的原因以及怎样预防空蚀做了很多的研究，这些研究使得我们能够在高于以前认为的合适水头下获得更高的比转速。更大的机组，更高的比转速，以及水轮机的设计上的简化和改进，这几个方面的进步使得水轮机一直以来在作为原动力之一拥有很重要的地位。1.水轮机的类型水轮机可以分为两大类：冲击式水轮机——利用高速水流冲击水轮机的一小部分时产生的动能；反击式水轮机——利用充满转轮和过水道的水流所拥有的水的压力和流速两者相结合来获得动力。反击式系列又分成两种通用的型式：弗朗西斯式（有时称作反击式）以及旋桨式。旋桨式又进一步再分为定轮叶式水轮机和以卡普兰式代表的转叶式水轮机。1.1冲击式水轮机在冲击式水轮机上，压力钢管中的水从喷嘴孔口中射出，这时水的的势能转换成动能。射流自由地射入水轮室内的空气中，撞击在转轮的碗状戽斗上。戽斗每旋转一周进入射流、经过并从射流转出一次。在这段时间内戽斗承受着射流的全部冲击力。这种冲击力产生一个高速锤击冲打在戽斗上。与此同时，戽斗受到离心力的作用而有脱离它的座盘的趋势，由此而产生的应力以及水流在戽斗的碗状工作面上的冲刷作用都很大，因而需要选用能抵御水力磨损和疲劳的高质量材料，一般都采用青铜和韧化铸钢，只有水头很低时才能用铸铁。1.2弗朗西斯式转轮就弗朗西斯式水轮机来说，来自蜗壳或水槽内的流速较低的水，通过位于转轮周围的导叶或一些闸门，然后流经转轮，并从转轮泄入安置在尾水位以下而不与大气相通的尾水管内。由于水充满所有的水道并作用在转轮的整个周围，因此，仅有一小部分动力来自水的流速所引起的动力作用，而大部分动力则都通过作用在转轮叶片前后工作面上的压力差取得。尾水管可以使能利用的水头得到充分的利用，这一方面是由于转轮下面垂直水柱所产生的吸出作用，另一方面是由于尾水管的出口面积大于紧接转轮下喉管的面积，从而使水流离开转轮叶片时的一部分动能得以利用。1.3旋桨式转轮旋桨式机组最适用于低水头电站，在它适用的水头范围内，已产生了显著的经济效果。这种水轮机的转速比较高，以致使发电机的价格较低，并使发电厂房的水下结构和水上结构的尺寸都比较小。低水头、小功率的旋桨式转轮，有时用铸铁来制造。水头高于20英寸时，都用一种更为可靠的材料──铸钢来制造。大直径的螺旋桨可用单个叶片固定在轮毂上制成。1.4转叶式水轮机转叶旋桨式水轮机是从定轮叶旋桨式水轮机发展而成的。卡普兰式水轮机是这类水轮机中为人们最为熟悉的一种。它的叶片可由液压伺服器调整到效率最大的角度。利用伺服器上的凸轮能使叶片的角度随阀门的开启位置而变化，从而在所有各种满负载百分率情况下都能保持高效率。由于转叶旋桨式水轮机组在闸门各种开度情况下效率都高，因此，它特别适用于那些必须在变负载和变水头条件下运行的低水头电站上。当然，这种机组的投资费用和维护费用要高于只能在一个最大效率点上运行的定轮叶旋桨式水轮机组。2火电和水电如上所述，涡轮机叶片是由燃料或流水的能量带动的。用燃料产生蒸汽驱动蒸汽涡轮机时，所产生的电称为火电。由于产生蒸汽的燃料是一般燃料如煤、燃料油等，或是原子能燃料即核燃料。直接燃烧煤产生水蒸气，煤是最简便、最古老的一种燃料。柴油等也可以作为产生蒸汽的燃料。原子燃料如铀、钍也可用于产生蒸汽。用传统燃料如煤、燃料油等（称为矿物燃料）产生蒸汽来带动水轮机时，这种发电厂一般称为普通火力发电厂或热电厂。但当原子燃料用于产生蒸汽时，这种发电厂（基本上属于火力发电厂）称为原子能发电厂或核电厂。一般火力发电厂是用锅炉产生蒸汽的，而原子能发电站是用核反应堆和蒸汽发生器代替锅炉产生蒸汽的。这两种情况产生的电能称为火电。该系统称为火力发电系统。然而，用流水的能量驱动水轮机时，所产生的电称为水电。这种系统称为水力发电系统，而发电厂称为水力发电厂或水电站。在水电系统中必须使具有一定势能和一定数量的水流流经水轮机。势能使水流