水利畢業(yè)設(shè)計(jì)英文翻譯-水輪機(jī)和水力發(fā)電分析解析

水利畢業(yè)設(shè)計(jì)英文翻譯--水輪機(jī)和水力發(fā)電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.typesofhydraulicturbinesHydraulicturbinesmaybegroupedintwogeneralclasses:theimpulsetypewhichutilizesthekineticenergyofahigh-velocityjetwhichactsupononlyasmallpartofthecircumferenceatanyinstant,andthereactiontypewhichdevelopspowerfromthecombinedactionofpressureandvelocityofthewaterthatcompletelyfillstherunnerandwaterpassages.Thereactiongroupisdividedintotwogeneraltypes:theFrancis,sometimescalledthereactiontype,andthepropellertype.Thepropellerclassisalsofurthersubdividedintothefixed-bladepropellertype,andtheadjustable-bladetypeofwhichtheKaplanisrepresentative.impulsewheelsWiththeimpulsewheelthepotentialenergyofthewaterinthepenstockistransformedintokineticenergyinajetissuingfromtheorificeofanozzle.Thisjetdischargefreelyintotheatmosphereinsidethewheelhousingandstrikesagainstthebowl-shapedbucketsoftherunner.Ateachrevolutionthebucketenters,passesthrough,andpassesoutofthejet,duringwhichtimeitreceivesthefullimpactforceofthejet.Thisproducesarapidhammerblowuponthebucket.Atthesametimethebucketissubjectedtothecentrifugalforcetendingtoseparatethebucketfromitsdisk.Onaccountofthestressessoproducedandalsothescouringeffectsofthewaterflowingovertheworkingsurfaceofthebowl,materialofhighqualityofresistanceagainsthydraulicwearandfatigueisrequired.Onlyforverylowheadscancastironbeemployed.Bronzeandannealedcaststeelarenormallyused.FrancisrunnersWiththeFrancistypethewaterentersfromacasingorflumewitharelativelylowvelocity,passesthroughguidevanesorgateslocatedaroundthecircumstance,andflowsthroughtherunner,fromwhichitdischargesintoadrafttubesealedbelowthetail-waterlevel.Alltherunnerpassagesarecompletelyfilledwithwater,whichactsuponthewholecircumferenceoftherunner.Onlyaportionofthepowerisderivedfromthedynamicactionduetothevelocityofthewater,alargepartofthepowerbeingobtainedfromthedifferenceinpressureactingonthefrontandbackoftherunnerbuckets.Thedrafttubeallowsmaximumutilizationoftheavailablehead,bothbecauseofthesuctioncreatedbelowtherunnerbytheverticalcolumnofwaterandbecausetheoutletofhedrafttubeislargerthanthethroatjustbelowtherunner,pellerrunnersnherentlysuitableforlow-headdevelopments,thepropeller-typeunithaseffectedmarkedeconomicswithintherangeofheadtowhichitisadapted.Thehigherspeedofthistypeofturbineresultsinalower-costgeneratorandsomewhatsmallerpowerhousesubstructureandsuperstructure.Propeller-typerunnersforlowheadsandsmalloutputsaresometimesconstructedofcastiron.Forheadsabove20ft,theyaremadeofcaststeel,amuchmorereliablematerial.Large-diameterpropellersmayhaveindividualbladesfastenedtothehub.adjustable-bladerunnersTheadjustable-bladepropellertypeisadevelopmentfromthefixed-bladepropellerwheel.Oneofthebest-knownunitsofthistypeistheKaplanunit,inwhichthebladesmayberotatedtothemostefficientanglebyahydraulicservomotor.Acamonthegovernorisusedtocausethebladeangletochangewiththegatepositionsothathighefficiencyisalwaysobtainedatalmostanypercentageoffullload.Byreasonofitshighefficiencyatallgateopenings,theadjustable-bladepropeller-typeunitisparticularlyapplicabletolow-headdevelopmentswhereconditionsaresuchthattheunitsmustbeoperatedatvaryingloadandvaryinghead.Capitalcostandmaintenanceforsuchunitsarenecessarilyhigherthanforfixed-bladepropeller-typeunitsoperatedatthepointofmaximumefficiency.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.classificationofhydelplantsHydro-plantsmaybeclassifiedonthebasisofhydrauliccharacteristicsasfollow:①run-offriverplants.②storageplants.③pumpedstorag(plants.④tidalplants.theyaredescribedbelow.Run-offriverplants.Theseplantsarethosewhichutilizetheminimumflowinariverhavingnoappreciablepondageonitsupstreamside.Aweirorabarrageissometimesconstructedacrossariversimplytoraiseandmaintainthewaterlevelatapre-determinedlevelwithinnarrowlimitsoffluctuations,eithersolelyforthepowerplantsorforsomeotherpurposewherethepowerplantmaybeincidental.Suchaschemeisessentiallyalowheadschemeandmaybesuitableonlyonaperennialriverhavingsufficientdryweatherflowofsuchamagnitudeastomakethedevelopmentworthwhile.Run-offriverplantsgenerallyhaveaverylimitedstoragecapacity,andcanusewateronlywhenitcomes.Thissmallstoragecapacityisprovidedformeetingthehourlyfluctuationsofload.Whentheavailabledischargeatsiteismorethanthedemand(duringoff-peakhours)theexcesswateristemporarilystoredinthepondontheupstreamsideofthebarrage,whichisthenutilizedduringthepeakhours.hevariousexamplesofrun-offtheriverpantare:GanguwalandKoltapowerhouseslocatedonNangalHydelChannel,MohammadPurandPathripowerhousesonGangaCanalandSardapowerhouseonSardaCanal.Thevariousstationsconstructedonirrigationchannelsatthesitesoffalls,alsofallunderthiscategoryofplants.StorageplantsAstorageplantisessentiallyhavinganupstreamstoragereservoirofsufficientsizesoastopermit,sufficientcarryoverstoragefromthemonsoonseasontothedrysummerseason,andthustodevelopafirmflowsubstantiallymorethanminimumnaturalflow.Inthisscheme,adamisconstructedacrosstheriverandthepowerhousemaybelocatedatthefootofthedamsuchasinBhakra,Hirakud,Rihandprojectsetc.thepowerhousemaysometimesbelocatedmuchawayfromthedam(onthedownstreamside).Insuchacase,thepowerhouseislocatedattheendoftunnelswhichcarrywaterfromthereservoir.Thetunnelsareconnectedtothpeowerhousemachinesbymeansofpressurepen-stockswhichmayeitherbeunderground(asinMainthonandKoynaprojects)ormaybekeptexposed(asinKundahproject).Whenthepowerhouseislocatednearthedam,asisgenerallydoneinthelowheadinstallations;itisknownasconcentratedfallhydroelectricdevelopment.Butwhenthewateriscarriedtothepowerhouseataconsiderabledistancefromthedamthroughacanal,tunnel,orpen-stock;itisknownasadividedfalldevelopment.Pumpedstorageplants.Apumpedstorageplantgeneratespowerduringpeakhours,butduringtheoff-peakhours,waterispumpedbackfromthetailwaterpooltotheheadwaterpoolforfutureuse.Thepumpsarerunbysomesecondarypowerfromsomeotherplantinthesystem.Theplantisthusprimarilymeantforassistinganexistingthermalplantorsomeotherhydelplant.Duringpeakhours,thewaterflowsfromthereservoirtotheturbineandelectricityisgenerated.Duringoff-peakhours,theexcesspowerisavailablefromsomeotherplant,andisutilizedforpumpingwaterfromthetailpooltotheheadpool,thisminorplantthussupplementsthepowerofanothermajorplant.Insuchascheme,thesamewaterisutilizedagainandagainandnowateriswasted.Forheadsvaryingbetween15mto90m,reservoirpumpturbineshavebeendevised,whichcanfunctionbothasaturbineaswellasapump.Suchreversibleturbinescanworkatrelativelyhighefficienciesandcanhelpinreducingthecostofsuchaplant.Similarly,thesameelectricalmachinecanbeusedbothasageneratoraswellasamotorbyreversingthepoles.Theprovisionofsuchaschemehelpsconsiderablyinimprovingtheloadfactorofthepowersystem.TidalplantsTidalplantsforgenerationofelectricpoweraretherecentandmodernadvancements,andessentiallyworkontheprinciplethatthereisariseinseawaterduringhightideperiodandafallduringthelowebbperiod.Thewaterrisesandfallstwiceaday;eachfallcycleoccupyingabout12hoursand25minutes.Theadvantageofthisriseandfallofwateristakeninatidalplant.Inotherwords,thetidalrange,i.e.thedifferencebetweenhighandlowtidelevelsisutilizedtogeneratepower.Thisisaccomplishedbyconstructingabasinseparatedfromtheoceanbyapartitionwallandinstallingturbinesinopeningthroughthiswall.Waterpassesfromtheoceantothebasinduringhightides,andthusrunningtheturbinesandgeneratingelectricpower.Duringlowtide，thewaterfromthebasinrunsbacktoocean,whichcanalsobeutilizedtogenerateelectricpower,providedspecialturbineswhichcangeneratepowerforeitherdirectionofflowareinstalled.Suchplantsareusefulatplaceswheretidalrangeishigh.RancepowerstationinFranceisanexampleofthistypeofpowerstation.Thetidalrangeatthisplaceisoftheorderof11meters.Thispowerhousecontains9unitsof38,000kW.Hydro-plantsorhydroelectricschemesmaybeclassifiedonthebasisofoperatingheadonturbinesasfollows:①lowheadscheme(head〈15m)，②mediumheadscheme(headvariesbetween15mto60m)，③highheadscheme(head〉60m).Theyaredescribedbelow:Lowheadscheme.Alowheadschemeisonewhichuseswaterheadoflessthan15metersorso.Arunoffriverplantisessentiallyalowheadscheme,aweirorabarrageisconstructedtoraisethewaterlevel,andthepowerhouseisconstructedeitherincontinuationwiththebarrageoratsomedistan；thebarrageoratsomedistancedownstreamofthebarrage,wherewateristakentothepowerhousethroughanintakecanal.MediumheadschemeAmediumheadschemeisonewhichusedwaterheadvaryingbetween15to60metersorso.Thisschemeisthusessentiallyadamreservoirscheme,althoughthedamheightismediocre.Thisschemeishavingfeaturessomewherebetweenlowhadschemeandhighheadscheme.Highheadscheme.Ahighheadschemeisonewhichuseswaterheadofmorethan60morso.Adamofsufficientheightis,therefore,requiredtobeconstructed,soastostorewaterontheupstreamsideandtoutilizethiswaterthroughouttheyear.Highheadschemesuptoheightsof1,800metershavebeendeveloped.Thecommonexamplesofsuchaschemeare:Bhakradamin(Punjab),Rihanddamin(U.P.),andHooverdamin(U.S.A),etc.Thenaturallyavailablehighfallscanalsobedevelopedforgeneratingelectricpower.Thecommonexamplesofsuchpowerdevelopmentsare:JogFallsiIndia,andNiagaraFallsinU.S.A.水輪機(jī)和水力發(fā)電摘要水的能量可以通過三種基本方法來獲得：利用水的重力作用、水的壓力作用或水的流速作用，或者其中任意兩種或全部三種作用的組合。在如今的實(shí)際應(yīng)用中，佩爾頓式水輪機(jī)或沖擊式水輪機(jī)是唯一只利用其中一種方法來獲取水能的，即利用一束或者好幾束高速的水流的作用獲得能量的一種水輪機(jī)。這種類型的水輪機(jī)通常應(yīng)用在高水頭電站上。法拉第曾經(jīng)指出：線圈在磁場中旋轉(zhuǎn)，就產(chǎn)生了電。因此，為了獲得電能，我們必須產(chǎn)生使“線圈”旋轉(zhuǎn)的機(jī)械能。用燃料或流水的能量帶動原動機(jī)（稱為渦輪機(jī)）就產(chǎn)生了機(jī)械能。這種機(jī)械能轉(zhuǎn)換成電能是通過電動機(jī)來實(shí)現(xiàn)的，電動機(jī)直接連接在渦輪機(jī)軸上，由渦輪機(jī)驅(qū)動。因此，就在發(fā)電機(jī)的出線端獲得電能，然后輸送到需要它做功的地區(qū)。發(fā)電需要的裝置或機(jī)械（即原動機(jī)+發(fā)電機(jī)）統(tǒng)稱為動力設(shè)備。安置所有機(jī)械和其他輔助設(shè)施的建筑稱為發(fā)電廠。關(guān)鍵詞水輪機(jī)水力發(fā)電水電站種類水頭系統(tǒng)從1925年開始，水輪機(jī)的最高效率達(dá)到93%或稍微高一點(diǎn)就沒有再提高了。就最大效率而言，水輪機(jī)的對水能的利用率已經(jīng)達(dá)到了實(shí)際發(fā)展的極限了。然而，在最近幾年里，水輪機(jī)的大小和單機(jī)容量卻增長的很快。另外，人們還對引起空蝕的原因以及怎樣預(yù)防空蝕做了很多的研究，這些研究使得我們能夠在高于以前認(rèn)為的合適水頭下獲得更高的比轉(zhuǎn)速。更大的機(jī)組，更高的比轉(zhuǎn)速，以及水輪機(jī)的設(shè)計(jì)上的簡化和改進(jìn)，這幾個(gè)方面的進(jìn)步使得水輪機(jī)一直以來在作為原動力之一擁有很重要的地位。1.水輪機(jī)的類型水輪機(jī)可以分為兩大類：沖擊式水輪機(jī)——利用高速水流沖擊水輪機(jī)的一小部分時(shí)產(chǎn)生的動能；反擊式水輪機(jī)——利用充滿轉(zhuǎn)輪和過水道的水流所擁有的水的壓力和流速兩者相結(jié)合來獲得動力。反擊式系列又分成兩種通用的型式：弗朗西斯式（有時(shí)稱作反擊式）以及旋槳式。旋槳式又進(jìn)一步再分為定輪葉式水輪機(jī)和以卡普蘭式代表的轉(zhuǎn)葉式水輪機(jī)。沖擊式水輪機(jī)在沖擊式水輪機(jī)上，壓力鋼管中的水從噴嘴孔口中射出，這時(shí)水的的勢能轉(zhuǎn)換成動能。射流自由地射入水輪室內(nèi)的空氣中，撞擊在轉(zhuǎn)輪的碗狀戽斗上。戽斗每旋轉(zhuǎn)一周進(jìn)入射流、經(jīng)過并從射流轉(zhuǎn)出一次。在這段時(shí)間內(nèi)戽斗承受著射流的全部沖擊力。這種沖擊力產(chǎn)生一個(gè)高速錘擊沖打在戽斗上。與此同時(shí)，戽斗受到離心力的作用而有脫離它的座盤的趨勢，由此而產(chǎn)生的應(yīng)力以及水流在戽斗的碗狀工作面上的沖刷作用都很大，因而需要選用能抵御水力磨損和疲勞的高質(zhì)量材料，一般都采用青銅和韌化鑄鋼，只有水頭很低時(shí)才能用鑄鐵。弗朗西斯式轉(zhuǎn)輪就弗朗西斯式水輪機(jī)來說，來自蝸殼或水槽內(nèi)的流速較低的水，通過位于轉(zhuǎn)輪周圍的導(dǎo)葉或一些閘門，然后流經(jīng)轉(zhuǎn)輪，并從轉(zhuǎn)輪泄入安置在尾水位以下而不與大氣相通的尾水管內(nèi)。由于水充滿所有的水道并作用在轉(zhuǎn)輪的整個(gè)周圍，因此，僅有一小部分動力來自水的流速所引起的動力作用，而大部分動力則都通過作用在轉(zhuǎn)輪葉片前后工作面上的壓力差取得。尾水管可以使能利用的水頭得到充分的利用，這一方面是由于轉(zhuǎn)輪下面垂直水柱所產(chǎn)生的吸出作用，另一方面是由于尾水管的出口面積大于緊接轉(zhuǎn)輪下喉管的面積，從而使水流離開轉(zhuǎn)輪葉片時(shí)的一部分動能得以利用。旋槳式轉(zhuǎn)輪旋槳式機(jī)組最適用于低水頭電站，在它適用的水頭范圍內(nèi)，已產(chǎn)生了顯著的經(jīng)濟(jì)效果。這種水輪機(jī)的轉(zhuǎn)速比較高，以致使發(fā)電機(jī)的價(jià)格較低，并使發(fā)電廠房的水下結(jié)構(gòu)和水上結(jié)構(gòu)的尺寸都比較小。低水頭、小功率的旋槳式轉(zhuǎn)輪，有時(shí)用鑄鐵來制造。水頭高于20英寸時(shí)，都用一種更為可靠的材料一一鑄鋼來制造。大直徑的螺旋槳可用單個(gè)葉片固定在輪轂上制成。轉(zhuǎn)葉式水輪機(jī)轉(zhuǎn)葉旋槳式水輪機(jī)是從定輪葉旋槳式水輪機(jī)發(fā)展而成的?？ㄆ仗m式水輪機(jī)是這類水輪機(jī)中為人們最為熟悉的一種。它的葉片可由液壓伺服器調(diào)整到效率最大的角度。利用伺服器上的凸輪能使葉片的角度隨閥門的開啟位置而變化，從而在所有各種滿負(fù)載百分率情況下都能保持高效率。由于轉(zhuǎn)葉旋槳式水輪機(jī)組在閘門各種開度情況下效率都高，因此，它特別適用于那些必須在變負(fù)載和變水頭條件下運(yùn)行的低水頭電站上。當(dāng)然，這種機(jī)組的投資費(fèi)用和維護(hù)費(fèi)用要高于只能在一個(gè)最大效率點(diǎn)上運(yùn)行的定輪葉旋槳式水輪機(jī)組。2火電和水電如上所述，渦輪機(jī)葉片是由燃料或流水的能量帶動的。用燃料產(chǎn)生蒸汽驅(qū)動蒸汽渦輪機(jī)時(shí)，所產(chǎn)生的電稱為火電。由于產(chǎn)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。直接燃燒煤產(chǎn)生水蒸氣，煤是最簡便、最古老的一種燃料。柴油等也可以作為產(chǎn)生蒸汽的燃料。原子燃料如鈾、釷也可用于產(chǎn)生蒸汽。用傳統(tǒng)燃料如煤、燃料油等（稱為礦物燃料）產(chǎn)生蒸汽來帶動水輪機(jī)時(shí)，這種發(fā)電廠一般稱為普通火力發(fā)電廠或熱電廠。但當(dāng)原子燃料用于產(chǎn)生蒸汽時(shí)，這種發(fā)電廠（基本上屬于火力發(fā)電廠）稱為原子能發(fā)電廠或核電廠。一般火力發(fā)電廠是用鍋爐產(chǎn)生蒸汽的，而原子能發(fā)電站是用核反應(yīng)堆和蒸汽發(fā)生器代替鍋爐產(chǎn)生蒸汽的。這兩種情況產(chǎn)生的電能稱為火電。該系統(tǒng)稱為火力發(fā)電系統(tǒng)。然而，用流水的能量驅(qū)動水輪機(jī)時(shí)，所產(chǎn)生的電稱為水電。這種系統(tǒng)稱為水力發(fā)電系統(tǒng)，而發(fā)電廠稱為水力發(fā)電廠或水電站。在水電系統(tǒng)中必須使具有一定勢能和一定數(shù)量的水流流經(jīng)水輪機(jī)。勢能使水流動，驅(qū)動水輪機(jī)的葉片，這樣與水輪機(jī)連接的發(fā)電機(jī)就發(fā)出電能。本章只涉及水力發(fā)電系統(tǒng)的內(nèi)容。3水力發(fā)電站的種類根據(jù)水力特性把水力發(fā)電站分為下列幾種：①徑流式電站，②蓄水式電站，③抽水蓄能電站，④潮汐電站。各類電站分述如下：（1）徑流式電站這類電站是在河流上游無適宜的水庫的情況下利用河流最小流量的電站。有時(shí)修建攔河堰壩，把水位提高并保持在預(yù)定的數(shù)值，只允許在很小的范圍內(nèi)變化。它可以單獨(dú)為電站服務(wù)，或者主要為其他目標(biāo)服務(wù)，兼顧電站。這種方案基本上是一種低水頭方案，它僅適用于枯水季流量值得開發(fā)的常年性河流。徑流式電站通常具有很小的蓄水庫容，有徑流時(shí)方能利用。這個(gè)很小的蓄水庫容是為滿足每小時(shí)負(fù)荷的