水轮机和水力发电文献翻译.docx

水轮机和水力发电文献翻译.docx

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水轮机和水力发电文献翻译

中文3840字

外文文献：

hydraulicturbinesandhydro-electricpower

Abstract

Powermaybedevelopedfromwaterbythreefundamentalprocesses:

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-electricpowerclassificationofhydelplants

headscheme

Therehasbeenpracticallynoincreaseintheefficiencyofhydraulicturbinessinceabout1925,whenmaximumefficienciesreached93%ormore.Asfarasmaximumefficiencyisconcerned,thehydraulicturbinehasaboutreachedthepracticablelimitofdevelopment.Nevertheless,inrecentyears,therehasbeenarapidandmarkedincreaseinthephysicalsizeandhorsepowercapacityofindividualunits.

Inaddition,therehasbeenconsiderableresearchintothecauseandpreventionofcavitation,whichallowstheadvantagesofhigherspecificspeedstobeobtainedathigherheadsthanformerlywereconsideredadvisable.Theneteffectofthisprogresswithlargerunits,higherspecificspeed,andsimplificationandimprovementsindesignhasbeentoretainforthehydraulicturbinetheimportantplacewhichithaslongheldatoneofthemostimportantprimemovers.

1.typesofhydraulicturbines

Hydraulicturbinesmaybegroupedintwogeneralclasses:

theimpulsetypewhichutilizesthekineticenergyofahigh-velocityjetwhichactsupononlyasmallpartofthecircumferenceatanyinstant,andthereactiontypewhichdevelopspowerfromthecombinedactionofpressureandvelocityofthewaterthatcompletelyfillstherunnerandwaterpassages.Thereactiongroupisdividedintotwogeneraltypes:

theFrancis,sometimescalledthereactiontype,andthepropellertype.Thepropellerclassisalsofurthersubdividedintothefixed-bladepropellertype,andtheadjustable-bladetypeofwhichtheKaplanisrepresentative.

1.1impulsewheels

Withtheimpulsewheelthepotentialenergyofthewaterinthepenstockistransformedintokineticenergyinajetissuingfromtheorificeofanozzle.Thisjetdischargefreelyintotheatmosphereinsidethewheelhousingandstrikesagainstthebowl-shapedbucketsoftherunner.Ateachrevolutionthebucketenters,passesthrough,andpassesoutofthejet,duringwhichtimeitreceivesthefullimpactforceofthejet.Thisproducesarapidhammerblowuponthebucket.Atthesametimethebucketissubjectedtothecentrifugalforcetendingtoseparatethebucketfromitsdisk.Onaccountofthestressessoproducedandalsothescouringeffectsofthewaterflowingovertheworkingsurfaceofthebowl,materialofhighqualityofresistanceagainsthydraulicwearandfatigueisrequired.Onlyforverylowheadscancastironbeemployed.Bronzeandannealedcaststeelarenormallyused.

1.2Francisrunners

WiththeFrancistypethewaterentersfromacasingorflumewitharelativelylowvelocity,passesthroughguidevanesorgateslocatedaroundthecircumstance,andflowsthroughtherunner,fromwhichitdischargesintoadrafttubesealedbelowthetail-waterlevel.Alltherunnerpassagesarecompletelyfilledwithwater,whichactsuponthewholecircumferenceoftherunner.Onlyaportionofthepowerisderivedfromthedynamicactionduetothevelocityofthewater,alargepartofthepowerbeingobtainedfromthedifferenceinpressureactingonthefrontandbackoftherunnerbuckets.Thedrafttubeallowsmaximumutilizationoftheavailablehead,bothbecauseofthesuctioncreatedbelowtherunnerbytheverticalcolumnofwaterandbecausetheoutletofhedrafttubeislargerthanthethroatjustbelowtherunner,thusutilizingapartofthekineticenergyofthewaterleavingtherunnerblades.

1.3propellerrunners

nherentlysuitableforlow-headdevelopments,thepropeller-typeunithaseffectedmarkedeconomicswithintherangeofheadtowhichitisadapted.Thehigherspeedofthistypeofturbineresultsinalower-costgeneratorandsomewhatsmallerpowerhousesubstructureandsuperstructure.Propeller-typerunnersforlowheadsandsmalloutputsaresometimesconstructedofcastiron.Forheadsabove20ft,theyaremadeofcaststeel,amuchmorereliablematerial.Large-diameterpropellersmayhaveindividualbladesfastenedtothehub.

1.4adjustable-bladerunners

Theadjustable-bladepropellertypeisadevelopmentfromthefixed-bladepropellerwheel.Oneofthebest-knownunitsofthistypeistheKaplanunit,inwhichthebladesmayberotatedtothemostefficientanglebyahydraulicservomotor.Acamonthegovernorisusedtocausethebladeangletochangewiththegatepositionsothathighefficiencyisalwaysobtainedatalmostanypercentageoffullload.

Byreasonofitshighefficiencyatallgateopenings,theadjustable-bladepropeller-typeunitisparticularlyapplicabletolow-headdevelopmentswhereconditionsaresuchthattheunitsmustbeoperatedatvaryingloadandvaryinghead.Capitalcostandmaintenanceforsuchunitsarenecessarilyhigherthanforfixed-bladepropeller-typeunitsoperatedatthepointofmaximumefficiency.

2.thermalandhydropower

Asstatedearlier,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.classificationofhydelplants

Hydro-plantsmaybeclassifiedonthebasisofhydrauliccharacteristicsasfollow:

①run-offriverplants.②storageplants.③pumpedstorageplants.④tidalplants.theyaredescribedbelow.

（1）Run-offriverplants.

Theseplantsarethosewhichutilizetheminimumflowinariverhavingnoappreciablepondageonitsupstreamside.Aweirorabarrageissometimesconstructedacrossariversimplytoraiseandmaintainthewaterlevelatapre-determinedlevelwithinnarrowlimitsoffluctuations,eithersolelyforthepowerplantsorforsomeotherpurposewherethepowerplantmaybeincidental.Suchaschemeisessentiallyalowheadschemeandmaybesuitableonlyonaperennialriverhavingsufficientdryweatherflowofsuchamagnitudeastomakethedevelopmentworthwhile.

Run-offriverplantsgenerallyhaveaverylimitedstoragecapacity,andcanusewateronlywhenitcomes.Thissmallstoragecapacityisprovidedformeetingthehourlyfluctuationsofload.Whentheavailabledischargeatsiteismorethanthedemand（duringoff-peakhours）theexcesswateristemporarilystoredinthepondontheupstreamsideofthebarrage,whichisthenutilizedduringthepeakhours.

hevariousexamplesofrun-offtheriverpantare:

GanguwalandKoltapowerhouseslocatedonNangalHydelChannel,MohammadPurandPathripowerhousesonGangaCanalandSardapowerhouseonSardaCanal.

Thevariousstationsconstructedonirrigationchannelsatthesitesoffalls,alsofallunderthiscategoryofplants.

（2）Storageplants

Astorageplantisessentiallyhavinganupstreamstoragereservoirofsufficientsizesoastopermit,sufficientcarryoverstoragefromthemonsoonseasontothedrysummerseason,andthustodevelopafi