毕业设计水利水电工程英文文献翻译.docx

毕业设计水利水电工程英文文献翻译.docx

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毕业设计水利水电工程英文文献翻译

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，andthustodevelopafirmflo