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.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
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