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SpecializedEnglish
for
Graduatesof2011
Contents
1HYDROPOWERPLANT
1
1.1Hydropower
1
1.2AdvantagesofHydropower
1
1.3DisadvantageofaHydroplant
2
1.4Multi-PurposeUses
2
1.4.1Irrigation
2
1.4.2Floodcontrol
2
1.4.3Navigation
2
1.4.4Recreation
2
1.4.5FishBreeding
3
1.5TypicalComponentsofaHydroelectricPlant
3
1.5.1DamorBarrage
3
1.5.2Water-ConduitSystem
3
1.5.3PowerHouse
3
1.5.4TailRace
3
1.5.5ElectricalPowerTransmission
4
1.6ClassificationofHydroelectricPlants
4
1.6.1Base-LoadandPeak-LoadPlants
4
1.6.2Plantscanalsobeclassifiedasfollows:
4
1.6.3ClassificationontheBasisofAvailableHeads
7
2HYDRAULICTURBINES
10
2.1Introduction
10
2.1.1Sub-systemsofaWaterTurbine
10
2.2ClassificationofWaterTurbines
10
2.3PeltonTurbine
12
2.3.1Injector
12
2.3.2Runner
12
2.3.3NumberofNozzles
13
2.3.4Distributor
14
2.3.5Casing
15
2.3.6JetBrake
16
2.3.7TailWaterDepressorSystem
16
2.4FrancisTurbine
17
2.4.1MainComponents
18
2.4.2ScrollCase
18
2.4.3StayVanesRing
18
2.4.4GuideVanesMechanism
19
2.4.5Runner
19
2.4.6DraftTube
21
2.4.7HeadCover
22
2.4.8BottomRing
22
2.4.9Shaft
22
2.4.10TurbinePitLiner
23
2.4.11DewateringofTurbine
23
2.5PropellerandKaplanTurbine
23
2.5.1Introduction
23
2.5.2ImprovementinEfficiency
24
2.5.3MainComponentsoftheRunner
24
2.5.4LocationofServomotor
25
2.5.5ScrollCase
26
2.5.6AutomaticAirValves
26
2.5.7ShaftoftheHydrounit
26
2.5.8Over-speedProtectiveDevices
27
2.6DeriazTurbine
27
2.6.1Introduction
27
2.6.2Servomotor
29
3HVAC
30
3.1Background
30
3.2Heating
31
3.3Ventilation
33
3.3.1Mechanicalorforcedventilation
33
3.3.2Naturalventilation
34
3.3.3AirborneIllnesses
34
3.4Airconditioning
34
3.5Energyefficiency
36
3.5.1Heatingenergy
36
3.5.2GeothermalHeatPump
37
3.5.3VentilationEnergyrecovery
37
3.5.4Airconditioningenergy
37
3.6AirFiltrationandCleaning
37
3.6.1CleanAirDeliveryRateandFilterPerformance
38
3.7HVACindustryandstandards
38
3.7.1International
38
3.7.2NorthAmerica(USA)
38
3.7.3Europe(UnitedKingdom)
39
3.7.4Australia
40
3.7.5Asia(India)
40
1HYDROPOWERPLANT
1.1Hydropower
Itisthepowergeneratedbyusingwaterastheenergy-supplyingagent.Inthiscase,waterisallowedtoflowfromahigherleveltoalowerlevelthroughaturbinewherethepotentialenergyofwaterisconvertedintokineticenergyandtheturbine,inturn,rotatesageneratortoproduceelectricity.
Hydropowergenerationdependsupontheavailabilityofrainwater.Cloudsareformedbecauseoftheheatingofseawaterbythesun.Theymovetowardstheland,wherelow-pressurezonesareformedandastheygetcooled,moisturestartsprecipitating.Therainwaterstartsmovingtowardslowerlevelsbecauseofgravity,throughasystemofnaturaldrainsconsistingofnullahs,rivulets,riversandsoon.Thiswatercanbestoredinreservoirscreatedontherivers,byconstructionofdamsandcanbeusedtogeneratepower.Aftergeneration,thewaterisletoutintotheriverandgraduallytravelsfurtherandultimatelyreachesthesea.Hereitisheatedupbythesuntostartthenextcycle.Therefore,hydropowerisnothingbutconversionofsolarenergyintoelectricitythroughacircuitousroute.
1.2AdvantagesofHydropower
Hydropowergenerationisnon-wastingself-replenishingandnon-polluting.
Itisaphysicalphenomenonandnochemicalchangeisinvolved.Watercomeoutunchangedfromtheturbineafterimpartingitsenergyandcanbeusedagaineitherforpowergenerationorforirrigation.Infact,thisisdoneinmulti-purposeriver-valleyschemesliketheChambalValleydevelopmentinIndiaandtheTennesseeValleydevelopmentinU.S.A.InthecaseoftheChambalValleydevelopment,powerisgeneratedwiththehelpofthesamewaterinthreepowerhouses,situatedoneafteranotherontheriver,beforebeingreleasedintoirrigationcanals.Asagainstthis,coal,oilornuclearfuelcanonlybeusedonce.
Thesupplyofwaterisautomaticandthewaterutilizedinoneseasonisreplenishedbynatureinthenextseason.Thewaterreachesthepowerhousesiteonitsown-nominingoperationsandtransportationareinvolvedasinthecaseofcoaloroil.
Waterpoweriscleanasitdoesnotproduceanypollutants,whereasinthecaseofthermalornuclearpowergenerationpollutionisinevitable,astoxicby-productsareemitted.
Thehydropowerplantshaveveryhighefficiencies.Theturbineefficiencyisabove90percentandtheoverallefficiencycanbeabove80percentwhichismuchhigherthanthatofthermalplants.Thehydro-plantsarelonglastingandmanyplantsarestillinserviceeven40yearsaftercommissioning.Thepercentageofoutagesisverylow,asshutdownsforrepairsandmaintenancearefewer.Theplantsareavailableforinstantloadingandasetcanstarttakingfullloadwithinfiveminutes,startingfromthestandstillposition,whereasthermalplantsmaytakeaboutfivetosixhours.
1.3DisadvantageofaHydroplant
Theinitialinvestmentsareveryheavyandthespecificcostishighcomparedtoathermalplant.Thetimeneededforconstructionisquitelonganditaffectstheeconomyadverselyasreturnsstartflowinginlate.Whenalakeisformed,landsubmergencecreatesitsownproblem.
Astheavailabilityofwatervariesfromyeartoyear,inlowrainfallyearstheplantcapacityisunder-utilized.
Anywaytheadvantagesfaroutweighthedisadvantages.
1.4Multi-PurposeUses
Asalreadystartedearlier,anumberofadditionalbenefitscanbeobtainedfromwaterstoredbesidesgeneratingpower,suchasirrigation,floodcontrol,navigationandsoon.Themulti-purposeuseofwatergivesmuchbetterreturnsoninvestmentandthereismarkedimprovementinthecost-benefitratio.
1.4.1Irrigation
Thewaterbeingdischargedfromapowerhousecanbefedintoacanalnetworktoprovideirrigationfacilitiestolandsituateddownstream.Asamatteroffact,inmanymulti-purposeprojectsinIndia,waterisstoredpredominantlyforirrigationpurposeswithpowergenerationplayingasecondaryrole.
1.4.2Floodcontrol
Creationoflakeonariverhastheinherentpossibilitiesoffloodmoderation.Thefloodwatersmaybefullyorpartlyabsorbedinthelakeandonlyregulatedquantitiesofwaterareallowedtopassdownstream,protectingthelowerareasfromfloods.Thisaspectassumesgreatimportanceinthecaseofrivers,whichgoondevastatinglargetractsoffertilelandandvaluablepropertyyearafteryear.
1.4.3Navigation
Theformationofstoragereservoirincreasesthenormalwaterlevelinariver.Manypoolsandshallowstretchesoftherivergetsubmergedunderwaterandasufficientdepthofwaterbecomesavailableforshiptonavigatethesestretches.Thusfacilitateseconomictransportofcargoandpassengers.
Themulti-purposedevelopmentoftheriverDanubeinEuropeisatypicalexampleofcombiningnavigationwithpowergeneration.It’slinkingupwiththeriverRhinehasallowedtheshipstopassfromtheNorthSeatotheBlackSea.Barrageshavebeenconstructedatanumberofpointsintheriverincreasingtheupstreamwaterlevelsandpowerisbeinggeneratedattheseplaces.Theonlyadditionalconstructionneededistoprovidenavigationallocksatthesitesofthebarragefortheuninterruptedmovementofaship.
1.4.4Recreation
Creationareservoirofwaterconsiderablyenhancesthebeautyandcharmofsurroundingareasandtouristresortsandpicnicspotsarebeingdevelopedintheseareas.
1.4.5FishBreeding
Itcantakeplaceonalargescaleandfishcanbemadeavailableeconomicallytothepopulationlivingintheneighboringareas.
1.5TypicalComponentsofaHydroelectricPlant
Themaincomponentsare(Fig.1.1):(i)Thedam,(ii)Thewater-conduitsystem,(iii)Thepowerhouse,(iv)Thetail-watersystem,(v)Theswitchyard,and(vi)Thetransmissionlines.
1.5.1DamorBarrage
Adamorabarrageisconstructedontherivercourseresultinginanincreaseintheupstreamwaterlevelbecauseoftheformationofareservoirwhosestoragecapacityisdecidedbythewaterrequirementforpowergeneration.
1.5.2Water-ConduitSystem
Water-conduitsystemcarrieswaterfromthereservoirtothepowerstation.Itmayconsistofapressuretunneland/orpipescalledpenstockswhichmaybelaidabovegroundorunderground.Onepenstockmayfeedanumberofturbines,whereanumberofbrancheshavetotakeoff.Flow-controlvalvesmaybeprovidedbeforewaterisadmittedtotheturbines.Asurgetankisoccasionallyprovidedtorestricttheeffectsofwaterhammer.
Fig.1.1Typicallayoutofahighheadhydroelectricplant
1.5.3PowerHouse
Thepowerhouseaccommodatestheturbinesandgenerators,thecontrolequipmentandinsomecasesthetransformers.Itslocationcanbeeitheratthesurfaceorundergroundanditmaybeawayfrom,atthefootof,orinthebodyof,thedam.
1.5.4TailRace
Thewater,afterpassingthroughtheturbine,isdischargedintothetailracewhich,inturn,carriesittoariver.
Thetailracecanbeanopenchannelasinthecaseofasurfacepowerhouse,oratunnelasinthecaseofanundergroundpowerhouse.Thedischargefromalltheturbinesiscollectedinthetailraceatitsbeginningbymeansofbranchchannels.Thetailracemaydischargeintotheoriginalriveritselfor,inrarecases,someotherriverwhenthereisaninter-basintransferofwater.
1.5.5ElectricalPowerTransmission
Theelectricalpowergeneratedbythegeneratorsisfedtothestep-uptransformersbymeansofcablesasthegeneratingvoltagemaybemuchlessthanthetransmissionvoltage.Thepoweristhensuppliedtothetransmissionnetworkviaaswitchyardwheretheswitchingandprotectiveequipmentisinstalled.Theswitchyardislocatedwithinashortdistanceofthepowerhouse.
Transmissionlinestakeoffindifferentdirectionstosupplypowertotheconsumers.
Inthecaseofcombinedhydropowerandirrigationmulti-purposeprojects,acanalnetworkisestablisheddownstreamofdam.
1.6ClassificationofHydroelectricPlants
Theycanbeclassifiedonthebasisoftheoperatingheads,theoutputorsomeotherimportantfeatures,suchasthenatureofduty.
1.6.1Base-LoadandPeak-LoadPlants
Everyhydro-plantisanindividualentityandnotwoplantsareidenticalasregardsthehead,availabilityofpowerandsoon.Ahydro-plantworksasabase-loadplantifthereiscontinuouspowergeneration.Thisisespeciallythecaseiftheflowthroughtheriverhastobemaintainedconstantformeetingtheirrigationornavigationrequirements.
Iftheconditionsprevailingatthepowerstationpermitregulatedreleases,theplantcanbeusedtogeneratepeakpower.Forexample,theRoselandplant(France)isdesignedtomeetthepeakwinterdemandfromwaterlargelystoredduringthesummerperiod.
1.6.2Plantscanalsobeclassifiedasfollows:
(a)Conventionalhydro-plantswithvalleystorage.
(b)Run-of-the-riverplants.
(c)Diversiontypeofplants.
(d)Pumpedstorageplants.
(e)Tidal-powerplants.
Valleystorageplants
Inthecaseofconventionalhydro-plants,areservoirhastobecreatedontherivertostoresufficientrainwater,forpowergenerationthroughouttheyearbyconstructionofadam.Thesetypesofplantsaresub-dividedintohigh-headplants,medium-headplants,andlow-headplants(Fig.1.2).
Itisdifficulttolaydownexactranges.However,thefollowinglimitsarerecommended(theyarearbitraryandareasgoodasanyotherarbitraryrangesrecommended):
(i)High-headplants-havingheadsofmorethan250m.
(ii)Medium-headplants-havingheadsbetween50mand250m.
(iii)Low-headplants-havingheadslessthan50m.
Fig.1.2TheGeheyanvalleystorageplant(China)
Today,theplantcapacitiesrangefromafewhundredkilowattstothousandsofmegawattswithindividualunitcapacitiesrangingfromfewhundredkWto700,000kWanditisratherdifficulttoclassifytheplantsoncapacitybasis.
Run-of-the-riverplants
Fig.1.3
\o"ChiefJosephDam"
ChiefJosephDam
near
\o"Bridgeport,Washington"
Bridgeport,Washington
,USA,isamajorrun-of-the-riverstationwithoutasizeablereservoir
Theseplantsgeneratepoweronriverswithacontinuousflowthroughouttheyearwithminorseasonalvariations.Suchconditionsprevailmainlyincoldercountriesbutrarelyintropicalregions.Thestorageneededisminorandcanbecreatedbybuildingabarrageacrosstheriver,whichraisesthewaterlevelcreatingsomeheadforpowergeneration.
Thesitechosenshouldbeonastablereachoftheriverwithstablebedandbanks.Themaximumfloodanticipatedshouldhavealowvalueandwatershouldnotcarrymuchsediment.Creatingasmallpooldoesnotcreateproblemsoflandacquisitionanddoesnotsubstantiallyaltertheoriginaltopographyalongthebanksoftheriverassubmergenceislow.Thispoolmayalsobeusefulfornavigation(Fig.1.3).
SuchplantsarequitepopularinEurope.AchainofsuchplantshavebeenconstructedontheDanubetofullyutilizeitspowerandnavigationpotential.
DiversionCanalPlants
Thesediversiontypeofplantscangeneratepower,takingadvantageoftheleveldifferenceonacurvedmeanderingstretchofariverwithasteepbed-slope.
Adiversioncanalwithaflatslopeinwhichtheflowfromtheriverisdivertedtakesofffromthehigherreachesofthemainriver.Aweirisconstructedattheendofthecanaltocreateasmallpoolofwater,calledtheforebay.Thewaterfromtheforebayisfedbymeansofthepenstockstothepowerhousesituatedinthelowreachoftheriver(Fig.1.4).
Fig.1.4Diversionhydropowerplant
PumpedStoragePlants
Apumped-storageplantusestworeservoirs,onelocatedatamuchhigherelevationthantheother.Duringperiodsoflowdemandforelectricity,suchasnightsandweekends,energyisstoredbyreversingtheturbinesandpumpingwaterfromthelowertotheupperreservoir.Thestoredwatercanlaterbereleasedtoturntheturbinesandgenerateelectricityasitflowsbackintothelowerreservoir.
Thesearepeakloadplantswherewaterispumpeduptoahigherlevelduringoffpeakperiodstogeneratepeakpowerduringthehighdemandperiod.
Fig.1.5Pumpedstorageplant
TidalPowerPlants
Thesedependontidesforgeneratingpower.Thissourceisunconventionalandalotofimportanceisbeinggiventothistypeofplant.
1.6.3ClassificationontheBasisofAvailableHeads
Therearevariousclassificationsofhydroelectricpowerplants.Basedonthetotalheadofwateravailablethehydroelectricpowerplantsareclassifiedintothreetypes:lowheadhydroelectricpowerplants,mediumheadhydroelectricpowerplants,andhighheadhydroelectrcipowerplants.
Lowheadhydroelectricpowerplants
Fig.1.6Cross-sectionofatypicallowheadplant
Thelowheadhydroelectricpowerplantsaretheonesinwhichtheavailablewaterheadislessthan30meters.Thedaminthistypeofpowerplantsisofverysmallheadmaybeevenoffewmetersonly.Incertaincasesweirisusedandinothercasesthereisnodamatallandmerelyflowingwaterintheriverisusedforgenerationofelectricity.Thelowheadtypesofhydroelectricpowerplantscannotstorewaterandelectricityisproducedonlywhensufficientflowofwaterisavailableintheriver.Thustheyproduceelectricityonlyduringparticularseasonswhenabundantflowofwaterisavailable.Sincetheheadofwaterisverysmallinthesehydroelectricpowerplants,theyhavelesserpowerproducingcapacity.InsuchplantsFrancis,PropellerorKaplantypesofturbinesareused.Alsonosurgetankisrequired.
Mediumheadhydroelectricpowerplants
Thehydroelectricpowerplantsinwhichtheworkingheadofwaterismorethan30metersbutlessthan300metersarecalledmediumheadhydroelectricpowerplants.Thesehydroelectricpowerplantareusuallylocatedinthemountainousregionswheretheriversflowsathighheights,thusobtainingthehighheadofthewaterindambecomespossible.Inmediumheadhydroelectricplantsdamsareconstructedbehindwhichtherecanbelargereservoirofwater.Waterfromthereservoircanbetakentothepowergenerationsystemwhereelectricityisgenerated.TheturbinesusedareFrancistypeofthesteelencasedvariety.
Fig.1.7Cross-sectionofatypicalmediumheadplant
Highheadhydroelectricpowerplants
Inthehighheadhydroelectricpowerplantstheheadofwateravailableforproducing
electricity
ismorethan300metersanditcanextendevenupto1000meters.Thesearethemostcommonlyconstructedhydroelectricpowerplants.Inthehighheadhydroelectricpowerplantshugedamsareconstructedacrosstherivers.Thereislargereservoirofwaterinthedamsthatcanstorewateratveryhighheads.Waterismainlystoredduringtherainyseasonsanditcanbeusedthroughouttheyear.Thusthehighheadhydroelectricpowerplantscangenerateelectricitythroughouttheyear.Thehighheadhydroelectric
powerplants
areveryimportantinthenationalgridbecausetheycanbeadjustedeasilytoproducethepoweraspertherequiredloads.
Whenconstructingthehighheadtypesofhydroelectricpowerplantsanumberoffactorsespeciallythoserelatedtotheenvironmentandnaturalecosystemofthelandandwatershouldbeconsidered.Thetotalheightofthedamdependsuponanumberoffactorslikequantityofavailablewater,powertobegenerated,surroundingareas,naturalecosystemetc.
Mainlyintheseplantspressuretunnelisprovidedbeforethesurgetank,whichinturnconnectedtopenstock.Apressuretunnelistakenofffromthereservoirandwaterbroughttothevalvehouse(notshowninpicture)atthestartofthe
\o"Penstocks"
penstocks
.Thepenstocksarehugesteelpipeswhichtakelargequantityofwaterfromthevalvehousetothepowerhouse.Thevalvehousecontainsmainsluicegatesandinadditionautomaticisolatingvalveswhichcomeintooperationwhenthepenstockbursts,cuttingfurthersupplyofwater.Surgetankisanopentankandisbuiltjustinbetweenthebeginningofthepenstocksandthevalvehouse.Inabsenceofsurgetank,thewaterhammercandamagethefixedgates.Normallythehighheadplantsare500metersaboveandforheadsabove500metersPeltonwheelsareused.
Fig.1.8Cross-sectionofatypicalhighheadplant
2HYDRAULICTURBINES
2.1Introduction
Hydraulicturbinesaremachineswhichconvertwaterenergyintomechanicalenergy.Sotheycanbeconsideredasmotorsrunbywater.Waterstoredinareservoirathigherlevelflowsthroughtheturbinetothetailracechannelsituatedatalowerlevelimpartingpotentialenergytotheturbine.
ThetheoreticalfoundationsofthemodernturbinewerelaidbyEuler.ThefirstpracticalturbinesweremadebyFourneyronandBourdin.Forneyroninstalleda40H.P.turbineatSt.Blassius,Francein1835.OtherprominentnamesinthefieldarePelton,FrancisandKaplan.TheimpulseturbineisnamedafterPeltonwhocontributedalottoitsdevelopment.ThemixedflowreactionturbineisnamedafterFrancis,whobuiltthefirstwelldesignedunitin1849.ThemovablebladepropellertypeturbineisnamedafterKaplan.
Thefunctionofawaterturbineistorotatethegeneratorcoupledtoittoproduceelectricity.Theconversionofenergytotheelectricalformisnecessarybecauseelectricalenergycanbetransmittedoverlongdistanceswithproportionatelyverysmalllossescomparedtomechanicalorhydraulicenergy.
2.1.1Sub-systemsofaWaterTurbine
Essentiallyanywaterturbinemusthavethefollowingsub-systems:
(i)Guidepassagestoadmitwatertotherotatingelementwithminimumlossofenergy.
(ii)Agoverningmechanismtoinstantaneouslyadjustthequantityofwaterbeingadmitted,tomatchtheloadfluctuations.
(iii)Arotatingelementorarunnerwheretheconversionofenergytakesplace.Atorqueisdevelopedwhichrotatesthegeneratorcoupledtotheturbine.
(iv)Passagestoleadthewateroutoftheturbinebody.
Inthecaseofwaterturbines,thedensityremainsconstantwhilewaterispassingthroughallabovestages.Insteamturbinesandgasturbinesthedensityvaries.Hencetheirconstructiondiffersmateriallyfromwaterturbines.
2.2ClassificationofWaterTurbines
Thewaterturbinesaredividedintotwomaincategories:theimpulsetypeandreactiontype(Fig.2.1).Intheimpulsetype,waterflowsoutofanozzleintheformofajetsuchthatallthepressureenergyisconvertedintokineticenergy.Thisjethitsoneofaseriesbucketsmountedonarunner.Becauseoftheimpact,therunnerisrotatedabouttheaxis.Thereforetheturbineiscalledtheimpulseturbine.Thewatercomesoutofthenozzleatatmosphericpressure.Hencethepressurethroughouttheturbineisatmospheric,i.e.,constant.Thereforetheturbineisalsocalledaconstantpressureturbine.
Fig.2.1Principleofthebasicimpulseturbine(left)andreactionturbine(right)
Thereactiontypeofturbineworksontheprincipleofreaction.Waterenterstheturbineathighpressureandlowvelocityintheguidepassage.Somepressureenergyisconvertedintokineticenergyandwaterthenenterstherunner(rotor)andpressureenergyissuccessivelyconvertedintokineticenergy.Asthewaterflowingthroughtherunnerisaccelerated,itcreatesareactionontherunnervaneandtherunnerisrotated(Fig.2.2).Asthestaticfluidpressureactsonbothsidesthevane,itdoesnotdoanywork.Workisentirelydoneduetoconversionofenergyintokineticform.Itistobenotedthatrelativevelocitygoesonincreasingfrominlettooutletthoughtheabsolutevelocitydecreases.Inareactionturbinewaterisunderpressureandtheturbineisfilledwithwaterwhenworking.Therefore,theturbinemustbeenclosedinacasingwhichshouldbeabletowithstandthepressure.Inthecaseofanimpulseturbine,thecasingprotectstherunneranddoesnotallowthewatertosplashout.Itdoesnotserveanyhydraulicfunction.Inareactionturbine,watercanbeadmittedallovertherunneratonetime.Therefore,itissometimescalledafulladmissionturbine.
Fig.2.2Francisturbine(reactiontype)
Onlythreeturbineshaveservedthetestoftime.TheyarePeltonturbinesoftheimpulsetypeandFrancisandKaplanturbinesofthereactiontype.
Therefore,thesethreewillbediscussedinsomedetail.Recently,anothertypeofturbineknownasDeriazturbineordiagonalflowturbinehasbeendevelopedwhichisacrossbetweenaFrancisturbineandaKaplanturbine.
2.3PeltonTurbine
ThePeltonturbine(Fig.2.3)isanimpulsetypeofturbine.ItwasnamedafterL.A.Pelon(1829-1908)whoin1880,patentedandimprovedtheformofimpulsewheels.Inimpulseturbine,waterflowsoutofanozzleintheformofajetintheatmosphere,convertinghydraulicenergyintokineticenergy.Thejetdeliversanimpacttooneofaseriesofbladesmountedontherunner,whichstartsrotating.Asthepressureisatmosphericandconstant,thisturbineisalsocalledconstantpressureturbine.Thisturbineisessentiallyahighheadturbineandiscurrentlybeingusedforaheadrangeof300mto1800m.ThespecificspeedrangeisfromNs=4toNs=70.
Theturbineessentiallyconsistsofthreecomponents:(i)theinjector(ii)therunnerand(iii)thecasing.
2.3.1Injector
Thefunctionoftheinjectorare(a)todirectthewaterreceivedfromthepenstockattheproperangleontherunner(b)tovarythequalityofwatertosuitinstantaneousloadconditions,therebygoverningtheturbine.
Theinjectorsarelocatedeitherattheendofabendfittedtothepenstockofinthecaseofmulti-nozzleturbines,orattheendofthedistributionbranches.
Theinjectorconsistsof(a)anozzle(b)aspearrodalsocalledaneedleand(c)adeflector.Thespearrodslidescoaxiallyinthenozzle.Itsmovementcontrolstheareaofthenozzleopeningandthereforethequantityofwaterbeingadmittedtotherunner.
Fig.2.3CrosssectionofaPeltonturbine
2.3.2Runner
Thisconsistsofacylindricaldiscwiththebladesmountedonitsperiphery(Fig.2.4).
Theblades,alsocalledbuckets,lookliketwinhemi-ellipsoidedcupsjoinedinthemiddlebymeansofaridge.Thisshapeisgiventoobtainmaximumefficiencyconditions.Thejetofwaterentersthebucketinthecenter,bifurcatesintotwoportionsandtravelsoverthebucketandleavesattheoutlettips.Thisbifurcationcounterbalancesanyax
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