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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