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  • Turbo MachinesTurboMachinesPumpsandTurbines

    ME 268ME268

  • TurboMachines

    Turbomachinesaredynamicfluidmachinesthateitherextractenergyfromafluid(turbine)oraddenergytoafluid(pump)asaresultofdynamicinteractionsbetweenth d i d th fl id (L ti T b t ithedeviceandthefluid.(LatinTurbomeanstospinorwhirl)

  • Classifications

    AccordingtoenergyconsiderationMachinesthatsupplyenergytofluid(Pumps)Anincreaseinpressuretakesplaceinpumps,fans,

    d llcompressorsandpropellers.

    Machinesthatextractsenergyfromfluid(Turbines)A decrease in pressure takes place in turbines wind millsAdecreaseinpressuretakesplaceinturbines,windmills.

    Machinesthatareacombinationofboth(Energytransmittersandtorqueconverters)

  • Classifications(contd)

    BasedondirectionofflowAxialflow

    Radialflow

    Mixedflow

    BasedonthemanneroftransmissionofenergyKineticdisplacement(Centrifugalpumpsandturbines)

    Positivedisplacement(Reciprocatingpumps)

  • Pumps

  • Pumps

    Apump isadeviceusedtomoveliquidsorslurries.Ap p qpumpmovesliquidsorgasesfromlowerpressuretohigherpressure,andovercomesthisdifferenceinpressurebyaddingenergytothesystem.

    MechanicalEnergy Hydraulicenergy

  • Pumps

    Fig: Tire pump Fig: Human heart Fig: Centrifugal pump

  • PumpsClassification(contd)

    Pumpsaredividedintotwofundamentaltypesbasedontheh h h h d dmannerinwhichtheytransmitenergytothepumpedmedia:

    kineticorpositivedisplacement.Inkineticdisplacement,acentrifugalforceoftherotatingp , g gelement,calledanimpeller,impelskineticenergytothefluid,movingthefluidfrompumpsuctiontothedischarge.Positive displacement uses the reciprocating action of one orPositivedisplacement usesthereciprocatingactionofoneorseveralpistons,orasqueezingactionofmeshinggears,orothermovingbodies,todisplacethefluidfromoneareainto

    th (i i th t i l f ti t di h )another(i.e.,movingthematerialfromsuctiontodischarge).Sometimesthetermsinlet(forsuction)andexitoroutlet(fordischarge)areused.( g )

  • PumpsApplications

    Todeliverfluidatahigherelevationoratalongg gdistance.

    Todeliverfluidatapressurizeddevice

    Forthecontrolofhydraulicsystems

    Fordrainagesystem,removingslurries,mud,waterg y g

    Forirrigationsystems

  • CentrifugalPumps

    Thehydraulicmachinesthatconvertsthemechanicalenergyintopressureenergybymeansofcentrifugalforceactingonthefluidarecalledcentrifugalpumps.

    Centrifugalpumpisradialflowtype.

    Usedforhighheadandrelativelylowflowrate

    3importantpartsareImpeller

    V l iVolute casing

    Suctionanddeliverypipes.

  • CentrifugalPumps

  • CentrifugalPumps(Contd)

    Therotatingpartofthecentrifugalpumpiscalledimpeller.Itisarotatingsoliddiskwithcurvedblades.Impellerscouldbeopen,semiopenorclosed.

    Open Semi - Open Closed

  • CentrifugalPumps(Contd)

    ForIncompressiblefluids(water)backwardcurvedvanes

    Backward curved Radial curved Forward curved

    areused(pumps)Forcompressiblefluids(air)forwardcurvedvanesareused(compressors)(compressors)

  • CentrifugalPumps(Contd)

    Casing isanairtightpassagesurroundingtheimpellerwhichconvertsthekineticenergyofthefluidleavingtheimpellerintopressureenergy.

    Suctionpipe isconnectedtotheinletofthepumpandth id i di d i t th fl id i D li iothersideisdippedintothefluidinasump.Deliverypipe

    isconnectedtotheoutletofthepumpandotherenddelivers the fluid at required heightdeliversthefluidatrequiredheight.

  • CentrifugalPumps(Contd)

    Workingprinciple

    Theimpelleriskeyedontoashaftwhichismountedonbearingsandiscoupledtoamotorwhichrotatestheimpellerimpeller.Thekineticenergyoftheimpelleristransmittedtothefluidanditsvelocityincreases.Th l t i t th ki ti f th fl idThevolutecasingconvertsthekineticenergyofthefluidtopressureenergy.Thepressureatthecenteroftheimpeller(eye)decreasesasthefluidflowsoutward.Thed i th fl id f th tdecreaseinpressurecausesthefluidofthesumptocontinuouslyflowthroughthesuctionpipes.Thehighpressurefluidisdeliveredthroughthedeliveryipipe.

  • CentrifugalPumps(Contd)

  • CentrifugalPumps(Contd)

  • CentrifugalPumps(Contd)

  • CentrifugalPumps(Contd)

    Priming

    Thepumpcasingmustbefilledwithliquidbeforethepumpisstarted,orthepumpwillnotbeabletofunction.

    Apumpissaidtobeprimedwhenalltheairinsuctioni i d i d li i t th l ipipe,casing,andindeliverypipeuptothevalveis

    drivenoutanditsplaceisoccupiedbyliquidtobepumpedpumped.

  • CentrifugalPumps(Contd)

    Cavitations

    Ifthesuctionpressureattheeyeoftheimpellerfallsbelowthevaporpressureofthefluidbeingpumped,thefluidwillstart to boilstarttoboil.

    Anyvaporbubblesformedbythepressuredropattheeyeoftheimpelleraresweptalongtheimpellervanesbythep p g p yflowofthefluid.Whenthebubblesenteraregionwherelocalpressureisgreaterthansaturationpressurefartheroutth i ll th b bbl b tl lltheimpellervane,thevaporbubblesabruptlycollapse.

    Thisphenomenoniscalledcavitation.

  • CentrifugalPumps(Contd)

    NPSH(Netpositivesuctionhead)To avoid cavitation in centrifugal pumps, the pressure ofToavoidcavitationincentrifugalpumps,thepressureofthefluidatallpointswithinthepumpmustremainabovesaturationpressure.The net positive suction head available (NPSHA) is theThenet positive suction head available (NPSHA)isthedifferencebetweenthepressureatthesuctionofthepumpandthesaturationpressurefortheliquidbeingpumpedpumped.Thenetpositivesuctionheadrequired(NPSHR)istheminimumnetpositivesuctionheadnecessarytoavoidcavitationcavitation.NPSHAmustbegreaterthanNPSHRtoavoidcavitation.

    NPSHA>NPSHR

  • CentrifugalPumps(Contd)

    Configurationofpumps

    PumpsinparallelForhighflowraterequirement

    Headorpressuredevelopedissameastheindividualpump

    Flow rate is the summation of the individual pumpsFlowrateisthesummationoftheindividualpumps

    PumpsinseriesFor high head or pressure requirementForhighheadorpressurerequirement

    Flowrateremainssameastheindividualpump

    Head or pressure is the summation of two pumpsHeadorpressureisthesummationoftwopumps.

  • CentrifugalPumps(Contd)

  • CentrifugalPumps(Contd)

    Highvelocityvs.Highpressure

    Watercanberaisedfromoneleveltoahigherlevelintwoways HighpressureandHighvelocity

    Highvelocitymethodisveryinefficientsincethefrictionincreaseswithproportionaltothesquareofthel itvelocity

    Highpressuremethodisefficientbecauseoflowvelocity and frictionvelocityandfriction.

  • Axialflowpump

    Turbinepumpo Usedwherehighflowrates

    atlowheadsarerequired

    o Axialflowpumpsareoften

    calledpropellerpumps.

    o For this type of pump the flowo Forthistypeofpumptheflow

    isprimarilyintheaxialdirection

    (paralleltotheaxisofrotation(p

    oftheshaft)

  • Centrifugal Pumps(Contd)

    SpecificSpeed(NS)SItisthespeedofapumpwithadischargingcapacityof1m3/secandaheadof1m.

    NS =nQ/H3/4

    n=speedofthepump

    Q=dischargeofthepump

    H=headofthepump

    Pumpselectionisdonebasedonthespecificspeed.

  • PositiveDisplacementPumps

    Apositivedisplacementpumpcausesaliquidorgastomovebytrappingafixedamountoffluidandthenforcing(displacing)thattrappedvolumeintothedischargepipe.Periodicenergyaddition

    Addedenergyforcesdisplacementoffluidinanenclosedvolumevolume

    Fluiddisplacementresultsindirectincreaseinpressure

    TwotypesofPDPsypReciprocatingPDP(Tubewell,diaphragmpump)

    RotaryPDP(Gearpump,Vanepump)

  • ReciprocatingPDP

    Inareciprocatingpump,avolumeofliquidisdrawnintothecylinderthroughthesuctionvalveontheintakestrokeandisdischargedunderpositivepressurethroughtheoutletvalvesonthedischargestroke.gThedischargefromareciprocatingpumpispulsating.Thisisbecausetheintakeisalwaysaconstantvolume.Oftenanairchamberisconnectedonthedischargesideofthepumptoprovideamoreevenflowbyeveningoutthepressure surges.pressuresurges.Reciprocatingpumpsareoftenusedforsludgeandslurry.

  • ReciprocatingPDP

  • Turbines

  • Turbines

    Turbinesaredevicesthatconverttheenergyoffluidintomechanicalenergy.

    Thefluidcanbewater,steam,fluegasetc

    Theenergyofthewatercanbeintheformofpotentialorkineticenergy.

    Steamturbineandgasturbineusesthethermalenergyofsteamandfluegasrespectively.

  • HydroelectricPowerPlant

  • Classification ofHydroelectricPowerPlant

    According to the International Energy Association (IEA),AccordingtotheInternationalEnergyAssociation(IEA),basedontheinstalledcapacity,hydroelectricstationscanbedividedareasfollows:

    o Microhydro installedcapacity30MW

  • TurbinesClassification

    AccordingtotheenergyusedImpulse turbineImpulseturbineReactionturbine

    DirectionofwaterflowA i l fl R di l i i lAxialflow RadialinaxialoutInwardflow Outwardflow

    AccordingtotheheadavailabletotheinletofturbineHighHeadTurbine(2501800m),PeltonWheelMediumHeadTurbine(50250m),FrancisTurbineLowHeadTurbine(

  • TurbinesClassification(Contd)

    ImpulseTurbineAll available head of water is converted into kineticAllavailableheadofwaterisconvertedintokineticenergyorvelocityheadinanozzle.Thewatershootsoutofthenozzleandhitsabucketwhichrotatesashaftshaft.WaterisincontactwithatmosphereallthetimeandwaterdischargedfrombucketfallfreelyTheflowissimilartoopenchannelflowandworksunderatmosphericpressure.Thekineticenergyofwaterisconvertedtomechanicalgyenergy.Thewaterenteringtheturbineexertsaforceinthedirection of the flow.directionoftheflow.Peltonwheelisanexample.

  • TurbinesClassification(Contd)

    ReactionTurbineh i fl k l i l d d i dTheentirewaterflowtakesplaceinclosedconduitandunderpressure.Attheentrancetoturbine/runneronlypartoftheenergyy p gyisconvertedtokineticenergy,remainingintop