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HydraulicsAirline Transition CourseLesson ObjectivesDevelopabasicunderstandingofhydraulicDevelopabasicunderstandingofhydraulictheoryandthephysicsrelatedtohydraulicstheoryandthephysicsrelatedtohydraulics FluidPowerFluidPower LawofConservationofEnergyLawofConservationofEnergy PascalsLawPascalsLaw HydrostaticParadoxHydrostaticParadox MechanicaladvantageMechanicaladvantage BernoullisprincipleBernoullisprincipleTypesofFluidTypesofFluidHydraulicSystemComponentsHydraulicSystemComponentsFluid PowerTHEORYHydraulicsystemsoperateaccordingtoPascalslaw.ThelawofBlaisePascalsays:Thepressure,inastatichydraulicfluidinaclosedsystemiseverywherethesame.However,whenthevelocityoftheflowisconstantonemayapplyPascalsLawaswell.Animation:Whenthemanjumpsonthesmallpiston,heinducesapressureinthesystem.Thispressurealsoworksonthelargepiston:becauseofthelargeareaofthispiston,theforceinducedbythepressureiscapabletoliftthecar.Thepressurecanbecalculatedwiththeformula:where:p=pressure(psi)F=force(pound)A=area(squareinch)Fluid PowerForce=energy exerted(F=MA)Force=energy exerted(F=MA)Pressure=a force that is applied over a given Pressure=a force that is applied over a given area(usually in psi)area(usually in psi)Pressure=Force/AreaPressure=Force/AreaWork=any time a force causes an object to Work=any time a force causes an object to movemove Work=Force x DistanceWork=Force x DistancePower=the amount of power required to Power=the amount of power required to accomplish a give amount of work in a certain accomplish a give amount of work in a certain period of timeperiod of time Power=(Force x Distance)/TimePower=(Force x Distance)/TimeLaw of Conservation of EnergyWeareabletotakeenergyandchangeitsWeareabletotakeenergyandchangeitsform,conserveitforlater,andreleaseitatform,conserveitforlater,andreleaseitatwill.will.WegetthesameamountofenergyoutasweWegetthesameamountofenergyoutasweputin.putin.UnfortunatelysomeenergyistransformedandUnfortunatelysomeenergyistransformedandlostintoanunusableform.lostintoanunusableform.Ex:Rubbingyouhandstogether,takesyourEx:Rubbingyouhandstogether,takesyourbodiesenergyandreleasesitasthermalenergy.bodiesenergyandreleasesitasthermalenergy.(UnlessyourinNorthDakotainJan.doingthisis(UnlessyourinNorthDakotainJan.doingthisisusuallyprettyuseless)usuallyprettyuseless)ThislossofenergyisusuallyreferredtoasThislossofenergyisusuallyreferredtoasinefficiencyinefficiencyTwo Forms of EnergyPotential:Potential:ExistsinanobjectExistsinanobjectbecauseofitsbecauseofitspositionposition Ex:ArubberbandEx:ArubberbandstretchedoutstretchedoutKinetic:Kinetic:ExistsinanobjectExistsinanobjectduetoitsmotionduetoitsmotion Ex:ArubberbandEx:ArubberbandafterIhaveletgoofafterIhaveletgoofit,asitfliestowardsit,asitfliestowardsyourfaceyourfaceHydrostaticParadoxParadox:Paradox:AtruestatementthatdoesnotreadilyappeartobeAtruestatementthatdoesnotreadilyappeartobetrue.true.HydrostaticParadox:HydrostaticParadox:ThepressureofafluidatthebottomoftheThepressureofafluidatthebottomofthecontainerwillbeeffectedbytheheightofthatcontainerwillbeeffectedbytheheightofthatcontainerbutnotitsshapeortheamountoffluid.containerbutnotitsshapeortheamountoffluid.Pascals Law“Pressure in an enclosed container is transmitted equally and undiminished to all parts of the container and acts at right angles to the enclosing walls.Pascals LawPressureexertedonafluidinaclosedcontainerPressureexertedonafluidinaclosedcontaineristransmittedequallyandundiminishedtoallistransmittedequallyandundiminishedtoallpartsofthecontainerandactsatrightanglestopartsofthecontainerandactsatrightanglestotheenclosingwalls.theenclosingwalls.ForceForceMechanical AdvantageConsider a teeter-totter.Consider a teeter-totter.Ex:A 5 lb.weight with a 10 ft.arm balances a 50 lb.Ex:A 5 lb.weight with a 10 ft.arm balances a 50 lb.weight with a 1 ft.arm.weight with a 1 ft.arm.The same may be maintained with a hydraulic The same may be maintained with a hydraulic systemsystemF1=F2A1A25 lbs=50 lbs1 sq.in.10 sq.in.Transmitting PressureF=A x PF=A x PTransmittingaforcethroughasmalltube.Transmittingaforcethroughasmalltube.Piston1Piston110in.10in.2 2Piston2Piston210in.10in.2 2Force2=100lbs.Force2=100lbs.Pressure10lbs./inPressure10lbs./in2 2Force1=100lbs.Force1=100lbs.Bernoullis Principle Becomes the exchange between kinetic energy(velocity/dynamic Becomes the exchange between kinetic energy(velocity/dynamic pressure)and potential energy(static pressure)pressure)and potential energy(static pressure)More kinetic energy(velocity/dynamic pressure)results in less More kinetic energy(velocity/dynamic pressure)results in less potential energy(static pressure)while total energy(total pressure)potential energy(static pressure)while total energy(total pressure)remains constantremains constantSystem ComponentsSystem ComponentsSystem ComponentsHydraulicReservoir:HydraulicReservoir:StoresfluidStoresfluid ServesasanexpansionchambertocompensateforheatServesasanexpansionchambertocompensateforheatexpansionexpansion ApointwherefluidcanpurgeitselfofanyairApointwherefluidcanpurgeitselfofanyair Alsocontainsstandpipesforaux.useAlsocontainsstandpipesforaux.useHydraulicPumpsHydraulicPumps FluidmoversFluidmovers DevelopspressureasresistanceisappliedDevelopspressureasresistanceisappliedHydraulicValves:HydraulicValves:OpensandclosestodirectorrestricttheflowofthefluidOpensandclosestodirectorrestricttheflowofthefluidAccumulators:Accumulators:Amethodtostorehydraulicfluid(whichisAmethodtostorehydraulicfluid(whichisnoncompressible)underpressurenoncompressible)underpressureSystem Components(cont)Filters:Filters:RemovescontaminantsRemovescontaminants MicronsareusedtodescribethesizeoftheparticlestheMicronsareusedtodescribethesizeoftheparticlesthefilterwillcollectfilterwillcollectFluidLines:FluidLines:UsedtotransferthefluidtotheactuatororfromtheUsedtotransferthefluidtotheactuatororfromtheactuatoractuatorSeals:Seals:Usedtominimizeleakageandlossofsystempressure,alsoUsedtominimizeleakageandlossofsystempressure,alsousedtokeepoutunwantedcontaminantsusedtokeepoutunwantedcontaminantsActuators:Actuators:UsedtoconvertpressureinthefluidintoworkUsedtoconvertpressureinthefluidintoworkPTUsPTUs PowerTransferUnits:UsedtotransferpowerfromonePowerTransferUnits:UsedtotransferpowerfromonehydraulicsystemtoanotherhydraulicsystemtoanotherSystem Components(cont)ReservoirsNonpressurized:Foaming is by minimized routing,through Foaming is by minimized routing,through swirling using centrifugal forceswirling using centrifugal forceFor lower altitude applicationsFor lower altitude applicationsPressurized:As aircraft fly higher foaming becomes more As aircraft fly higher foaming becomes more of a problemof a problemPressurizing the reservoir minimizes this Pressurizing the reservoir minimizes this problem.problem.Hydraulic ReservoirStandpipe:For larger aircraft systems,a standpipe is For larger aircraft systems,a standpipe is incorporatedincorporatedA standpipe allows fluid to flow through A standpipe allows fluid to flow through standpipe for normal operationsstandpipe for normal operationsWhen fluid level decreases below the When fluid level decreases below the standpipe,ex:a hydraulic leak,the standpipe standpipe,ex:a hydraulic leak,the standpipe can not draw anymore fluidcan not draw anymore fluidLeaving some fluid left for priority systems Leaving some fluid left for priority systems Hydraulic PumpsHand pumps:Hand pumps:Used for emergency Used for emergency gear extension on gear extension on some A/Csome A/C Single action pumps Single action pumps fluid with one stroke,fluid with one stroke,only when the handle only when the handle is being moved one is being moved one directiondirection Double action Double action pumps fluid with both pumps fluid with both strokesstrokesDash 8 Alternate Gear Dash 8 Alternate Gear Extension hand pumpExtension hand pumpHydraulic Pumps(cont.)Powerpumps:Powerpumps:Constantdisplacement:Constantdisplacement:MovesagivenamountoffluideachtimeitrotatesMovesagivenamountoffluideachtimeitrotatesIfRPMchanges,amountoffluidandpressurechangesIfRPMchanges,amountoffluidandpressurechangesSomesortofpressurereliefisrequiredtopreventSomesortofpressurereliefisrequiredtopreventrupturingalineordamagetothesystemrupturingalineordamagetothesystemPowerPumps(cont.):PowerPumps(cont.):Variabledisplacement:Variabledisplacement:MoveavolumeoffluidproportionaltothedemandsofMoveavolumeoffluidproportionaltothedemandsofthesystemthesystemPump TypesTheaxialpistonpumpTheaxialpistonpumpThe gearmotor:The gearmotor:Two meshing gearsTwo meshing gears Constant displacementConstant displacementPump TypesPump TypesVane PumpVane Pump fixed outputfixed outputVane PumpVane Pump variable outputvariable outputGerotor Pump:Gerotor Pump:Constant displacementConstant displacementPump TypesPiston-type Hydraulic Piston-type Hydraulic motormotor Variable displacementVariable displacementPump TypesHydraulic ActuatorsLinear type:Piston inside a cylinderPiston inside a cylinderHydraulic pressure is applied to either side to Hydraulic pressure is applied to either side to force the piston to moveforce the piston to moveNote:The side which the pressure is being applied results in a Note:The side which the pressure is being applied results in a different amount of force due to a difference of surface areadifferent amount of force due to a difference of surface areaHydraulic AccumulatorsUsedtostorehydraulicfluidunderpressureUsedtostorehydraulicfluidunderpressureSincehydraulicfluidcannotbecompressedwemustSincehydraulicfluidcannotbecompressedwemusthavesomesortofmechanismtoapplypressure,havesomesortofmechanismtoapplypressure,understorage,againstthehydraulicfluidunderstorage,againstthehydraulicfluidAdiaphragm,inthecasing,separates,containedAdiaphragm,inthecasing,separates,containedpressurizedgasfromthehydraulicfluidwhilestillpressurizedgasfromthehydraulicfluidwhilestillapplyingpressureapplyingpressureAshydraulicpressureisapplieditpushesagainstAshydraulicpressureisapplieditpushesagainstthediaphragm,avalveclosesandthepressureisthediaphragm,avalveclosesandthepressureisstoredstoredOncethehydraulicpressureisneeded,thevalveisOncethehydraulicpressureisneeded,thevalveisopenedandthehydraulicpressureisreleasedopenedandthehydraulicpressureisreleasedHydraulic AccumulatorsAccumulators can be Accumulators can be used for:used for:Unfeathering a Unfeathering a propellerpropeller Alternate brakesAlternate brakesPTUsUsed to transfer hydraulic pressure from one system to another.Think of a turbo charger on a carExhaust gas turns a turbine,which is Exhaust gas turns a turbine,which is connected to another turbine to compress airconnected to another turbine to compress airThe PTU uses hydraulic pressure from one system to turn a turbine,which is connected to another system to provide pressure with in that systemTypes of FluidsTypes of FluidsTypes of FluidsVegetable base:MIL-H-7644,Vegetable base:MIL-H-7644,essentially castor oilessentially castor oil Rubber seals neededRubber seals needed used older systems,unlikely to be in any modern used older systems,unlikely to be in any modern systemssystemsMineral base:MIL-H-5606Mineral base:MIL-H-5606 Kerosene-type petroleum/doesnt mix well with waterKerosene-type petroleum/doesnt mix well with water Good lubricating propertiesGood lubricating properties Mixes easily with additives to prevent foaming and Mixes easily with additives to prevent foaming and corrosioncorrosion Neoprene seals neededNeoprene seals needed Dyed redDyed red FlammableFlammableTypes of Fluids(cont.)Synthetic Phosphate Ester:MIL-H-8446(Skydrol)Used on modern high-speed jet aircraftUsed on modern high-speed jet aircraftWide range of operating temperaturesWide range of operating temperaturesSusceptible to contamination by waterSusceptible to contamination by waterMust not be allowed to drip onto electrical Must not be allowed to drip onto electrical wiring(breaks down the wiring)wiring(breaks down the wiring)Teflon seals Teflon seals Dyed purpleDyed purplep经常不断地学习,你就什么都知道。你知道得越多,你就越有力量pStudyConstantly,AndYouWillKnowEverything.TheMoreYouKnow,TheMorePowerfulYouWillBe写在最后谢谢你的到来学习并没有结束，希望大家继续努力Learning Is Not Over.I Hope You Will Continue To Work Hard演讲人：XXXXXX 时 间：XX年XX月XX日
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