【7A文】航空飞机气动通用系统英文培训课件.ppt

《【7A文】航空飞机气动通用系统英文培训课件.ppt》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。

PNEUMATICSGeneral Pneumatics,fromtheGreekｹνευματικός(means-comingfromthewind)Pneumaticswasfirstdocumentedin60A.DPascal'sprinciple,statesthatpressureisconstantthroughoutastaticfluid. Pneumaticsaregenerallyusedforapplicationsinvolvinglessforcethanhydraulicapplications. Pneumaticsmaybecontrastedwithhydraulics,whichusesincompressibleliquidmediasuchasoilorwaterinsteadofair.Airiscompressible,isconsideredtobeafluid,andmostindustrialapplicationsuseapproximately80to100poundspersquareinch(psi)gaugepressure,ascomparedtohydraulicswhicharecommonlyusedfrom1,000to5,000psi,andinsomecases10,000psiandhigher. Bothpneumaticsandhydraulicsareapplicationsoffluidpower.Physicalpneumaticprinciplesconcludethatthepressurethatformsincompressibleliquidscanbeharnessedtoahighpotentialofpower. Pneumaticsystemscanprovidescompressedairataconstantflowratetoairconditioningunits,whereitstemperatureiscontrolledanditisductedintothecabin.Pressurizationsystems,restrictstheescapeofairfromthecabintomaintainproperpressurizationinthecabin.Thepneumaticsystemalsoprovidescompressedairforenginestarting. Theenginecompressors,auxiliarypowerunit,oragroundunitcanbeusedtosupplythepneumaticsystem.Thepneumaticmanifoldisnormallysuppliedfromtheengines.TheAPUoranexternalairsourcemayalsobeused. Instructionalpurposesonly PNEUMATICS-APPLICATIONS APPLICATIONSSomeexamplesPressurizationAnti-iceDe-iceRainremovalLiftenhancementAirconditioningEnginestartingPneumaticbrakingOther PressurizationPressurizedairforthecabincomesfromthecompressorstagesintheaircraft'sjetengines.Movingthroughthecompressor,theoutsideairgetsveryhotasitbecomespressurized.Theportiondrawnoffforthepassengercabinisfirstcooledbyheatexchangersintheenginestrutsandthen,afterflowingthroughductinginthewing,isfurthercooledbythemainairconditioningunitsunderthefloorofthecabin. Thecooledairthenflowstoachamberwhereitismixedwithanapproximatelyequalamountofhighlyfilteredairfromthepassengercabin.Thecombinedoutsideandfilteredairisductedtothecabinanddistributedthroughoverheadoutlets. Comparedtoothermodesoftransport,officebuildingsandotherenclosedspacesoccupiedbylargenumbersofpeople,today'sjetlinersprovideanenvironmentthatissuperiorinmanyrespects.Forexample,intheheatingandcoolingseasons,mostofficebuildingsprovideafarlowerpercentageofoutsideair--oftenaslowas20percentorevenless.Inaddition,buildingstypicallyhaveamuchlowerair-changerate,andthey'reseldomequippedwithhigh-efficiencyfilterslikethosefoundinairplanes. Afurtheradvantageforairplanepassengers:theoutsideairthatentersjetlinercabinsatcruisingaltitudesisgenerallymuchcleanerthanwhatisavailableforventilatingbuildingsandsurfacemodesoftransportation. Studieshaveconfirmedtheoverallsafetyandeffectivenessofcabinairsystems.Oneofthestudies,conductedfortheU.S.Government,wasthemostcomprehensiveofall.Itinvolvedanindependenttestingservicetakingairsampleson92randomlyselectedairlineflights.Thelevelsofpollutantssuchasfungiandbacteriawerefoundtobesimilartoorlowerthanthoseencounteredinnormalindoorenvironments.Also,levelsofcarbondioxidewerefoundtoaveragelessthanone-thirdthelimitrecommendedbytheAmericanConferenceofGovernmentalIndustrialHygienists.StudiesconductedbyBoeingandbyairlineshaveshownsimilarresults. Anti-iceAiracquiredfromenginebleedairisusedtopreventiceformationbyusingtheheatenergyoftheairtoheatthesurroundingsurface'sabovefreezing.Howeverthissystemdrawspowerfromtheenginetherebyreducingthrustpotential.Someaircraftdirectthisbleedairoverthefrontwindshieldforicepreventionaswellastheleadingedgesofthewingandtailsurfaces. Instructionalpurposesonly De-iceAiracquiredfromenginebleedair,vacuumpumps,oraircompressorstoremoveiceformationbyusingpressureoftheairtoinflate“boots”ontheflightcriticalareasoftheaircraft.The“boots”inflateandbreakthesurfacecohesionoftheicesotheforwardmotionoftheaircraftcanblowitoff. RainremovalAirisacquiredfromenginebleedair,vacuumpumps,oraircompressorstoremoverainfromthewindshield.Thishighvelocityair“blows”awayanywaterthatmaycomeincontactwiththatsurface.Instructionalpurposesonly LiftenhancementAiracquiredfromenginebleedair,vacuumpumps,oraircompressorsisdirectedtocriticalliftareasofthewingandcontrolsurfacestostrengthentheboundaryairnexttothewingssurface. AIRCONDITIONINGAirconditioningsystemsgeneratecoolairtothecabinandvitalequipment.Thesourceofthiscoolairiseitherintheformtwosystems;Freonbasedgassystem.DrivenbyelectricormechanicaldrivesystemClosedsystemUsesFreonastheheattransferagentAirbasedgassystemDrivenbybleedairfromthejetengines,orauxiliarysourceOpensystemUsesoutsideairastheheattransferagent Theairiscompressed,reachingthemaximumpressureandtemperatureinthecycle,byacentrifugalcompressor,drivenbybleedairfromthejetengines.Thehotairisdirectedtoaexpansionturbinewhereitisexpanded.Thisexpansioncausestheairtocoolwithoutachangeinpressure.Theair,nowcooled,isdirectedtoamixingchamber;herehotairfromthebleedairsystemismixedwithcoldairfromtherecyclingmachineforentrytothecabin.AIRCYCLEDEVICE BASICAIRCYCLEDEVICEMixingBoxCompressionandExpansionTurbinesDriveTurbineBleedAirCabinAirCEDTColdAirHotAirInstructionalpurposesonly Instructionalpurposesonly EnginestartingAirCartX-bleed EnginestartingInstructionalpurposesonlyAirCartX-bleed PneumaticBrakingThepneumaticbrakingsystemisanalternatesystemandisawayofprovidingpressuretomainbrakesintheeventofhydraulicsystemfailureinstalledonvariousaircraft.Thereisnoantiskidordifferentialbrakingavailablefromthepneumaticsource.Apneumaticbrakecontrolvalveoperatedbyahandleonthecaptain'sinstrumentpanelopensandmodulatesairbottlepressuretoatransfertube.Pressurizedhydraulicfluidfromthistubeisroutedtoashuttlevalveoneachmainwheelbrake.Theshuttlevalvemovestoblockthehydraulicpressureportofthemainbrakelineandpermitsfluidfromthistubetoapplythebrakes.Pneumaticbrakingisonlyusedwhenhydraulicpressureislost. Instructionalpurposesonly OtherApplicationsDiscuss Afewquestions….. 1.Airconditioningunits(opensystem)useoutsideairastheheattransferagent.True/False 1.Airconditioningunits(opensystem)useoutsideairastheheattransferagent.True 2.Pneumaticsaregenerallyusedforapplicationsinvolving_______forcethanhydraulicapplications.More/Less 2.Pneumaticsaregenerallyusedforapplicationsinvolving_______forcethanhydraulicapplications.Less 3.Anti-skidordifferentialbrakingwillnotbeavailablewhenusingpneumaticbrakes.True/False 3.Anti-skidordifferentialbrakingwillnotbeavailablewhenusingpneumaticbrakes.True 4.Acentrifugalcompressor,compressesairtoincreaseits____________&____________. 4.Acentrifugalcompressor,compressesairtoincreaseitsPressure&Temperature. 5.Someaircraftanti-icesystemsdrawpowerfromtheenginetherebyreducingthrustpotential.True/False 5.Someaircraftanti-icesystemsdrawpowerfromtheenginetherebyreducingthrustpotential.True 6.Pascal'sprinciple,statesthatpressureisconstantthroughoutastaticfluid.True/False 6.Pascal'sprinciple,statesthatpressureisconstantthroughoutastaticfluid.True 7.AJetlinerscabinair,isgenerallymuchcleanerthanwhatisavailableforventilatingbuildingsandsurfacemodesoftransportation.True/False 7.Ajetlinerscabinair,isgenerallymuchcleanerthanwhatisavailableforventilatingbuildingsandsurfacemodesoftransportation.True-Why? 8.Airfromenginebleedair,canbeusedtoremoverainfromthewindshield.True/False 8.Airfromenginebleedair,canbeusedtoremoverainfromthewindshield.True EndPneumatics THEEND