《气动技术》双语电子教案-吴洪明-Chapter1-Fact

FactsandTheoryofAirForindustrialpneumatics《气动技术》双语电子教案吴洪明Chapter1WUHANUNIVERSITYOFTECHNOLOGYLOGISTICSENG.DEPT.武汉理工大学物流工程系ContentsCompositionofairAtmosphericpressureIndustrialcompressedairPressurePressureunitsPressureandforceThegaslawsConstanttemperatureConstantpressureConstantvolumeGeneralgaslawAdiabaticcompressionWaterincompressedairLowtemperaturedryingFlowofcompressedairAirqualityClickthesectiontoadvancedirectlytoit《气动技术》双语电子教案吴洪明Chapter1CompositionofairTheairwebreatheisspringy,squashyandfluidinsubstanceWetakeitforgrantedthatwhereverthereisspaceitwillbefilledwithairAiriscomposedmainlyofnitrogenandoxygenCompositionbyVolumeNitrogen78.09%N2Oxygen20.95%O2Argon0.93%ArOthers0.03%《气动技术》双语电子教案吴洪明Chapter1AtmosphericpressureTheatmosphericpressureiscausedbytheweightofairaboveusItgetslessasweclimbamountain,moreaswedescendintoamineThepressurevalueisalsoinfluencedbychangingweatherconditions《气动技术》双语电子教案吴洪明Chapter1StandardAtmosphereAstandardatmosphereisdefinedbyTheInternationalCivilAviationOrganisation.Thepressureandtemperatureatsealevelis1013.25millibarabsoluteand288K(15OC)1013.25mbar《气动技术》双语电子教案吴洪明Chapter1ISOAtmospheresISORecommendationR554StandardAtmospheresforconditioningand/ortestingofmaterial,componentsorequipment20OC,65%RH,860to1060mbar27OC,65%RH,860to1060mbar23OC,50%RH,860to1060mbarTolerances±2OC±5%RHReducedtolerances±1OC±2%RHStandardReferenceAtmospheretowhichtestsmadeatotheratmospherescanbecorrected20OC,65%RH,1013mbarNoqualifyingaltitudeisgivenasitisconcernedonlywiththeeffectoftemperature,humidityandpressure《气动技术》双语电子教案吴洪明Chapter1AtmosphericpressureWeseevaluesofatmosphericpressureonaweathermapThelinescalledisobarsshowcontoursofpressureinmillibarThesehelppredictthewinddirectionandforceLOW1015mb1012mb1008mb1000mb996mb《气动技术》双语电子教案吴洪明Chapter1MercurybarometerAtmosphericpressurecanbemeasuredastheheightofaliquidcolumninavacuum760mmHg=1013.9millibarapproximatelyAwaterbarometertubewouldbeover10metreslong.Hg=13.6timesthedensityofH2OForvacuummeasurement1mmHg=1Torr760Torr=nilvacuum0Torr=fullvacuum760mmHg《气动技术》双语电子教案吴洪明Chapter1AtmosphereandvacuumThepowerofatmosphericpressureisapparentinindustrywherepickandplacesuctioncupsandvacuumformingmachinesareusedAirisremovedfromonesideallowingatmosphericpressureontheothertodothework《气动技术》双语电子教案吴洪明Chapter1IndustrialcompressedairPressuresarein“barg”gaugepressure(thevalueaboveatmosphere)ZerogaugepressureisatmosphericpressureAbsolutepressuresareusedforcalculationsPa=Pg+atmosphereForquickcalculationsassume1atmosphereis1000mbarForstandardcalculations1atmosphereis1013mbarLowrangeTypicalIndustrialrange01234567891011121314151617012345678910111213141516AbsolutepressurebaraGaugepressurebargFullvacuumAtmosphereExtendedIndustrialrange《气动技术》双语电子教案吴洪明Chapter1Pressure1bar=100000N/m2(Newtonspersquaremetre)1bar=10N/cm2Formeasuringlowerpressuresthemillibar(mbar)isused1000mbar=1barFormeasurementsinpoundspersquareinch(psi)1psi=68.95mbar14.5psi=1bar《气动技术》双语电子教案吴洪明Chapter1PressureunitsTherearemanyunitsofpressuremeasurement.Someoftheseandtheirequivalentsarelistedbelow.1bar=100000N/m21bar=100kPa1bar=14.50psi1bar=10197kgf/m21mmHg=1.334mbarapprox.1mmH2O=0.0979mbarapprox.1Torr=1mmHgabs(forvacuum)Moreunitsofpressure《气动技术》双语电子教案吴洪明Chapter1Pressureandforce《气动技术》双语电子教案吴洪明Chapter1PressureandforceCompressedairexertsaforceofconstantvaluetoeveryinternalcontactsurfaceofthepressurecontainingequipment.LiquidinavesselwillbepressurisedandtransmitthisforceForeverybarofgaugepressure,10Newtonsareexerteduniformlyovereachsquarecentimetre.《气动技术》双语电子教案吴洪明Chapter1PressureandforceThethrustdevelopedbyapistonduetoairpressureistheeffectiveareamultipliedbythepressureThrust=D240PNewtonspDmmPbarWhereD=TheboreofacylinderinmmP=Thepressureinbar.WerequireananswerinNewtons1bar=100000N/m2D2isthereforedividedby1000000tobringittom2andPismultipliedby100000tobringittoN/m2.Theresultisadivisionby10shownintheproduct40above《气动技术》双语电子教案吴洪明Chapter1PressureandforceTheforcecontainedbyacylinderbarrelistheprojectedareamultipliedbythepressurelDForce=D.l.P10NewtonsWhereD=thecylinderboremml=lengthofpressurisedchambermmP=thepressureinbar《气动技术》双语电子教案吴洪明Chapter1PressureandforceIfbothportsofadoubleactingcylinderareconnectedtothesamepressuresource,thecylinderwillmoveoutduetothedifferenceinareaseithersideofthepistonIfathroughrodcylinderisappliedinthiswayitwillbeinbalanceandnotmoveineitherdirection《气动技术》双语电子教案吴洪明Chapter1PressureandforceInabalancedspoolvalvethepressureactingatanyportwillnotcausethespooltomovebecausetheareastotheleftandrightareequalandwillproduceequalandoppositeforcesP1andP2arethesupplyandexhaustpressuresP1P2《气动技术》双语电子教案吴洪明Chapter1PressureandforceInabalancedspoolvalvethepressureactingatanyportwillnotcausethespooltomovebecausetheareastotheleftandrightareequalandwillproduceequalandoppositeforcesP1andP2arethesupplyandexhaustpressuresP1P2《气动技术》双语电子教案吴洪明Chapter1PressureandforceInabalancedspoolvalvethepressureactingatanyportwillnotcausethespooltomovebecausetheareastotheleftandrightareequalan