Experimental study of an auto-controlled automobile air conditioning system with an externally-contr

压缩机

AppliedThermalEngineering27(2007)

927–933

/locate/apthermeng

Experimentalstudyofanauto-controlledautomobileair

conditioningsystemwithanexternally-controlled

variabledisplacementcompressor

Zhao-gangQi

a

a,*

,Jiang-pingChena,Zhi-jiuChena,WeiHub,BinHe

c

InstituteofRefrigerationandCryogenics,ShanghaiJiaoTongUniversity,Shanghai200030,PRChinab

ShanghaiDelphiAutomotiveAirConditioningSystemCo.Ltd.,Shanghai201204,PRChinac

ShanghaiSANDENBEHRAutomobileAirConditioningCo.Ltd.,Shanghai200025,PRChina

Received11May2006;accepted28August2006

Availableonline27October2006

Abstract

Inthispaper,anexperimentalstudyofanauto-controlledmobileairconditioning(MAC)systemwithanexternally-controlledvar-iabledisplacementcompressor(EVDC)isperformedandanalyzed.AnewdisplacementcontrolmethodofEVDCisdevelopedconcern-ingaboutevaporatorcharacteristicsandin-cartemperature uctuation,whichindicatethequalityoftheMACsystem.Basedonoccupant’sthermalcomfort,thewind-tunneltestresultsshowthattheMACsystemwithanEVDCcanmaintainthedeviationofin-cartemperaturenomorethan2°Ccomparedwiththeoccupants’desiredone.ThisMACsystemgivestheoccupantsagoodthermalcomfortsensationintherapidchangingenvironment.ThecomparisonshowsthatthedischargepressurechangesofEVDCvaryfasterthanthatofthe xeddisplacementcompressor,whichre ectsthee ectoftheinternalclimatechanges.Ó2006ElsevierLtd.Allrightsreserved.

Keywords:Mobileairconditioning(MAC);Externally-controlledvariabledisplacementcompressor(EVDC);Controllogic;Performance

1.Introduction

Theoperationconditionofmobileairconditioning(MAC)systemisconsiderablydi erentfromtheresidentialairconditioning.Theambienttemperature,solarradiation,vehiclespeedhavegreatin uencesonthesystemperfor-mance.Itisatypicaltransient,nonlinear,complicatedandparameter-coupledsystem.Recently,withtheuseofexternally-controlledvariabledisplacementcompressors(EVDC)inMACindustry,agreatnumberofcontrollogicsofadjustingEVDCcharacteristicsmaketheMACsystemmorecomplicated.Nowadays,oneoftheresearchempha-sesforengineersandautomotiveindustryistocombinethesecharacteristicsintothecontrolstrategyandtodeveloptheadvancedandhighe ectivecontrollingdevices.

*

Correspondingauthor.Tel.:+862162933242;fax:+862162932601.E-mailaddress:qizhaogang@(Z.-g.Qi).

ItisacommonthoughtthattheliteratureregardingMACisnotabundantduetothefactthatthis eldistech-nologicallyandproductionoriented,andstronglyin u-encedbythemarketcompetition.Jabardaetal.[1]developedasteady-statecomputermodelofMACsystemwithVDCtosimulateandvalidatebyexperiments.TianandLi[2]alsodevelopedasimulationmodelandvalidated.TheirstudiesrevealedthatthereisaperformancebandforthesystemparameterrelationshipduetothefrictionalforcesbetweenthemovingcomponentsoftheEVDCwithinwhichallthesteady-statepointsfall.Nowadays,thecontrolstrategiesofSISO(singleinput,singleoutput)andMIMO(multipleinput,multipleoutput)havebeenproposedtoreachthetargetoftemperature,humidityandvolumecontrol[3,4].PIDauto-tuningwasappliedintoHVACsystemtocontroltheoutputsignalaccordingtothetransientcharacteristicofcontrolobjective,whichwasmoreadaptiveforactualairconditioningsystem[5–7].

1359-4311/$-seefrontmatterÓ2006ElsevierLtd.Allrightsreserved.doi:10.1016/j.applthermaleng.2006.08.017

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928Z.-g.Qietal./AppliedThermalEngineering27(2007)927–933

NomenclatureTe,surf

evaporatorsurfacetemperaturemeasuredbyresistancetemperaturedetector(RTD)

Te,surf,lowerlowerlimitvalueofevaporatorsurfacetem-perature

Te,surf,upperupperlimitvalueofevaporatorsurfacetem-perature

Tin-carcompartmenttemperaturemeasuredbyin-car

T-typethermocouple

Tsetsettemperature

Vdis

Vmin

displacementofcompressor

theminimaldisplacementofcompressor

Greeksymbolsae ectfactorofevaporatorsurfacetemperature

onthedisplacementofcompressor

be ectfactorofcompartmenttemperatureonthe

displacementofcompressor

Ingeneral,thecontrolvalveisusedtocontrolthedis-placementofEVDCinthetraditionalcontrolmethod,whosecontrolparametersalwaysweresuctionanddis-chargepressureofcompressor,orsuctionanddischargetemperature.Precisepressureandtemperaturetransducersimprovethesystemcost.AfterlotsofsimulationofVDC,YuanandChen[8]introducedanovelelectronicvalvewhoseactionisdeterminedbyspringforce,suctionpressureofcompressor,dischargepressureofcompressor,crankcasepressureandtheelectriccurrent.Theypresentedthatthecompressordisplacementcanbeadjustedaccordingtotheouterconditionsandpassengers’requirements.TianandLi[9]studiedtheMACsystemwithanEVDCnumerically.Theircalculationalresultsshowedthatthecompressordis-placementisdeterminedbynotonlythechangingvaluesbutalsothechangingdirectionofexternalparametersintheMACsystem.Theyalsofoundthattheircontrolmethodledtoatimelagwhentheambientconditionchan-ged.Benoualietal.[10]describedthemaindi erencesbetweeninternalandexternallycontrolcompressorsindetail,basedonanexperimentalstudyanalyzingtheirper-formancecharacteristics.Theydevelopedacontrolalgo-rithmforEVDCtakingintoaccountthefastvariationsoftheenginespeedoftypicalurbandrivingcyclesbasedontheperformancecharacteristics.Theirexperimentsresultsshowedthatthiscontrolmethodgainpossibleenergysavingcomparedwiththeinternalcontrolcompressor.

Asdescribedabove,mostopenliteratureswerefocusedonthesimulationandalgorithmdevelopmentoftheMACsystem.Inthepresentpaper,takingthesteadyin-cartem-peratureasthetarget,anewdisplacementcontrolmethodofEVDCisproposedandanexperimentalstudyoftheMACsystemwithanEVDCisperformedandanalyzed.2.ControlstrategyofEVDC

Inthispaper,theEVDCisanexternally-controlledvar-iabledisplacementcompressor,whichisdriventhroughabeltrollerconnectedwiththeengine.TheEVDCcanadjustthedisplacementthroughthecontrolvalvethatisdrivenbyanelectro-motor.AlotofexperimentalresultsshowthattherelationshipbetweenthedisplacementofEVDCandinputvoltageofEVDCisnonlinear.

InordertomaintainasteadyoperationofMACsystem,theevaporatorsurfacetemperaturemustbewithinaspe-ci crange(4–6°Cingeneral).Iftheevaporatorsurfacetemperatureislessthanthisrange,thedisplacementofcompressorshouldbedecreasedinordertoavoidtheevap-oratorfrosting.Iftheevaporatorsurfacetemperatureisgreaterthanthisrange,thecompressorshouldincreasedis-placementorbeinfulldisplacementoperationinordertosupplytheenoughsystemcoolingcapacity.

Ontheotherhand,thein-cartemperaturein uencestheMACsystemperformancegreatly.Thein-cartemperaturegreaterthanthepassenger’sdesiredtemperaturemeansmorecoolingcapacity.Whenthein-cartemperatureislessthanthepassenger’sdesiredtemperature,thesystemcool-ingcapacityshouldbedecreased.

Basedontheaboveanalysis,thedisplacementcontrolmethodisdeterminedbytheevaporatorsurfacetempera-tureandin-cartemperatureinsteadofsuctionanddis-chargepressureorsuctionanddischargetemperature,whicharethemainfactorsa ectthetransientdisplacementofEVDC.

Thedisplacementcontrolfunctionofvariabledisplace-mentcompressorbasedontheevaporatorsurfacetemper-atureandin-cartemperatureisasfollows:

Vdis¼aÂðTe;surfÀTe;surf;lowerÞ=ðTe;surf;upperÀTe;surf;lowerÞ

þVminþbÂðTin-carÀTsetÞð1ÞwhereTe,surfandTinÀcararemeasuredbyaresistancetemperaturedetector(RTD)andaT-typethermocouplelocatedinHVACandvehiclecompartments,respectively.Tsetisthein-cartemperaturepassengerdesiredtoachieve.aisthee ectfactorofevaporatorsurfacetemperatureonthedisplacementofcompressor.bisthee ectfactorofcompartmenttemperatureonthedisplacementofcompres-sor.Vministheminimaldisplacementofcompressorwhenthecompressorisoperatedinrealenvironment.Thevalueofaandbaredeterminedbylotsofcompressorbenchtests.

Aremarkablecharacterofthiscontrolstrategyistoachieveenergysaving.WecanreachthistargetthroughadjustingtheupperlimitvalueTe,surf,upperandlowerlimitvalueTe,surf,lower,whichissetaccordingtothecontrol

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requirements.ChangingTe,surf,upperandTe,surf,lowerinarel-ativehighrange,thecalculationaldisplacementwilldecreasecorrespondingly.Thepowerofcompressorthatisdrivenbyenginealsowilldecreaseandtheenginee -ciencywillincrease.

Asdescribedabove,itisdi culttorevealtherelation-shipbetweenthedisplacementandtheinputvoltageofdri-venmotorexactlyusingasimplecorrelation.Ingeneral,wecangetatableofthedisplacementversustheinputvoltageofdrivenmotorthroughexperiments.Forthesakeofthesimpli cationandthegeneralizationofthecontrolsystem,onlythelowerandupperlimitvaluesoftheinputvoltageareneeded.Theothermiddleinputvoltagesderivefromthelineardivisionofthelowerandupperlimitvalues.Experimentalresultsshowthatthelinearprocessisaccept-able.Fig.1showsthe owchartofdisplacementcalcula-tionofEVDC.Aftergainingthedisplacement,theinputvoltageofdrivenmotorcouldgetthroughlookupingtherelationshiptable.3.Experimentalsetup

Anauto-controlledautomotiveairconditioningsystemwithanEVDCisexperimentedinthewind-tunnel.Forthereasonofcomparison,anauto-controlledautomotiveairconditioningsystemwitha xeddisplacementcompres-sor(FDC)isalsotested.

Fig.2showstheschematicdiagramofthewind-tunnel.TheschematicdiagramofMACsystemisshowninFig.3.Thesystemconsistsofanexternally-controlledvariabledisplacementcompressor,aparallel owcondenser,alaminatedevaporator,H-typethermalexpansionvalve,controlpanel,aT-typethermocouple,aresistancetemper-aturedetector(RTD)andhoses.SomeSCM(SingleChipMicyoco)areassembledincontrolpanel.

Thetemperaturesignalsmeasuredbytheresistancetemperaturedetector(RTD)andT-typethermocouplearetransmittedintothecontrolpanel.Gainingthe

Fig.2.AschematicdiagramoftunneltestequipmentofMAC.

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930Z.-g.Qietal./AppliedThermalEngineering27(2007)927–933

Fig.3.AschematicdiagramofautomobileairconditioningsystemwithaEVDC.

Table1

Somemaincomponents’geometriesComponentsStyle

Geometry

EvaporatorLaminated268mm·225mm·90mmCondenserParallel ow670mm·463mm·16mmCompressorPXE16(EVDC)

Displacement:163(cm3)ExpansionThermostaticexpansionDenfoss2.5tonofvalve

valve

refrigeration

Table2

TheprecisionofthemeasureddevicesItems

Range

PrecisionVehiclespeed

0–200(kmhÀ1

)±0.1(kmhÀ1)AmbienttemperatureÀ30–60°C±1(°C)Relativehumidity15–95%

±5%

Sunlightpower0–1100(WmÀ2)±50(WmÀ2)Airvelocity

0–140(kmhÀ1)±0.5(kmhÀ1)Thermocouple(T-type)±0.1(°C)Pressuretransducer

0–18(bar)

±0.1(bar)

calculationaldisplacementbytheSCM,theinputvolt-ageofelectro-motordrivencontrolvalvecanbedeter-minedbytheoutputsignalofcontrolpanel.Eachinputvoltageofelectro-motorhasacorrespondingcompressordisplacement.

Somemaincomponents’geometriesareshowninTable1.Theexperimentsandambientconditionsareorga-nizedaccordingtotheShanghaiEnterpriseStandard[11].TheprecisionofthemeasuredinstrumentsisshowninTable2.RefrigerantusedintheexperimentsisR-134a.4.Resultsanddiscussion

4.1.PerformanceofEVDCsystem

Theevaporatorsurfacetemperaturechangesunderthedi erentambientconditionsareshowninFig.4.Thedesiredpassengercompartmenttemperatureis25°C.

Therangeofevaporatorsurfacetemperatureisalmostfrom5°Cto7°C,whichmeanstheevaporatorsurfacetemperaturechangesareasmallvalue.Forthedisplace-mentcontrolmethodofEVDC,theevaporatorsurfacetemperaturecanresultinasmallchangeofthedisplace-mentofcompressorregardlessofthesunload.

Thein-cartemperaturechangesunderthedi erentambientconditionsareshowninFig.5wherethepassen-gers’desiredtemperatureis25°C.Underdi erentambientconditions,thedeviationofin-cartemperatureisnomorethan2°C,especiallyat35°C,in-cartemperaturealmostretainat25°CduringthewholetestperiodbecausetheEVDCchangesthedisplacementquicklyandaccuratelywiththeambientconditionschanges.Forthedi erenttestperiodsandconditions,thecomparisonbetweenmeasuredin-caraveragetemperatureandthestandard[11]isshowninTable3.TheperformanceofMACsystemwithEVDChasagoodagreementwiththestandard[11].

Fig.6showsthatthedischargepressureofcompressorunderdi parisonbetweenEVDCandFDCsystem

Fig.7showsthatthecomparisonofin-cartemperaturebetweenEVDC(externally-controlledvariabledisplace-mentcompressor)systemandFDC( xeddisplacementcompressor)systemwhenambienttemperatureis35°C.Themeasurementstartedwhenthein-cartemperatureissteadyintwosystems.ForEVDCsystem,thein-cartem-peraturehardlychangesbeforetheambientconditionchanges.OtherwiseforFDCsystem,thereisanobvious uctuationbeforetheambientconditionchanging.Duringthewholetestperiod,thein-cartemperatureinEVDCsys-temcanconserveatasteadyvalueeventhoughthesunloadchangesabout24minlater.Otherwisein-cartemper-atureinFDCsystemhasagreatdecreaseatabout24minwhenambientconditionchanges,whichleadstoabadthermalcomfortandconsumesmoreenergy.

ThecomparisonofdischargepressureofcompressorisshowninFig.8whenambienttemperatureis35°C.Itpre-sentsthatduringthesteadytestperiodthedischargepres-sureofcompressorofEVDCsystemissteadierthanthatofFDCsystemeventhoughthecurveofdischargepressureofEVDCisawavestyle.ItisshowninFig.8thattheperfor-manceofrespondingtotheambientconditionschangesofvariabledisplacementcompressorisbetterthanthatof xeddisplacementcompressor.ThewavecrestofEVDCdischargepressureisabout15slaterwhenambientcondi-tionchangesandthemain uctuationlastsonlyabout30sandthenatarelativesteadywave.FortheFDCsystem,thewavecrestofFDCdischargepressureisabout1minlaterandthewhole uctuationlastsatleast1.2minandthenatarelativesteady

wave.

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Fig.4.Evaporatorsurfacetemperaturechangesunderthedi erentambient

conditions.

Fig.5.In-cartemperaturechangesunderthedi erentambientconditions.

Table3

Comparisonofin-cartemperatureateachmeasuredperiodundersummerconditionsTime(min)20406080110130160

Vehiclespeed(km/h)50805080

0(Idle)1100(Idle)

AircirclemodeRecycleRecycleFreshairFreshairRecycleFreshairFreshair

Standardin-caraveragetemperature(°C)624622626624633624640

Measuredin-caraveragetemperature(°C)23.6202523.632.623.839

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Fig.6.DischargepressureofEVDCunderthedi erentambient

conditions.

parisonofin-cartemperaturebetweenEVDCandFDCsystem.

Table4showsthatthemax uctuationtemperatureofEVDCunderthedi erentambientconditionsissmallerthanthatofFDC.Itmeansthattheperformanceofanauto-controllerMACsystemwithavariabledisplacementcompressorisbetterthanthatofMACsystemwitha xeddisplacementcompressor,becausetheformercansupplythepassengersmorecomfortablethermalenvironment.

5.Conclusions

Inthispaper,anewdisplacementcontrolmethodforthevariabledisplacementcompressorisdevelopedandthewind-tunnelexperimentsareperformed.Thecontrolmethodisproposedbasedontheevaporatorsurfacetem-peratureandin-cartemperaturechanges.The

experimental

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parisonofdischargepressurebetweenEVDCandFDCsystem.

Table4

Thecomparisonofmax uctuationofin-cartemperatureAmbienttemperature(°C)

Max uctuationtemperatureofEVDC(°C)Max uctuationtemperatureofFDC(°C)

221.01.3

310.81.3

350.51.5

[3][2]

resultsshowthatthedeviationofthein-cartemperaturefromthepassengers’desiredtemperatureisnomorethan2°Candtheperformanceisbetterespeciallyunderthehighambienttemperature.TheperformanceofaMACsystemwithavariabledisplacementcompressorisbetterthanthatofaMACsystemwitha xeddisplacementcom-pressor.Thecompressorresponsetothein-cartemperatureandambienttemperaturechangesofEVDCisquickerthanthatofFDC.ItisshownthattheEVDCsystemcansupplythepassengerswithamorecomfortableandsteadycom-partmentenvironmentthroughthecomparisonbetweenEVDCandFDCsystem.Acknowledgements

Theauthorswouldliketoacknowledgethe nancialsupportprovidedbyShanghaiMunicipalScienceandTechnologyCommission(GrantNo.03dz11013),andinparticular,Mr.LIYu-qin,Mr.ZHOUJiang-fengfortheirenormoushelpinexperimentsorganization.References

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