道路吸尘清扫车吸嘴的颗粒去除性能的数值模拟研究大学毕业论文英文文献翻译及原文.docx

道路吸尘清扫车吸嘴的颗粒去除性能的数值模拟研究大学毕业论文英文文献翻译及原文.docx

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道路吸尘清扫车吸嘴的颗粒去除性能的数值模拟研究大学毕业论文英文文献翻译及原文

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道路吸尘清扫车吸嘴的颗粒去除性能的数值模拟研究

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2017.02.14

附录Ⅱ

Numericalstudyonparticleremovalperformanceofpickupheadforastreetvacuumsweeper

BofuWu*,JinlaiMen,JieChen

SchoolofMechanicalEnglishShanghaiJiaoTongUniversity，Shanghai,200240,China

ABSTRACT

Thepurposeofthispaperistoinvestigatetheparticleremovalperformanceofpickupheadforastreetvacuumsweepernumerically.Anintegrated3Dnumericalmodelwasconstructedbasedonparticlesuctionprocessincomputationalfluiddynamics（CFD）software.Theairflowthroughthepickupheadwastreatedasacontinuum,whileparticlesweremodeledasdispersedphase.TheReynoldsstressmodel（RSM）anddiscreteparticlemodel（DPM）werechoseninordertopredicttheairandparticlesflowaccurately.Thenumericalsimulationresultsshowthatthesweeper-travelingspeedandthepressuredropacrossthepickupheadhavegreateffectsontheparticleremovalperformance.Theremovalefficiencyofparticlesincreaseswiththelowersweeper-travelingspeedorthehigherpressuredrop,andsmallsizeparticleshavehighergradeefficiencythanthatoflargesizeparticlesunderthesameoperatingconditions.Moreover,theremovalmassflowrateofparticlesincreaseswiththehighersweeper-travelingspeed.Therefore,atrade-offshouldbeconsideredamonghighremovalefficiency,lowenergyconsumption,andhighremovalmassflowrate.Throughthenumericalsimulation,theeffectivenessofstreetvacuumsweeperforremovingparticlesfromroadsurfaceisevaluated,andanoptimaloperatingconditionisobtained.Besides,moreinformationisgeneratedtobetterunderstandtheparticlesuctionprocessofthepickuphead.

Keywords:

Pickuphead;Particleremovalperformance;CFD;Sweeper-travelingspeedPressuredrop

1.Introduction

Currently,thereisawidespreadconcernoverthepollutionofparticlematter.Dustandsiltarethemajorsourcesofparticlematterpollution,theremovalofwhichthereforeattractsconsiderableattention[1].Streetsweepingistypicallypracticedtoremovetheaccumulationofdustandsiltfromroadsurfacetoimproveaesthetics,publichealthy,andstormwaterquality,soitisconsideredasaneffectivepollutantcontrolpracticeformanylocalauthorities[2,3].Pickupheadisthekeycomponentofstreetvacuumsweeper,whichisdesignedtopickupparticlesefficientlyfromroadsurfaceandsendthemtodustcollectionhoppersmoothly.Theparticleremovalperformanceofthepickupheadisthemostimportantindexforastreetvacuumsweeper.

Manyresearcheshavebeenperformedonestimatingtheparticleremovalperformanceofstreetsweeping.Forexample,astudybyChangetal.[4]evaluatedtheeffectivenessofstreetsweepingandwashingforcontrollingambienttotalsuspendedparticlesbyexperiments,whichindicatedthatthestreetsweepingandwashingprocesswaseffectiveatremovingdustandsiltfromurbanroads.However,someresearcherssuchasVazeandChiew[5]consideredthatthecontributionofstreetsweepingtoenvironmentalqualitywasnotveryclear,andmayhaveanadverseimpactbecausestreetsweepersdidnotpickupsmallersizeparticleseffectively.KangandStenstorm[6]studiedthestreetsweepingeffectivenessasastormwatermanagementpracticebyusingstatisticalpoweranalysis.Theypointedoutthattheeffectofstreetsweepingshouldnotbeunderestimatedbecausesomepreviousresearcheswerebasedoninsufficientdata.Therefore,newmethodswereneededtoevaluatethestreetsweepingeffectiveness.

Astheparticleremovalperformanceforstreetvacuumsweepervariesbasedonsweepingtechnology,operatingconditions,sweepingfrequency,streetdirtloadingandparticlesizedistribution[7],itisnecessarytodeveloparepeatableandreliablemethodtocalculatetheparticleremovalperformanceofpickupheadforastreetvacuumsweeper.Inordertoevaluatetheparticleremovalperformanceofpickuphead,engineersgenerallyconcentrateontwoparameters,thesweeper-travelingspeedandthepressuredropacrossthepickuphead.Theirinfluencesontheparticleremovalefficiencyandtheparticleremovalmassflowratedirectlyrelatetotheperformanceofthestreetvacuumsweeper.Chenetal.[8]investigatedtheinfluenceofsweeperstructureandsweeper-travelingspeedontheparticleremovalperformancebyexperiments.Theyfoundthatthewingplateofpickupheadandthesweeper-travelingspeedhadgreatinfluenceonthecriticalpickupvelocityofparticles.Meanwhile,theyanalyzedtherelationshipoftheparticlepickupvelocitiesandtheairflowrates.

Withtherapiddevelopmentofthecomputertechnology,thecomputationalfluiddynamics（CFD）hasbeensuccessfullyadoptedtostudyvariousindustrialpneumaticconveyingprocesses[9,10].Althoughmanyworkshavestudiedtheparticleremovalperformancebyexperimentsoverthepastdecades,fewworksconsideredtheparticleremovalperformanceofpickupheadusingCFD.Xuetal.[11]conducteda3Dnumericalsimulationontheflowfieldofpickupheadandgassystemforahighwaymechanicalsweeper.Theyanalyzedtheinteractionbetweenthepickupsystemandthefiltersystem,andoptimizedthecombinedsystembasedonnumericalresults.Zengetal.[12]employedtheCFDtechnologytosimulatetheflowfieldofpickuphead.Thestudyshowedthattheperformanceofstreetsweepingwasimprovedsignificantlybychangingthestructureofpickuphead,andthenumericalsimulationprovedthattheCFDwasaneffectivetooltocalculatetheflowfieldcharacteristicsofpickuphead.However,theseworksdidnotaccountfortheinfluenceofparticlesontheflowfieldduringtheinvestigation,sotheparticleremovalefficiencyandtheparticleremovalmassflowratecannotbeobtained.Moreimportantly,influencesofthesweeper-travelingspeedandthepressuredrop,whicharethemostimportantparameters,shouldnotbeneglectedwhilemodelingtheperformanceofpickuphead.

Gascycloneisthedevicethatutilizescentrifugalforcetoseparateparticlesfromcarriergas,whereaspickupheadforastreetvacuumsweeperisthedevicethatemploysvacuumpressuretosuckupparticlesfromroadsurface.Therefore,theparticleremovalperformanceofpickupheadwillbealsocalculatedbyusingtheCFDapproach,whichhasbeenvalidatedbythesuccessfulinvestigationoftheparticlecollectionperformanceofgascyclones[13,14].

Theaimofthepresentstudyistoinvestigatetheparticleremovalperformanceofpickupheadundervarioussweeper-travelingspeedsandpressuredropusingcommercialCFDprogramFluent6.3.ThenumericalCFDmodelisverifiedbysweepingfieldexperiments.Basedonthenumericalresults,thebalanceamongtheparticleremovalefficiency,thepressuredropacrossthepickupheadandtheremovalmassflowrateisconsidered,andanoptimaloperatingconditionisobtained.

2.Sweepingfieldexperiments

Astreetvacuumsweeperwithanenginepowerof57kwwasusedinthiswork.Itusedanelaboratelydesignedvacuumsystemfordustspickup.Fig.1showedthatthestreetvacuumsweeperwaspickingupsandparticlesfromexperimentalroadsurfacebyusingapickuphead.Asstreetvacuumsweepermovesforward,thecentrifugalfanmountedonthesweeperestablishesavacuuminthedustcollectionhopper.Particleslayatrestontheroadsurfaceinitiatetoroll,slideandbounceascertainairflowvelocityisreached,andthentheyarevacuumedthroughthefournarrowslots（front,rear,leftandright）intothepickuphead.Afterenteringthepickuphead,mostparticlesarepickedupbytheairflowandthensentfromoutletintothedustcollectionhopperthroughavacuumhose,butsomewillescapefromtherearnarrowslottotheoutsideofthepickuphead.TheschematicdiagramofthepickupheadusedinthesweepingfieldexperimentsisshowninFig.2,anditsmaindimensionsaregiveninTable1.

Fig.1.Pickingupsandparticlesfromroadsurfaceinthefieldexperiments.

Fig.2.Schematicdiagramofthepickuphead.

Inthefieldexperiments,thesafetyfactorwasvitalimportantbecauseitwouldbedangerousifmeasurementsstoppedtraffic.Therefore,aroadwithouttrafficwaschosen,asshowninFig.1.Ontheroadsurface,a2.0m×1.8msamplingsurfacewasselectedandpaintedwhite.Sandswerespreaduniformlyonthesamplingsurfaceastestparticleswiththedensityof2500kg/m3,andthemassloadingwassetas0.1kg/m2.ThesandparticlesizedistributionYdbymasscanbedefinedbyusingRosin–Rammlerdistribution

wheredpistheparticlediameter,d̅istheparticlemeandiameterandnisthespreadparameter.

Calculatedfromthesanddata,theparticlemeandiameterandthespreadparameterare81μmand5.95,respectively.ThecumulativesizedistributionofsandparticlesisplottedinFig.3.

Fig.3.Thecumulativesizedistributionofsandparticles.

Thesweepingfieldexperimentswerecarriedoutatthesweepertravelingspeedof6,7,8,9,10,11,12,13,and14km/h,andtheparticleremovalefficiencywasobtainedbymeasuringthemassofthecollectedsandsfromthesamplingsurfacebeforeandaftersweeping.Theairflowvelocityandpressuredropmeasurementswereperformedusinghot-wireanemometryandmanometer,respectively.

3.Physicalmodelandgridgeneration

Inordertosimulatetheparticlesuctionprocessdescribedabove,severalassumptionsweremadeinthisstudy,asillustratedinFig.4.

1）Thepickupheadmovedforwardataconstanttravelingspeedduringstreetsweeping.

2）Aroundthefournarrowslots,therewasanexter