已阅读5页,还剩3页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
.PowderTechnology11220007986Studiesontheeffectofswirlnumbersonstronglyswirlingturbulentgas-particleflowsusingaphase-DopplerparticleanemometerL.X.Zhou),Y.Li,T.Chen,Y.XuDepartmentofEngineeringMechanics,TsinghuaUniersity,Beijing100084,PeoplesRepublicofChinaAbstractTheeffectofswirlnumbersontheflowbehaviorofstronglyswirlingturbulentgas-particleflowswithswirlnumbersofss0.47,1.0,.1.5and2.1insudden-expansionandcyclonechambersisstudiedusinga2-Danda3-DphaseDopplerparticleanemometersPDPA.Theaxialandtangentialtime-averagedandtherootmeansquareRMSfluctuationvelocitiesofgasandparticlephasesandparticleconcentrationaremeasured.Theresultshowsthattheswirlnumberhasanobviouseffectontheaxialvelocityprofiles,theRankinevortexstructureoftangentialvelocityprofiles,therelationshipbetweentwo-phasevelocities,theturbulenceintensitylevelandtheanisotropyofturbulence.Keywords:Gas-particleflows;Stronglyswirlingflows;PDPAmeasurement1.IntroductionSwirlinggas-particleflowsareencounteredincycloneseparators,cyclonecombustors,hydrocyclonesandswirlwxburnerrcombustors1,2.However,mostofthepresentwxstudiesarelimitedtoasinglegas-phaseflowfield35.wxYuuetal.3studiedthegasflowfieldinacycloneseparatorusingprobeandhot-wiresystems,andtheresultsshowareductionofgasaxialandtangentialvelocitiesinthepresenceofparticles.TheprobemeasurementsmadewxbySilvaandNebra4givesimilarresults.ThestudiesbywxOgawaetal.5demonstratedthattherewasnodistinctdifferencebetweenthedust-ladengasflowandthepureairflowinacyclonechamber.Obviously,probemeasure-mentscannotgivegas-particletwo-phaseflowfield.Stud-iesusingconventionalandmodifiedLaserDopplerVe-.wxlocimeterLDV2,6showsimilarbehaviorofgasandparticleflowfieldse.g.,Rankinevortexstructuresof.tangentialvelocityprofilesandslipvelocitybetweengasandparticlephasesinswirlingflows.However,eventhemodifiedLDVmeasurementscannotgivereliableresults,becauseitisunabletoidentifyparticlesizesandtheeffectofparticlesizeisincludedintheparticleturbulentfluctuation.ThephaseDopplerparticleanemometer)Correspondingauthor.Tel.:q86-10-6278-2231;fax:q86-10-6278-5569.E-mailaddress:L.X.Zhou.PDPAmeasurementsallowobtainingthedetailedinfor-mationofparticlevelocity,sizeandconcentration.ThePDPAwasfirstusedtostudysudden-expansionswirlinggas-particleflowwithswirlingnumberss0.47bySom-wxmerfeldandQiu7.Theirresultsdemonstratethedifferentbehaviorofparticlesofdifferentsizesinswirlingflows.However,noPDPAmeasurementsofstronglyswirlinggas-particleflowsarereported.Inthispaper,thePDPAsystemisusedtostudystronglyswirlinggas-particleflowsinsudden-expansionandcy-clonechamberswithtangentialinlets.Theswirlnumberswerevariedfrom1.0to1.5and2.1.Theresultsarecomparedwiththoseforthecaseofss0.47andana-lyzed.Thepurposeofthisstudyistoclarifytheeffectofswirlnumbersonthebehaviorofswirlinggas-particleflows.2.Experimentalset-upandmeasurementmethodsTheexperimentalset-upisshowninFig.1aandb.Itconsistsofatestsection,afeedingsystemandaPDPA.system.ThetestsectionisaplexiglasschamberFig.1b.withoneaxialinletf60mmplustwosymmetric.rectangulartangentialinlets68=32mm.Thechamberisatubeof812-mmlengthandaninnerdiameterof120mm.Ononeside,aslotisopenedandapieceofopticalglassismounted.Theexittubeisacylinderof1500mm()L.X.Zhouetal.rPowderTechnology1122000798680.Fig.1.a1:Dataprocessor;2:signalprocessor;3:converter;4:transformer;5:powersupply;6:waterpurifier;7:laser;8:lasercon-troller;9:splittinggroup;10:emitterunit;11:receiver;12:testsection;13:flowstabilizer;14:cycloneseparator;15:powderfeeder;16:flow.meter;17:valve;18and19:compressor.bExperimentalset-up.lengthand96mmdiameter,towhichalargersudden-ex-pansionchamberisconnectedforprotectingthetestsec-tionfromthedisturbanceofdownstreamflows.Acycloneseparatorisusedtocollecttheparticles.Twoblowerswithvariableflowratessupplytheaxialandtangentialflowsviathevalves,wherebytheflowratemaybeadjusted.Theflowratesweremeasuredbythreeseparateflowmeters.Sphericalglassbeadsofsizesrangingfrom0to150mmwereusedinmeasurements.TheparticlesizedistributionisshowninFig.2.Particlesbelow10mmweretakenasthegastracer.Thisavoidedmismatchedrefractiveindicesbetweenseedinganddispersed-phaseparticlesandalsoeliminatedinterferencebetweenparticles.Thewidesizedistributionallowsobtainingthedifferentbehaviorofpar-Fig.2.Particlesizedistribution.Fig.3.PDPAinstrumentation:1,laser;2,splitter;3and4,lens;5,measuringvolume;6,receiver;7,filter;8,detector.ticleswithdifferentsizes.Particlesareintroducedfromtheaxialinletusingascrewfeeder.A3-DPDPA,madebyDantecInc.,anda2-DPDPAmadebyAerometrics,wereusedtomeasuresudden-ex-pansiongas-particleflows.Asforthemeasurementtechnique,the3-DPDPAwithabackwardscatteringarrangementisshowninFig.3.Itisawell-knownandwidelyusedtechnique.TheparticlevelocityismeasuredbasedontheDopplerfrequencyshift.TheparticlesizeandconcentrationaremeasuredbasedonthephasedifferencecausedbyMiescatteringandthenumberofparticlespassingthemeasuringvolumeduringacertaintimeinterval.TheparametersoftheopticalsystemareshowninTables1and2.Themeasurementswereperformedatfivecross-sec-tionsinthechamber,andforeachsection,thereareabout2535measuringlocationsalongthediameter.Inthesingle-phaseflowmeasurement,morethan1000samplesweretakenateachmeasuringlocation,while20005000samplesweretakenfortwo-phaseflowmeasurement.TheinletflowconditionsaregiveninTables35.Theswirlnumberisdefinedas:D3r222rwurdrH0Ss,D3r22DrurdrH40whereDistheinletdiameterandDisthechamber34diameter.Duringtheexperiments,thetangentialinletflowveloc-itywasconstant,andtheaxialinletflowvelocitywasTable1TransmittingopticsUUUxyz.Wavelengthofthelasermm514488476.FrequencyshiftMHz404040.Beamseparationmm747474.Diameterofmeasuringvolumemm1.351.351.35.Focallengthofthelasermm500500500.Fringeseparationmm3.53.313.23Fringenumber363636()L.X.Zhouetal.rPowderTechnology1122000798681Table2ReceivingopticsThemaximumdetecteddiameter260.24mm53Themaximumdetectedconcentration2=10rcmOff-axialangle1478Focallengthofreceivinglength600mmThevaluablesignlevely6dBThemaximumphaseerror258Themaximumsphericalerror15%.increasedfrom0case1to12mrscase3,andinturn,decreasedtheswirlnumberfrom2.1downto1.0.3.ExperimentalresultsanddiscussionFigs.412showthemeasurementresultsforcyclonic.gas-particleflowswithss2.1case1.Thecomparisonbetweentheparticle-ladengasandthepuregasflowfieldisgiveninFigs.47.Figs.4and5showthegeneralbehaviorofcyclonictwo-phaseflowfieldw-shapedaxialvelocityprofileswithanannularreverseflowzoneandRankine-vortextangentialvelocityprofilesoftwophases.Itcanbeseenthatthepresenceofparticlesreducesthegastangentialvelocityeverywhere.Thegasaxialvelocitydecreasesinthenear-wallzone,butincreasesinthenear-axiszone.ThemeasuredfluctuationvelocitiesFigs.6and7showthecentralpeakandtheincreasedvaluenearthewall,becauseofthelargevelocitygradientinthesolid-bodyrotationregionandtheregionnearthewall.Thecomparisonbetweenthesetwofiguresshowsthattheaxialfluctuationvelocitiesaremuchsmallerthanthetangentialones,demonstratingthehighanisotropyofturbulentfluc-tuations.Moreover,thesefiguresindicatethatthepresence.ofparticlesreducesgasrootmeansquareRMStangentialfluctuationvelocityalmosteverywhereandaxialfluctua-tionvelocityinmostregionsbutincreasesthelatteroneinreverseflowzones.Forparticleconcentration,alargeamountofparticles.almostconcentratesinthenear-wallregionFig.12duetothestrongcentrifugalforce.Figs.811givethecomparisonbetweenthetwo-phasetangential,axialvelocitiestogetherwiththeRMSfluctua-.tionvelocitiesfortwo-particlesizes60and100mm.Table3.Inletflowconditioncase1Axialinletvelocity0mrsTangentialinletvelocity10mrsSwirlnumber2.1Particlemeandiameter76.3mm3Particlematerialdensity2400kgrmParticlemassloading0.01kg-solidrkg-gasTable4.Inletflowconditioncase2Axialinletvelocity5mrsTangentialinletvelocity10mrsSwirlnumber1.5Particlemassloading0.01kg-solidrkg-gasFigs.8and9showthattheparticletangentialvelocitylagsbehindthegastangentialvelocityalmosteverywherewiththelargerparticleshavinglowervelocitiesduetotheirhigherinertia.Theparticleaxialvelocitylagsbehindthegasaxialvelocityonlyinthenear-wallregion.ItcanbeseenfromFigs.10and11thattheparticleturbulentfluctuationislowerthanthegasfluctuationinmostre-gionsbothinaxialandtangentialdirections,andthelargertheparticlesize,thesmallertheparticlefluctuation.Figs.13,1518givethemeasurementresultsforthe.sudden-expansionflowswithss1.5case2.AscanbeseenfromFig.13,inthiscasetheaxialvelocitiesoftwophaseshavenow-shapeddistributionsasthatforthecases.ofss2.1Fig.4and0.47Fig.14,butarehigherneartheaxisandlowerwithasmallpeaknearthewall.Theparticleaxialvelocitylagsbehindthegasoneinmostregions,andthevelocityslipbetweentwophasesincreaseswiththeincreaseinparticlesize,buttherelativeslipisnotverylarge.Inthenear-wallregion,theparticleaxialvelocityisslightlylargerthanthegasvelocity.Theparti-cletangentialvelocitylagsbehindthegastangentialveloc-.ityFig.15,andthelargertheparticlesize,themorethelag.Inthefirstandsecondsections,thestructureofrigidbodyrotationintangentialvelocityprofilesisnotobviousbecauseoftheinjectionofaxialnon-swirlingflows.Inthesubsequentsections,duetotheincreasingeffectofcentrifugalforce,thetangentialvelocitydistributionoftwophasesshowsanobviousRankine-vortexstructurewiththegraduallyvanishingeffectofinletconditions.Fig.16givestheparticleandthegasaxialfluctuationvelocitieswithhigherv
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 安徽省宿州市商贸城消防安全测试题七(含答案)
- 吉林省白城市园区消防安全测试题十九(含答案)
- 2024年湖南省娄底市双峰县中考模拟预测生物试题
- HDAC6-IN-34-DataSheet-生命科学试剂-MCE
- 科技馆软装设计合同范本
- 铁路工程地勘合同范本
- 公共安全管理横向课题合同书
- 广播电视服务合同范本
- 教科版科学一年级下册第一单元《我们周围的物体》测试卷A4版可打印
- 网络行业正规劳动合同范本
- 2024年湖北武汉铁路职业技术学院招聘预告高频考题难、易错点模拟试题(共500题)附带答案详解
- 国际职场交流英语(中级)智慧树知到答案2024年昆明理工大学
- 校外劳动实践基地协议书
- 黑龙江大庆一中2024届高考化学二模试卷含解析
- 基于SWOT-AHP的连云港港口物流发展战略研究分析 物流管理专业
- 2024年广西壮族自治区贺州市中考一模数学模拟试题
- 改革后-topik考试作文纸
- 《热学》(李椿 ) 电子教案().ppt
- K19系列发动机气门喷油器调整方法.ppt
- 水凝胶的应用和研究进展
- 企业所得税汇算清缴业务约定书 .doc
评论
0/150
提交评论