Numerical simulation of flow field in three types of standar

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AdvancedPowderTechnologyxxx(2010)

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AdvancedPowderTechnology

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Originalresearchpaper

Numericalsimulationof ow eldinthreetypesofstandardcycloneseparators

H.Sa khania,c,*,M.A.Akhavan-Behabadia,M.Shamsb,M.H.Rahimyana

a

SchoolofMechanicalEngineering,CollegeofEngineering,UniversityofTehran,Tehran,IranDepartmentofMechanicalEngineering,K.N.ToosiUniversityofTechnology,Tehran,Iranc

KIASACo.,3848,IndustrialEstateNo.1,Arak,Iran

b

articleinfoabstract

Thenumericalsimulationofthe uid owandparticledynamicsispresentedbyCFDtechniquestochar-acterizetheperformanceofthethreetypesofstandardcyclones.Thethreetypesofcyclonesnamed1D3D,2D2Dand1D2D.Thelengthofcylindricalpartofthebodyisequalto1,2and1timesofthebodydiameter,respectively;andthelengthoftheconicalpartis3,2and2timesofthebodydiameter.TheReynoldsaveragedNavier–StokesequationswithReynoldsstressturbulencemodel(RSM)aresolvedbyuseofthe nitevolumemethodbasedontheSIMPLEpressurecorrectionalgorithminthecomputa-tionaldomain.TheEulerian–Lagrangiancomputationalprocedureisusedtopredictparticlestrackinginthecyclones.Thevelocity uctuationsaresimulatedusingtheDiscreteRandomWalk(DRW).Thedepen-dencyofcyclonecharacteristicsonitsdiameterisinvestigatedandD50(Cut-Point)iscalculatedfordif-ferentParticleSizeDistributions(PSDs).Thenumericalresultsarecomparedwiththeexperimentaldataandthetheoreticalmodelandgoodagreementisobserved.

Ó2010TheSocietyofPowderTechnologyJapan..PublishedbyElsevierB.V.andTheSocietyofPowder

TechnologyJapan.Allrightsreserved.

Articlehistory:

Received24November2009

Receivedinrevisedform25December2009Accepted7January2010AvailableonlinexxxxKeywords:CFD

Gas–solid1D3Dcyclone2D2Dcyclone1D2Dcyclone

1.Introduction

Cyclonesarewidelyusedintheairpollutioncontrolandgas–solidseparationforaerosolsamplingandindustrialapplications.Withtheadvantagesofrelativesimplicitytofabricate,lowcosttooperate,andwelladaptabilitytoextremelyharshconditions,thecycloneseparatorshavebecomeoneofthemostimportantparticleremovaldeviceswhicharepreferablyutilizedinscienti candengineering elds.

Sincecycloneshavebeenusedextensivelyinvariousindustries,aconsiderablenumberofexperimental,numericalandtheoreticalinvestigationshavebeenperformedonthecycloneseparatorstothepresent.Amongthose,Stairmand[1]presentedoneofthemostpopulardesignguidelineswhichsuggestedthatthecylinderheightandtheexittubelengthshouldbe,respectively,1.5and0.5timesofthecyclonebodydiameterforthedesignofahighef ciencycy-clone.Intheagriculturalprocessingindustry,2D2Dcyclone(Shep-herdandLapple[2,3])and1D3Dcyclone(ParnellandDavis[4])designsarethemostcommonlyusedabatementdevicesforpartic-ulatemattercontrol.TheDinthe2D2Ddesignationreferstothebarreldiameterofthecyclone.ThenumbersprecedingeachDre-latetothelengthofthebarrelandconesections,respectively.A

*Correspondingauthor.Address:SchoolofMechanicalEngineering,CollegeofEngineering,UniversityofTehran,Tehran,Iran.Tel.:+982188005677;fax:+982188013029.

E-mailaddresses:H.Sa khani@me.ut.ac.ir,sa khani_hamed@http://doc.guandang.net(H.Sa khani).

2D2Dcyclonehasabarrelandconelengthstwotimesthebarreldiameter,whereasa1D3Dcyclonehasabarrellengthequaltothebarreldiameterandaconelengthofthreetimesthebarreldiameter.ParnellandDavis[4] rstdevelopeda1D3Dcycloneforcottonginsinanattempttoprovideamoreef cient nedustcollector.Thiscyclonedesignisreferredtoasthetraditional1D3Dcyclone.HoltandBaker[5]andFunketal.[6]conductedfur-therexperimentalresearchonthiscyclonedesignandreportedasigni cantimprovementinef ciencybymodifyingthetraditional1D3Ddesigntoemploya2D2Dinlet.Thismodi ed1D3Dcyclonedesignisreferredtoas1D3Dinthisarticle(Fig.1aandTable1).Wang[7]indicatedthat,comparedtoothercyclonedesigns,1D3Dand2D2Darethemostef cientcyclonecollectorsfor nedust(particlediameterslessthan100lm).Mihalskietal.[8]re-ported‘‘cyclinglint”nearthetrashexitforthe1D3Dand2D2Dcy-clonedesignswheretheParticulateMatter(PM)intheinletairstreamcontainedlint ber.Mihalskireportedasigni cantincreaseintheexitPMconcentrationforthesehighef ciencycyclonede-signsandattributedthistosmallballsoflint ber‘‘cycling”nearthetrashexitcausingthe nePMthatwouldnormallybecollectedtobepertedtothecleanairexitstream.SimpsonandParnell[9]introducedanewlow-pressurecyclonecalledthe1D2Dcyclonesforthecottonginningindustrytosolvethecycling-lintproblem.Wangetal.[7,10]studiedthethreeaforementionedcyclonessimultaneouslyandtheyproposedamathematicalmodelforcal-culatingpressuredrop,numberofactiveturnsandD50forthecyclones.

0921-8831/$-seefrontmatterÓ2010TheSocietyofPowderTechnologyJapan..PublishedbyElsevierB.V.andTheSocietyofPowderTechnologyJapan.Allrightsreserved.doi:10.1016/j.apt.2010.01.002

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H.Sa khanietal./AdvancedPowderTechnologyxxx(2010)xxx–xxx

Fig.1.(a)De nitionofthecyclonedimensionalparameters;(b)CFDMeshforthecyclones(1D3D).

Table1

Falsetimestepsusedforthesimulation.Parameters

Pressure

u(x-velocity)v(y-velocity)w(z-velocity)

k(turbulentkineticenergy)e(turbulentdissipationrate)Reynoldsstresses

Falsetimestep0.20.40.40.40.50.50.5

1D3D,2D2Dand1D2Dwhichtherehasnotbeenanyinformationaboutthe ow eld.Subsequently,comparisonsofthepressure,turbulenceintensityandvelocitydistributionfortheforegoingcy-cloneswithtwodifferentdiametersaremadetoinvestigatethedependencyofcyclonescharacteristicsonitsdiameter.2.Flowsimulation

Foranincompressible uid ow,theequationofcontinuityandbalanceofmomentumaregivenas:

Thecomplexityofthegas–solid owpatternincycloneshaslongbeenamatterofmanyexperimentalandtheoreticalworks.Atpresent,laserDoppleranemometry(LDA)andhot-wireane-mometryarefrequentlyemployedtostudyexperimentallythe owstructureinthecyclones.Asforthetheoreticalwork,compu-tational uiddynamics(CFD)codeshaveproventobeausefultoolforsimulatingcycl …… 此处隐藏：20300字，全部文档内容请下载后查看。喜欢就下载吧 ……