锅炉燃烧器外文翻译.docx

锅炉燃烧器外文翻译.docx

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锅炉燃烧器外文翻译

Experimentalstudyonflowandcombustioncharacteristicofanovelswirlingburnerbasedondualregisterstructureforpulverizedcoalcombustion

abstract:

Anovelspoutstructurewhichcontainsdual-gearrings（DGR）anddoubleconicalflaring（DCF）forswirlingburnerisproposed.Flowfieldoutsidethenovelburner（DGR–DCFburner）isstudiedinanunconfinedenvironmentcomparingwithaconventionalone.TheeffectsofDGRandDCFstructures,secondaryairdistributionandswirlingintensityonreverseflowandturbulencearediscussed.Resultssuggestthatthenovelburnerstabilizesreverseflowandenhancesturbulenceoftheflowfieldunderdifferentairdistributionsandswirlingintensities.Thenovelburnerisfurtherstudiedinawall-firedpilotfurnace.Gastemperaturedistribution,NOxemissionandunburnedcarbonintheflyashareresearched.Higherignitiontemperatureneartheburnerspoutandamorestabletemperaturefieldinthefurnaceisformedwiththenovelburner.ReductionofNOxemissionandunburnedcarbonintheflyashareachieved.Themomentumratio（M）ofinnersecondaryairtoouterprimaryairisdefinedtouniformthesecondaryairdistribution.IncreaseofMraisesthetemperaturelevelneartheburnerspout.NOxemissionandtheunburnedcarbonintheflyashbothattaintheirminimumwithM=4.428intheexperimentrange.

2014ElsevierInc.Allrightsreserved.

Keywords:

Swirlingburner、Spoutstructure、Flow、Combustion、Airdistribution

1.Introduction

Coalisthefundamentalfossilenergysourceintheworld.Thepulverizedcoalburnerisconsideredasanimportantcombustionequipmentwhichaffectsthecoalcombustionefficiency,safeandstableoperationofboilersystemandpollutionemission.Researchershavedonealotofstudiesoncoalcombustionandpollutionemissioncontrol,suchasdense-dilutecombustion,low-NOxburner,flowfieldorganization,fluegasdesulfurationanddenitration.Becauseofitsconvenientadjustment,lowercostandimportanteffectoncombustion,swirlingburnerofpulverizedcoalisalwaysahottopicforthermalengineeringresearchers.Smartetal.presentedthedevelopmentofacoalfiredprecessingjetburner,theprogramofwhichbeganin1994becauseofthefurtherincentivefortheutilityboilermarket,andwereperformedindepthin1999.TheystudiedtheeffectofprecessingjetmomentumratioandgunpositiononNOxemission,heatfluxandignitiondistanceindetail.Theresultsshowedapositiveinfluenceoftheuseofprecessingjetoncombustioncharacteristic.Costaetal.focusedonthegastemperatureandspeciesintheburnerregionofafrontwallfiredboiler.TheyobtainedtemperaturelevelintheburnerregionandNOxconcentrationabovetheboilernosein1997.Theworkprovidedaconsiderableefforttominimumvariationsonboileroperatingconditionsandareferencefor3Dmathematicalmodelevaluationanddevelopment.Bollettinietal.operatedastudyonscalingofnaturalgasburnersandintegratedsubstantialexperimentaldatafromscaling400projectswithCFDsimulationin2000.In2001MilaniandSaponarointroducedthedilute/flamelesscombustiontechnologyandthehighvelocityburners,theemphasisofwhichisonfluiddynamicentrainmentandmixingoffluegases.ThetemperaturedistributionofflamelesscombustionwasdifferentwithconventionalflamecombustionandtheNOxformationwascontrolled.Nettletonstudiedtheeffectofswirlingangelsofsecondaryairstreamonflamestabilityandsuggestedsomeexplanationfortheexistenceofstabilitylimitsin2004.Guetal.analyzedtherelationamongtheNOxformation,gasflowandpulverizedcoalmovinginaswirlingburnerwithnumericalsimulation.Theauthorsfoundthatthemaximumparticlepenetrationdepthintotheinternalrecirculationzone（IRZ）LdavandeffectivetimeofIRZτeavleadtotheminimumoutletNOemission.Chacónetal.developedanewmethodologyforthedesignandptimizationofalowNOx-CO,naturalgasburnerbynumericalsimulationtocomplywithNOxemissionlimitsofEuropeancountries.Jingetal.researchedtheeffectrulesofoutersecondaryairvaneangelsandprimaryairratioonflow,combustioncharacteristicandNOxemission.Lietal.studiedthefurnacetemperature,heatfluxandcharburnoutwithdoubleswirlingflowburneratdifferentloads.

ToimproveboththecombustionperformanceandNOxemission,optimizationsofswirlingburnerstructureforpulverizedcoalareproposedandstudiedcontinuously.TheBabcock&WilcoxCompanyinNewOrleans,LaRueandWolfproposedanimprovedburnerwithasplashplate,deflectorandadiffusertodecreasethenozzlepressuredropandNOxformationin1983.Babcock-HitachiKabushikiKaishainTokyoprovidedacoalcombustionapparatusforNOxreductionwhichcomprisescoalpipe,multi-airpassagewaysandbluffbodyin1985.SteinIndustrieinFranceprovidedanaxialconduitforfeedingfuelin1987,whichisadjustableforvaryingthepreliminarymixingchamberlengthandsupportstheignitionandcombustion.TheBabcock&WilcoxCompanyalsoin1989proposedaflamestabilizingringandretractablegaselementtocreatealowoxygen/fuelrichflameresultinginreducedNOxformation.Tenovaalsostartedin2002aresearchprogram,whichledtoanewfamilyoflowNOxburnersnamedFlexyTech

TSXbasedontheflamelesstechnologywhichallowstoreachalowNOxemission.Orfanoudakisetal.havestudiedtheeffectofswirlnumberonflowandparticlecharacteristicespeciallynearinternalrecirculationzone（IRZ）inthenear-burnerregionofamulti-fuellaboratoryburnerin2005.Lietal.in2008madeacomparisonbetweenanenhancedignition-dualregister（EI-DR）burnerandcentrallyfuelrich（CFR）swirlingburnerexperimentallyoncombustioncharacteristic,andfoundthatCFRburnershavehighercombustionefficiency,lessNOxemissionandmorestableflameatlowloadina300MW（e）wall-firedutilityboiler.Toburnlowrankcoalcentrally-fuelrichswirlingcoalcombustionburnerwasproposedandstudiedbothexperimentallyandnumericallybyChenetal.Theyfocusedonthegas-particleflowanalysistocontrolthegastemperaturelevelandNOxformation.Withdevelopmentofmeasurementtechnologyandnumericalcalculation,theinvestigationsonswirlingburnersbecomemorecomprehensive.Allouisetal.proposedanewdiagnostictoolbasedonfastinfraredimagingtotestthecombustionstabilityforburnersandhelpadjustingflame.Khanaferetal.usedcomputationalfluiddynamicssimulationcoupledwithchemicalequilibriumcalculationtoanalyzeNOxformationinswirlingburners.Allthestudiesontheswirlingburnermentionedabovehavemainlyfocusedontheeffectsofairdistribution,swirlingintensityandretrofitstructuresoncombustionandNOxemission.

However,littlestudyofnovelflameringandflaringeffectontheswirlingburner,whichhavesignificantimpactonflowandcombustion,hasbeenreported.Inthispaper,anovelburnerspoutwithdual-gearrings（DGR）anddoubleconicalflaring（DCF）isproposedasshowninFigs.1and2.Coldairtestandcombustionexperimentarecarriedoutunderdifferentsecondaryairdistributions,swirlingintensitiesandcoaltypes.Theflowcharacteristic,combustionperformanceandNOxemissionarediscussed.Comparingwithaconventionalone,thenovelburnerisprovedtobehelpfultoobtainstable,efficientandcleancombustionforpulverizedcoal.

2.Novelburnermodel

Theproposednovelstructureswereinstalledonaradialdualregisterburner,whichisgeometricsimilaritywiththeratioof1:

6totheprototype,thedualregisterswirlingburnerofWGZ1246/18.-1boilermadebyWuhanBoilerGroupCo.,Ltd.InChina.DGRwassetintheinnerprimaryairpipeoutletinordertoenhancetheturbulenceandmixingofprimaryairandpulverizedcoalinthefuel-richandoxygen-leanzoneinFig.1.DCFwassetontheouterprimaryairpipe,soastoinduceouterprimaryairtowardscenterrecirculationzoneanddelaythemixingofsecondaryairandprimaryairasFig.2shows.Thenovelburnerspoutisexpectedtoreducetheignitionheatandformafuel-richfieldnearthespoutintheignitionzone.

Fig.1.DesignconceptofDGRininnerprimaryairpipe（a）traditionalinnerprimaryairspout（up）;（b）DGRintheinnerprimaryairspout（down）.

Fig.2.DesignconceptofDCFontheouterprimaryairpipe（a）traditionalspout（up）;（b）DCFspout（down）.

3.Coldairteststudy

3.1.Coldairtestprocedureandmethods

Duetothelimitationofflowfieldmeasurementunderapracticalcombustionstate,theisothermalmodelingexperimentisusuallyoperatedtostudytheflowcharacteristic.Accordingtothemodelingprinciple,theairflowwithmorethan1.0×10∧5ofthecriticalRenoldsnumbertosecondself-modelingzonewasselected.

AdimensionlesscoordinateisbuiltwithRandXintwodirectionsfordescribingflowfieldposition.R=r/d3,andX=x/d3,whererrepresentstheradialdistanceoffthecentralaxisoftheburner,xstandsfortheaxialdistanceofftheendoftheburner’sjet,whiled3isthediameterofISAduct.

Twosetsofmeasuringpointarrayswereintroduced.A6×31arraywassetnexttotheburnerspoutinwhichtheradialdistancebetweentwoclosedmeasuringpointswasDR=0.1,whiletheaxialdistancewasDX=0.3.Meanwhile,a5×29arraywassetafterinwhichDR=0.2andDX=1.0.A1050Atypedual-channelhotwireanemometerwiththerangeof0–30m/sandresolutionof0.01m/swasusedtomeasurevelocityandturbulenceinstantaneously,whilethedirectionofvelocitywasobtainedbyribbontracermethod.Themeasurementerroris5%ofindicationor0.025m/sunderthetemperaturerangefrom18℃to93℃.