锅炉燃烧器外文翻译Word下载.docx
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锅炉燃烧器外文翻译Word下载.docx
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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.Chacó
netal.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℃.
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