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Simulation and analysis of airflow stability during fire in mine belt roadway

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Simulation and analysis of airflow stability during fire in mine belt roadwayof,in,and,fire,mine,belt,Mine

    Simulation and analysis of airflow stability

    during fire in mine belt roadway JoURNALoFCoALSCIENCE&ElFGI]NEERING

    (CHINA)DOI10.1007/s12404010.-04089

    PP375-380V0L16No.4Dec.2010

    Simulationandanalysisofairflowstabilityduringfireinmine

    beltroadway

    ZHANGShengzhu',CHENGVVei.min,LIQiu-jin.,ZHANGRui,LUOChuanlong'

    (1.FacultyofResourcesandSafetyEngineering,ChinaUniversityofMinfngandTechnology(Beijing),Beijing100083,

    China;2.CollegeofResourceandEnvironmentalEngin~ering,ShandongUniversityofSdenceandTechnology,Qing0ao

    266510.,China;3.ShanghaiInstituteofWorkSafetyScience,Shanghai200233,China)

    TheEditorialOffi(eefJoumalofCoalScienceandEngineering(China)andSpringer--VerlagBerlinHeidelberg2010

    AbstractAccordingtofluiddynamicsanalysisduringthefire,thecriteriak-etwo-.equation modeIforsolvingthree.,dimension~Iturbulencewasdetermined.thepollutantsgenerated inthefiredisasterweresetbyadoptingMixturemultiphaseflcw.andtheSIMPLEalgo. rithmwasusedforsolvingonthebasisofcomprehensivecOnsideratiOnontheheatradia

    tionandcomponentstransmissionduringfire.Bysimulatingtheairflcwflowingstateinside thetunneIduringfiredisasterofdownwardventilation.driftventilation.andascensionaI ventilation,respectively,withregardtotheactuaIsituationofNo.1,No.3,andNo.5belt roadwayinKongzhuangCoalMine.thevelocityvectordistributionsofpollutantsunder differentinletairvolumeswereobtained.andthedamagedegreeandinfluentialfactorsof disasterwerealsoclear.whichishelpfultocontroIandavoiddisasterduringbeltroadway fire.

Ke~ordsbeltroadway,disasterairflow,,stability,numericalsimulation

    Enhancingcoalltransportationcapacittyunder- groundthoughbeltconveyorshoweverpotentially leadstofrequentfirehazardstomineinitsproduction becauseofitsvvo],rkingprinciple.slructuralJcharacter-. istiesspecialloperatingenvironment,andsoon.T'he themaleffectgeneratedduringnrerdndactingoillhe undergroundairfl~owwillaffectthestabilfityofvent:ila-. donsystemandresultinspreadoftoxicsubstances releasedfr"O1TIbeltcombustionthLroughunstableair-. flGwandwiderangeofheavycasualties.Forexample, thefireaccidentoccurringo131hesecondconveyorin blindinclineshalfiofPinghuCoalMineofFengcheng CoalMiningBuleauiLnJian2xiProvinceon1No

    vember,2000.Inordertosimulateminefire,R.E. Greuerand1winhavecompiledprogramsfor

    tT'ansientsimulatdon.T.RStefanovandotherfo,reign scholarshavestudiedthest,;aleofairf1cwduringfitic (Wangeta1..1996;WuandBaker,2000;Kunsch. 2002;Jurij,2003).ManyChinesescholars,suchas ZhouXinquanandWamgDeming.haveconducted

    broadresearchesontheflowinglawofairf1owduring flrejfflthemine.twodimensiona1transientsimulation. andcompressibleunsteadvf1ow(0ieta1.,1995:Zhou andJ996;mg2004;Zhouandng2004;

    Songeta1.,2006).Intheprocessofminebeltroadway nre.flvarietyoffactorsincludingroadwaydipangle. inletairf1owvolume.andthespatialrelationshipof1he surroundingroadwayswiHaffecttheflowofairnow. 0nthebasisofactualsftmationofrni~ebeltroadway,

thestabilityoftheairfl0wduringlhedisasterissimu

    Receiveed:23March2010

    }SupportedtytheInternationalScienceandTechnologyCooperationProjects(2009DFA71

    840);BasicResearchBusinessProjectsofChiraAcademy0f SafetyScienceandTechnology(2009JBKY07) E.mail:zhangshengzh5168@163.com

    latedbyFluentCFDsoftware.Togetherwithagood understandingoftheflowinglawanditsinfluential factors,ourresearchcancontributetoairflowcontrol anddisasteravoidance.Thisismeaningfultocope withbeltroadwayfire.

    b".?々《鬟C(}{

    ,

    i{{lt

    Intheprocessofbeltfire.thetherma1effects generatedbythefirewillactonundergroundairflow. Themaininfluencesaremanifestedasbuoyancyeflfect andthechokeeffect,whichcallchangetheflowdirec

    tionofairflowandfirefumeandcausethedisorderof airflowstate.Thedisorderphenomenaofairflowin. eludeairflowreversal,fumeinverseretreating,fume rollback,andsoon.

    1.1TheBuoyancyeflfect

    Thetemperatureofairwillincreasebecauseof thethermaleffectsduringfire.Thehotairoflower densitycreatesakindofupliftintheroadwaywith heightdifference.ThemagnitudeOfthisupliftisde. terminedbytheheightdifferenceofroadwayandthe airdensitydifferencebeforeandafterfire.Thisther-

malpowergeneratedinminefireisakindofbuoy

    ancyforce.whichisalsoknownasfirepressure (Wang,2007).Thecalculationoffirepressureis showninFormula(1:

    Png(1)

    where,Pfisthefirepressure,Pa;PGisthedensityof fumeafterfire,kg/m;gistheaccelerationofgravity, m/s;istheheightdifferenceofroadway,m;I, aretheairtemperaturebeforeandafterfire,K. Themagnitudeoffirepressureisrelatedtofire andtheheightdifferenceofroadwaythatthefume flowsthrough.Thefirepressureactsasfansinventi

    lationsystem.Itsactiondirectionisthesameasfanin anascensionalventilationroadwayandiscontraryto fanindownwardventilationroadway.Moreover,its forceissmallindriftventilation.

    1.2Theehokeeffect

    Becauseoftheinfluenceoffireandsmokether- maleffects,airvolumeofmainventilationflueand flankingbranchoftenchangeswiththedevelopment offire.Theexpansionofairinsidetheroadwayby heatleadstotheincreaseofflowingresistanceand reductionofairmassflow.Assumingthatthefrontof ventilationroadwayisaffectedbyfiretheairflow massflowofthisroadwaycanbecalculatedbyFor. mulaf2):

    ,

    ?11.j,tl}.iI,,{l?t

    M:

    R/J

    where,Pisthefrictionwork,J:Rtistheventilation resistancecoefficientofroadway;Pistheairdensity, kg/m.

    AsthePandRtareconstant,thenM.

    Therefore,whenbeltroadwayfirebreaksout,theair densitydecreases,andthemassflowofairbecomes smaller

    2Ie:;j,,I川》citI《譬li!'ol'belt洲一

    (1?a

    2.1Thecontrolequationsoffluidflow

    Intheprocessoffire.theflowoffluidisdomi- natedbythephysicsconservationlaws,includingthe 1awofmassconservation.thelawofmomentumcon

    servation,andthelawofenergyconservation(Wang, 2004).Atthesametime,CO,smoke,andotherpo1. 1utantsarereleasedfromthebeltbyheat,andtheflow processcontainsmixingandinteractionofdifferent components,sotheflowalsocomplieswithcompo

    nentconservationequation.Massconservationequa. tion:

    

    bp

    

    +

    a(p

    u)+

    af

    a(pv

    av

).O(pw)——

    一一=

    0f3)

    where,tisthetime;"isthevelocityvector;,,and arethecomponentsofvelocityvectorinthedirec

    tionofx.1,andz.

    Themomentumconservationequationofmi

    crounitindirectionduringflowingisshownasfol

    lows:

    州塑bx+

    +~ffyx++

    (4)

    where.Pisthepressureonthefluidmicrounit;

    r,,

    andrarecomponentsofviscousstress

    producedbytheroleofmolecularviscositywhich actsonmicro.unitsurface;:.isthebodyforceof microunit,andmomentumconservationequationsin Ydirectionandinzdirectionareobtainedjnthesame way.

    Energyconservationequation

    O(pT)+diV(iv[grad71j+(5)

    where,Tisthetemperature;kistheheattransfercoef- ficientoffluid;Sristheinnerheatsourceoffluidand heatpartconve~edfrommechanicalenergyasaresult ofviscousinteraction.

    Massconservationequationofcomponents:

    jl\1/IcItllml',lli,,)i1HKIly,'(,{,Ijl'rhNmbilhydulil/gl'ilil1.;]cbeltH?'l,y377 a(pcs)+diV(

")=diV[grad()]+(6)

    where,cisthevolumeconcentrationofcomponents: pcisitsmassconcentration;Disitsdiffusionco

    emcient;Sisitsgenerationrate.

    AlthoughthesefourbasicEqs.(2)(6)havedif-

    ferentdependentvariablestheyallreflecttheconser

    vationpropertyofphysicalquantityinunitvolume andtime.Transformingcontrolequationsintouniver

    saldifferentialequationsandconsideringtheirnu

    mericalsolutionunderproperinitialconditionand boundarycondition,theproblemofflowandheat transmissionoffluidcouldbesolved

    2.2Thestandardktwo-equationsolvingmo-

    del

    Asforthesolutionofthree..dimensionalturbu.. 1ence,theindirectnumericalsimulationmethodisap. plied.Onthebasisoftheapproximatetreatmentof turbulenceinacertaindegreeandestablishing庀一?

    two--equationmodelbyintroducingtheturbulentki-- neticenergykanddissipationrating?respectively,

    thechangeofmeanflowfieldcausedbyturbulence couldbecalculated.andtheparameterdistributionin tunnelduringfirecouldbegrasped.

    Thestandard?modelcanbeshownasfol

    OWS:

    at=

    专竹,l\'j.

    (7)

    ++

肘?

    竿

    here,isthekineticenergyoffuid;lltistheturbu

    lentviscosity;Gkisthegenerationitemofturbulent kineticenergy;Cl?andC2?aretheempiricalcon

    stants,andthevaluearetakenas1.44and1.92.re. spectively;tYkandarethecorrespondentPrandtl numberofturbulentkineticenergykanddissipation rating?andthevaluearetakenas1.0and1.3.respec. tively.

    3Simulationofaint10?stabilitydurinofire

    inbeltroad~vay

    RegardingtheactualsituationofNo.1,No.3and No.5beltroadwayinKongzhuangCoalMine.airflow stabilitysimulationwascarriedoutinascensiona1. drift.anddownwardventilationroadwaytoanalyze theinfluenceoffiredisasterundertheconditionof normalairsupplyandreducedairvolume.No.1belt roadwayisdownwardventilation.No.3beltroadway isdriftventilation.andNo.5beltroadwayisascen. sionalventilation.Thespecificparametersofthese threebeltroadwaysareshowninTrLb1e1.

    Insimulation,threekindsofairflowvelocityare takenintocOnsiderati0n,whichstandfornormalair supply,whereinairsupplyishalfofthenormalstate, andnoairsupply.Theairflowinletwassetasvelocity inlet.thepollutantsinletwassetaccordingtotheposi. tionofbeltconveyer'sheadintheroadway,andits boundaryconditionwasalsosetasvelocityinlet;the airflowoutletwassetasfreeflow.Thegeometric

    modelsareshowninFig.1.Themodelsweremeshed byGambitfirst,thefirekineticanalysiswascarried outbyFluent.andthepollutantsproducedincombus. tionwerespecifiedbyMixturemultiphaseflowmode1. TheinletmaterialwasthemixtureofCO,HC1.C0,. andunsaturatedhydrocarbon.TheP1modelwasused tosetheatradiation.andthestandardk-?two.equa

    tionmodelwasusedtosolveturbulentflow.Consid

    eringthecomponenttransmissioninflowprocess.the SIMPLEalgorithmwasadoptedincalculationto simulatethedistributionofrelatedparametersinbelt roadway.

    Table1ThespecificparametersofNo.1,No.3,andNo.5beltroadway

    3.1AirflowstabilitysimulationofNo.1beltroad- way

    Thevelocityvectorsofpollutantsduringfireun

    derdifferentairsupplyareshowninFig.2. AsisshowninFigs.2

    ityofinletwaskepton1.8

    and3,whenairflowveloc

    m/sduringfirecatastrophe,

    thepollutantsflewintheprimarydirectionunderthe effectofairflowwithoutreflux.Whenairflowvelocity

ib?l!l1Jhitict,:l,;i\7()

    繁警

    .露?|

    (a)1.6m/s

    _?l

|

    Lt

    fb)O.8m/s (c)0.1m/s 1.37

    123

    1.1o

    9.61×1oi

    8.26×lo1

    6.9l×】oi

    556×10

    4-22×10

    287x10-l 1.52x10i

    166xl02

    7.93×l0'1

    714x10-t 6-35×l0..

    556~10

    4.76x10-

    3.97x10?

    3.18x10-?

    2.39~10 1.59×l0

    802×1

    '993×l0

    .._5.56x10-_lll一,—: Fig.5Thepartialenlargementdiagramofpollutants

    velocityvectorwhenvelocityis0.1m/s

    Whenairflowvelocityofinletwaskepton

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