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78 工Konishiet01./S日ifetyScience53(2013)73-81
piling"isinfluencedbythesizeofconectedvesels，thelength anddiameteroftheconnectedholesorpipes，thechemicalcompo- sitionandtheconcentrationofgasmixture.Theignitionandflame propagationphenomenaduringthecourseoftheexplosionwere verifiedbythesmal-scalecombustionchambershowninFig.9. Fig.10ilustratesthelocusoftheflamefront，andthenumbers inthefigureshowtheelapsedtimeafterignition.Thepositionof the flame front and the flame spread rate calculated from the diameteroftheflamenucleusareshowninFig.1.
At4.2msafterignition，theflamenucleussuroundstheigni- tionplug(Fig.9b).Theflameismovingawayfromtheignition pointasaroughlysphericalshapeandthediameteroftheflame nucleusincreaseswithtimeinFig.9candd.Theflamespeed rangesfrom2mfsto5mfsandalaminarflamemaybeestab- lished. By that time，the flame within compartment B burns smoothly，withtheflamesurfaceremaininglamina.rAt25.0ms afterignition，theflamefrontissentopropagatetowardscom- partment仁 throughthe5m mclearancelocatedundercompart- mentsBandCshowninFig.ge.Astheflamefrontpropagates throughtheclearance，flamejetsareformedincompartment仁 Theflamebecomesturbulentandtheflamespeedincreasesto therangeof10-20mfsinFig.9.fTheflamespeedincreasedrapidly andfinalycausedanexplosion.Theexplosiondeformedtheparti- tionbetweencompartmentsCandAasshowninFig.9g.However， thepapershetscoveringtheopeningsofcompartmentsBandC werenotdamaged.InFig.9h，at37.5ms，thealuminummembrane thatwasplacedontheupperpartofcompartmentAwasblown awaybytheexplosion.
Fairweathereta.l(19)reportedstudiesofpremixedflame propagationinacylindricalveselwithtwointernalbafles.They concludedthatflamepropagationthroughtheveselswassub- stantialylaminaruntiltheflameencounteredthefirstbafle.A significantoverpresurewasgeneratedinthelaterstagesofexplo- sionsduetorapidturbulentcombustionintheshearlayersand recirculationzonesinducedbythebafles.PhylaktouandAndrews (193)conductedmethanefairexplosionsina0.5m diameter， 0.5m longveselconnectedtoanidenticalveselthrougha 76m mdiameter，1.7m longtube.For10%methanefairmixtures thepipegasvelocitiesrangedfrom70to130mfs.Inourexperi- ments，laminarflamespreadvelocitiesrangedfr
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flowgeneratedhighturbulencelevelsinthethirdveselandacel- eratedto20-80mfsandresultedinaviolentexplosioninthethird vese.lLarsenaandEckhofb(20)determinedthecriticalhole diametersforexplosiontransmisionformaprimarychamberinto asecondarychamberandpresentedtheminimumtubediameter forflametransmisiondependsstrongonthelocationoftheigni- tionpoint.For4.2vol%propaneinair，flametransmisionintosec- ondchamberandsucesiveexplosionwasnotocuredwhenthe distancebetweenignitionpointandholeentranceexcedsfour timestheholediameter.Inoursmalscalecombustionchamber asshowninFig.9，thedistancebetweenignitionpointandrectan- gularslotis80m mandtheequivalentholediameteris25mm. Overlokingadiferenceoffueltypes，flametransmisionmay haveocured.Maremontieta.l(19)simulatedagasexplosion intwolinkedveselsbyusingtheCFDcodeAutoReaGas.Thecom- putedvaluesofturbulenceintensityatvaryingdiametersofthe conectingpipedemonstratedthatturbulenceinducedinboth veselsrepresentamajorfactorafectingtheexplosionviolence. Theefectofpipediameteronexplosiondevelopmentwascalcu- latedforthrediferentpipediametersfor50m m，76m mand 200mm.Therateofpresureriseinthesecondveselfor50m m pipeis20，000barfs，onthecontrary，whena200m mpipeisused， therateofpresureriseis65barfs.Inourthesmal-scalecombus- tionchamberexperiment，theequivalentdiameteris24mm.For mock-upboat，aholeconnectedcompartmentsBandC，asshown inFig.2d，has35m minequivalentdiameter.Thesmalerdiameter
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