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1、Chapter11ExamplesofSprayCombustionModeling-211.1Sprayignition/combustionmodelingTheignitionprocessescanbeconventionallydividedintwogroups:auto-ignitionwhichtakesplacewhenthecombustiblemixtureispreheated(e.g.bycompression)onalargescaletothetemperatureabovetheauto-i
2、gnitionlevel,andforcedignition,whenonlyasmallpartofthecombustionvolumeispreheated(e.g.byaspark).Theprocessesfollowingignitioninacombustiblemixturecanresultinavarietyofdifferentcombustionregimesrangingfromflamedeflagration(slowpropagation)todifferentkindofdetonatio
3、ns.Someofthesecombustionregimes,ifrealized,canbeextremelydestructive[1].Thedeterminationofinitialandboundaryconditionsunderwhichthesecombustionregimescanberealizedisstilladifficultprobleminthemodelingsinceitrequiresaccountingforinteractionofcomplexchemicalkinetics
4、,moleculartransport,turbulence,andheattransfer.Inthecaseofmultiphasecombustion,whenfuel,oxidizerorproductsareinthedifferentphases,themodelingproblembecomesevenmorecomplex.Withoutthesecomplicationstheignitionprocesscouldbeonlytheinitialstageofthecombustionprocessof
5、arelativelyshortdurationcharacterizedbytheignitiondelaytimes.Themodelingphilosophyinthiscaseiswellestablished[2]andprovedtobeeffectiveforawidevarietyofapplications.Moreover,manysoftwaretoolsrequiredtoimplementthismethodologyareavailablenow(seee.g.[3]).Acommoneleme
6、ntofthemodelingstrategyisacouplingoflargereactivechemicalsystemsdescribedbycomplexkineticmechanismswithcomputationalfluiddynamicsmodelsrealizedindifferentgeometries(e.g.variouskindsofreactors,combustionchambers,etc).Weshallfollowthismethodologytoillustratetheignit
7、ionmodelingofdifferentfuelsinparticularconditions:1)thehotspotignitionofgaseoushydrogen/air/steammixturesoccupyingcompartmentsconnectedbyanarrowpassage,2)auto-ignitionofliquidautomotivefuels(dieseloil,gasoline,n-heptane,bio-dieselfuel)inaconstantvolumevesselatcond
8、itionstypicalforinternalcombustionengines(ICE),3)theevaluationofanimpactofdirectinjectionofsmallamountofethanolintoahotcombustionchamberofthegasolineSIe
