Detailed Kinetics in Combustion Simulation：ManifestationModel Reductionand Computational Diagnostics.docx

Chapter2Detai1edKineticsinCombustionSimu1ation：Manifestation9Mode1Reduction9andComputationa1DiagnosticsPengZhaoAbstractInthischapter,theessentia1featureofrea1isticcombustionchemistryisfirstintroduced.Manifestationsofnon1ineardetai1edchemistryinhomogeneouscombustionsystemsaswe11asconvective-diffusivesystemsaredemonstrated,withusefu1insightsonturbu1entcombustionandguidancefortheadoptionofdetai1edchemistryincombustionmode1ing.Recentprogressonpremixedandnonpremixedcoun1erowcoo1f1ame1etsissystematica11ydiscussed,shedding1ightonthe1oca1behaviorofdetai1edChemiStryinturbu1entreactingows.Inaddition,anoverviewcoveringmode1reduction,stiffnessremova1,andothercomputationa1methodstofaci1itatechemistryintegrationisprovidedtoshowthefeasibi1itytoaccommodaterea1isticchemistryin1aminarandturbu1entcombustionmode1ing.1astbutnotthe1east,typica1methodsofcomputationa1diagnosticsarereviewedtoshowthenecessityandcapabi1ityofprobingandunderstandingcombustionmode1ingresu1tsingenera1.KeywordsDetai1edchemistry,NTCMode1reductionStiffnessremova1Coo1f1ame,Computationa1diagnostics2.1IntrinsicComp1exitiesinDetai1edChemica1KineticsAmoderncombustionresearcherhasat1eastfivemajortasksinchemica1kinetics,inc1udingidentificationofthespeciesinvo1ved,identificationofthereactionsbetweenthespecies,determinationoftheparametersinvo1vedintherateconstants,so1vingtheordinarj,differentia1equations(ODE)forthechemistrysourceterm,andunderstandingthecoup1edbehaviorofchemistryandf1uidf1owdescribedbythegoverningpartia1differentia1equations(PDE).C1ear1y,thefirstthreetasksareP.Zhao(DepartmentofMechanica1Engineering,Oak1andUniversity,Rochester,MI48309,USAe-mai1:pengzhaooak1and.edu;zhaodbustc©SpringerNatureSingaporePte1td.201845S.Deeta1.(eds.).Mode1ingandSimu1ationofTurbu1emCombustion,Energy,Environment,andSustainabi1ity,https:/doi.org/10.1007/978-981-10-7410-3_2responsibi1itiesofthechemists,whi1ethe1asttwoshou1dbeaccomp1ishedbythosewhoworkoncombustionphysicsandmode1ing.Thenumberonecha11engeinchemica1kineticsisthattherma1pyro1ysisandoxidationoffue1sconstant1yinvo1vemanyintermediatespeciesande1ementaryreactions,1eadingtothehighdimensiona1ityofa11combustionprob1ems.Consequent1y,extensiveebrtshavebeenspentonthedeve1opmentofchemica1kineticmode1soverthepastfewdecades,focusingonincreasing1ycomp1exfue1mo1ecu1esandb1ends.Unsurprising1y,thesizeofthechemica1mechanismssignificant1ygrowswithincreasingfue1mo1ecu1arsize(1uand1aw2009).Giventhemo1ecu1arstructureofthefue1,thenumbersofspeciesandreactionscanbeuptoafewthousandsandtensofthousands,respective1y.Suchfeaturesdirect1y1eadtoimmensedifficu1tiesinthecomputationandunderstandingcombustioninc1udingsubprob1emsofuncertainquantification(UQ)(WangandSheen2015),mode1reduction(1amandGoussis1994),andstiffnessremova1(1ueta1.2009a,b).Throughthecombinedapproachofquantumchemistryca1cu1ationsand1aserspectroscopytechniques,thetransitionstate,rateconstant,andotherinformationonmanye1ementaryreactionscanbeacquiredquitesatisfactori1y(Mi11ereta1.2(X)5;Pi11ing2(X)9).However,quantifyingthee1ementaryreactionratesonebyoneisextreme1ytime-consuming,andisstrong1y1imitedbythecomputationa1costforcomp1exfue1s.Consequent1y,kineticmode1ersfirsttrytoidentifya11possib1ee1ementaryreactionpathwaysbasedonexistingknow1edge,andtheneitherobtainknownreactionrateconstantsbasedonavai1ab1eca1cu1ationsandmeasurement(usua11yasma11portion)orestimatethosewherethere1atedca1cu1ationsormeasurementsarenotfeasib1e.Thiseventua11y1eadstotheconstructionofdetai1edreactionmechanisms(Westbrooketa1.2009).Inthesereactionmechanisms,pre-ca1cu1atedormeasuredreactionratesinevitab1yhaveuncertaintiesintherateconstants,andestimatedratesareassociatedwith1argeruncertainties.Itisa1sohigh1ypossib1ethattherecou1dbeanincomp1etephysica1understandingormissingreactionpathwaysinthemode1construction,asinthecaseofarecent1ydiscovered1ow-temperaturereactionpathway(Ja1aneta1.2013).Theuncertaintiesinthemode1descriptionandreactionrateconstantswou1deventua11ybereectedinthemode1ingresu1tssuchasignitionde1aytimeand1aminarf1amespeed,generatingbiasedcomparisonagainstexperimenta1measurements,andhencenecessitatingUQincombustionsystems.Whi1eitisre1ative1ystraightforwardtoeva1uateuncertaintyforhomogeneousand1aminarcombustionsystems,uncertaintyinducedbychemica1kineticsinturbu1entcombustionmode1ingissti11underinvestigation(Mue11ereta1.2013).Acrucia1questionthatcou1dberaisedforchemistsandcombustionmode1ersis:whichreactionratesdoweneedaccurate1y,whichreactionratesdoweon1yneedtheirorderofmagnitude,andwhichreactionisthe“rateContro11ingwreactionofareactingsystem?Theanswerre1iesontheunderstandingofcombustionchemistryandtheuti1izationofcomputationa1diagnostics.Anothermajorprob1emresu1tingfromthehighdimensiona1ityofthekineticmode1istheunaffordab1ecomputationa1cost,inthatevenifa11thee1ementaryF*nUuctiX*.cnton.extinction,turbu1entmungtturbunce<efn1rtnnsportmteractx.ernNomIeNOm).combustionnUbi1i(ieCbemiai15&InmportPrOCeUwm»miTkneFMtChemistrv,o*dWEHtfrmp