Reacti ting ng flow modeling ng and applica cati tions ns in - PowerPoint PPT Presentation

Reacti ting ng flow modeling ng and applica cati tions ns in STAR-CCM+ Yongzhe gzhe Zhang, ng, CD-adapco pco

LES: : Scaled d Combust ustor Bet etter er flow and mixing ng accurac racy Results lts in bett etter er predic iction ion with th PVM combus bustion tion model dels ~32.7 .7 million ion cells ls Δ t = 1x10-6 s

LES Flare: : Impr mproved d predi dicti ction n of combus usti tion n effici ciency ncy PVM model el ~15 million lion cells ls Δ t = 5x10-5 5 s A Validation of Flare Combustion Efficiency Predictions from Large Eddy Simulations. Anchal Jatale, Philip J. Smith, Jeremy N. Thornock, Sean T Smith, Michal Hradisky. University of Utah. Combustion and Flame.

Applicat ication ion trend More Large ge Eddy y Simulatio mulation n (LES) ES) – Better prediction of instantaneous flow characteristics and turbulence structures – Computationally expensive Include ude Detailed d Chemi mistr try – Better prediction of autoignition and emissions (CO/NOx) – Models • Complex Chemistry model • Tabulated Chemistry model

Complex Chemistry Model Transport equation of chemical species Nonlinear, stiff ordinary differential equations (ODEs) Effici icient t ODE solve ver Analyti lytica cal l Jacob cobia ian Load bala lancin cing for parall llel l compu mputi ting Computa tati tional Chemistry mistry reducti ction : Offli line (DRG) Cost Storage/Re /Retrie trieva val l Sch cheme me(IS ISAT AT) Equil ilib ibriu ium m Time Scale le (Init itia iali liza zati tion) Dars-CFD FD Turbule lence ce- Eddy y Dissip ipati tion Conce cept (EDC) chemi mistry stry Interactio ction

Equi quili libri brium um Time e Scale e Model (EqTS TSM) ‏ Motiva vati tion – A better initial condition can greatly accelerate DARS-CFD Model – The model assumes the species composition to relax towards the local chemical equilibrium at a characteristic time scale determined based on the local flow and chemistry time scales – Quickly provides an reasonable initial condition to DARS-CFD – Results similar to PPDF equilibrium, but more flexible: • no stream limitation/no precomputed table needed/easier to set up – Can be used as a standalone model to obtain a quick approximate solution

Tabula ulated ed Chemis mistr try y Model Motiva vati tion – Detailed chemistry is important to predict autoignition and emissions (CO/NOx) – Computationally expensive to include a full set of species Tabulated d Detailed d Chemi mistr stry y for turb rbul ulent nt combustion ustion – Precompute chemistry table and retrieve during CFD computation • Can use large mechanism – Dimension reduction to chemistry – Consider turbulence-chemistry interactions. Existi ting ng models – PPDF with equilibrium – PPDF with laminar flamelets – PVM (Progress variable model) – FGM (Flamelet Generated Manifold)

FGM combus bustion tion model Simi milar r to the existi sting ng PVM model: – A tabulated detailed chemistry model – A progress variable is used to bridge the CFD side and the table Impr mproveme ment nts s comp mpared d to the exist sting ng PVM model – Table is from flamelet manifold • A turbulent flame is an ensemble of laminar flamelets – Option of using progress variable variance • Presumed Beta PDF in progress variable space – Option of considering heat loss ratio – Flexible progress variable definition • Chemical enthalpy – Sum over all species • Species weights – Defaults: YCO+YCO2

FGM table le genera eratio tion in DARS-BASI ASIC Generated table can directly be loaded into STAR-CCM+ for • 9 further construction

Validation tion with h IFRF F glass s furnace nace Heat loss effect is important

Latest t model l additions tions (v 9.04 04-10.0 0.04) 4) Includ lude e det etailed ed chemist mistry y with an affor ordabl able e computation putational al cost – Equilibrium Time Scale – Flamelet Generated Manifold (FGM) Cope e with h more e comple plex conf nfigurat igurations ions – Inert stream – Reacting channels Expand nd appli licati cation on coverages erages – Polymerization – Surface chemistry with multiple sites and open sites 11

Reacti tion n models s in STAR-CCM+ Non-Premixe Premixed Combust stio ion Premixe mixed Combusti stion Multi ti-co compo mponent t Gas Parti tiall lly-Pre Premixe mixed Combust stio ion Reactio Emissio ssion Models s (Soot/ t/NO NOx/CO) x/CO) ction Models Eddy y Conta tact ct Model l (ECM) Multi ti-co compo mponent t Liquid id Polyme ymeriza izati tion Parti ticle cle Reactio ction ls Lagrangia ian Multi tiphase se Coal l combu mbusti stion Eule leria ian Multi tiphase se Interphase se Reactio ction Surfa face ce Chemistry mistry Reacti cting Channel

Latest t model l additions tions (v 9.04 04-10.0 0.04) Includ lude e det etailed ed chemist mistry y with an affor ordabl able e computation putational al cost – Equilibrium Time Scale – Flamelet Generated Manifold (FGM) Cope e with h more e comple plex conf nfigurat igurations ions – Inert stream – Reacting channels Expand nd appli licati cation on coverages erages – Polymerization – Surface chemistry with multiple sites and open sites 13

Inert t stream eam for r PPDF combu mbust stion ion model el Motiva vati tion – To reduce the PPDF table size for complex configurations where one stream, or part of the stream, is inert (negligible reactivity and sole effect is for dilution) Inert t str tream m treatm tment nt – Only consider its dilution effects to the reacting mixture – Compared to take it as active • Smaller table size • Faster table generation • Faster interpolation Inert t strea tream m model – A transport equation for the mixture fraction solved for inert stream – Species mass fractions from reacting and inert streams – Temperature from local total enthalpy and mean species

Reacti cting ng Channel nel Co-Si Simu mulation ation Applic ication ation Modelin eling of Proces ess side – Process heaters – Cracking furnaces – Steam reformers Modeling eling Challen llenges es – Firebox side has multiple burners – Process side has many tubes – Full 3-D modeling is computationally intensive Perform ormanc ance e Considerat ideration ions – Uniform heat distribution – Emissions 3-D vs 1-D – Conversion rate Comput mputationally Comput mputationally less s expensi sive expe pensi sive

Reacti cting ng Channel nel Co-Si Simu mulation ation An elega gant nt way to fully ly couple le Firebo rebox side e and Proces ess side Gas-Pha Phase: e: [ FireB eBox Side] e] – 3-D, turbulent flow – Combustion models – Heat transfer Proces ess Side Side Reacti ting g Chann nnel: el: [Proc oces ess Side] de] – 1-D Plug Flow Reactor (PFR) – Inlet composition, temperature – Process-side reactions – No meshing, solving with STAR-CCM+ Burner er Couplin ling – Temperature is provided to the process side – Heat flux is returned back to firebox side

Output put from om Co-simul simulation ation : Process ess Side Axial l distr trib ibution ution of Temperature, erature, Heat t Flux, , and Species ies convers ersions ions CH4 Mass Fraction H2 Mass Fraction

Polymeri ymeriza zation tion Expand and our applica cati tion n coverage age Polym ymeriza rizati tion on Process cess – monomers are linked by chemical reactions to form long chains – starts with mixing a Monomer (M) and an Initiator (I) in a Solvent (S) – Steps involved: initiation/propagation/transfer/branching/termination – Final product is polymers of varying lengths and structure. Polym ymerizati zation on Moment nt Model for free radical cal polym ymerizati tion – Scalar Transport Equations for Moments are solved in STAR-CCM+: live/dead polymers – source terms of the above moment transport equations depend on the sub processes of polymerization. – Provide: total polymer concentrations, NACL/NAMW, WACL/WAMW, polydispersity index

Industri ustrial-Sca Scale Stirred d Tank k Reactor – Styrene ne Polym ymerization zation Steady (Implicit Unsteady) • K-Epsilon Turbulence • Realizable K-Epsilon Two-Layer • Two -Layer All Y+ Wall Treatment • Multi-Component Liquid • Polymerization • Segregated Flow • Segregated Fluid Enthalpy • Three Dimensional • MRF, RBM • Polyd ydisp ispersit sity index

Multi tiple ple sites s for surface ce chemi mistr try Chemical vapor deposition (CVD) reactor

Open sites es for r surface ce chemi emistr stry Adsorption ption reacti tion n descr cripti tion – Atomic Site • AsH3(g)+Ga(s)->AsH3(s)+Ga(b) – Open Site • O(s)+AsH3(g)->AsH3(s) Open sites s treatm tment nt – Considered as a species – Contains no element (empty) – Named as OPEN in the CHEMKIN kinetics input file

Application ication extens nsions ions Large ge Eddy Simul mulation ation (LES) S) with h det etailed ed chemist mistry – Gas turbine combustors – Burners, Furnaces and Incinerators – Fires High h speed ed flows ws – Scramjet – Rocket engine nozzles Multipha phase se react ctions ions – Coal reactors: Pulverized/Fluidized bed – Surface chemistry (SCR/CVD) Optimiz mizations tions – Chemistry – Combustor design