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 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) CCM CCM 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 be directly loaded into STAR-CCM+ for • 9 further construction

A A glass ss furna nace ce simul mulati tion n using ng FGM model Furnace ce dimen mensio sions: s: 3.8m m x 0.88m m x 0.955m, m, fuel l inle let t diamet meter: : • 1.2cm cm Natural l gas s at 283 K at Fuel l Inlet • 10 % exce cess ss air at 1373 K at Air Inlet • Compariso ison with experime iment t at four measu surin ing poin ints; ts; • x= 0.6m, , x = 0.9m, , x =1.2m m and x = 1.8m Illustrati stration of approxima ximate te regio ion of NO x formati tion (light t blue), , • mixin ing & combusti stion (red)

Boundar ndary y Condi diti tions ns Quantity Fuel Inlet Air Inlet Glass Chamber Wall Walls Velocity (m/s) 125.0 10.0 - - Temperature 283.0 1373.0 - - (K) Heat Flux - - 90.0 2.0 (kW/m 2 )

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) 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

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

Combu bustion stion models ls for r multi ti-co compo ponent ent gas Multi ti-compo component t Gas Combustio stion Premixe mixed Non-Pre Premixe mixed Parti tiall lly-Pre Premixe mixed Emissio ssion Combustio stion Combustio stion Combustio stion Dars-CFD FD Dars-CFD FD Dars-CFD FD SOOT Premixe mixed Eddy- Eddy-Bre Breaku kup Eddy-Bre Breaku kup NOx Breaku kup (PEBU BU) (EBU) U) (EBU) U) CO CO Coherent t Flame me PCFM Model l (CFM) Presu sume med PDF (PPDF DF) Turbule lent t Flame me PTFC Speed Closu sure (TFC) Progre ress ss Variabl iable Model l (PVM) Premixe mixed PVM (PPVM) VM) Flamel melet Genera rate ted Manif ifold ld (FGM)

Develo elopment ent objectiv ectives es Meet et all aspects ects of requi uirement rements s from om our clients nts – Wider er applic icatio tion coverage rage – Ac Accuracy racy – Effic icie iency cy – Robu bustn tness ess – Ease e of use – New mode del l develo lopme ment – Imp mprovem ement ents to existin isting g models dels 16

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 17

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