State e of the e Art of Mode delin ing g of Combustion bustion - PowerPoint PPT Presentation

State e of the e Art of Mode delin ing g of Combustion bustion and d po pollutan utants ts in in S Spa park rk Ign gnit ited ed Engi gine e Marc ZELLAT

INTRODU ODUCTION CTION : Some me key factor or for modeling eling 1. Downzoning (fuel efficiency) 2. Gas exchange 3. Mixture preparation  Spray, Droplets wall interaction  Liquid film 4. Spark 5. Main flame propagation  Laminar flame properties : speed , thickness  Mean and turbulent propagation 6. Wall heat transfer 7. Kinetics for Auto-Ignition (knock) 8. Emissions

INTRODU ODUCTION CTION 1D code e are well establi ablished hed for engine ine compon ponent ents design ign cy iciency But they still ll need d input ut paramet meter ers from combustion bustion (and other physics,…) stion Effici The combust bustion ion approx oximat imated ed by 0D model l rely on Wiebe be function ion 90% 90% Combusti 50% 50% ing Rate te rnin 10% 10% Burn Spra ray, y, mix ixing, ing,.. Spar ark, k, comb mbustion, ustion,.. Ne Needs for predicti ictive e and accurate urate 3D D models ls

STAR-CD D SI-ENGIN ENGINE E COMBUS MBUSTI TION ON MODELL ELLIN ING G Recent progress is attributed to the development of models which explicitly take into account the fact that combustion occurs in the wrinkled or corrugated flame regime (or broken reaction zone) EXAMPLES IN STAR-CD ARE :  Coherent Flame Model (CFM-ITNFS)  Weller 1 equation Flame Wrinkling model  Weller 3 equations model  ECFM-3Z / ECFM-CLEH  G-equation Level set Model

Intr troducti uction on : Schem hemat atic ic of f Premix ixed Regimes Flame brush is thickene ned Flame struc uctu ture re changes es Karlol olwitz witz > 1 1 Laminar flame me thicknes ess > smalles lest t turbulen ent t scal ale Karlol olwitz witz < 1 1 Laminar flame me thicknes ess > smalles lest t turbulen ent t scal ale Engine ne flames es * & Level l set field * Pete ters, rs, Reit itz

G-equat uation ion - Model el conce ncept t * Introd oduce uce n a as ve vect ctor or normal al to front flame me : The flow field d propagati ation on : Thus the sum of flow ve veloc ocity ity and burnin ing ve veloc ocity ity in normal directio ction A f field d of G c can now be derived d : *N.P .Pete ters rs , , H.Pit itsh sh

G-equat uation ion or Level set et approa oach G-equ quation ation det etermi rmines nes flame e locati tion n in spark-ignit gnition/ n/ma main n combustion stion stage ges – • The non — reacting cting scalar r G l locate e the Flame Front nt   G     t  U G S G  t Curvat atur ure e term : Usual ally ly small ll and neglected lected * The above equ quati tion n avoids ds comp mplicati ations ns with th counter er-gradient radient diffus fusion, n, and sinc nce e G is no-reacting acting scalar ar, , there re is non need for a s source ce term closur ure *Reitz

Turbule rbulent nt fl flame structur ucture Ensem emble ble averaged raged flamel elets ets   G     t  U G S G  t Due to the increa reased ed surfac ace e area , turbulen ulent flame e brush h propag agat ates es at enhan anced ed veloc ocity ity      G G        G u G s    i T t x G i       G G     t   2 c G    s   x x k t i i G ’ variance from which we can obtain flame thickness Averaged ed C p profi file le Insta tanta taneous us C profile le        c a erf a G l a 1   3 1 F t , 2

Addition onal al equat ations ions for r mixtur ure inhomogen omogenei eity ty          Z Mixture re Frac raction ion           Fuel el t Z u Z D      i Z     t x x  x  i i t i                       t Z u Z D Z      i Z     t x x  x  Mixture re Fract raction ion fluc uctua uatio ion i i t i       Z Z     t   2 c Z    s   x x k t i i   5/6    Back ckgro ground und : AIR+EGR GR u       Turbu rbulen lent Burnin rning g velocit locity 0   s ( ) s ( ) 1 A s  T l   0   ( )   l  1 Effective ive Turbu rbulent lent Burning rning velocit locity   s s ( )P(Z)dZ T T 0

POST-FLA FLAME ME COMBUS BUSTION TION REACTIONS CTIONS A : : L Laminar nar flame e speed B: Post-fl flmame chemist stry C: Nox Model – NORA)à D : : Soot ot model (Secti tiona nal met ethod) A Güld lder er cor orrelat elation ion for r Laminar minar Fla lame e speed peed B 7 species Equilibrium : C CO2 , C CO , H2O , O OH , O , N , N,H2, Zeld ldovich (thermal) N 2 O N 2 NNH NNH N 2 O Prompt pt NO (Fenim imore re) C NNH NNH N NO NO HCN,NCN CN • PAH volume: 28 m     3 0 . 3 10 PAH • There are 20 (or more) sections of volume  20 sections of diameter D       3 3 3 3 3     PAH PAH PAH PAH 2 20 PAH 2 4 8 2 2 2 2 2  1 3  1 3  1 3        1 3  1 3     6 3 6 3 6 3 6 3 6 3 D            PAH PAH PAH         2 4 PAH 20 PAH 8 2    soot             2 2 2 2 2

Applicat cation ion I I : GDI Spray y Guide : Full load d RPM Var ariat ation ion 2000 00 – 3000 00 – 5800 00 RPM

Applicat cation ion I I : GDI – Spray y guided – Full ll load RPM vari riat ation ion Pressu ssure re histo story Pressu ssure re histo story Apparen rent t rate te of Heat t Rele lease se 2000 00 RPM M Experim periments ents Predic ediction ion 3000 00 RPM M 5800 00 RPM M

Full load : Engine cases : OP3, OP4 and OP5 CO and CO2 Levels at end of closed cycle [%] EXPERIMENTAL STAR-CD CO emissions : EXPERIMENTAL STAR-CD 6 CO2 emissions : 5 14 12 4 10 8 3 6 2 4 2 1 0 OP3 OP4 OP5 0 2000 00 3 000 00a a 5800 800 2000 00 3 000 00a a 5800 800 OP3 OP4 OP5 NOx emissions : IMEP on clo lose sed d cyc ycle le [bar ar EXPERIMENTAL STAR-CD 25 EXPERIMENTAL RUN 3000 24 2500 23 2000 22 1500 21 20 1000 19 500 18 0 OP3 OP4 OP5 2000 00 3 000 00a a 5800 800 2000 00 3 000 00a a 5800 800 OP3 OP4 OP5

Fir ired Engine ine case e : 2000 3000 3000a a 5800 5800 Full ll l load Soot Dis istrib tribut ution ion Dia iamet meter er So Soot Dis istribution tribution Soot Dis istribut tribution ion Dia iamet meter er Dia iamet meter er

Applicat cation ion II II : GDI – Wall guided – Hi High RPM Full load

Applicat cation ion II II : GDI – Wall guided – Hi High RPM Full load Conf nfigu igurati ration on 1 Conf nfigu igurati ration on 2 Low T.K.E Hig igh T.K.E

App pplicat cation ion II II : GDI – Wall guided – Hi High RPM Full load Conf nfigurat iguration ion 1/2 Conf nfigur igurat ation ion 1 Pressu ssure re histo story Apparen rent t rate te of Heat t Rele lease se Low w T.K.E Conf nfiguration iguration 2 Hig igh T.K. K.E Experim periments ents Pr Predict ediction ion

App pplicat cation ion II II : GDI – Wall guided – Hi High RPM Full load Conf nfigurat iguration ion 2 cy iciency . Fr stion Effici From the in inst stantaneous energy rgy action ion 90% bala lance (i (incl cluding wall ll heat tr transfe sfer) r) Combusti : Ge Get th the inst stantaneous eff ffecti ctive heat 75% rnt Frac rele lease se 50% ss Burn _ Inte In tegrat rate ove ver time ti th the  Combusti stion effici iciency cy Mass inst in stan antaneo eous us in in-cyli cylinder er che hemic ical al 10%-90% dura rati tion  heat rele lease se  50% % anch chorin ring 10% Ex Exper periment iments Predic ediction ion Inputs ts to 1D code