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

• r 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 But they still ll need d input ut paramet meter ers from combustion bustion (and other physics,…) The combust bustion ion approx

• ximat

imated ed by 0D model l rely on Wiebe be function ion

Burn rnin ing Rate te

10% 10% 90% 90% 50% 50%

Combusti stion Effici iciency cy

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)

• Coherent Flame Model (CFM-ITNFS)
• Weller 1 equation Flame Wrinkling model
• Weller 3 equations model
• ECFM-3Z / ECFM-CLEH
• G-equation Level set Model

EXAMPLES IN STAR-CD ARE :

Intr troducti uction

• n : Schem

hemat atic ic of f Premix ixed Regimes

Flame brush is thickene ned Flame struc uctu ture re changes es

Engine ne flames es * & Level l set field

* Pete ters, rs, Reit itz

Karlol

• lwitz

witz > 1 1 Laminar flame me thicknes ess > smalles lest t turbulen ent t scal ale Karlol

• lwitz

witz < 1 1 Laminar flame me thicknes ess > smalles lest t turbulen ent t scal ale

G-equat uation ion - Model el conce ncept t *

Introd

• duce

uce n a as ve vect ctor

• r normal

al to front flame me : The flow field d propagati ation

• n :

Thus the sum of flow ve veloc

• city

ity and burnin ing ve veloc

• city

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-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 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

G S G U t G

t 

      

G-equat uation ion or Level set et approa

• ach

Curvat atur ure e term : Usual ally ly small ll and neglected lected *

*Reitz

Turbule rbulent nt fl flame structur ucture

G S G U t G

t 

      

Ensem emble ble averaged raged flamel elets ets 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

• city

ity G’ variance from which we can obtain flame thickness

Insta tanta taneous us C profile le Averaged ed C p profi file le

 

3 1 , 2

1

F t

c a erf a G l a       

2

i T i t s t i i

G G G u G s t x G G G c G x x k                                

Addition

• nal

al equat ations ions for r mixtur ure inhomogen

• mogenei

eity ty

Mixture re Frac raction ion Mixture re Fract raction ion fluc uctua uatio ion Turbu rbulen lent Burnin rning g velocit locity Effective ive Turbu rbulent lent Burning rning velocit locity

Back ckgro ground und : AIR+EGR GR Fuel el

t i Z i i t i

Z Z u Z D t x x x                              

2

t i Z i i t i t s t i i

Z u Z D Z t x x x Z Z c Z x x k                                                  

5/6

( ) ( ) 1 ( )

T l l

u s s A s                    

1

( )P(Z)dZ

T T

s s  



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

• t model (Secti

tiona nal met ethod)

B 7 species Equilibrium

: C CO2 , C CO , H2O , O OH , O , N , N,H2,

A Güld

lder er cor

• rrelat

elation ion for r Laminar minar Fla lame e speed peed

N2O N2 NNH NNH N NO NO HCN,NCN CN

Zeld ldovich (thermal) Prompt pt NO (Fenim imore re) NNH NNH N2O

• PAH volume:
• There are 20 (or more) sections of volume  20 sections of diameter

3 28 m

10 3 .



 

PAH

 

2 3

PAH

 2 3 2

PAH

  2 3 8

PAH

  2 3 4

PAH

  2 3 220

PAH

 

3 1

2 3 6       

PAH

 

3 1

2 3 2 6        

PAH

 

soot

D

3 1

2 3 4 6        

PAH

 

3 1

2 3 8 6        

PAH

 

3 1 20

2 3 2 6        

PAH

 

C D

Applicat cation ion I I : GDI Spray y Guide : Full load d RPM Var ariat ation ion

2000 00 – 3000 00 – 5800 00 RPM

Experim periments ents Predic ediction ion

Applicat cation ion I I : GDI – Spray y guided –Full ll load RPM vari riat ation ion

Pressu ssure re histo story Apparen rent t rate te of Heat t Rele lease se

2000 00 RPM M 3000 00 RPM M 5800 00 RPM M

Pressu ssure re histo story

Full load : Engine cases : OP3, OP4 and OP5 CO and CO2 Levels at end of closed cycle [%]

1 2 3 4 5 6 OP3 OP4 OP5 EXPERIMENTAL STAR-CD

CO emissions :

2 4 6 8 10 12 14 OP3 OP4 OP5 EXPERIMENTAL STAR-CD

CO2 emissions :

500 1000 1500 2000 2500 3000 OP3 OP4 OP5 EXPERIMENTAL STAR-CD

2000 00 3 000 00a a 5800 800 NOx emissions : 18 19 20 21 22 23 24 25 OP3 OP4 OP5 EXPERIMENTAL RUN

IMEP on clo lose sed d cyc ycle le [bar ar

2000 00 3 000 00a a 5800 800 2000 00 3 000 00a a 5800 800 2000 00 3 000 00a a 5800 800

Fir ired Engine ine case e : 2000 3000 3000a a 5800 5800 Full ll l load

Soot Dis istrib tribut ution ion So Soot Dis istribution tribution Soot Dis istribut tribution ion Dia iamet meter er 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

• n 1

Conf nfigu igurati ration

• n 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

Pressu ssure re histo story Apparen rent t rate te of Heat t Rele lease se

Experim periments ents Pr Predict ediction ion Conf nfigur igurat ation ion 1 Low w T.K.E Conf nfiguration iguration 2 Hig igh T.K. K.E

App pplicat cation ion II II : GDI – Wall guided – Hi High RPM Full load Conf nfigurat iguration ion 2

10% 50% 75%

Ex Exper periment iments Predic ediction ion

Combusti stion Effici iciency cy

Mass ss Burn rnt Frac action ion

90%

• Combusti

stion effici iciency cy

• 10%-90% dura

rati tion

• 50%

% anch chorin ring Inputs ts to 1D code

. Fr

From the in inst stantaneous energy rgy bala lance (i (incl cluding wall ll heat tr transfe sfer) r) : Ge Get th the inst stantaneous eff ffecti ctive heat rele lease se _ In Inte tegrat rate

• ve

ver ti time th the in inst stan antaneo eous us in in-cyli cylinder er che hemic ical al heat rele lease se

 G-eq equa uatio tion n in STAR-CD D V4.26 26 has been n investigat estigated ed and valida idated ed for differe erent nt engine ne configurations igurations  Mainly full load combus mbusti tion

• n have

e been en investigat estigated  G-eq equa uatio tion n in STAR-CD D demonstrat

• nstrate

e good d capab abilit ities es under these se condi diti tion

• n (Homo

mogeneou geneous s and GDI)  Applica ication tion and va validat datio ion n to SI-GDI GDI (homog homogen eneous eous ) an and PFI engines nes

• Good match for global thermodynamic quantities
• Good match for combustion history
• Good match for combustion history ( 10%-90% burn , 50% anchoring,

combustion efficiency)  Applica icatio tion n to part load and valida idatio tion n for emiss ssion ions s investigat estigations

• ns
• Link G-equation to soot sectional method – good level of soot
• Ling G-equation to N.O.R.A NOx models – good match wit NOX

SUMMAR MARY