2010-Combustion-Symposium_Wang.pdf

FormationofNascentSootandOtherCondensedPhaseMaterialsinFlames

HaiWangUniversityofSouthernCalifornia

WorksupportedbyNSF,SERDPandDOE(CEFRC)

WhyDoesCondensedPhaseMatterForm?

G=H TS

Progressvariable

GastoSolidTransformation

Type1:enthalpydriven(heatrelease)

metaloxidescarbides,nitrides

Type2:entropydriven

sootC3H8 solidcarbon+4H2(H >0,butS >0)

DrivingForce Soot

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

Sootformationisentropydriven(H2 goesfree).Condensedphasecarbonformsasanaerosol(kineticsdriven).

Condensedphasematerialisubiquitousinflames

http://www.historyforkids.org/learn/science/fire.htm

http://hearth.com/what/historyfire.html

World'soldesttattoos(Tyroleaniceman,tzi)wereetchedinsoot(c.3,300BC)

Lampblack(soot)usedinprehistoriccavepaintings(35,0035,0010,00010,000ybpybp)

G. Nelson Eby, http://faculty.uml.edu/nelson_eby/Forensic%20Geology/PowerPoint%20Presentations.htm

SootMicrostructures/Composition

http://www.atmos.umd.edu/~pedro/soot2.jpg

3.5

105106 atoms

http://www.asn.ubordeaux.fr/images/soot.jpg Courtesy:Boehman

Maturesoot:

C/H ~8/1 =1.8g/cc

SootasaVersatileMaterial OldandNew

daneshema.com

sci.waikato.ac.nz

carbonblack 3rdgenerationsolarcells

directmethanolfuelcells

renewableenergy

heattransfer

http://www.asn.ubordeaux.fr/images/soot.jpg

SootasParticulateAirPollutants

http://www.spacemart.com/images/cruiseshipsmokestackemissionbg.jpg]

http://www.sfgate.com/blogs/images/sfgate/green/2009/06/03/dieselsmoke.jpg

http://www.soot.biz/images/soot/soot_250x251.jpg

http://farm1.static.flickr.com/216/499969453_44089c6c1d.jpg

http://www.parks.ca.gov/pages/491/images/sierra_3_steam_locomotive.jpg

SootandtheClimate Sootdepositionresponsiblefor95%polaricemelting

Dirtysnowreducesicealbedo

Browncloudscausesregionalwarming

Contrailrelatedcloudalbedo

DrivingForcesbehindSootResearch(1)The80s &90s:Amajorbreakthrough inunderstandingcarbonformation willhavebeenachievedwhenitbecomespossibleinatleastonecasetoaccountfortheentirecourseofnucleationandgrowthofcarbon onthebasisofafundamentalknowledgeofreactionratesandmechanisms.

Palmer&Cullis,1965

Frenklach,Wang,Proc.Combust.Inst. 23(1990)1559.

Frenklach,Wang,in:SootFormationinCombustion:MechanismsandModelsofSootFormation,Bockhorn,Ed.SpringerVerlag,Berlin,1994,pp162190.

Colket,Hall,inSootFormationinCombustion:MechanismsandModelsofSootFormation, Bockhorn,Ed.SpringerVerlag,Berlin,1994,pp442468.

Mauss, Schafer,andBockhorn,Combust.Flame 99,697705(1994)

Bockhorn,ed.SootFormationinCombustion:MechanismsandModelsofSootFormation,SpringerVerlag,Berlin,1994.

Kennedy Modelsofsootformationandoxidation,Prog.EnergyCombust.Sci. 23(1997)95132. Data:Jander &Wagner,Simulation:

Kazakov,Wang,Frenklach(1994)

DrivingForcesbehindSootResearch(2)Themostrecentdecade:Predictivetoolsforcombustionenginedesigns

Network Reactor Simulation

Fuel-spray shear layer

Recirculation zones

Quench zones

Burn-out zones

Network Reactor Simulation

Fuel-spray shear layer

Recirculation zones

Quench zones

Burn-out zones

Fuel injector/swirler

Fuel-rich front end

Quench Zone

Lean, Burn-Out Zone

Soot Mass w/Jet-A

CourtesyofColket

Bai,Balthasar,Mauss,FuchsProc.Combust.Inst. 27(1998)1623.Pitsch,Riesmeier,Peters Combust.Sci.Technol. 158(2000)389.Wen,Yun,Thomson,Lightstone Combust.Flame 135(2003)323.Wang,Modest,Haworth,TurnsCombust.Theor.Model. 9(2005)479.Lignell,Chen,Smith,Lu,LawCombust.Flame 151(2007)2.Mosback,Celnik,Raj,Kraft,Zhang,Kubo,KimCombust.Flame 156(2009)1156.

Haworth Prog.EnergyCombust.Sci. 36(2010)168259.

KineticMechanismofSootFormation

CourtesyofDAnna

Bockhorn,DAnna,Sarofim,Wang,eds.,CombustionGeneratedFineCarbonaceousParticles,KarlsruheUniversityPress,2009.

KineticMechanismofSootFormation

CourtesyofDAnna

Bockhorn,DAnna,Sarofim,Wang,eds.,CombustionGeneratedFineCarbonaceousParticles,KarlsruheUniversityPress,2009.

GasPhaseChemistry

PAHChemistry

Nucleation

Massgrowth

RecentHighlights(1)

AtomisticModelforParticleInception(AMPI),combiningkineticMonteCarloandmoleculardynamics,showevolutionofincipientsootstructures:

CourtesyofVioli

RecentHighlights(2)

Balthasar,Frenklach(2005)

KineticMonteCarlosimulationexplainstheoriginofsphericityofnascentsootparticles

10-1

100

101

0.70.8

0.91.0

1.1

(

1

/

N

)

d

N

/

d

l

o

g

(

D

p

)

Particle Diameter, Dp

(nm)

Distance from Burner, Hp (cm)

246810

2030

10-1

100

101

0.70.8

0.91.0

1.1

(

1

/

N

)

d

N

/

d

l

o

g

(

D

p

)


(nm)


246810

2030

Abidetal.(2009)C2H4O2Ar flame =2.1

Eventually

RecentHighlights(3)

ParticleSizeDistributions

Chemicalmakeup

CourtesyofKraft

Stochasticsimulationswithdetailedchemistryandaerosoldynamicsareabletopredictparticlesizedistribution&sootchemicalcompositions

ExperimentsFacilitateModelComparison

Measuredandcomputed(USCMechII)temperatureincloseagreement)removedtheneedtoshifttimezero.

Burnerstabilizedstagnationflameapproach C2H4/O2/Ar flame( =2.1)

Abidetal.(2009)

Distance,H (cm)1.2

5001.00.80.60.40.20.0

1000

1500

T

e

m

p

e

r

a

t

u

r

e

,

T

(

K

)

1.2

Hp =0.55cm0.6

0.7

0.8

1.0

Distance,H (cm)1.2

5001.00.80.60.40.20.0

1000

1500

T

e

m

p

e

r

a

t

u

r

e

,

T

(

K

)

1.2

Hp =0.55cm0.6

0.7

0.8

1.0

1.2

0.6

0.7

0.8

1.0

Diameter,Dp (nm)3 5 10 20 50

108

1010

d

N

/

d

l

o

g

D

p

Hp =0.55cm

1.2

0.6

0.7

0.8

1.0

Diameter,Dp (nm)3 5 10 20 50

108

1010

d

N

/

d

l

o

g

D

p

Hp =0.55cm

cooling assembly

1cmHp

stagnation plate/sample probe (Ts)

Tbr

xu

v

to SMPScarrier N2

DetailedPSDFsbymobilitysizingprovideaddedresolutiontoprobingsootnucleationandmass/sizegrowthchemistry

CurrentProblems&Questions

PAH precursorchemistryanditsdependencyonfuelstructures;

Whatisthemechanismofparticleinception?

Isthecompositionofnascentsootidenticaltomaturesoot?

IstheHACA mechanismcompete?

PAH PrecursorChemistry(1)

+H+H

+C2H2

(H)

+C2H2H

+C2H2H

+C2H2+H(H2)

+H

+H(H2)

+H

+H(H2)

+H

+H(H2)

+H

+H(H2)

+H

+H(H2)

+H

+C2H2+C2H2

+H(H2)

+H

+H(H2)

+H

+C2H2(H)

+H(H2)

+H

+H(H2)

+H

+C2H2H

+C2H2H +H(H2)

+H

+H(H2)

+H

+C2H2 (H)

TheHydrogenAbstractionCarbonAddition(HACA)Mechanism(Frenklach)

Steinsstabilomersassootbuildingblock

Capturethreeimportantfactorsofmolecularweightgrowth

Flame PAHchemistry formation

Hatom chain activationbranching

C2H2 dominant buildingspecies block

HighT heat Arrheniusrelease kinetics

PAH PrecursorChemistry(2) EarlierworkaimedatdevelopingconsistentthermodynamicJPhysChem 97(1993)3867.

transportCombustFlame 96(1994)163.

chemicalkineticJPhysChem98(1994)11465;CombustFlame 110(1997)173;ProcCombustInst 23(1990)1559.

descriptionsofPAH formation

Lessonslearned:PAH formationissensitivetoamultitudeofelementaryreactionsandlocalflameconditions.

-0.5 0.0 0.5 1.0

H+O2=O+OHHO2+H=OH+OH

HO2+OH=O2+H2OHCO+O2=CO+HO2

CH+H2=CH2+HCH2+O2=CO2+H+H

CH2*+H2=CH3+HC2H2+O=CH2+CO

C2H2+OH=C2H+H2OC2H2+H(+M)=C2H3(+M)

HCCO+H=CH2*+COHCCO+CH3=C2H4+CO

C2H3+O2=C2H3O+O

C2H2+CH2*=C3H3+HC2H2+CH2=C3H3+H

C3H3+OH=C3H2+H2OC3H3+OH=C2H3+HCO

C3H3+C3H3=>A1c-C6H4+H=A1-

C4H2+H=n-C4H3

A1+H=A1-+H2A1+OH=A1-+H2O

A1-+H(+M)=A1(+M)n-A1C2H2+C2H2=A2+H

A2+OH=A2-1+H2OA2-1+H(+M)=A2(+M)

A2C2HA*+H(+M)=A2C2HAA2C2HA+OH=A2C2HA*+H2

A2C2HA*+C2H2=A3-4P2+H=P2-+H2

P2-+C2H2=A3+HA3+H=A3-4+H2

A3-4+H(+M)=A3(+M)A3-4+C2H2=A4+H

Logarithmic Sensitivity Coefficient

Main flamechemistry

First aromaticring

Aromatic growthchemistry

Spectralsensitivityofpyreneconcentration90TorrburnerstabilizedC2H2/O2/Ar flame(Bockhorn),H =0.55cm

Wang&Frenklach,C&F (1997)


-0.5 0.0 0.5 1.0







C2H3+O2=C2H3O+O




C4H2+H=n-C4H3


A1-+H(+M)=A1(+M)n-A1C2H2+C2H2=A2+H

A2+OH=A2-1+H2OA2-1+H(+M)=A2(+M)


A2C2HA*+C2H2=A3-4P2+H=P2-+H2

P2-+C2H2=A3+HA3+H=A3-4+H2

A3-4+H(+M)=A3(+M)A3-4+C2H2=A4+H


Main flamechemistry

First aromaticring




-0.1 0 0.1 0.2 0.3 0.4HO2+H=2OHCH3+HO2=CH3O+OH2CH3=H+C2H5C2H3+O2=CH2CHO+OC2H4+OH=C2H3+H2OC2H3+H=C2H2+H2C2H3(+M)=C2H2+H(+M)CH3+OH=CH2*+H2OCH3+H(+M)=CH4(+M)HCO+M=CO+H+MH+OH+M=H2O+MHCO+H2O=CO+H+H2OHCO+H=CO+H2CO+OH=CO2+H

H+O2=O+OH

= 1, T0 = 403 K

detailed model

simplified model

Sensitivity Coefficient

Youetal.Proc.Combust.Inst.(2009)

ndodecaneairflamespeed


-0.5 0.0 0.5 1.0







C2H3+O2=C2H3O+O




C4H2+H=n-C4H3


A1-+H(+M)=A1(+M)n-A1C2H2+C2H2=A2+H

A2+OH=A2-1+H2OA2-1+H(+M)=A2(+M)


A2C2HA*+C2H2=A3-4P2+H=P2-+H2

P2-+C2H2=A3+HA3+H=A3-4+H2

A3-4+H(+M)=A3(+M)A3-4+C2H2=A4+H


Main flamechemistry

First aromaticring




Lessonslearned:PAH formationissensitivetoamultitudeofelementaryreactions.

AccuratepredictionofPAH formationmayrequireaprecisioninmainflamechemistrycurrentlyunavailable.

PAH formationcanbehighlysensitivetofuelstructures.

4D01: Hansen,Kasper,Yang,Cool,Li,Westmoreland,Owald,KohseHinghaus, Fuelstructure

dependenceofbenzeneformationprocessesinpremixedflamesfueledbyC6H12 isomers

Possibly a large number of pathways toPAHshaveyetbeenconsidered.

PAH PrecursorChemistry(4)ThermodynamicOriginofPAH Formation/GrowthBeyondHACA

C2H2 5 5 4 4 3 2 2 1 0H 1 0 1 0 0 1 0 0 1H2 0 1 1 2 2 2 3 3 3

0.0

0.5

0.5

1.0

G

(

k

c

a

l

/

m

o

l

-

C

)

r

+C2H2(H)+H(H2)

+H(H2)

+C2H2+C2H2(H)

+H(H2)

+C2H2

+C2H2(H)

+H (+M)

+H (+M)

+H (+M) +H (+M)

+H (+M)

C2H2 5 5 4 4 3 2 2 1 0H 1 0 1 0 0 1 0 0 1H2 0 1 1 2 2 2 3 3 3

0.0

0.5

0.5

1.0

G

(

k

c

a

l

/

m

o

l

-

C

)

r

+C2H2(H)+H(H2)

+H(H2)

+C2H2+C2H2(H)

+H(H2)

+C2H2

+C2H2(H)

+H (+M)

+H (+M)

+H (+M) +H (+M)

+H (+M)

WhileHACA capturesthethermokinetic requirementsforPAH formation,itsreversibilityopensittocompetitionsfromotherpathways

PAH PrecursorChemistry(5)KnownPathwaysbeyondHACA

0

20

40

60

80

100

120

140

2C3H3

+H

E

n

e

r

g

y

(

k

c

a

l

/

m

o

l

)

0

20

40

60

80

100

120

140

2C3H3

+H

E

n

e

r

g

y

(

k

c

a

l

/

m

o

l

)

Propargylcombination(Fahr&Stein1990)

RatecoefficientcalculationrequirehighqualityPES (e.g.,CASPT2),RRKM/Masterequationmodeling,flexible,variational transitionstatetheory

Sequentialdehydrogenationfromcycloparaffins (Westmoreland2007)

Phenyladdition/cyclolizationpathway(Koshi2010)

Fulvenallene+acetylene(Bozzelli 2009)

Cyclopentadienyl+acetylene(Carvallotti etal.2007)

Cyclopentadienyl+cyclopentadienyl(Colket1994;Mebel 2009)

MillerandKlippenstein(2003)

PAH PrecursorChemistry(6)Recentadvanceinprobingflamebymolecularbeamsynchrotronphotoionizationmassspectrometrywillbecriticaltofurtherprogress.

CourtesyofQi

Photoionizationmassspectraofflamespeciesofburnerstabilizedaromatics/oxygen/50%argonflames(30Torr,C/O=0.68)determinedbymolecularbeamsynchrotronphotoionizationmassspectrometry.

1:benzene2:toluene3:styrene4:ethylbenzene5:oxylene6:mxylene7:pxylene

PAH PrecursorChemistry Summary

1. PAH formationissensitivetomainflamechemistry,localflameconditions,fuelstructureandcomposition.

2. Forrealfuelsandtheirsurrogate,thenumberofpathwaystoaromaticsiscurrentlyundefined;anditremainstobeseenwhetherthisnumberisfinite.

3. Requirestheoreticalapproachesbeyondonereactionatatimetypecalculations.

4. Needtoaccountfortheformationofaromaticradicals

SootNucleation(1)

C/H

1.22

~2

~10

C

B

A

C/H

1.22

~2

~10

C

B

A

Violi/DAnna

Frenklach/WangMiller

Homann

SootNucleation(2)

Secondordernucleationkinetics dimerizationofsootprecursorsleadstoPersistentbimodality.

FirstordernucleationkineticsgivesPSDFsthatarepersistentlyunimodal.

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100 101 102 103

D

i

m

e

n

s

i

o

n

l

e

s

s

N

u

m

b

e

r

D

e

n

s

i

t

y

,

n

i

/

C

o

Particle Size Parameter, i

1 2 3 4 5 10

Particle Diameter, D (nm)

Dimensionless time x = 1

x = 5

x = 20

x = 50

Zhaoetal.(2003a)

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

100 101 102 103Di

m

e

n

s

i

o

n

l

e

s

s

N

u

m

b

e

r

D

e

n

s

i

t

y

,

y

Particle Size, i

x = 10x = 20

x = 50

SootNucleation(3)

Zhaoetal.2003

Porous plug burner

Porous plug burner

Shielding Ar C2H4/O2/Ar Cooling water

Kr85

NDMA

P

Model 3080Electrostatic Classifier

Model 3025A

UCPC

Exhaust

SMPS System

Secondary air

P1

Diluent

N2 at 29.5 lpm

P2

Exhaust

Flow meter

Filter

orifice

Cooling water

Cooling water

Sample Probe System

Kr85

NDMA

P


Model 3025A

UCPC

Exhaust

SMPS System

Kr85

NDMA

P


Model 3025A

UCPC

Exhaust

SMPS System

Secondary air

P1

Diluent

N2 at 29.5 lpm

P2

Exhaust

Flow meter

Filter

orifice

Cooling water

Cooling water

Sample Probe System

10-4

10-3

10-2

10-1

100

101

102H = 0.55 cm H = 0.60 cm H = 0.65 cm

10-4

10-3

10-2

10-1

100

101

102H = 0.7 cm H = 0.8 cm H = 0.9 cm

N

o

m

r

a

l

i

z

e

d

D

i

s

t

r

i

b

u

t

i

o

n

F

u

n

c

t

i

o

n

,

n

(

D

)

/

N

10-4

10-3

10-2

10-1

100

101

102

4 6 8 10 30 503

H = 1.0 cm

4 6 8 10 30 503

H = 1.1 cm

4 6 8 10 30 503

H = 1.2 cm

Particle Diameter, D (nm)

MeasuredPSDFsareindeedbimodal

SootNucleation(5)Massspectrumoffragmentsfromphotoionizationofnascentsootshowperiodicity

100Torracetyleneoxygenflame( =3.25)

CourtesyofGrotheer

SootNucleation(1)

C/H

1.22

~2

~10

C

B

A

C/H

1.22

~2

~10

C

B

A

Violi/DAnna


Homann

SootNucleation(6)

10-1

100

101

0.70.8

0.91.0

1.1

(

1

/

N

)

d

N

/

d

l

o

g

(

D

p

)


(nm)


246810

2030

10-1

100

101

0.70.8

0.91.0

1.1

(

1

/

N

)

d

N

/

d

l

o

g

(

D

p

)


(nm)


246810

2030

Abidetal.(2009)

T

SootNucleation(1)

C/H

1.22

~2

~10

C

B

A

C/H

1.22

~2

~10

C

B

A

Possible,butnotgeneral Violi/DAnna


Homann

SootNucleation(7)

10

100

10 100

coroneneB

i

n

d

i

n

g

E

n

e

r

g

y

(

c

k

a

l

/

m

o

l

)

Number of C atoms

ovalene

circumcoronene

chrysene benzo[ghi]perylenepyrene

anthracene & phenanthrene

naphthalene

10-5

10-4

10-3

10-2

10-1

100200

400

600

800

1 2 3 4 5 6 7

R

e

l

a

t

i

v

e

C

o

n

c

e

n

t

r

a

t

i

o

n

Number of Aromatic Rings

B

o

i

l

i

n

g

/

S

u

b

l

i

m

a

t

i

o

n

T

e

m

p

e

r

a

t

u

r

e

(

K

)

10

100

10 100

coroneneB

i

n

d

i

n

g

E

n

e

r

g

y

(

c

k

a

l

/

m

o

l

)

Number of C atoms

ovalene

circumcoronene

chrysene benzo[ghi]perylenepyrene

anthracene & phenanthrene

naphthalene

10-5

10-4

10-3

10-2

10-1

100200

400

600

800

1 2 3 4 5 6 7

R

e

l

a

t

i

v

e

C

o

n

c

e

n

t

r

a

t

i

o

n

Number of Aromatic Rings

B

o

i

l

i

n

g

/

S

u

b

l

i

m

a

t

i

o

n

T

e

m

p

e

r

a

t

u

r

e

(

K

)

HerdmanandMiller(2008)

Bindingenergyofcoronene=25kcal/mol

SootNucleation(8)

6

0 1

1+ 1 4exp 1 i Bi i B

H E h k Th k T

3 2 23 01

422

6

1

2ln

ln 11

i B

i B

u B

h k Ti Bh k Ti

h pS BR m ek T

h k T ee

Is25.4kcal/molenoughtobindapairofcoronenetogether?

2coronene (coronene)2

Assumptions:vi =200cm1

B (cm1)=1510xMW2.12

2 =1-100

-50

0

50

100

150

0 500 1000 1500 2000 2500

G

o

(

k

c

a

l

/

m

o

l

)

T (K)

Binding

Nonbinding

G toopositivetoallowbindingabove700K Entropytearsthedimerapart.

OvaleneE0 =35kcal/molCircumcoroneneE0 =63kcal/molEventheywouldnotbind>1600K.

-60

-40

-20

0

20

40

60

0 500 1000 1500 2000 2500

G

o

(

k

c

a

l

/

m

o

l

)

T (K)

coroneneovalene

circumcoronene

SootNucleation(8)

6

0 1

1+ 1 4exp 1 i Bi i B

H E h k Th k T

3 2 23 01

422

6

1

2ln

ln 11

i B

i B

u B

h k Ti Bh k Ti

h pS BR m ek T

h k T ee

Is25.4kcal/molenoughtobindapairofcoronenetogether?

2coronene (coronene)2

Assumptions:vi =200cm1

B (cm1)=1510xMW2.12

2 =1OvaleneE0 =35kcal/molCircumcoroneneE0 =63kcal/molEventheywouldnotbind>1600K.

SootNucleation(1)

C/H

1.22

~2

~10

C

B

A

C/H

1.22

~2

~10

C

B

A

Violi/DAnna

Frenklach/Miller

Homann

Possible,butnotgeneral

SootNucleation(9) Polyacenesaresingletdiradicals(thougharguable).

Groundstatepolyacenesarecloseshellsinglets,buttheadiabaticS0T1excitationenergyisonly13kcal/molforheptacene Hajgatetal.(2009).

Applicationsinorganiclightemittingdiodesandorganicsemiconductorsandcapacitors.

SootNucleation(10)

Zigzagedgesofgraphenehavelocalizedelectronicstates

Kobayashi1993;Klein1994

Zigzagedgeshaveanopenshellsingletgroundstate

e.g.,Fujita etal.1996;Nakada 1996

Finitesizedgrapheneshaveradicalorevenmultiradicalcharacteristics.

e.g.,Nakano etal.2008,Nagai2010

Sidechaincaninduceradicalcharacteristics

Nakano etal.2007

Nonlinearopticsapplications.

i = 1 2 3 4

j = 1

2

3

i j y i j y1 1 0.000 1 3 0.0372 1 0.050 2 3 0.2173 1 0.149 3 3 0.5104 1 0.281 4 3 0.806

zigzag edge

A

r

m

c

h

a

i

r

e

d

g

e

i = 1 2 3 4

j = 1

2

3

i j y i j y1 1 0.000 1 3 0.0372 1 0.050 2 3 0.2173 1 0.149 3 3 0.5104 1 0.281 4 3 0.806

i j y i j y1 1 0.000 1 3 0.0372 1 0.050 2 3 0.2173 1 0.149 3 3 0.5104 1 0.281 4 3 0.806

zigzag edge

A

r

m

c

h

a

i

r

e

d

g

e

Nagaietal.2010UBHandHLYP/631G(D)calculations0 y 1y =0:closeshellsinglety =1:openshellsinglet(diradical)

SootNucleation Summary

If PAHswithradicalsdoplayaroleinsootnucleation,weneedto

UnderstandthenatureandstructuresofthesePAHspecies,

Determinetheirbindingenergieswithrelevantspecies,includingaromatics,

Probetheminflames(howeversmalltheirconcentrationsmaybe),

Accountforthemechanismoftheirformation.

SootMassGrowth(1)

SiH + H Si + H2 (1)Si + H SiH (2)Si + C2H2 Si+2H + H (3)

1

3 2 231 2

Hmol C-atom 2 S -H C Hcm s H

fs i

b

kkk

ThemassgrowthrateisproportionaltoHatomconcentration

HACA Mechanism

SootMassGrowth(2)Babysootisentirelyunlikematuresoot.

Comparisonofmobility andTEMmeasurementsshowsnascentsootisliquidlike ratherthanbeingcarbonizedandrigid.

SmallangleneutronscatteringandthermocoupledensitometrysuggestthatnascentsoothasC/H ~1 and =1.5g/cc.

Photoionizationaerosolmassspectrometry indicatesthatnascentsootisrichinaliphatics(inadditionaromatics).

Thepresenceofaliphaticssuggeststhatnascentsootisnotalwayspurelyaromatic.

ThemassofnascentsootcontinuetoincreaseinpostflamewhereHatomsaredepleted,incontrasttoHACA prediction presenceofpersistentfreeradicalsonsootsurface?

Wangetal.2003;Oktem etal.2005,Zhaoetal.2007

SootMassGrowth(3)C2H4O2Ar flame( =2.07,Tf =173650K)

Sunnysideupmorphology(TEM&AFM)suggestsanaromaticcorealiphaticshellstructure.

MicroFTIR measurementsagainshowaliphaticdominance Thermaldesportion/chemicalionization(extremesoft)showbroadmassspectrum,

suggestingthatnascentsootisalkylated. Thelargealiphatic/aromaticratioagainsuggestthattheinitialaromaticcoremaycontain

persistentfreeradicals. Abidetal.2008;Cainetal.2010

SootMassGrowth(4)Evidencesupportingpersistentfreeradicals

ElectronSpinResonancespectraofanthracite,acoalcontaining littletonooxygenatedcompounds,showameasurableconcentrationoffreeradicals(Retcofsky,Stark&Friedel 1968).

Sootvolumefractionobservedtowardsthestagnationsurfacecan bepredictedonlyifsootsurfacepersistsitsradicalnature(Wangetal1996).

SootfrompyrolysisofC2H4,C2H2 andjetfuelsurrogateshasappreciableamountsoffreeradicalsofaromatic nature.Thespinconcentrationsis~1021 pergram(1in50everyCatoms) (Eddings,Sarofim&Pugmire 2005).

Soot,anotherwisehydrophobicmaterial,hastheabilitytouptakewater(Popovicheva 2003).

BindingenergybetweenCH3 andH2O is1.5kcal/mol(CrespoOtero etal.2008),increasesto24kcal/molforC2C4 alkylradicals(Lietal.2009).

SootMassGrowth SummaryNascentsoothasaromaticcore/aliphaticshellstructure.

SootmassgrowthwithoutthepresenceofHatom.

Immediatequestionsandhypothesis:IsHACA mechanismcomplete?Dopersistentfreeradicalsexistonnascentsootsurfaces?

Resonantlystabilizedfreeradicalsofsemiquinoneandphenoxylorigins(Dellinger2001).

Radicalsduetostrainenergyinhexaphenylethaneandacenaphthenederivatives(Damesetal.2010).

SootMassGrowth SummaryRadicalsduetostrainenergyinhexaphenylethaneandacenaphthenederivatives(Dames,Sirjean,Wang2010).

0

10

20

30

40

50

60

70

0 2 4 6 8

M06-2X/6-31+G(d,p) electronic energy*M06-2X/6-31+G(d,p) Isodesmicexpt60

ONIOM62

C

e

n

t

r

a

l

B

D

E

(

k

c

a

l

/

m

o

l

)

7

9

11

13

1

4

5

SootMassGrowth SummaryNascentsoothasaromaticcore/aliphaticshellstructure.

SootmassgrowthwithoutthepresenceofHatom.

Immediatequestionsandhypothesis:IsHACA mechanismcomplete?Dopersistentfreeradicalsexistonnascentsootsurfaces.

Resonantlystabilizedfreeradicalsofsemiquinoneandphenoxylorigins(Dellinger2001).

Radicalsduetostrainenergyinhexaphenylethaneandacenaphthenederivatives(Damesetal.2010).

Delocalizedaromatic radicalsonzigzagedgespropagatedintosootstructures(Cainetal.2010 3D02).

SootFormation

CurrentPrevious(Calcote1982,Bockhorn1994)

fuel + oxidizer

CO, H2, CO2, H2O, C2H2

TheScienceofSootFormation

A.Ciajolo andA.TregrossiSysiphus rollingasootparticleuphill.

OurView NaturesView

http://www.historyforkids.org/learn/science/fire.htm

TheScienceofSootFormation

A.Ciajolo andA.TregrossiSysiphus rollingasootparticleuphill.

OurView NaturesView

Sysiphus stoping asootparticlefallingoffapotentialenergycliff.

OtherCondensedPhaseMatters

Whenwearestuck

Axelbaum variousnanoparticlesynthesis

Calcote carbideandnitride

Frenklach diamondthinfilmsandparticles,SiC andSinanoparticles

Kennedy YandEu oxidenanoparticles

Harris diamondthinfilms

Howard fullerenesandcarbonnanotubes

Roth variousoxidenanoparticles

Zachariah synthesis,characterizationandfundamentaltheoriesofnanoparticles

OtherCondensedPhaseMatters MetalOxide

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

H

,

T

S

,

G

(

k

c

a

l

/

m

o

l

-

C

)

r

r

r

Metaloxideformationissimpler,kineticallyandthermodynamically,thansootformation

TitaniaTiO2

SilicateSiO2

CourtesyofPratsinis

CourtesyofPratsinis

OtherCondensedPhaseMatters MetalOxide

UnintendedBenefitsofSootResearch

Trickslearnedinsimplifyingfluiddynamicsandvariousaspectsofthermodynamicsandchemicalkineticsleadtobetterdesignsformaterialssynthesis.

Characterizationmethodsforsootformationextendtheiruseinmaterialscharcaterization.


Collectionplate

Nozzle Collectionplate

Nozzle

0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)

5 minute

Alumina substrate

14 m

1070 ppm TTIP, 300 RPM 5 minute

Alumina substrate

14 m

1070 ppm TTIP, 300 RPM

increased precurso

r concentration

unburned gas& precursor

substrate


substrate

0

100

200

300

10 15 20 25 30

Time (hrs)

R

e

s

i

s

t

a

n

c

e

,

R

(

M

)

12 3

45

6

0

5

10

15

20

25

0

2

4

6

8

10

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

C

u

r

r

e

n

t

D

e

n

s

i

t

y

,

i

(

m

A

/

c

m

2

)

P

o

w

e

r

D

e

n

s

i

t

y

,

p

(

m

W

/

c

m

2

)

Voltage,V(V)

9.2% photoconversion efficiency

(a)

(b)

(c) (d)

Collectionplate


Nozzle

0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)

5 minute

Alumina substrate

14 m


Alumina substrate

14 m


increased precurso

r concentration


substrate


substrate

0

100

200

300

10 15 20 25 30

Time (hrs)

R

e

s

i

s

t

a

n

c

e

,

R

(

M

)

12 3

45

6

0

5

10

15

20

25

0

2

4

6

8

10

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

C

u

r

r

e

n

t

D

e

n

s

i

t

y

,

i

(

m

A

/

c

m

2

)

P

o

w

e

r

D

e

n

s

i

t

y

,

p

(

m

W

/

c

m

2

)

Voltage,V(V)


(a)

(b)

(c) (d)

Chemicalsensors:(1)280,(2)140,(3)93,(4)46,(5)18and(6)5PPMCOexposure

DyeSensitizedSolarCellusingFlamefabricatedphotoanode

ScalableonedimensionalmesoporousTiO2 filmsynthesis


Collectionplate


Nozzle

0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)

5 minute

Alumina substrate

14 m


Alumina substrate

14 m


increased precurso

r concentration


substrate


substrate

0

100

200

300

10 15 20 25 30

Time (hrs)

R

e

s

i

s

t

a

n

c

e

,

R

(

M

)

12 3

45

6

0

5

10

15

20

25

0

2

4

6

8

10

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

C

u

r

r

e

n

t

D

e

n

s

i

t

y

,

i

(

m

A

/

c

m

2

)

P

o

w

e

r

D

e

n

s

i

t

y

,

p

(

m

W

/

c

m

2

)

Voltage,V(V)


(a)

(b)

(c) (d)

Collectionplate


Nozzle

0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)0

2

4

3 4 5 6 7 8 9 10 20

[

d

N

/

d

l

o

g

(

D

p

)

]

/

N

Dp (nm)

5 minute

Alumina substrate

14 m


Alumina substrate

14 m


increased precurso

r concentration


substrate


substrate

0

100

200

300

10 15 20 25 30

Time (hrs)

R

e

s

i

s

t

a

n

c

e

,

R

(

M

)

12 3

45

6

0

5

10

15

20

25

0

2

4

6

8

10

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

C

u

r

r

e

n

t

D

e

n

s

i

t

y

,

i

(

m

A

/

c

m

2

)

P

o

w

e

r

D

e

n

s

i

t

y

,

p

(

m

W

/

c

m

2

)

Voltage,V(V)


(a)

(b)

(c) (d)

Chemicalsensors:(1)280,(2)140,(3)93,(4)46,(5)18and(6)5PPMCOexposure

DyeSensitizedSolarCell usingFlamefabricatedphotoanode

ScalableonedimensionalmesoporousTiO2 filmsynthesis

SummaryWhatisthevalueandfutureofsootresearch? Ononelevelthereisvalueincreatingmodelsasanintegralpartofenginedesigncodes,butthelargestimpactperhapswillbetoapplywhatwehavelearnedaboutsootformationinflamestomanydifferentprospectsofnanoparticlesynthesis.

Thegreatestbenefitsofcurrentknowledgewilllienotinincrementalimprovementsinsootreductionbutincreatingparticlesofvalueinenergy,catalysisandyetunimaginedfields.

2010-Combustion-Symposium_Wang.pdf

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Transcript of 2010-Combustion-Symposium_Wang.pdf