Computational and Experimental Study of the Structure of ...€¦ · OO Z st = 1+ sY FF /Y OO −1 Mixture Fraction (Conserved Scalar) StoichiometricMixture Fraction . MACCCR Fuel

MACCCR Fuel Summit, September 2011

Mitchell D. Smooke and Alessandro Gomez

Department of Mechanical Engineering and Materials ScienceYale University, New Haven, CT 06520‐8286

Computational and Experimental Study of the Structure of Diffusion Flames of Jet Fuel and its

Surrogates at Pressures up to 40 atm


Laminar Flames with Complex Chemistry

Broad objectives: probing diffusion flames as flow reactors to study – the chemistry of critical jet fuel components and/or surrogate(s)

– soot formation under conditions of incipient sooting

– all of the above at high pressures

and develop data base for validation of chemical appropriate kinetic mechanisms


Approach• One‐dimensional counterflow flame • Use baseline (methane/ethylene) flame as a “controlled” flow

reactor providing a fixed time‐temperature baseline and constant stoichiometric mixture fraction

• Add O(1000) ppm liquid fuel (JP8, surrogate, surrogate components)


Type 1 Flame Zst < 0.5

fuel

oxidizerflame

stagnationplane

Z =sYF − (YO −YOO )

sYFF + YOO

Zst = 1+ sYFF / YOO( )−1

Mixture Fraction (Conserved Scalar)

Z=0

Z=1

ZST < 0.5

mass fraction

Stoichiometric Mixture Fraction


Z=0

Z=1

ZST > 0.5

mass fraction

fuel

oxidizer

flame

stagnationplane

Type 2 Flame Zst > 0.5

Z =sYF − (YO −YOO )

sYFF + YOO

Zst = 1+ sYFF / YOO( )−1

Mixture Fraction (Conserved Scalar)

Stoichiometric Mixture Fraction


• Methane based

• Max. Temp= 2150K

• Strain Rate≈ 160 s‐1

• Stoich. mixture fraction Zf= 0.79

• Fixed temperature profile

• Flame on fuel side of stagnation plane

Non‐sooting Flame Set

GSP

Fuel

Oxidizer

Flame

• Ethylene based



• Zf= 0.19


• Flame on oxidizer side of stagnation plane

Incipient Sooting Flame Set

GSP

Fuel

Oxidizer

Flame

Selection of Flames Spanning a Broad Range of Conditions


Experimental ConditionsCH4

Baseline

CH4

+Toluene

CH4

+Iso-Octane

CH4

+ Decane

CH4

+Princeton-3

C2H4

Baseline

C2H4

+Toluene

C2H4

+Iso-Octane

C2H4

+Decane

C2H4

+Princeton-3

Fuel

Sid

e

Molar Composition

N2 0.897 0.899 0.900 0.901 0.906 0.728 0.730 0.731 0.733 0.739CH4 0.103 0.100 0.099 0.098 0.092C2H4 0.272 0.268 0.267 0.266 0.257

C2H6 Impurities < 30ppm < 30ppm < 30ppm < 30ppm < 30ppm 270ppm 270ppm 270ppm 270ppm 270ppm

Toluene 440 ppm 439 ppm 865 ppm 865 ppmIso-Octane 599 ppm 598 ppm 1177 ppm 1176 ppm

n-Decane 774 ppm 773 ppm 1525 ppm 1521 ppm

Mass Flux(g/(cm2·min)

2.8 2.87 2.90 2.93 3.11 1.62 1.65 1.66 1.67 1.73

Temperature (K) 435

Oxi

dize

r sid

e

Molar Composition

N2 0.227 0.227 0.227 0.227 0.227 0.814 0.814 0.814 0.814 0.814O2 0.773 0.773 0.773 0.773 0.773 0.186 0.186 0.186 0.186 0.186

Mass Flux(g/(cm2·min)

3.19 3.29 3.33 3.37 3.61 1.89 1.91 1.91 1.92 1.95

Temperature (K) 380

Strain Rate (s-1) 154 158 160 161 171 94 95 95 95 98

zf 0.79 0.19


• Methane based







GSP

Fuel

Oxidizer

Flame

• Ethylene based



• Zf= 0.19




GSP

Fuel

Oxidizer

Flame



Black symbols: baseline flame (no dopant)Open symbols: single-component flameFull symbols: flame doped with Princeton-3

a) Decane 865ppmb) Iso-Octane 1180ppmc) Toluene 1525ppmd) Princeton-3: a)+b)+c)

1000 K

Doped Ethylene Flames: General Structure, C1-C2s

C1‐C2s

No dopant synergy


Iso-Octane- main source of C3 and C4 speciesDecane- contributes to C3 and C5 species

Toluene- main source of extra BenzeneIso-Octane- also contributes through C3 species

Doped Ethylene Flames: General Structure, C3-C6s


C3-C4 species from alkanes cracking contribute to aromatic growthSurrogate mixture generates typical compounds in jet fuel

Doped Ethylene Flames: Aromatic Growth


• Methane based







GSP

Fuel

Oxidizer

Flame

• Ethylene based



• Zf= 0.19




GSP

Fuel

Oxidizer

Flame



Black symbols: baseline flame (no dopant)Open symbols: single-component flameFull symbols: flame doped with Princeton-3

0

100

200

300

400

500

600

700

800

900

1 2 3 4 5 6 7 8 9 10Z, mm

ppm Toluene

Iso‐Octane

Decane

Toluene

Iso‐Octane

Decane

a) Decane 775ppmb) Iso-Octane 600ppmc) Toluene 440ppm

Princeton-3: a)+b)+c)

Doped Methane Flames: General Structure

1000 K

Interaction Effects between Surrogate Components at

“Low” Temperatures


Methane Flames: Low Temperature Chemistry and Interactions

Concentration levels low-temperature chemistry is active in decane and iso-octane, but weak in toluene

Profile shifts low-temperature chemistry is delayed for iso-octane but accelerated for decane and toluene through component interactions

Open symbols: single-component dopingFull symbols: surrogate doping


Low Temperature Synergistic effects on Aromatic growth

Open symbols: single-component dopingFull symbols: surrogate doping


Principal Observations

• Experimental testbed for to account for diffusive-reactive effects and test/validate kinetic mechanism in flames

• Application to Princeton-3 surrogate and its components• Incipiently sooting flame (low-Zf flame ethylene baseline)

– No interaction effects in components decomposition at low temperature

– Synergistic effects for aromatic growth • Nonsooting flame (high-Zf flame methane baseline)

– Interaction effects in component decomposition at low (?)temperatures in surrogate

– Synergistic effects for aromatic growth


High‐Pressure CounterflowFlames


Critical Scaling

Flow Laminarity

Buoyancy/inertia

Re =Udν

< Recr ≈ 2,300

Counterflow

Coflow

Figura and Gomez, CNF to appear

Burner separation

Strain rateFlame height


Critical Scaling (cont’ed)• Spatial resolution challenges:

• Mixing layer thickness decreases with p‐1/2

Where α and a are the thermal diffusivity and the strain rate, respectively.

• Use of He as inert to maintain laminar conditions, avoid buoyancy instabilities and preserve reasonable spatial resolution for flame probing.

δ T

δ T0 ≈

αa

a0

α 0

∝p0⋅ a0

p⋅ a


Experimental system

• Pressure chamber can operate at up to 40 atm.• Counterflow combustor, 7 mm inlet diameter, mounted on vertical translational stage, can stabilize blue flat flame at 30 atm.

20 cm

Pressure chamber Counter flow combustor

12 cm


7.1mm

(a)

(b)

(c)

a) high shroud flow‐ YFF = 0.335, Zst = 0.4, a = 40/s, P = 30 atm;

b) low shroud flow‐ YFF = 0.33, Zst = 0.41, a = 30/s, P = 18 atm;

c) wrinkled flame with same conditions as in b) but with the (heavier) oxidizer stream being fed from the top and high shroud flow.

•Helium in shrouds suppresses the peripheral soot (that is massively produced at elevated pressures) under still laminar conditions.

•Flat fames are stabilized when the heavier (oxidizer) mixture is injected from the bottom under buoyancy‐stable conditions.

Using Helium as Inert


High Pressure Scaling (Exp)

Rescaled T scans with Thin Filament pyrometry up to 30 atm

δdiff =Dtherm

ap0

p

Characteristic diffusionlength

Reduced temperature

)()(

BCMax

BCred TT

TTT−−

=


Domain of Operation

Black : N2‐diluted flames

Ad: adiabatic limit

Rec: critical Reynolds

SR: spatial resolution

Helium as inert extends the operability at higher pressuresthicker flames delayed turbulent transition


Conclusions• We established scaling laws to stabilize high-pressure steady

laminar counterflow flames with well characterized boundaryconditions

• We validated the scaling by stabilizing steady non-sooting orincipiently sooting flames at pressures up to 30 atm usingHelium as inert in the high-pressure range.

Current Activity

• We have adapted the burner to gas sampling forsubsequent GC-MS analysis.

• We are developing a high spatial resolution“thermophoretic” sampling technique, using fine wiresto probe thin flames at high pressures.

• Funding permitting, we will adapt the rig to doping bysurrogate components.


Publications acknowledging AFOSR support

1. Jahangirian, S., McEnally, C. S., and Gomez, A., Combust. Flame 156:1799-1809 (2009). 2. Tosatto, L., Mantia, B. L., Bufferand, H., Duchaine, P., and Gomez, A. Proc. Combust. Inst., 32 (2009) 1319–1326. 3. Bufferand, H., Tosatto, L., Mantia, B. L., Smooke, M. D., and Gomez, A., Combust. Flame 156:339-356 (2009). 4. Figura, L. and Gomez, A., “Laminar Counterflow Steady Diffusion Flames under High Pressure (P ≤ 30 Bar) Conditions,”

to appear in Combust. Flame.5. Tosatto, L., Bennett B.A.V., D., and Smooke, M. D., Comb. Theory and Modelling, 15, (2011).6. Tosatto, L., Lu, T., Bennett, B. A. V., and Smooke, M. D., Comb. and Flame, 158, (2011). 7. Carbone, F. and Gomez A., in preparation8. Carbone, F. and Gomez A., in preparation

Research supported by the Air Force Office of Scientific Research (Grant # FA9550-06-1-0018, Dr. Julian Tishkoff, Program Manager) and partially supported

by NSF (Grant #CBET-0651906, Dr. Arvind Atreya, Program Director).

Postdoc: Francesco CarboneGraduate students: Lorenzo Figura, Luca TosattoVisiting students: Hugo Bufferand, Saeed Jahangirian, Patrick DuchaineCollaborators: Beth Bennett (Yale), Charles Mc Enally (Yale), Eliseo

Ranzi’s group (Milan)

Acknowledgements

Documents

Computational and Experimental Study of the Structure of ...€¦ · OO Z st = 1+ sY FF /Y OO −1 Mixture Fraction (Conserved Scalar) StoichiometricMixture Fraction . MACCCR Fuel