Computational and Experimental Study of the Structure of ...€¦ · OO Z st = 1+ sY FF /Y OO −1...
Transcript of Computational and Experimental Study of the Structure of ...€¦ · OO Z st = 1+ sY FF /Y OO −1...
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
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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)
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
• 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
• Max. Temp= 2050K
• Strain Rate≈ 95 s‐1
• Zf= 0.19
• Fixed temperature profile
• Flame on oxidizer side of stagnation plane
Incipient Sooting Flame Set
GSP
Fuel
Oxidizer
Flame
Selection of Flames Spanning a Broad Range of Conditions
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
• 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
• Max. Temp= 2050K
• Strain Rate≈ 95 s‐1
• Zf= 0.19
• Fixed temperature profile
• Flame on oxidizer side of stagnation plane
Incipient Sooting Flame Set
GSP
Fuel
Oxidizer
Flame
Selection of Flames Spanning a Broad Range of Conditions
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
C3-C4 species from alkanes cracking contribute to aromatic growthSurrogate mixture generates typical compounds in jet fuel
Doped Ethylene Flames: Aromatic Growth
MACCCR Fuel Summit, September 2011
• 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
• Max. Temp= 2050K
• Strain Rate≈ 95 s‐1
• Zf= 0.19
• Fixed temperature profile
• Flame on oxidizer side of stagnation plane
Incipient Sooting Flame Set
GSP
Fuel
Oxidizer
Flame
Selection of Flames Spanning a Broad Range of Conditions
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
Low Temperature Synergistic effects on Aromatic growth
Open symbols: single-component dopingFull symbols: surrogate doping
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
High‐Pressure CounterflowFlames
MACCCR Fuel Summit, September 2011
Critical Scaling
Flow Laminarity
Buoyancy/inertia
Re =Udν
< Recr ≈ 2,300
Counterflow
Coflow
Figura and Gomez, CNF to appear
Burner separation
Strain rateFlame height
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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−−
=
MACCCR Fuel Summit, September 2011
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
MACCCR Fuel Summit, September 2011
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.
MACCCR Fuel Summit, September 2011
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