Energy Frontier Research Center for Combustion Science
Stanford University Contribution
R. K. Hanson and D. F. DavidsonDepartment of Mechanical Engineering
Stanford University
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• Butanol Studies
• Ignition Delay Times
• Species Time-Histories
• Reaction Rate Constants
• Methyl Ester Studies
• Ignition Delay Times
Long-Term Objectives
• Generate high-quality fundamental kinetics database using shock tube/laser absorption methods
Leading to:
• Improved detailed mechanisms for next-generation fuels
First Targets:
• Isomers of butanol; large bio-derived methyl esters
2
3
Stanford Shock Tube & Laser Facilities
DriverSection
Shock TubeDriven Section
Ring Dye Lasers(UV & Vis)
Diode Lasers(Near IR & Mid-IR)
CO2 Lasers(9.8-10.8 µm)
Shock Tubes (4)
Large Diameter Tubes (15 cm and 14 cm)
High Pressure Tube (5 cm) heatable to 150C
Aerosol Tube (11 cm)
Optical Diagnostics
Laser Absorption(UV, Vis, Near-IR, Mid-IR)
Advantages of Shock Tubes Near-Ideal Constant Volume Test PlatformWell-Determined Initial T & P Clear Optical Access for Laser Diagnostics
Ti:Sapphire Laser(Deep UV)
He-Ne Laser(3.39 µm)
UV/Vis/IREmissionDetectors
Transmitted Beam Detector
PressurePZT
VS VRSP5 T5
Butanol Studies:
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1. Ignition Delay Times of the 4 Isomers1050-1500 K, 1.5-42 atm, φ=0.5, 1, 4% O2
2. Multi-Species Time-Histories in 1-ButanolOH, H2O & butanol during pyrolysis and oxidation
3. Direct Rate Constant Measurements1-butanol+OH products
1-Butanol Ignition Delay Times:Pressure Dependence (1.5 to 42 atm)
• Data acquired using both low-pressure and high-pressure shock tubes
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0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
100
1000
1-Butanol, 4% O2, Φ = 1
1.5 atm
19 atm
1111 K1250 K1429K
t ign
[µs]
1000/T5 [1/K]
3.0 atm
42 atm
1-Butanol Ignition Delay Times:Pressure Dependence (1.5 to 42 atm)
• Data acquired using both low-pressure and high-pressure shock tubes
• τign scales as P-0.67
over wide pressure range for φ=1
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0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
100
1000
1-Butanol, 4% O2, Φ = 1
1111 K1250 K1429K
t ign
[µs]
1000/T5 [1/K]
All data (1.5-42 atm)normalized to 20 atmusing P-0.67
1-Butanol Ignition Delay Times:Comparison with MIT Mechanism (1.5 to 42 atm)
• Low Pressures: Good agreement with MIT mechanism (Harper,Green 8/10)
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0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
100
1000
P = 1.5 atm
Lines (MIT 2010)
1-ButanolΦ = 1, 4% O2/Ar
1111 K1250 K1429K
t ign
[µs
]
1000/T [1/K]
P = 3 atm
1-Butanol Ignition Delay Times:Comparison with MIT Mechanism (1.5 to 42 atm)
• Low Pressures: Good agreement with MIT mechanism (Harper,Green 8/10)
• High Pressures:Significant differences (up to 50%) between model and experiment
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0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
100
1000
1000K P = 1.5 atm
P = 19 atm
Lines (MIT 2010)
1-ButanolΦ = 1, 4% O2/Ar
1111K1250K1429K
t ign
[µs
]
1000/T [1/K]
P = 3 atm
P = 42 atm
Butanol Ignition Delay Times:Variation with Isomer (1.5 atm)
• 1-butanol fastest
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0.60 0.64 0.68 0.72 0.76 0.80 0.84
100
1000
1-butanol2-butanoliso-butanoltert-butanol
1190 K1389 K
t ign
[µs]
1000/T [1/K]
1667 K
Butanol Ignition Delay Times:Variation with Isomer (1.5 atm)
• 1-butanol fastest
• 2-butanol and iso-butanol similar
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0.60 0.64 0.68 0.72 0.76 0.80 0.84
100
1000
1-butanol2-butanoliso-butanoltert-butanol
1190 K1389 K
t ign
[µs]
1000/T [1/K]
1667 K
OH
OH
Butanol Ignition Delay Times:Variation with Isomer (1.5 atm)
• 1-butanol fastest
• 2-butanol and iso-butanol similar
• Tert-butanolslowest (~2-3x) with larger EA
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0.60 0.64 0.68 0.72 0.76 0.80 0.84
100
1000
1-butanol2-butanoliso-butanoltert-butanol
1190 K1389 K
t ign
[µs]
1000/T [1/K]
1667 K
Butanol Ignition Delay Times:Comparison with MIT Mechanism (1.5 atm)
• 1-, 2-butanol:Good agreement with MIT (8/10) model
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0.60 0.64 0.68 0.72 0.76 0.80 0.84
100
1000
1-butanol2-butanol
1190 K1389 K
t ign
[µs]
1000/T [1/K]
1667 K
Butanol Ignition Delay Times:Variation with Isomer (1.5 atm)
• 1-, 2-butanol:Good agreement with MIT (8/10) model
• iso-, tert-butanol:Poorer agreement with model
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0.60 0.64 0.68 0.72 0.76 0.80 0.84
100
1000
iso-butanoltert-butanol
1190 K1389 K
t ign
[µs]
1000/T [1/K]
1667 K
Butanol Ignition Delay Times:Comparison with Other Laboratories
• 1-Butanol (low P):Good agreement with Moss et al. (RPI)
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0.55 0.60 0.65 0.70 0.75 0.80
100
1000
Current Study Moss et. al. (2008)
1333 K
t ign
[µs]
1000/T [1/K]
1667 K
1-Butanol/3%O2/Ar
1.2 atm, φ=1
MIT Model (2010)
Butanol Ignition Delay Times:Comparison with Other Groups
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0.55 0.60 0.65 0.70 0.75 0.80
100
1000
1333 K1667 K
Current Study Oehlschlaeger et al. (RPI)
t ign
[µs]
1000/T [1/K]
2-Butanol/6%O2/Ar1.2 atm, φ=1
MIT Model (2010)
• 1-Butanol (low P):Good agreement with Moss et al. (RPI)
• 2-, tert-, & iso-butanol :Poor agreement with RPI data
Species Time-Histories:1-Butanol
Pyrolysis and Oxidation
Species: OH, H2O, 1-Butanol
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1-Butanol Pyrolysis:OH and H2O Species Time-Histories
• First speciestime-history data for 1-butanol pyrolysis
• Goal: quantify evolution of all keyC, H & O species
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1431 K, 1.49 atm,1% 1-butanol in argon
10 100 1000
10
100
1000
10000 H2O
Mol
e Fr
actio
n [p
pm]
Time [µs]
OH
1-Butanol Pyrolysis:OH and H2O Species Time-Histories
• Significant differences between MIT model and data
• Future Work: Carbon and oxygen closure by addition of CO, CH2O, CH4, C2H4, C3H6, C2H2measurements
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1431 K, 1.49 atm,1% 1-butanol in argon
10 100 1000
10
100
1000
10000 H2O
Mol
e Fr
actio
n [p
pm]
Time [µs]
OH
MIT Model
1-Butanol Oxidation:OH and H2O Species Time-Histories
• First time-history data for 1-butanol oxidation
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1433 K, 1.51 atm, φ=1 1000 ppm 1-butanol in O2/argon
10 100 1000
10
100
1000
10000
H2O
Mol
e Fr
actio
n [p
pm]
Time [µs]
OH
1-Butanol Oxidation:OH and H2O Species Time-Histories
• First time-history data for 1-butanol oxidation
• Major differences in model and data time scales
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1433 K, 1.51 atm, φ=1 1000 ppm 1-butanol in O2/argon
10 100 1000
10
100
1000
10000
H2O
Mol
e Fr
actio
n [p
pm]
Time [µs]
OH
MIT Model
1-Butanol Oxidation:OH and H2O Species Time-Histories
• First time-history data for 1-butanol oxidation
• Major differences in model and data time scales
• Future: Complete picture of ignition by addition of fuel, intermediates, and product profiles
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1433 K, 1.51 atm, φ=1 1000 ppm 1-butanol in O2/argon
10 100 1000
10
100
1000
10000
H2O
Mol
e Fr
actio
n [p
pm]
Time [µs]
OH
Elementary Reaction Rate Constant Measurements:
1-Butanol+OH Products
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1-Butanol + OH Products
• Importance of OH+Fuel reactions under lean conditions
• No previous data
• Large uncertainty in estimations of OH rate constant for 1-butanol oxidation
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0.7 0.8 0.9 1.0 1.11E12
1E13
1E14 1000K
Reac
tion
Rate
[c
c/m
ol/s
]
1000/T, (1/K)
Black et al. 2010 (NUI) Moss et al. 2008 (RPI) Harper et al. 2010 (MIT) Westbrook model 2010 (LLNL)
1250K
1-Butanol + OH Products
3 Part Strategy:
1. Fast OH source: TBHP (tert-butyl-hydroperoxide)TBHP OH + CH3 + CH3COCH3
2. pseudo-first order removal1-butanol >> OH
3. Monitor OH using laser absorptionppm detection sensitivity
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Representative OH Laser Absorption Data
• OH laser absorption provides high SNR
• Strong sensitivity to title reaction
• Low overall uncertainty: +/- 14%
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Reflected Shock Conditions: 1165K, 2 atm
150ppm C4H9OH/10ppm TBHP/Ar
0 10 20 30 40 50 60
0
5
10
15
k=2.1x1013 Best Fit k=1.0x1013
k=4.2x1013
OH
[pp
m]
Time [µs]
Arrhenius Plot: 1-Butanol+OH Products
• Excellent agreement with recent theory byZhou, Simmie et al. (2010)
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0.7 0.8 0.9 1.0 1.11E12
1E13
1E14 1000K
Reac
tion
Rate
[c
c/m
ol/s
]
1000/T, (1/K)
Zhou, Simmie (2010) Moss et al. 2008 (RPI) Westbrook et al. (LLNL) Black et al. 2010 (NUI) Harper et al. 2010 (MIT)
1250K
Methyl Ester Studies:
1. Use of Aerosol Shock Tubeaccess to low-vapor-pressure fuels
2. Bio-Derived Methyl Esters and Surrogatesmethyl decanoate, methyl oleate
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Aerosol Shock Tube for Low-Vapor-Pressure Fuels
• Does not require heated shock tube• Eliminates fuel cracking and partial distillation• Provides access to low-vapor-pressure fuels:
Jet fuel, diesel, bio-diesel surrogates
Laser
Detector
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Aerosol Shock Tube Operation Regime
• Unheated ST provides access up to C3 methyl esters
• Heated ST provide access up to methyl decanoate(C10:0)
• AST provides access up to large (C25:0) methyl esters
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Shock Tube Access to Fuels: Saturated Methyl Esters
T5=1000K, P5=10atmΦ=1 in air
Preliminary τign Data for Methyl Decanoateand Comparison with Diesel
• Previous AST studies have provided Diesel τign data
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Preliminary τign Data for Methyl Decanoateand Comparison with Diesel
• First ignition delay data for bio-diesel surrogate methyl decanoate(C11H22O2, C10:0)
• Critically needed for model validation
• Experiments in progress at other conditions
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First τign Data for Methyl Oleate (9/10/10)
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• Demonstrates abilityof 2nd Gen AST to study very-low vapor pressure compounds
C19H36O2, C18:1
Future Work• Rate constant measurements of Butanol+OH for all isomers
i.e., 2-butanol, iso-butanol, tert-butanol
• Extend τign measurements to low temperatures
• Establish ignition delay time and species time-history databasefor methyl oleate (C19H36O2), methyl stearate (C19H38O2)
• Extend species time-history measurementsto CO, CO2, CH2O, CH4, C2H4, C3H6, …
• Continued collaboration with EFRC mechanism team
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Acknowledgements
• Visit Stanford website http://hanson.stanford.edu/ for
Fundamental Kinetics Database Using Shock Tubes
• Thanks to our four shock tube/laser jockeys:
Dr. S. Vasu (OH) I. Stranic (τign) M. Campbell (τign) R. Cook (OH, H2O) 34