Energy Frontier Research Center for Combustion Science

Stanford University Contribution

R. K. Hanson and D. F. DavidsonDepartment of Mechanical Engineering

Stanford University

1

• 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

5

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

6

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