Chemical Kinetics Studies ofAlt ti F lAlternative Fuels

Chih-Jen (Jackie) SungChih Jen (Jackie) SungDepartment of Mechanical Engineering

University of Connecticuty

Prepared for2010 MACCCR and CEFRC Conferences2010 MACCCR and CEFRC Conferences

Princeton, NJ

September 23, 2010

Accomplishments – Year 1

•• AutoignitionAutoignition of of nn--ButanolButanol at Low to Intermediate at Low to Intermediate Temperatures and Elevated Pressures*Temperatures and Elevated Pressures*Temperatures and Elevated PressuresTemperatures and Elevated Pressures–– PPCC = 15 = 15 –– 30 bar; 30 bar; TTCC = 675 = 675 –– 925 K925 K

A t i iti f M th l E i t d• Autoignition of Methanol: Experiments and Computations– PC = 7 – 30 bar; TC = 850 – 1100 K

• Nanoparticle-Enhanced Combustion of Liquid Fuels– PC = 15 – 28 bar; TC = 772 – 825 K

• Laminar Flame Speeds of Moist Syngas Mixtures• Laminar Flame Speeds of Moist Syngas Mixtures

** Bryan Weber, Kamal Kumar, Yu ZhangBryan Weber, Kamal Kumar, Yu Zhang

Summary: n-Butanol Autoignition

• Simulated ignition delays computed using four reaction mechanisms available in the literature are much longer than experimental ignition delaysexperimental ignition delays.

• Although the reaction mechanisms have not been validated in the temperature and pressure range studied here, the degree of p p g gdifference is still rather surprising.

• Sensitivity analysis at low temperatures shows the impotence of h d b i i f b l b HO fhydrogen abstraction reaction from n-butanol by HO2 to form-hydroxybutyl radical.

• Reaction path analysis on the mechanism of Black et al (2010)Reaction path analysis on the mechanism of Black et al. (2010) reveals several pathways which may need to have their rates adjusted and at least two pathways which are missing entirely.– Propanal formation and tautomerization of but-1-en-1-ol to butanal.

Autoignition of n-Butanol:Experiments vs. Simulations

10n-Butanol/O2/N2, =1.0, PC=15 bar

Current DataBl k t l (2010)

1

Black et al. (2010)Moss et al. (2008)Grana et al. (2010)Harper et al. (2010)

y (s

)io

n D

elay

0.1

Igni

ti

0.011.15 1.2 1.25 1.3 1.35 1.4

O2 : N2 = 1 : 3.76

1000/TC (1/K)

Rapid Compression Machine Operation

Autoignition of n-Butanol:RCM Simulations

40

45n-Butanol/O2/N2, =1.0, PC=15 bar

Current DataBl k t l (2010)

30

35

40 Black et al. (2010)Moss et al. (2008)Grana et al. (2010)Harper et al. (2010)

)

20

25

ssur

e (b

ar)

TC = 758 K

10

15Pre

s

0

5

0 02 0 0 02 0 04 0 06-0.02 0 0.02 0.04 0.06

Time (s)

Experimental Reproducibility

30

35n-Butanol/O2/N2, =1.0, PC=15 bar, TC=758 K

O2 : N2 = 1 : 3.76

• Each compressed pressure 25

30

End of Compressionand temperature condition

is repeated at least 6 times 15

20

essu

re (b

ar) End of Compression

to ensure reproducibility.10

5

Pre

Ignition Delay

0

5

0 03 0 02 0 01 0 0 01 0 02 0 03 0 04-0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04

Time (s)

Mixture Preparation (1)

104Saturated Vapor Pressure vs. Temperature

orr)

102

103

ssur

e (T

o

101n-butanolap

or P

res

0.1

1 iso-octaneethanolmethanoln-decanera

ted

Va

0.01250 275 300 325 350 375 400

Satu

r

Temperature (K)Temperature (K)

Mixture Preparation (2)

• Homogeneous test mixture prepared in a stirred, heated stainless steel tank of known volume– Gaseous components in the test mixture are determined

manometrically

– Liquid fuel components are added on a gravimetric basis

• Add air/fuel under ambient temperature conditions

• Preheat temperature (below the boiling points of the liquid fuel components)– Continuous magnetic stirring

– Soak time ~ 1.5 hours for complete vaporization of the liquid componentsliquid components

Composition Confirmation• Liquid calibration standards and gas samples

withdrawn from the mixing tank are analyzed using GCMSTh i d iti f i iti l i i t k• There is no decomposition for initial mixing tank temperature of 87˚C

• iso-Octane is used as an internal standard for checking the concentration of n butanolchecking the concentration of n-butanol

• Composition checks show actual concentration is within 4% of expected concentration

Autoignition of n-Butanol (1)

906 K 898 K35

n-Butanol/O2/N2, =0.5, PC =15 bar

T • Increasing compressed924 K 879 K866 K

853 K834 K25

30TC

Increasing compressed temperature reduces ignition delay834 K

824 K15

20

ssur

e (b

ar) ignition delay

monotonically.

N t t i iti813 K10

15

Pres • No two-stage ignition

and no NTC behavior f d f h

0

5

-0.02 0 0.02 0.04 0.06 0.08 0.1

O2 : N2 = 1 : 3.76 found for the conditions tested.

Time (seconds)

Autoignition of n-Butanol (2)

0.1n-Butanol/O2/N2, PC = 15 bar

= 0.5 = 1 0 = 1.0 = 2.0

y (s

)tio

n D

elay

0.01Igni

t

1 1 1 1 2 1 3 1 4 1 5

O2 : N2 = 1 : 3.76

1 1.1 1.2 1.3 1.4 1.5

1000/TC (1/K)

Autoignition of n-Butanol (3)

0 1

n-Butanol/O2/N2, PC = 15 bar

(a) O2 Mole % = 20.3

n-Butanol/O2/N2, PC = 15 bar

(b) Fuel Mole % = 3.380.1

y (s

)

0.1

y (s

)

nitio

n D

elay

nitio

n D

elay

0.01

Fuel Mole % = 1.69, = 0.5Fuel Mole % = 6.77, = 2.0

Ign

0.01

O2 Mole % = 40.6, = 0.5O2 Mole % = 10.2, = 2.0

l Ig

n

1.1 1.15 1.2 1.25 1.3 1.35 1.4 1.45

, Fuel Mole % = 3.38, = 1.0

1000/TC (1/K)1.15 1.2 1.25 1.3 1.35 1.4 1.45 1.5

O2 Mole % = 20.3, = 1.0

1000/TC (1/K)C C

Autoignition of n-Butanol (4)

0.1n-Butanol/O2/N2, = 1.0

O2 : N2 = 1 : 3.76(s

) PC = 15 bar

ion

Del

ay

P 30 b

0.01

Igni

ti PC = 30 bar

1 15 1 2 1 25 1 3 1 35 1 4 1 45 1 51.15 1.2 1.25 1.3 1.35 1.4 1.45 1.5

1000/TC (1/K)

Autoignition of n-Butanol (5)

100Correlated Ignition Delay

)=10A [XO2]a [Xn-Butanol]b PCn exp(Ta /TC)

10-1-1

.4 P

C-1

.5)

A = -(8.5 ± 0.8)a = -(1.7 ± 0.2)b = -(1.4 ± 0.2)n = -(1.5 ± 0.3)T = 9730 3 ± 1035 5

0.0169 < Xn-Butanol < 0.06760.1015 < XO2 < 0.406

15 < PC < 30 bar675 < TC < 925 K

10 3

10-2

Xn-

But

anol

- Ta = 9730.3 ± 1035.5 675 < TC < 925 K

10-4

10-3

/ (X

O2-

1.7

10-51 1 1 1 2 1 3 1 4 1 5 1 6

CorrelationExperiments

1 1.1 1.2 1.3 1.4 1.5 1.6

1000/TC (1/K)

Ignition Delay Comparison

0.1n-Butanol/O2/N2, = 1.0

O2 : N2 = 1 : 3.76

0.01

y (s

)

0.001

on D

elay

0.0001Current Data, PC = 30 barCurrent Data, PC = 15 barHeufer et al (2010) 10 11 bar

Igni

ti

10-50.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

Heufer et al. (2010), 10-11 barHeufer et al. (2010), 18-22 barHeufer et al. (2010), 36-42 bar

1000/T (1/K)

Sensitivity Analysis

H+O2O+OH

NC4H9OH+OHC4H8OH-3+H2O

n-Butanol/O2/N2, =1.0, PC =15 atm, O2 : N2 = 1 : 3.76

• NUI mechanism is most sensitive to the reaction of

CH3+HO2CH3O+OH

CH2O+HO2HCO+H2O2

NC4H9OH+HO2C4H8OH-2+H2O2700 K1100 K1800 K

sensitive to the reaction of n-butanol+HO2 to form hydroxybutyl

H2O2(+M)2OH(+M)

HO2+OHH2O+O2

CH3+HO2< >CH3O+OH -hydroxybutyl.

• The sensitivity is i ifi l d d

NC4H9OH+HO2C4H8OH-1+H2O2

NC4H9OH+HO2C4H8OH-3+H2O2

CH3+HO2CH4+O2 significantly reduced at higher temperatures.

-40 -30 -20 -10 0 10 20Percent Sensitivity

Reaction Path Analysis (1)

• A Reaction Path Diagram shows the percent of

the reactant destroyed to form the product

indicated by the arrowindicated by the arrow.

• The percent destruction represents the cumulative

destruction of each reactant up to the point in time

where the mole fraction of fuel has been reduced

20% compared to the initial value.p

Reaction Path Analysis (2)

• n-Butanol (C4H9OH) is destroyed by H-atom abstraction producing 5 radicals.

• These radicals are not equally produced• These radicals are not equally produced.

Reaction Path Analysis (3)

Reaction Path Analysis (4)

Reaction Path Analysis (5)800 K, 15 atm, and =1.0

• Several fuel decomposition pathways have been reported in the literature, but are missing from the mechanism by Black et al. (2010).

• These missing pathways, or other pathways with questionable reaction rates, may be causing the discrepancy between experimental results and simulations.

• Quantum calculations on fuel decomposition reaction rates and speciation measurements during the ignition process are needed.

Future Work

• Autoignition of Butanol Isomers

• Autoignition of other Emerging Biofuels

(e.g. iso-pentanol, 2-buten-1-ol)

• Autoignition of Gasoline/Bio Alcohol Blends• Autoignition of Gasoline/Bio-Alcohol Blends

• In situ Absorption Spectroscopy in Rapid p p py p

Compression Machine