Download Experiment DWG

Second Annual CEFRC Conference
Summary and Plan:
Experiments
D. Davidson, F. L. Dryer, N. Hansen,
R. K. Hanson, C. J. Sung, H. Wang
DWG Goals
• Provides fundamental data in support of the three
thrusts of reaction mechanism development, from
foundational fuels, alcohols to biodiesels.
Methods
• Shock tube/laser diagnostics (Hanson/Davidson)
• Variable-pressure turbulent flow reactor (Dryer)
• Rapid compression machine (Sung)
• Burner stabilized flame with synchrotron photoionization MS
(Hansen)
• Burner stabilized-stagnation flame (Wang)
• Premixed counterflow flame (Sung)
Highlights - Butanols
•Shock-tube measurements (Hanson/Davidson) of ignition delay times of butanolO2-Ar mixtures and OH time history provided critical test for the reaction models
of n-butanol combustion.
1471 K
1667 K
1316 K
2-but
1-but
tign [us]
1-butanol
2-butanol
i-butanol
t-butanol
Lines
- Grana et. al.
1000
(2010)
1190 K
100
t-but i-but
10
0.60
0.64
0.68 0.72 0.76
1000/T5 [1/K]
0.80
0.84
Highlights - Butanols
•Flow-reactor study (Fryer) shows that t-butanol has no low-temperature oxidation
chemistry characteristic of RO2 and provides species time-history data for model
validation.
• Analysis of Derived Cetane Number (DCN) demonstrates the chemical structureskinetic effects on t-butanol, and that blending several percent of alcohol into
diesel leads to little to no deterioration of the cetane number.
Highlights - Butanols
• Low-pressure burner stabilized n-butanol1
1
3 Flame
Flame
2 Oßwald*
Flame
Flame3 1
oxgen-argon flames wereFlame
studied
byFlame 2 FlameFlame
3.6 n-C4H9OH 3.3
3.6 7.2 n-C43.3
H9OH 17.8 7.2
3.6
4H9OH
Synchrotronn-CPhotoionization
mass
24.1
H2
24.1
H2
24.1
2
spectrometry H(Hansen/Yang).
O2
16.7
16.7
O2
57.2 42.8
24.1
• Comparison with
the MIT 24.1
modelO2shows
good24.1 42.8
48.2
Ar
80.0
80.0
Ar
25 50.0
48.2
agreement forArthe main flame
structure,
but48.2 50.0
pressure
pressure 25
25
30 1515
the data point
to room for 15
improvements
for15 15 pressure
1.4
1.2
1.4 1.0
1.2 Ratio 1.7 1.0
1.4
Equivalence Ratio
Equivalence
Ratio
Equivalence
minor species.
Flame
Flame
Oßwa
2
mol% 3.3
17.8
mol%
mol% 16.7
57.2
mol% 80.025
Torr 2530
1.21.7
Highlights - Butanols
• RCM studies (Sung) shows the order of reactivity to be
n-butanol>2-butanol≈i-butanol>t-butanol at 15 bar (in agreement with Stanford
shock-tube results), but
n-butanol>t-butanol>2-butanol>i-butanol at 30 bar
Highlights - Butanols
• Burner-stabilized stagnation flame studies (Wang) of n- and i-butanol flames show that
(a) the fuel-rich chemistry and soot formation is highly sensitive to the fuel structure
(b) alcohols do not always lead to reduced soot formation.
dN/dlogDp (cm-3)
10
11
Hp = 0.90 cm
Hp = 0.90 cm
Hp = 0.90 cm
i-C4H10
i-C4H9OH
n-C4H10
Hp = 1.00 cm
n-C4H9OH
C/O = 0.69
10
10
10
10
10
10
9
8
7
11
Hp = 1.40 cm
Hp = 1.40 cm
Hp = 1.40 cm
i-C4H10
i-C4H9OH
n-C4H10
Hp = 1.40 cm
n-C4H9OH
C/O = 0.69
10
10
10
10
10
9
8
7
10
100
10
100
10
100
10
100
Diameter, Dp (nm)
Figure 1: Summary of the development of the PSDFs for iso-butane (C/O = 0.63), iso-butanol (C/O = 0.63),
n-butane (C/O = 0.63) and n-butanol (C/O = 0.69) at two representative burner-to-probe distances.
Highlights - Esters
• Ignition delay times measured for methyl
oleate blend and methyl decanoate
(Hanson/Davidson).
• Chemical structures examined in premixed
flat flames of methylbutanoate,
methylisobutanoate, and ethylpropanoate
using MBMS (Hansen)
Highlights – Elementary Kinetics
•
OH + 1-butene (k1)
trans-2-butene (k2)
cis-2-butene (k3) + OH
k1, Smith 1987
k2, Smith 1987
3E13
2.5E13
abs
k1 , Tully 1988
2E13
abs
k1 , Sun and Law 2010
1.5E13
3
•
Rate coefficient of unimolecular t-butanol → H2O + i-C4H8 was determined in VPFR
(Dryer)
Rate coefficients of OH + butene isomers → products were determined behind
reflected shock waves (Hanson/Davidson)
Measurements of the third-body efficiency in H + O2 (+M) → HO2 (+M), M = H2O, CO2
are underway (Dryer)
k1, k2, k3 [cm /mol/s]
•
(theory)
1E13
Current data
5E12
k1
k2
k3
0.6
0.8
1.0
1.2
1000/T [1/K]
1.4
1.6
Highlights – Foundational Fuels
• MBMS measurements of species profiles
in iso-butene flames show missing
reaction (Hansen/Yang/Wang)
CH2 2
CHCHCH+ M
CHCH
CHCH
2 +M
2 2
H3+CCHCC
C CH22 2 2 H +HH+ C
H3H
C
CH
C
H3C3 CHC
H
3 CH
2H2CC C
3
2C C
CH
CH
CHCH
CH22 CH
2 –2 H
CHCH
2
150 CH
2 2
2 2
-4
CH2
100
-4
( *10
Mole Fraction
)
( *10 )
Fraction
Mole
C
CH2
H
+ HH
3C
2C
CC
150
50
CH
CH
2 2+ H (-H)
CH
+M
CH
22
CH3
CH4
H1,3-C
+ H24C
H6 C
CH3
CH4
100
0
200
CH2
5
10
15
C6H6
C7H8
C6H6
C7H8
10
30
20
0
0
CH2O
30
20
20
0
0
31
20
Allene
C3H3
C3H4
C3H5
400
5
10
15
Distance from Burner
(mm)
1Distance
from Burner (mm)
0
60
20
C2H2
C2H4
200
C4H2
C4H4
C4H6
Allene
C3H3
C3H4
C3H5
40
100
10
0
0
10 0
CH2
0
3
C4H2
100
C4H4
C4H6
2
50
60
C2H2
C2H4
20
0
20
10
0
CH2O
0
5
10
15
20
Highlights – Foundational Fuels
• RCM studies (Sung) shows that water promotes autoignition of H2/O2/N2 mixtures, but
it suppresses ignition at 7 atm.
Future Plans (Revised)
• VPFR and VPLFR for measurements of k(T,P) and kinetic model validation data for simple
alcohols, esters, and furans, with a focus on t-butanol.
• An expanded database of shock-tube ignition delay times and species time-histories
(OH, H2O, CH2O, CO, C2H4) for a large range of hydrocarbons (formaldehyde, methanol,
DME, MB, methyl formate, and other small esters).
• Direct rate measurements for methyl ester decomposition and OH + methyl esters.
• Quantify HO2 diagnostics.
• Complement ALS flame-sampling MBMS with LIF and REMPI : iso-butanol and isopentanol.
• Development of a JSR with MBMS, for low-T and high-P studies.
• RCM studies of autoignition of butanol isomers under elevated P and low-tointermediate T and gasoline surrogate/bio-alcohol blends, moist syngas, and methyl
butanoate.
• IR spectroscopy techniques for following CO, CH4, H2O, and H2O2 concentrations in RCM.
• Efficient numerical techniques for propagating and minimizing kinetic model
uncertainties, and for designing bang-for-the-buck experiments.
• Experimental and numerical techniques for probing diffusion collision cross section of
large species.
• Foundational fuel experiments – to be determined.