Article
pubs.acs.org/EF
Experimental Study on Ethane Ignition Delay Times and Evaluation
of Chemical Kinetic Models
Erjiang Hu,* Yizhen Chen, Zihang Zhang, Xiaotian Li, Yu Cheng, and Zuohua Huang
State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, People’s Republic
of China
ABSTRACT: The ignition delay times of ethane were measured using a high-pressure shock tube at different pressures (p = 1.2,
5.0, and 20.0 atm) and equivalence ratios (ϕ = 0.5, 1.0, and 2.0) with different argon diluent ratios. Correlations of the measured
ignition delay times were provided. The measurements were compared to calculations from several representative chemical
kinetic models to evaluate their performances. Results showed that Aramco Mech 1.3 could well reproduce the measured ignition
delay times over a wide range, while GRI Mech 3.0 significantly overpredicted the measurements at stoichiometric and high
equivalence ratio. To find out the reasons for the differences and similarities of the mechanisms on calculating the ignition delay
time of ethane, sensitivity analysis and reaction pathway analysis were conducted. It is observed that the mechanisms have similar
pathway for ethane consumption, while they have significant differences for ethyl radical decomposition reactions. Results also
indicated that the incompleteness of the C2H5 + O2 reaction channels and the underestimation of the rate constant of reaction
C2H4 + H (+M) = C2H5 (+M) might be responsible for the overestimation of GRI Mech 3.0 on ethane ignition. The
mechanisms studied give similar prediction at a high equivalence ratio because reactions with a significant difference on rate
constants do not show a high sensitivity coefficient at the condition.
1. INTRODUCTION
Ethane is an important component in natural gas, an alternative
fuel that is widely used in internal combustion engines and
many other combustion devices. Moreover, ethane is a critical
intermediate generally generated in the oxidation and pyrolysis
processes of hydrocarbon fuels; therefore, its kinetic mechanism is fundamental for the hierarchical construction of higher
hydrocarbon fuel models. Therefore, an accurate and reliable
kinetic mechanism that can describe its combustion process
under wide ranges is beneficial to our understanding on the
combustion of ethane and other hydrocarbons. However, the
working conditions of practical combustion devices are much
broader than the applicable range of most mechanisms that are
currently used. Given that the experimental studies on ethane
combustion are not as extensive as for methane, it is worthwhile
to extend the ethane ignition database, which can serve for the
validation of chemical kinetic modeling. A mechanism can be
used with credence if it is validated by a wide range of
experimental data.
Shock-tube studies on the ignition delay time of ethane can
be backed to the 1970s.1−3 In 1981, Hidaka et al.4 measured the
ignition delay times of ethane along with other C2 hydrocarbons in a shock tube at pressures below 0.5 atm. Lamoureux
et al.5 obtained the ignition delay data of low hydrocarbons
(methane, ethane, and propone) behind reflected shock waves.
They compared their data to the calculation results of GRI
Mech 3.0,6 reporting its overestimation on ethane ignition
delay times for rich-fuel mixtures. Tranter et al.7 obtained the
concentration data of intermediate species during ethane
pyrolysis and oxidation processes at very high pressures (34.0
and 61.3 MPa) in a high-pressure single-pulse shock tube. They
also studied the oxidation on rich and stoichiometric ethane
mixtures at 40 atm using the same apparatus8 and reported that
neither of the mechanisms that they studied could well
© 2015 American Chemical Society
reproduce their experimental data at a rich ethane condition.
In 2007, de Vries et al.9 summarized previous ethane ignition
data in the literature and compared them to their measurements. They reported the convergence of different experimental data and advised further studies on the ethane
oxidation modeling study at fuel-rich and high-pressure
conditions. Recently, Aul et al.10 measured the ignition delay
times of methane, ethane, and methane/ethane mixtures. The
ignition delay data were used to validate Aramco Mech 1.0,11
and the rate constants of some important reactions were
discussed in the paper.
Many studies have been published concerning the chemical
kinetic mechanisms of ethane. The mechanism published by
Kilpinen et al.12 contained reactions describing ethane
oxidation. Dagaut et al.13 built a detailed kinetic mechanism
for ethane oxidation with a strong hierarchical structure after
measuring the concentration profiles of species at high
temperatures (800−1200 K) and high pressures (1−10 atm)
in a jet-stirred reactor. The mechanism was based on previous
studies and validated with a jet-stirred reactor and shock-tube
data. Hunter et al.14 noticed the importance of other reaction
channels of C2H5 + O2 in addition to the C2H4 + HO2
production. They expanded GRI Mech 1.1 with a C2 submechanism and adjusted the reaction rate constants of two key
reactions according to their measured species profiles in a flow
reactor. Hidaka et al.15 introduced a model with 157 reactions
and 48 species, which could both simulate ethane oxidation and
pyrolysis. In this model, certain reaction rate constants were
adjusted on the basis of their measured species concentration
Received: March 3, 2015
Revised: June 11, 2015
Published: June 15, 2015
4557
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
data in a shock tube. Naik and Dean16,17 developed a detailed
mechanism of ethane oxidation and pyrolysis with 863
reactions and 112 species. The mechanism incorporated the
results of ab initio studies of the important low-temperature
pathways of the C2H5 + O2 reaction and applied many
pressure-dependent rate coefficients. In 2013, Zhang et al.18
observed the underestimation of USC Mech 2.019 on the
ignition delay times of ethane while studying C1−C4 alkanes.
They replaced the rate constant of C2H4 + H (+M) = C2H5
(+M) by the rate constant in Aramco Mech 1.320 and found
that the modified mechanism could well reproduce the
experimental data. The similar phenomenon was also noticed
by Pan et al.21 when calculating the ignition delay times of
ethane using LLNL C4Mech.22
Although much research has been devoted to ethane ignition
in a shock tube, its ignition delay data are still far from
comprehensive. Therefore, one of our main purposes for this
research is to extend the ethane ignition database by providing
ignition delay data covering a broad parameter range by varying
pressure, equivalence ratio, and diluent ratio. Two experiments
were duplicated first to ensure the reliability of our
experimental measurement. The validated data were thus
used to evaluate the performances of currently accepted
mechanisms. Key reactions were identified by sensitivity
analysis and reaction pathway analysis and then discussed in
detail.
Figure 1. Typical end-wall pressure and OH* chemiluminescence
measurements with the corresponding ignition delay time for a
stoichiometric ethane/O2/Ar mixture at 1.1 atm and 1255 K.
Table 1. Compositions of the Testing Mixtures
2. EXPERIMENTAL AND NUMERICAL METHOD
mixture
ϕ
Xethane (%)
XO2 (%)
XAr (%)
p (MPa)
1
2
3
4
5
6
0.5
1.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
0.75
1.5
2.0
7.0
3.5
1.75
2.625
5.25
7.0
92.0
95.5
97.25
96.625
93.25
91.0
0.12, 0.5, 2.0
0.12, 0.5, 2.0
0.12, 0.5, 2.0
0.5
0.5
0.2, 0.5
Diego Mech.30 They are summarized in Table 2. Two software tools,
CHEMClean and CHEMDiffs,31 were used to compare the species
and reactions in the mechanisms studied.
All measurements in this study were conducted in a shock tube, which
has been described in detail in previous literature.23,24 Therefore, only
a brief introduction of our experimental apparatus and method is given
here. In this study, the testing mixtures were prepared manometrically
in a 128 L stainless-steel tank and then mixed spontaneously by
molecular diffusion for 12 h. The purities of ethane, oxygen, and argon
were 99.9, 99.995, and 99.999%, respectively. The shock tube is 8.8 m
long with an inner diameter of 11.5 cm. It is separated by polyester
terephthalate (PET) films into two sections: a 4.0 m long driver
section and a 4.8 m long driven section. The testing mixture (C2H6/
O2/Ar mixtures) and driver gas (N2 and Ar) are entered into the
driven section and the driver section, respectively. Sudden venting of
the gas between the two films triggers the diaphragm rupture and the
generation of the shock wave. The shock wave reaches the reaction
zone and ignites the mixture. PET films with different thicknesses
should be used for conditions with different driver pressures. Four
pressure transducers (PCB, 113B26) are placed on the side wall with
the same length interval of 30 cm to calculate the velocity of the
incident shock wave. A photomultiplier (Hamamatsu, CR131)
installed at the end wall can filter the OH* emission centered at
430 ± 10 nm. A digital recorder (Yokogava, scopecorder DL750) is
used to record all measurements. The temperature behind reflected
shock waves is calculated using the reflected shock module in the
software Gaseq25 with an uncertainty of ±25 K.
The definition of ignition delay time is the interval between the time
when the incident shock wave arrives at the end wall and the point at
the zero baseline by extrapolating the steepest slope of the OH*
chemiluminescence signal measured at the end wall, as shown in
Figure 1. The C2H6/O2/Ar mixtures were tested at 1.2−20 atm, and
their compositions are shown in Table 1. We used the constantvolume, adiabatic, and zero-dimensional reactor in CHEMKIN II
package26 with the SENKIN/VTIM approach27,28 to carry out our
simulations. The boundary effect of the facility (dp/dt) was considered
in the calculation, and the dependent pressure rise is set to 4%/ms
according to the earlier research.29 The ignition delay time in the
simulation is defined as the time interval between the beginning of the
simulation and the maximum rate of temperature rise (max dT/dt).
Chemical kinetic mechanisms employed in this study are GRI Mech
3.0,6 USC Mech 2.0,19 Aramco Mech 1.3,20 LLNL C4Mech,22 and San
Table 2. Summary of the Mechanisms Employed in This
Study
mechanism
author
update
date
number of
reactions
number of
species
GRI 3.06
USC 2.019
LLNL C422
San Diego30
Aramco 1.320
Smith et al.
Wang et al.
Marinov et al.
William et al.
Curran et al.
1999
2007
2004
2014
2013
325
784
689
244
1542
53
111
155
50
253
3. RESULTS AND DISCUSSION
In this section, we first repeated an experimental condition of
the previous study9 for the purpose of validation of our
measurement. Then, we presented our data of ethane ignition
delay times at various pressures, equivalence ratios, and diluent
ratios. Finally, calculations were conducted employing different
mechanisms and compared to experimental data for evaluating
their performances. Important reactions and reaction pathways
were analyzed as well.
3.1. Comparison to Previous Data. Figure 2 gives the
comparison between the present measurement and previous
data under identical experimental conditions: p = 2.0 atm, ϕ =
1.0, and Xethane = 2%. It can be seen that our measurement is
highly consistent with the previous study.9 Therefore, the
present ignition data can be used with confidence in evaluating
the performances of kinetic mechanisms.
3.2. Ignition Delay Time Measurements. Figure 3
summaries the experimental conditions (pressure, dilution,
and equivalence ratio) of the present and previous studies on
4558
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
where τign is the ignition delay time in microseconds,
concentrations are in moles per centimeter cubed, T is the
temperature in kelvin.
From Figure 4, we also observed the influences of initial
parameters to ethane ignition. Figure 4a gives the ignition delay
times of ethane at three pressures (p = 1.2, 5.0, and 20 atm) for
the fuel-lean (ϕ = 0.5) mixture. It is observed that the same
mixture has a shorter ignition delay time at a higher pressure. A
similar phenomenon is observed in panels b and c of Figure 4
for stoichiometric (ϕ = 1.0) and fuel-rich (ϕ = 2.0) mixtures.
Figure 4d shows the ignition delay times of the stoichiometric
mixtures with different diluent ratios at the same pressure (p =
5.0 atm). The ignition delay time increases with the increase of
the diluent ratio. Figure 4e rearranges and presents the ignition
data for different equivalence ratios at the same pressure,
showing that the increasing equivalence ratio increases the
ignition delay time. To summarize, the rising of the pressure
and the decrease of the equivalence ratio and diluent ratio have
a promoting effect on ethane ignition. The same conclusion can
also be found from the equation of the correlation, where the
indexes of the composition concentrations and their sum
represent their influences on the ignition delay. In general, the
measured ignition delay times show good Arrhenius
exponential dependence upon the reciprocal temperature.
3.3. Comparison to Chemical Kinetic Models. One of
the objectives of this study is to use our measured ethane
ignition data to evaluate the performances of existing models at
different ranges. Current chemical kinetic mechanisms are
commonly constructed with a hierarchical structure; therefore,
the chemical kinetic models of hydrocarbon are inevitably
dependent upon the accuracy of ethane chemistry. In this study,
we tested several generally accepted hydrocarbon models,
namely, GRI Mech 3.0,6 USC Mech 2.0,19 Aramco Mech 1.3,20
LLNL C4Mech,22 and San Diego Mech,30 to evaluate their
performances on ethane ignition prediction. Figure 5 gives the
calculation results of different models on the ignition delay
times of ethane against the measurement at various conditions.
It is seen that Aramco Mech 1.3 and San Diego Mech yield
relatively satisfactory agreement, while USC Mech 2.0 and
LLNL C4Mech generally underpredict the ethane ignition
delay. The underestimations of USC Mech 2.0 and LLNL
C4Mech have been reported before.18,21
As shown in Figure 5, GRI Mech 3.0 gives a significant
overprediction on the ignition delay times of ethane, especially
for fuel-lean and stoichiometric mixtures. GRI Mech 3.0 is a
widely accepted mechanism for its valid and accurate simulation
of methane and natural gas. Given its poor prediction on ethane
ignition, it should be prudent not to use it for simulations on
natural gas with a non-negligible fraction of ethane. Although
the poor agreement between the GRI Mech 3.0 calculation and
the experimental data has been noticed before,5 no chemical
analysis or reasons for the phenomenon were given in the
literature.
A preliminary comparison of the mechanisms using
ChemClean and ChemDiffs is given in Tables 3 and 4. The
values in parentheses are the number of species or reactions in
the mechanism, and the values in the table present the number
of identical species or reactions between two mechanisms with
exactly the same reactants and products. In Table 4, the former
value is the number of reactions with exactly the same
Arrhenius parameters, while the latter value is the number of
identical reactions but with different reaction rate constants. It
is observed that the relative similarity of the mechanisms
Figure 2. Comparison between present measured data and the
measured data from ref 9.
Figure 3. Summary of the measurement conditions including previous
and current studies of ethane ignition delay times.
the ignition delay times of ethane with a three-dimensional plot.
It can be seen that most of the previous data were situated at
the low- and middle-pressure ranges, while the current study
broadens the database of ethane shock-tube studies by covering
a wide range of experimental conditions.
Figure 4 shows the measured ignition delay times of ethane
with their correlations at different pressures, equivalence ratios,
and diluent ratios. The correlations of the ignition delay times
with the temperature and the concentrations of ethane, oxygen,
and argon were obtained using the multivariable linear
regression method. The activation energy acquired is 32.9
kcal/mol, which falls in the range of previous studies (29.9−
55.2 kcal/mol)9,21
⎛ 16600 K ⎞
0.57
⎟[C H ]
τign = 1.39−10 exp⎜
[O2 ]−1.02 [Ar]0.06
⎝ T
⎠ 2 6
(1)
4559
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
Figure 4. Measured ignition delay times of C2H6/O2/Ar mixtures at different pressures, equivalence ratios, and diluent ratios.
different mechanisms have a similar portion for C 2 H 6
consumption pathways at various conditions. This is because
the mechanisms studied have an identical or a close reaction
rate constant for important hydrogen abstraction reactions. For
example, the reaction rate constants of C2H6 + H = C2H5 + H2
and C2H6 + OH = C2H5 + H2O are close, as shown in panels a
and b of Figure 7.
Figure 6 also presents the main consumption pathway of
C2H5. For each mechanism studied, C2H5 (+M) = C2H4 + H
(+M) and C2H5 + O2 = C2H4 + HO2 are critical consumption
pathways of the ethyl radical. However, the portions of C2H5
consumed respectively through the two pathways vary at
different conditions for different mechanisms. At a low
equivalence ratio, the flux of C2H5 + O2 = C2H4 + HO2 of
GRI Mech 3.0 is much higher than that of other mechanisms.
For GRI Mech 3.0, the majority of the ethyl radical is
consumed by hydrogen abstraction reactions with O2, while for
studied is not high. However, their performances differ at
certain conditions, while they agree well at the others. In the
following section, reaction pathway and sensitivity analysis were
carried out to explain the similarities and differences of their
prediction on the ignition delay times of ethane.
3.4. Sensitivity Analysis and Reaction Pathway
Analysis. Reaction pathway analysis of ethane oxidation was
performed using the five mechanisms at different pressures and
equivalence ratios. From Figure 6, it can be seen that most
C2H6 molecules are decomposed via hydrogen abstraction
reactions with H, OH, O2, and CH3 radicals forming C2H5
molecules. At different equivalence ratios, the dominant
consumption pathway differs. At a low equivalence ratio, the
majority of C2H6 molecules is consumed via a hydrogen
abstraction reaction with OH radicals, while at a high
equivalence ratio, the main pathway of C2H6 consumption is
a hydrogen abstraction reaction with H radicals. However,
4560
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
Figure 5. continued
4561
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
Figure 5. Comparison of experimental and calculated ignition delay times of ethane at different pressures, equivalence ratios, and dilution ratios.
Table 3. Species in Commona
GRI 3.0 (53)
Aramco 1.3 (253)
USC 2.0 (111)
LLNL C4 (155)
San Diego (50)
a
GRI 3.0 (53)
Aramco 1.3 (253)
USC 2.0 (111)
LLNL C4 (155)
35
34
33
31
66
46
36
60
34
31
San Diego (50)
The values in parentheses are the number of species in the mechanism, and the values in the table present the number of identical species.
Table 4. Reactions in Commona
GRI 3.0 (325)
GRI 3.0 (325)
Aramco 1.3 (1542)
USC 2.0 (784)
LLNL C4 (689)
San Diego (247)
49;
93;
50;
21;
88
72
79
77
Aramco 1.3 (1542)
USC 2.0 (784)
LLNL C4 (689)
120; 124
57; 104
29; 80
85; 140
28; 89
27; 65
San Diego (247)
a
The values in parentheses are the number of reactions in the mechanism, and the former value in the table is the number of reactions with exactly
the same Arrhenius parameters, while the latter value is the number of identical reactions but with different reaction rate constants.
ϕ = 2.0, where the models agree well. The sensitivity coefficient
is calculated by the following formula using the definition given
by Petersen et al.:32
other mechanisms, the ethyl radical is mainly consumed by
decomposition to acetylene. At a high equivalence ratio, the
C2H5 consumption pathway for all mechanisms studied is
dominated by C2H5 (+M) = C2H4 + H (+M). At this
condition, all mechanisms give a similar prediction of the
ignition delay time and good agreement with experimental data.
Sensitivity analysis was performed using GRI Mech 3.0 at the
condition of T = 1250 K, p = 1.2 atm, and ϕ = 0.5, where a
significant gap between the calculated and measured results was
observed, and at the condition of T = 1250 K, p = 1.2 atm, and
Si =
τ(2.0ki) − τ(0.5ki)
1.5τ(ki)
(2)
where τ is ignition delay time of the combustible mixture, Si and
ki are the sensitivity coefficient and rate constant of the ith
reaction, respectively. A positive sensitivity coefficient demon4562
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
Figure 6. Reaction pathway analysis of ethane calculated by five mechanisms at three conditions.
strates that the corresponding reaction inhibits the overall
ignition process and vice versa.
The elementary reactions with the highest sensitivity
coefficients are listed in Figure 8. Given that GRI Mech 3.0
4563
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
Figure 7. Comparison of reaction rate constants: (a) C2H6 + H = C2H5 + H2 (GRI Mech 3.0, Aramco Mech 1.3, and USC Mech 2.0 have an
identical rate constant, and LLNL C4Mech and San Diego Mech have an identical rate constant), (b) C2H6 + OH = C2H5 + H2O (USC Mech 2.0,
LLNL C4Mech, and San Diego Mech have an identical rate constant), (c) C2H4 + H + M = C2H5 + M, and (d) C2H5 + O2 = C2H4 + HO2.
Reaction C2H6 + H = C2H5 + H2 is an important reaction
controlling the ignition of ethane because it is the main
pathway of ethane consumption. Figure 7a gives its reaction
rate constant, and it can be seen that all of the mechanisms
studied have an identical or a similar value for the reaction,
which should not cause the difference of performance between
mechanisms. Reaction C2H5 (+M) = C2H4 + H (+M) is a
pressure-dependent reaction. Both the sensitivity and reaction
pathway analyses prove their importance in the ethane
oxidation process. The reaction rate constant employed in
Aramco Mech 1.3 was originally derived from the research of
Miller and Klippenstein,33 but with the high- and low-pressure
limits multiplied by a factor of 0.7. Later studies18,21 indicated
that the adjusted value gives better results when compared to
experimental data. Further experimental and calculation studies
may justify such adjustment or give a more accurate calculated
value of the rate constant. As shown in Figure 7c, there are
significant differences between the rate constants employed in
the models and the value in Aramco Mech 1.3 is twice as large
as the value in GRI Mech 3.0. The discrepancy in describing
this reaction may be one of the reasons why the overall
predictions differ for GRI Mech 3.0 and Aramco Mech 1.3.
Many studies have been carried out on the detailed chemistry
of the C2H5 + O2 reaction. Studies34−36 indicated that the
reaction C2H5 + O2 may undergo a complicated transition state
before producing C2H4 + HO2. The reaction first forms an
unstable adduct C2H5O2, which may produce C2H4 + HO2 or
react in the reverse direction. In addition to the channel C2H5 +
O2 = C2H4 + HO2, other channels may also be important in the
reaction. Aramco Mech 1.3 takes the value recommended by
Figure 8. Sensitivity analysis of ignition delays calculated by GRI Mech
3.0 at T = 1250 K, p = 1.2 atm, and ϕ = 0.5 and 2.0.
can give good agreement on the ignition delay of methane, the
overestimation of ethane at a low equivalence ratio may be
attributed to the ethane-specific reactions with high sensitivity
coefficients, as listed below.
R74:
C2H4 + H ( +M) = C2H5 ( +M)
R78:
C2H6 + H = C2H5 + H 2
R175:
C2H5 + O2 = C2H4 + HO2
4564
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Energy & Fuels
■
DeSain et al.,37 including multiple channels of the C2H5 + O2
reaction. However, the release date of GRI Mech 3.0 predated
these studies and, thus, did not incorporate other channels into
the model. A comparison of the values of the mechanisms is
given in Figure 7d. The value given in GRI Mech 3.0 is about 1
time higher than the value of Aramco Mech 1.3. Therefore, the
inaccuracy of GRI Mech 3.0 could be attributed to its
incompetence in describing the reaction C2H5 + O2.
At ϕ = 2.0, the mechanisms give reasonable agreement with
each other and the experimental data. It can be seen from
Figure 7 that those important reactions, such as C2H5 (+M) =
C2H4 + H (+M) and C2H5 + O2 = C2H4 + HO2, do not have
high sensitivity coefficients at this condition; thus, the
differences of their reaction rate constants do not significantly
affect the result of ethane ignition prediction. From Figure 6,
the reactions with high sensitivity coefficients at ϕ = 2.0 are not
the main pathway of reaction. Therefore, GRI Mech 3.0 gives a
similar prediction to other mechanisms at a high equivalence
ratio.
REFERENCES
(1) Bowman, C. T. An experimental and analytical investigation of
the high-temperature oxidation mechanisms of hydrocarbon fuels.
Combust. Sci. Technol. 1970, 2 (2−3), 161−172.
(2) Burcat, A.; Crossley, R. W.; Scheller, K.; Skinner, G. B. Shock
tube investigation of ignition in ethane−oxygen−argon mixtures.
Combust. Flame 1972, 18 (1), 115−123.
(3) Cooke, D.; Williams, A. Shock tube studies of methane and
ethane oxidation. Combust. Flame 1975, 24, 245−256.
(4) Hidaka, Y.; Tanaka, Y.; Kawano, H.; Suga, M. Mass spectrometric
study of C2 hydrocarbons oxidation in shock waves. J. Mass Spectrom.
Soc. Jpn. 1981, 29 (2), 191−198.
(5) Lamoureux, N.; Paillard, C.-E.; Vaslier, V. Low hydrocarbon
mixtures ignition delay times investigation behind reflected shock
waves. Shock Waves 2002, 11 (4), 309−322.
(6) Smith, G. P.; Golden, D. M.; Frenklach, M.; Moriarty, N. W.;
Eiteneer, B.; Goldenberg, M.; Bowman, C. T.; Hanson, R. K.; Song, S.;
Gardiner, W. C., Jr. GRI-Mech 3.0, 1999; http://www.me.berkeley.
edu/gri_mech/.
(7) Tranter, R. S.; Sivaramakrishnan, R.; Brezinsky, K.; Allendorf, M.
D. High pressure, high temperature shock tube studies of ethane
pyrolysis and oxidation. Phys. Chem. Chem. Phys. 2002, 4 (11), 2001−
2010.
(8) Tranter, R.; Amoorthy, H. R.; Raman, A.; Brezinsky, K.;
Allendorf, M. High-pressure single-pulse shock tube investigation of
rich and stoichiometric ethane oxidation. Proc. Combust. Inst. 2002, 29
(1), 1267−1275.
(9) de Vries, J.; Hall, J. M.; Simmons, S. L.; Rickard, M. J.; Kalitan, D.
M.; Petersen, E. L. Ethane ignition and oxidation behind reflected
shock waves. Combust. Flame 2007, 150 (1), 137−150.
(10) Aul, C. J.; Metcalfe, W. K.; Burke, S. M.; Curran, H. J.; Petersen,
E. L. Ignition and kinetic modeling of methane and ethane fuel blends
with oxygen: A design of experiments approach. Combust. Flame 2013,
160 (7), 1153−1167.
(11) Healy, D.; Donato, N.; Aul, C.; Petersen, E.; Zinner, C.;
Bourque, G.; Curran, H. n-Butane: Ignition delay measurements at
high pressure and detailed chemical kinetic simulations. Combust.
Flame 2010, 157 (8), 1526−1539.
(12) Kilpinen, P.; Glarborg, P.; Hupa, M. Reburning chemistry: A
kinetic modeling study. Ind. Eng. Chem. Res. 1992, 31 (6), 1477−1490.
(13) Dagaut, P.; Cathonnet, M.; Boettner, J. C. Kinetics of ethane
oxidation. Int. J. Chem. Kinet. 1991, 23 (5), 437−455.
(14) Hunter, T.; Litzinger, T.; Wang, H.; Frenklach, M. Ethane
oxidation at elevated pressures in the intermediate temperature
regime: Experiments and modeling. Combust. Flame 1996, 104 (4),
505−523.
(15) Hidaka, Y.; Sato, K.; Hoshikawa, H.; Nishimori, T.; Takahashi,
R.; Tanaka, H.; Inami, K.; Ito, N. Shock-tube and modeling study of
ethane pyrolysis and oxidation. Combust. Flame 2000, 120 (3), 245−
264.
(16) Naik, C. V.; Dean, A. M. Detailed kinetic modeling of ethane
oxidation. Combust. Flame 2006, 145 (1), 16−37.
(17) Naik, C. V.; Dean, A. M. Modeling high pressure ethane
oxidation and pyrolysis. Proc. Combust. Inst. 2009, 32 (1), 437−443.
(18) Zhang, J.; Hu, E.; Zhang, Z.; Pan, L.; Huang, Z. Comparative
study on ignition delay times of C1−C4 alkanes. Energy Fuels 2013, 27
(6), 3480−3487.
(19) Wang, H.; You, X.; Joshi, A. V.; Davis, S. G.; Laskin, A.;
Egolfopoulos, F.; Law, C. K. USC Mech Version II. High-Temperature
Combustion Reaction Model of H2/CO/C1−C4 Compounds, 2007;
http://ignis.usc.edu/USC_Mech_II.htm.
(20) Metcalfe, W. K.; Burke, S. M.; Ahmed, S. S.; Curran, H. J. A
hierarchical and comparative kinetic modeling study of C1−C2
hydrocarbon and oxygenated fuels. Int. J. Chem. Kinet. 2013, 45
(10), 638−675.
(21) Pan, L.; Zhang, Y.; Zhang, J.; Tian, Z.; Huang, Z. Shock tube
and kinetic study of C2H6/H2/O2/Ar mixtures at elevated pressures.
Int. J. Hydrogen Energy 2014, 39 (11), 6024−6033.
4. CONCLUSION
Ethane chemistry is of great importance in chemical kinetic
modeling of hydrocarbons. Ethane ignition delay times were
measured using a shock tube at different pressures (p = 1.2, 5.0,
and 20.0 atm) and equivalence ratios (ϕ = 0.5, 1.0, and 2.0)
with different argon diluent ratios. A correlation of ignition
delay times as a function of the pressure, temperature, and mole
fractions of fuel and oxygen was calculated using the multiple
regression method. Experimental results were compared to the
calculated results of several chemical kinetic mechanisms. The
results suggested that Aramco Mech 1.3 and San Diego Mech
can give good agreement with experimental data. A significant
overestimation of GRI Mech 3.0 was observed. Reaction
pathway analysis indicated that the first step of ethane ignition
is hydrogen abstraction reactions with H, OH, O, and CH3
radicals, and most ethane molecules are consumed by reaction
C2H6 + H = C2H5 + H2 for mechanisms studied. However, the
consumption pathway of the ethyl radical differs at different
conditions and for different mechanisms. Sensitivity analysis
suggested that C2H5 (+M) = C2H4 + H (+M) and C2H5 + O2 =
C2H4 + HO2 are controlling reactions in ethane oxidation at ϕ
= 0.5. The significant differences of their reaction rate constants
cause the difference of performance on ethane ignition. The
sensitivity coefficients of the two reactions are not significant at
a high equivalence ratio, and thus, the predictions of the
mechanisms studied agree well with themselves.
■
Article
AUTHOR INFORMATION
Corresponding Author
*E-mail: [email protected].
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
This work is supported by the National Natural Science
Foundation of China (51306144 and 91441118) and the
National Basic Research Program (2013CB228406). The
authors also appreciate the funding support from the
Fundamental Research Funds for the Central Universities.
4565
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566
Article
Energy & Fuels
(22) Marinov, N. M.; Pitz, W. J.; Westbrook, C. K.; Vincitore, A. M.;
Castaldi, M. J.; Senkan, S. M.; Melius, C. F. Aromatic and polycyclic
aromatic hydrocarbon formation in a laminar premixed n-butane
flame. Combust. Flame 1998, 114 (1), 192−213.
(23) Zhang, J.; Niu, S.; Zhang, Y.; Tang, C.; Jiang, X.; Hu, E.; Huang,
Z. Experimental and modeling study of the auto-ignition of n-heptane/
n-butanol mixtures. Combust. Flame 2013, 160 (1), 31−39.
(24) Hu, E.; Jiang, X.; Huang, Z.; Zhang, J.; Zhang, Z.; Man, X.
Experimental and kinetic studies on ignition delay times of dimethyl
ether/n-butane/O2/Ar mixtures. Energy Fuels 2012, 27 (1), 530−536.
(25) Morley, C. Gaseq: A Chemical Equilibrium Program for Windows,
Version 0.79, 2005.
(26) Kee, R. J.; Rupley, F. M.; Meeks, E.; Miller, J. A. CHEMKIN-III:
A FORTRAN Chemical Kinetics Package for the Analysis of Gas Phase
Chemical and Plasma Kinetics; Sandia National Laboratories: Livermore, CA, 1996; SAND96-8216.
(27) Lutz, A. E.; Kee, R. J.; Miller, J. A. SENKIN: A FORTRAN
Program for Predicting Homogeneous Gas Phase Chemical Kinetics with
Sensitivity Analysis; Sandia National Laboratories: Livermore, CA,
1988; SAND87-8248.
(28) Chaos, M.; Dryer, F. L. Chemical-kinetic modeling of ignition
delay: Considerations in interpreting shock tube data. Int. J. Chem.
Kinet. 2010, 42 (3), 143−150.
(29) Tang, C.; Man, X.; Wei, L.; Pan, L.; Huang, Z. Further study on
the ignition delay times of propane−hydrogen−oxygen−argon
mixtures: Effect of equivalence ratio. Combust. Flame 2013, 160
(11), 2283−2290.
(30) Combustion Research Group, Department of Mechanical and
Aerospace Engineering, University of California, San Diego. ChemicalKinetic Mechanisms for Combustion Applications; Combustion Research
Group, Department of Mechanical and Aerospace Engineering,
University of California, San Diego: La Jolla, CA; http://
combustion.ucsd.edu.
(31) Rolland, S.; Simmie, J. M. The comparison of detailed chemical
kinetic mechanisms: Application to the combustion of methane. Int. J.
Chem. Kinet. 2004, 36 (9), 467−471.
(32) Petersen, E.; Davidson, D.; Hanson, R. Kinetics modeling of
shock-induced ignition in low-dilution CH4/O2 mixtures at high
pressures and intermediate temperatures. Combust. Flame 1999, 117
(1), 272−290.
(33) Miller, J. A.; Klippenstein, S. J. The H + C2H2 (+M) ⇄ C2H3
(+M) and H + C2H2 (+M) ⇄ C2H5 (+ M) reactions: Electronic
structure, variational transition-state theory, and solutions to a twodimensional master equation. Phys. Chem. Chem. Phys. 2004, 6 (6),
1192−1202.
(34) Bozzelli, J. W.; Dean, A. M. Chemical activation analysis of the
reaction of ethyl radical with oxygen. J. Phys. Chem. 1990, 94 (8),
3313−3317.
(35) Wagner, A. F.; Slagle, I. R.; Sarzynski, D.; Gutman, D.
Experimental and theoretical studies of the ethyl + oxygen reaction
kinetics. J. Phys. Chem. 1990, 94 (5), 1853−1868.
(36) Quelch, G. E.; Gallo, M. M.; Schaefer, H. F., III Aspects of the
reaction mechanism of ethane combustion. Conformations of the
ethylperoxy radical. J. Am. Chem. Soc. 1992, 114 (21), 8239−8247.
(37) DeSain, J. D.; Klippenstein, S. J.; Miller, J. A.; Taatjes, C. A.
Measurements, theory, and modeling of OH formation in ethyl + O2
and propyl + O2 reactions. J. Phys. Chem. A 2003, 107 (22), 4415−
4427.
4566
DOI: 10.1021/acs.energyfuels.5b00462
Energy Fuels 2015, 29, 4557−4566