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1
Methane Absorbance Measurements at
Pressure/Temperature Conditions Associated With
Hypersonic Flight
Daanish Maqbool1 and Christopher Cadou
2
University of Maryland, College Park, MD, 20742
A facility constructed for simulating high pressure and
temperature fuel flows in
endothermic cooling channels for hypersonic air-breathing engine
components has been
used to investigate methane absorption at elevated temperature
and pressure. Absorption by
two rovibrational lines around 1654 was measured at pressures
ranging from 1 to 15 atm
and at 300 and 700K. The results show that measured integrated
absorbance differs
substantially from HITRAN predictions and can lead to errors of
more than 40% in
predicted concentration. This is probably because HITRAN relies
almost entirely on
spectroscopic data acquired at atmospheric temperature and
pressure but more detailed
investigations are required to confirm these findings and to
better quantify the discrepancy.
Nomenclature
C = concentration
D = diffusion coefficient
E = error
= molar absorptivity
H = height of channel
I = Intensity
k = absorption coefficient
L = length scale
P = pressure
Pe = Peclet number
Re = Reynolds number
= density
Sc = Schmidt number
T = temperature/transmittance
u = velocity
= viscosity
= optical frequency/wavenumber
x = length
I. Introduction
ne thermal protection strategy being considered for hypersonic
engines is active cooling of internal engine
components by endothermically decomposing fuel in
millimeter-scale passages machined into the
components1. An important additional benefit of this approach is
that the decomposition products typically have
lower ignition delay and reaction times making it easier to
complete combustion in the high speed engine
environment2. However, the thermodynamics of the gas-phase
cracking process favors soot-producing pathways that
would quickly clog the small cooling passages2,3
and cause a catastrophic loss of cooling performance. An
interdisciplinary team of researchers from the University of
Virginia, North Carolina State University, and the
1Research Assistant, Department of Aerospace Engineering, Univ.
of Maryland, College Park, MD 20742
2Associate Professor, Department of Aerospace Engineering, Univ.
of Maryland, College Park, MD 20742,
Associate Fellow of AIAA
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53rd AIAA Aerospace Sciences Meeting 5-9 January 2015,
Kissimmee, Florida
AIAA 2015-1156
Copyright 2015 by Daanish Maqbool and Christopher Cadou.
Published by the American Institute of Aeronautics and
Astronautics, Inc., with permission.
AIAA SciTech
-
American Institute of Aeronautics and Astronautics
2
University of Maryland is pursuing a solution to this problem
where mixed metal acid catalysts are used to promote
non-soot producing endothermic decomposition pathways. Part of
this effort involves making non-intrusive
measurements of fuel and decomposition product concentration
profiles along the length of cooling micro-channels
at temperatures and pressures that are representative of
injection conditions in hypersonic engines (up to 50 atm and
1100 K). Chemical kinetic analyses indicate that knowledge of
the concentrations of stable species like CH4, C2H2,
C2H4, and C2H6, and radical species like CH3 and C3H3 will be
especially important for understanding the
decomposition process. However, making non-intrusive
measurements of these species is challenging not only
because of the small size of the cooling passages but because of
the lack of spectroscopic data at the appropriate
temperatures and pressures.
This paper describes the development of a facility for
investigating the endothermic decomposition of liquid
hydrocarbon fuel surrogates like dodecane (C12H26) in
micro-channels and its first use to acquire some of the basic
absorption data needed to make non-intrusive measurements of
species concentrations in microchannels at
conditions that are representative of the hypersonic
environment. The focus of the latter effort is on measuring
absorption line strength of the R(3) line in the 23 manifold of
methane (~1654 nm) at high temperature and pressure. This line was
selected not only for its relevance to the endothermic
decomposition problem but also for its
usefulness in the development of non-intrusive equivalence ratio
sensors for gas turbine combustors that are accurate
at realistic combustor temperatures and pressures.
II. Experiment Design
A. Determination of representative hypersonic conditions
Calculations were performed to identify fuel injector conditions
that are representative of flight between Mach 3 and
7 at altitudes between 30,000 and 100,000 feet. Atmospheric
conditions as a function of altitude are determined
using the International Standard Atmosphere (ISA). Static
pressure and temperature of the air entering the
combustor are plotted in Fig. 1 (log scale) for incoming Mach
numbers of 0.3 and Mach 1.5. The dashed lines show
the boundary beyond which dodecane (i.e. the fuel surrogate of
interest here) is supercritical. The green box shows
the region accessible in the experimental facility.
Fig. 1: Representative hypersonic combustor inlet
conditions.
103
10-1
100
101
102
103
Temperature (K)
Pre
ssure
(atm
)
Mach 7 at
30,000 ft
Mach 3 at
30,000 ft
Mach 3 at
100,000 ft
Super-
-critical
Mach 7 at
100,000 ft
Mcombustor
= 0.3
Mcombustor
= 1.5
Supercritical
Experiment Test Conditions
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B. Determination of flow rates
Fig. 2 is a schematic illustration of the lower half of the flow
in the simulated cooling channel. A fuel surrogate
in this case dodecane heavily diluted with N2 to avoid coking
upstream enters from the left. The wall supported
catalyst initiates decomposition to lighter species (H2, CH4,
etc.) that diffuse off the surface back into the flow. The
channel has a 4 mm x 4 mm square cross-section and is 152 mm (6
inches) long. These dimensions were selected to
be consistent with what one might find in a practical
endothermic cooling application and to be consistent with
similar experiments being carried out at other laboratories. The
objective is to make non-intrusive measurements of
chemical composition at different axial locations in order to
observe the streamwise evolution of the decomposition
process. However, it is important that the experiments span the
full range of conditions that could be encountered in
the real flow.
Fig. 2: Diffusive transport in the microchannel.
The Peclet number is a convenient parameter for describing mass
transport in this flow. It is defined as follows
D
uH
D
uLScPem ===
Re (Eq. 1)
where H is the cross-sectional dimension of the passage, u is
the convective velocity, and D is the diffusion
coefficient of the particular species of interest. When the
Peclet number is large, the time required for a molecule to
diffuse from the core flow to the wall is much larger than the
time required for the molecule to be convected
downstream and the decomposition rate is said to be transport
limited. Conversely, when the Peclet number is small,
the time required to diffuse to the wall is much smaller than
the time to be convected downstream and the
decomposition rate is determined by the activity of the catalyst
and is said to be rate limited. Since the channel
dimensions (H) and the diffusion coefficient (D) are fixed
parameters of the experiment, exploring the full range of
operating conditions from transport limited to rate limited is
achieved by varying the flow velocity (u).
It should be noted that determining the diffusion coefficient
upon which these calculations are based is not
necessarily trivial for the supercritical conditions expected in
the experiment. One could use numerical tools that
rely on molecular dynamics4 (such as CANTERA
5) or empirical correlations (such as the Wilke-Change
6, Stokes-
Einstein7, or He-Yu
7) to calculate the diffusion coefficients of the various
species into N2. Unfortunately, however,
these methods give results that vary by over two orders of
magnitude. This is mainly because the correlations have
been developed for specific industrial processes that are not
relevant here and because CANTERA uses gas
dynamics models which are strictly valid only in the gaseous
phase. In order to avoid getting bogged down in a
different problem, the approach taken here is to compute all
diffusion coefficients using CANTERA in order to
ensure some measure of consistency. The results of these
calculations for the diffusion of several important species
into N2 are tabulated in Table 1. These diffusion coefficients
are averaged (4.85e-6 m2/sec) for the purpose of
determining the general range of u.
Wall
H2, CH4, C2H4, C6H6,
etc. diffusing upward
C-L
C12H26 diffusing
downward Catalytic Surface
Tfuel
Twall
Interrogation
Beam
Dodecane Species Boundary
Layer
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Table 1: CANTERA results for diffusion into N2.
Solute (diffusion into N2) D (m2/sec.) CANTERA
Hydrogen (H2) 1.39e-5
Methane (CH4) 4.22e-6
Ethylene (C2H4) 3.20e-6
Benzene (C6H6) 1.82e-6
Dodecane (nC12H26) 1.11e-6
The range of Peclet numbers of interest here is 0.1 to 100 and
is chosen to span the range from rate-limited to
transport-limited performance. Under these conditions, the
corresponding flow velocities (using Eq. 1) will range
between 0.000121 and 0.121 m/s. Assuming a 90% dilution (by
volume) with N2, and given the state of the N2-fuel
mix (from CANTERA), the required mass flow rate of the fuel is
between 4.33e-8 kg/sec (43.4 ug/sec) to 4.33e-5
kg/sec (43.3 mg/sec). Given the available fuel metering pump (an
Eldex Laboratories Model 1LMP metering pump
that can meter between 0.002 and 2.5 mL/min. at up to 6000 psi),
Peclet numbers as low as 1 should be attainable.
C. Overall Design
Fig. 3 is a sketch of the experiment layout. The test section is
a rectangular channel with two sides (top and
bottom) serving as the catalyst surface, and the other two sides
formed by Zinc-Selenide windows for optical access
in the IR-region. It is housed in a pressure vessel equipped
with optical ports and a 3-zone tube furnace (Fig. 4). The
vessel can be pressurized up to 50 atm with Nitrogen in order to
ensure that the fuel inside cannot oxidize in case the
test section leaks or breaks. The internal dimensions of the
pressure vessel are 0.254 m (10 inches) in diameter and
0.6096 m (24 inches) in length.
Nitrogen from the high pressure environment enters the test
section via a 1.82 m (6 foot) long tube coiled inside
the furnace as shown in Fig. 5. This ensures that the Nitrogen
enters the test section at the furnace temperature. A
thermocouple monitors the temperature of the N2-fuel mix before
it enters the test section. The flow rate of the
Nitrogen is controlled by a choked flow orifice downstream of
the test section and the fuel flow rate is set
independently by the metering pump.
The flow is probed optically at various downstream locations
through the 6 inch long ZnSe windows using a
Thermo-Nicolet Nexus 870 FT-IR spectrometer with a Thorlabs
BF20LSMA optic fiber. Unreacted fuel leaving the
test section is condensed out in an external shell-and-tube heat
exchanger before the gas stream is exhausted to the
atmosphere.
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Fig. 3: Experiment Layout.
Fig. 4: Pressure vessel with tube furnace inside.
High Pressure
N2
Tube Furnace (up to 1100 K)
Test Section
Pressure Chamber
Pump
Water
N2
Pressure Controller
N2
Condensed Fuel
N2
Independently Set Temperature
Independently Set Fuel Flow
Rate
Independently Set System Pressure
Do not want to release vaporized fuel at 800 C and
50 atm into air
Shell and Tube heat exchanger
condenses reaction products for safe ejection
Choked Orifice Flow
Meter
Measure P, T
Fuel
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Fig. 5: Test section with heating coil for N2.
III. Spectroscopic Measurements
A. Absorption Spectroscopy
Absorption spectroscopy is a well-established technique for
making non-intrusive measurements of species
concentration. The Beer-Lambert law8,9
describes the relationship between optical absorption and
absorbing-species
concentration:
CdxkI
dI)(
)(
)(
0
= (Eq. 2)
In this expression, I0 is the initial light intensity, dI is the
measured change in transmitted intensity, is the optical frequency
(typically in cm
-1), C is the concentration in moles/m
3, dx is the differential path length, and k is a
coefficient that accounts for the variation of absorption with
wavelength. Note that k may also depend on
temperature and pressure. Integrating over the optical path
length L and converting natural logarithms to base 10
gives:
CLAI
dI)()(
)(
)(log
0
10
== (Eq. 3)
where A is the absorbance and is the molar absorptivity, The
wavelength-integrated absorbance (
== ))( CLCLdA is the sum of the absorbance over a particular
absorption feature or the entire absorbing rovibrational band. In
cases where the molar absorptivity is not known directly,
concentration can be
inferred from a calibration:
.ncalibratio
sample
ncalibratio
ncalibratio
sample
sample CL
L
A
AC = (Eq. 4)
B. Selection of Absorption Lines
This experiment will use absorption spectroscopy to infer
concentrations of species of interest at different axial
locations in a test section. As explained in the previous
section, at a given temperature and pressure, and for a given
geometry (i.e. path length), absorbance (or transmittance) is
just a function of the concentration. A higher
absorbance implies a higher concentration and vice versa.
Absorption lines to probe must be selected for each
species of interest. These lines should be as strong as possible
(to facilitate detection) and should be free of
interference from absorption by other species in the experiment.
Table 2 shows the main species involved in
dodecane cracking. Spectroscopic data for four of these species
are available in HITRAN12
and their respective
linestrengths are plotted in Fig. 6. The figure shows that
interference-free lines for CH4 can be sought in the region
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2700-2900 cm-1
, for C2H2 in the region 6400-6700 cm-1
, for C2H4 in the region 900-1100 cm-1
, and for C2H6 in the
narrow region 800-820 cm-1
.
Fig. 6: Linestrengths for species of interest (from HITRAN
12/SpectralCalc
29). Minimum intensity (Icut) is 1e-23
cm-1
/(mol-cm-2
).
C. Motivation for Methane and Spectroscopic Challenges
The chemical species of interest in dodecane cracking are listed
in Table 2 along with references to spectroscopic
data for these molecules taken from the HITRAN 2012
database13
. The table shows that most of the data available
for these species has been acquired at temperatures and
pressures that are much lower than those of interest in this
work. Other databases (GEISA, JPL Mol. Spec., etc.) are, to the
authors knowledge, also intended for low-
temperature studies. This could pose a problem for the use of
non-intrusive measurement techniques if the
spectroscopic parameters of these molecules (line positions,
line strengths, pressure broadening coefficients, etc.) are
substantially different at the elevated pressures and
temperatures of interest here. So, the first step of this
research
endeavor is to establish the degree to which the spectral
parameters of the various molecules of interest vary with
temperature and pressure.
Table 2: Species of interest in dodecane cracking.
Species Spectral Data
T (K) P(atm) Reference
CH4
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American Institute of Aeronautics and Astronautics
8
high pressures and temperatures, and is accessible through the
inexpensive borosilicate glass windows of the
pressure vessel.
Table 3: Previous spectroscopic investigations of methane.
D. Experiment Setup
Fig. 7 shows the experiment setup for making the measurements
described in the previous section. White light
from a Thermo-Nicolet Nexus 870 FT-IR is channeled into a
Thorlabs BF20LSMA optic fiber using a custom-
assembled fiber coupler using Thorlabs cage-and-tube kit
components. The light exits the fiber into a Thorlabs
RC04SMA-P01 reflective collimator. The 0.66 mm (0.26 in.)
diameter collimated beam passes through the pressure
vessel and furnace (which host the gas mixture to be probed) via
two 0.0127 m (0.5 inch) thick Borosilicate
windows. An MCT/A* detector on the other side of the vessel
receives the beam and interfaces with the
spectrometer. The resolution of the spectrometer is 0.5 cm-1
and the spectra represent the average of 600 scans.
It was determined that 600 scans were adequate to resolve the
main features of interest by computing the change
in mean transmittance with the number of scans which should be
set high enough that the mean transmittance is
independent of the number of scans. The mean transmittance () is
defined as = , where T is the
transmittance ( = ) at a given wavenumber (), and 1 and 2 are
the lower and upper limits of the wavenumber range of interest. For
the test case at 700 K and 15 atm, averaging 100 scans gives
=93.0929, 350 scans gives = 92.9397, and 600 scans gives =92.9326.
While is not an indication of the level of random noise in the
signal (because the random noise component should integrate to
zero), the convergence in values indicates that 600
scans is at least sufficient to resolve physical features. Of
course, higher numbers of scans are still desirable to
reduce noise, especially given the challenge of obtaining good
Signal-to-Noise Ratio (SNR) in this apparatus, but
600 scans appears to represent a good compromise between
accuracy and measurement time.
Author Year Wavelenngth Temperature Pressure Ref
Max Min Max Min Max Min
(nm) (nm) (K) (K) (atm) (atm)
Frankenberg 2008 1670.84 1616.81 296.15 295.65 0.123 0.888
21
Gharavi et. al. 2005 1650.98 1653.99 908 296 0.021 0.003 22
Darnton and Margolis 1973 1662.33 1659.41 300 100 1.711 0.658
23
Nagali et. al 1996 1645.57 1645.53 295 292 0.017 0.004 24
Margolis 1988 1818.18 1618.12 296.2 295.6 0.059 0.002 25
Margolis 1990 1818.18 1618.12 220 180 0.026 26
Li et. al 2011 1653.73 1653.73 578 297 1.000 1.000 20
Lackner 2003 1687.42 1683.90 296 296 0.010 1.283 27
Niederer 2011 11111.11 833.33 80 80 0.007 28
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Fig. 7: Top View of Spectroscopic Measurement Setup.
IV. Results
The upper sections of each plot in Fig 8 show percent
transmittance of 6% mixtures of methane (CH4) in
nitrogen (N2) around 1654 nm at temperatures of 300 K and 700 K
and at several pressures between 1 and 15 atm.
The lower section of each plot shows error computed by taking
the difference between the measured transmittance
and that predicted using SpectralCalc29
and the HITRAN database12
. Fig. 9 shows corresponding absorbance at each
condition. The residual is the difference between the measured
and predicted values normalized by the maximum
measured absorbance of each peak. Thus, the absorbance used for
normalization in the left half of the plots
corresponds to the peak at ~6057 cm-1
and the value used for normalization in the right half of the
plot corresponds
to the peak ~6057 cm-1
.
The results illustrate the competing effects of pressure and
temperature. Generally speaking, raising the
temperature decreases absorbance, because it lowers the density
and thus the total number of light-molecule
interactions. Conversely, raising the pressure increases the
density resulting in more interactions and higher
absorbance. Pressure broadening is also apparent in all cases
but is not strong enough to render individual peaks
indistinguishable for these lines under these conditions.
It is also apparent from Figs. 8 and 9 that there are
differences between the measured and HITRAN-predicted
spectra that seem to increase with temperature. The importance
of these differences for making non-intrusive
measurements of concentration is determined by computing the
error in predicted concentration. The error is
defined as:
= 100 (Eq. 5)
where CH and CM are the concentrations computed using Eqn. 4 and
the Hitran (H) and measured (M) absorbance
spectra. Since all measurements and HITRAN simulations have been
performed at one path length and one
concentration, Eq. 5 reduces to:
Fiber
Coupler
Optic
Fiber
Collimator
Borosilicate
Windows
MCTA*
Detector Test Vessel Spectroscope
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= 100 1 (Eq. 6)
Fig. 10 shows percent error in predicted concentration as a
function of pressure at two temperatures: 300K and
700K. To obtain respective values, the absorbance was integrated
between 6046 cm-1 and 6048 cm-1 for the peak at ~6047 cm
-1, and between 6056 cm
-1 and 6058 cm
-1 for the peak at ~6057 cm
-1. While error is relatively modest at
300K (a few percent which probably of the order of the
uncertainty in the measurement although this has not been
calculated yet) and remains so at pressures up to about 5 atm,
it grows substantially beyond this point and errors in
predicted concentration of 30-40% are observed when using either
line. The results are even worse at 700K where
the error at 5 atm is already ~30-40%. However, the high
temperature results in particular expose an important
problem with the experiment which is generally low absorbance
(and thus SNR) throughout. The problem was so
severe at 700K and 1 atm that the absorption features of
interest disappeared and hence no comparisons between
HITRAN and experiment were possible.
V. Conclusions and Future Work
A facility has been constructed for simulating the high pressure
and temperature fuel flows encountered in
miniature channels used for cooling hypersonic air-breathing
engine components via endothermic fuel
decomposition. Before the facility may be used to measure
chemical composition as a function of downstream
distance in the optically accessible cooling channels, it is
necessary to establish the efficacy of the non-intrusive
absorption-based technique used to measure chemical composition.
To this end, the absorption by two rovibrational
transitions of methane around 1654nm has been explored at two
temperatures (300K and 700K) over pressures
ranging from 1 to 15 atm. These lines were selected for their
additional usefulness in the development of non-
intrusive equivalence ratio sensors for gas turbines19,20
. The results show that measured integrated absorbance
differs
substantially from that predicted by HITRAN and can lead to
substantial errors of more than 40% in predicted
concentration. This is probably because HITRAN relies almost
entirely on spectroscopic data acquired at
atmospheric temperature and pressure but a more detailed
investigation is required to confirm these findings and to
better quantify the discrepancy. In particular, uncertainty
levels associated with each data point in Fig. 10 need to be
determined, the range of conditions needs to be expanded
(experiments 50 atm and 1100K are planned), experiments
at concentrations other than 6% need to be performed, and the
SNR of the measurement system needs to be
improved. Once these steps have been taken, we will move on to
C2H2, C2H4, C2H6, and other molecules relevant to
dodecane cracking.
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300 K 700 K 1
atm
5 a
tm
10
atm
15
atm
Wavenumber (cm
-1)
Wavenumber (cm
-1)
Fig. 8: Spectroscopic Measurements of Methane
(Transmittance).
0
20
40
60
80
100
120%
Tra
nsm
issio
n
6040 6045 6050 6055 6060-10
0
10
-1
Err
or
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060
-10
0
10
-1
Err
or
Experiment
HITRAN (SPECTRA)
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060-10
0
10
-1
Err
or
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060-10
0
10
-1
Err
or
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060-10
0
10
-1
Err
or
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060-10
0
10
-1
Err
or
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060-505
1015
-1
Err
or
0
20
40
60
80
100
120
% T
ransm
issio
n
6040 6045 6050 6055 6060
-15-10-50
-1
Err
or
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300 K 700 K 1
atm
5 a
tm
10
atm
15
atm
Wavenumber (cm
-1)
Wavenumber (cm
-1)
Fig. 9: Spectroscopic Measurements of Methane (Absorbance).
0
0.1
0.2
0.3
0.4A
bsorb
ance
6040 6045 6050 6055 6060-40-20
02040
-1
Resid
ual (%
)
0
0.1
0.2
0.3
0.4
Absorb
ance
Experiment
HITRAN (SPECTRA)
6040 6045 6050 6055 6060-100
0
100
-1
Resid
ual (%
)0
0.1
0.2
0.3
0.4
Absorb
ance
6040 6045 6050 6055 6060-20
0
20
-1
Resid
ual (%
) 0
0.1
0.2
0.3
0.4
Absorb
ance
6040 6045 6050 6055 6060-50
0
50
-1
Resid
ual (%
)
0
0.1
0.2
0.3
0.4
Absorb
ance
6040 6045 6050 6055 6060-10
0
10
20
-1
Resid
ual (%
)
0
0.1
0.2
0.3
0.4
Absorb
ance
6040 6045 6050 6055 6060
-40-20
020
-1
Resid
ual (%
)
0
0.1
0.2
0.3
0.4
Absorb
ance
6040 6045 6050 6055 6060
0
20
40
-1
Resid
ual (%
) 0
0.1
0.2
0.3
0.4
Absorb
ance
6040 6045 6050 6055 6060
-40
-20
0
-1
Resid
ual (%
)
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Fig. 10: Percent error in predicted values of .
References 1Lander, H. and Nixon, A. C., Endothermic Fuels for
Hypersonic Vehicles, AIAA Journal of Aircraft, Vol. 8, No. 4,
April,
1971. 2Wickham, D. T., Alpetkin, G. O., Engel, J. R., and
Karpuk, M. E., Additives to reduce coking in endothermic heat
exchangers,
AIAA-99-2215, 35th AIAA/ASME/SAE/ASEE Joint Propulsion
Conference and Exhibit, 20-24 June, 1999, Los Angeles,
California. 3Meng, F., Liu, G., Qu, S., Wang, L., Zhang, X., and
Mi, Z., Catalytic Cracking and Coking of Supercritical n-Dodecane
in
Microchannel Coated with HZSM-5 Zeolites Ind. Eng. Chem. Res.
2010, 49, 89778983. 4Kee, R. J., Coltrin, M. E., and Glarborg P,
Chemically Reacting Flow: Theory and Practice, John Wiley &
Sons, 2005. 5Goodwin, D. G., Cantera Users Guide, Division of
Engineering and Applied Science, California Institute of
Technology,
Pasadena, CA (http://www.cantera.org). 6Wilke, C. R. and Chang,
P., Correlation of Diffusion Coefficients in Dilute Solutions,
American Institute of Chemical
Engineering Journal 1 (1955), p. 264. 7Medina, I., Determination
of diffusion coefficients for supercritical fluids, Journal of
Chromatography A, 1250 (2012) 124
140, 26 April, 2012. 8Robinson, J. W., Atomic Spectroscopy,
Marcel Dekker, 1996. 9Valeur, B. and Berberan-Santos, M. N.,
Molecular Fluorescence, Wiley-VCH Verlag GmbH & Co. KGaA, 2013.
10Rothman, L. S. et al., The HITRAN Molecular Spectroscopic
Database and HAWKS (HITRAN Atmospheric Workstation):
1996 EDITION, J. Quant. Spectrosc. Radiat. Transfer Vol. 60, No.
5, pp. 665710, 1998. 11Brown, L. R. et al., Methane Line Parameters
in HITRAN, Journal of Quantitative Spectroscopy & Radiative
Transfer 82
(2003) 219238. 12Rothman, L. S. et al., The HITRAN 2008
molecular spectroscopic database, Journal of Quantitative
Spectroscopy &
Radiative Transfer 110 (2009) 533572. 13Rothman, L. S. et al.,
The HITRAN 2012 molecular spectroscopic database, Journal of
Quantitative Spectroscopy &
Radiative Transfer 130 (2013) 450. 14Gomez, L., Jacquemart, D.,
Lacome, N., and Mandin, J.-Y., New line intensity measurements for
12C2H2 around 7.7 um and
HITRAN format line list for applications, Journal of
Quantitative Spectroscopy & Radiative Transfer 111 (2010)
22562264. 15Blanquet G, Bouanich J.P., Walrand J., and Lepe`re
M.,Self-broadening coefficients in the v7 band of ethylene at room
and
low temperatures, J Mol Spectrosc 2003; 222:28490. 16J. F.
Brannon Jr. and P. Varanasi, Tunable Diode Laser Measurements on
the 951.7393cm-1 line of 12CH4 at Planetary
Atmospheric Temperatures, Journal of Quantitative Spectroscopy
& Radiative Transfer 47, 237 (1992). 17A.S. Pine and C.P.
Rinsland, The role of torsional hot bands in modeling atmospheric
ethane, Journal of Quantitative
Spectroscopy & Radiative Transfer 62, 445-458 (1999). 18V.M.
Devi et al., Multispectrum measurements of spectral line parameters
including temperature dependences of N2 and self-
broadened half-width coefficients in the region of the 9 band of
12C2H6, Journal of Quantitative Spectroscopy & Radiative
Transfer 111, 2481-2504 (2010).
0 5 10 150
10
20
30
40
50
Pressure (atm)
7 APercentE
rror
Line 1 (~6047 cm -1)
Line 2 (~6057 cm -1)
300 K
700 K
Dow
nloa
ded
by U
NIV
ERSI
TY O
F M
ARY
LAN
D o
n A
ugus
t 8, 2
015
| http:
//arc.
aiaa.o
rg | D
OI: 1
0.2514
/6.201
5-1156
-
American Institute of Aeronautics and Astronautics
14
19H. Li, S. Wehe, K. McManus, Near-Infrared Diode Laser Sensor
for Real-Time Equivalence Ratio in Gas Turbine
Combustors, AIAA-2009-5522, 45th AIAA/ASME/SAE/ASEE Joint
Propulsion Conference & Exhibit, 2-5 August 2009,
Denver, CO
20H. Li, S. Wehe, K. McManus, "Real-time equivalence ratio
measurements in gas turbine combustors with near-infrared diode
laser sensor", Proceedings of the Combustion Institute 33 (2011)
21C. Frankenberg1, T. Warneke2, A. Butz1, I. Aben1, F. Hase3, P.
Spietz2, and L. R. Brown; "Methane spectroscopy in the near
infrared and its implication on atmospheric retrievals", Atmos.
Chem. Phys. Discuss., 8, 1002110055, 2008, 10022-10055 22M.
Gharavi, S. Buckley, "Diode laser absorption spectroscopy
measurement of linestrengths and pressure broadening
coefficients of the methane 2nu3 band at elevated temperatures",
Journal of Molecular Spectroscopy 229 (2005) 7888 23L. Darnton, J.
Margolis, "The Temperature Depenence of the Half Widths of some
Self- and Foreign-Gas-Broadened Lines of
Methane", J. Quanr. Specrrosc. Radiar. Tra&r. Vol. 13, pp.
969-976. Pcrgamm Press 1973 24V. Nagali, S. Chou, D. Baer, R.
Hanson, J. Segall, "Tunable diode-laser absorption measurements of
methane at elevated
temperatures", APPLIED OPTICS, Vol. 35, No. 21, 20 July 1996,
4026-4032 25J. Margolis, "Measured line positions and strengths of
methane between 5500 and 6180 cm-1", APPLIED OPTICS / Vol. 27,
No. 19 / 1 October 1988, 4038-4051 26J. Margolis, "Empirical
values of the ground state energies for methane transitions between
5500 and 6150 cm-1",20 May 1990
/ Vol. 29, No. 15 / APPLIED OPTICS, 2295-2302 27M. Lackner, G.
Totschnig, F. Winter, M/ Ortsiefer, M-C Amann, R. Shau, J.
Rosskopf, "Demonstration of methane pectroscopy
using a vertical-cavity surface-emitting laser at 1.68 mwith up
to 5 MHz repetition rate", Meas. Sci. Technol. 14 (2003) 101
106 28J. M. G. Niederer, "The Infrared Spectrum of Methane", ETH
Zurich Dissertation, 2011 29Gordley, L.L, B. T. Marshall and D.
Allen Chu, (1994), Linepak: algorithms for modeling spectral
transmittance and
radiance, Journal of Quantitative Spectroscopy & Radiative
Transfer, Vol. 52, No. 5, pp. 563-580
Dow
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LAN
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t 8, 2
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| http:
//arc.
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/6.201
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