114RK-0014 Reaction Kinetics
9th U. S. National Combustion Meeting
Organized by the Central States Section of the Combustion Institute
May 17-20, 2015
Cincinnati, Ohio
Capturing Soot Formation with the Use of Iso-Octane as a
Surrogate for Fischer-Tropsch Fuel
A. Makwana, Y. Wang, M. Linevsky, S. Iyer,
R. Santoro, T. Litzinger, J. O’Connor*
Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA
*
Corresponding Author Email: [email protected]
The goal of this work is to support the development of surrogate fuel mixtures that replicate the chemistry and flame
characteristics of renewable Fischer-Tropsch (FT) fuels. In particular, we focus on capturing soot formation and
growth with the use of iso-octane as a surrogate for FT jet fuel. An axisymmetric, co-flow, laminar flame configuration
is used to study soot formation for non-premixed and rich-premixed mixtures at atmospheric pressure. A laser
extinction technique is used to obtain spatially resolved soot volume fraction results, and thermocouple measurements
provide profiles of gas temperatures in both the radial and axial directions. Comparisons of flame temperature
measurements from both FT and iso-octane flames indicate that the temperatures are the same in both the axial and
radial profiles within the uncertainty of the measurement. The flame temperatures for the non-premixed flame are 50100 degrees Celsius higher throughout the flame than those for the rich-premixed flame. Laser extinction
measurements with both fuels show that the soot volume fraction profiles are very similar for FT fuel and iso-octane.
Additional analysis shows the impact of premixing air on soot formation and the differences in time-scales of soot
formation with and without the presence of oxygen.
Keywords: Surrogate fuel, Fischer-Tropsch, iso-octane, soot
1. Introduction
The Department of Defense (DOD) is pursing numerous initiatives for reducing its fuel needs
and changing the mix of energy sources that it uses. In 2011, the DOD consumed approximately
117 million barrels of oil [1]. Specifically, gas turbine engines (GTEs) consume about 73% of the
DOD’s total fuel and are the major source of carbon monoxide (CO), unburned hydrocarbons
(UHC), oxides of nitrogen (NOx), and soot produced at military airbases [2]. The soot emitted has
harmful effects on human health and the environment [3-6]. Scarce energy resources, stricter
environmental requirements, worldwide air traffic growth, and rising fuel prices all lead to an
increasing interest for understanding alternative jet fuels.
Previous programs’ field studies of actual engines, e.g. Bulzan et al. [7] and Miake-Lye et al.
[8] compared the emissions from engines fueled with petroleum-based fuels to several proposed
alternative fuels and blends. The results indicate that the most significant effect of transitioning
from JP-8 to alternative jet fuel is a change in soot emissions. It has also been observed that
changes occur in emissions of specific hydrocarbon species, some of which are classified as
Hazardous Air Pollutants (HAP). Generally, there is little or no change observed in NOx emissions.
Experimental investigations found that a significant reduction in soot emissions (both mass and
particle number) could be achieved through the use of synthetic paraffinic alternative fuels, both
neat and in blends with petroleum-derived fuels [9].
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114RK-0014 Reaction Kinetics
Future advances in the design of combustion-based aero-propulsion engines will rely, in part,
on computational modeling predictions of fuel combustion kinetics. Normal jet fuels such as JetA and JP-8 are complex mixtures of hundreds of chemical components. Even Fischer-Tropsch
(FT) fuels, which are less complicated in composition, are still not thoroughly understood with
respect to combustion and emission characteristics. Consequently, a number of researchers use
surrogate fuels, which typically consists of one or several pure hydrocarbon components from the
representative classes of real jet fuels to reproduce the combustions characteristics or, in some
cases, the physical properties of fuels [10-14]. This method reduces the complexity of creating a
detailed model for predicting combustion processes.
The goal of this work is to aid in the development of surrogate fuels by understanding soot
formation processes, which contain some of the most complex hydrocarbon (HC) reactions. In
particular, we are interested in understanding sooting processes of alternate jet fuels manufactured
using a Fisher-Tropsch process from coal, natural gas, or other hydrocarbon feedstocks. FT
technology is a catalytic process that converts synthesis gas (CO+H2) into a mixture of
hydrocarbons (synthetic fuel) [15]. The FT fuels don’t contain sulfur and have higher thermal
stability than petroleum-derived jet fuels [16, 17]. FT fuels are typically composed of normal- and
iso-parrafins (>99% by volume) and less than 0.2% aromatics [18].
This work investigates the possibility of using iso-octane (2,2,4-trimethylpentane) as a
surrogate for FT fuel. This one-component surrogate was selected to match the molecular structure,
hydrogen to carbon ratio, and molecular weight of the FT fuel. Table 1 shows a comparison of
properties of the two fuels.
Table 1. Fuel properties.
Fuel property
FT
Iso-octane
Hydrogen to carbon ratio
2.14*
2.25
Molecular weight (g/mol)
151.38*
114.23
Threshold soot index (TSI)
n/a
6.8**
Density (g/mL)
0.759*
0.690
Heat of combustion (MJ/Kg)
43.9*
47.81***
42*
-12
Flash point (℃)
*FT fuel quantified by GC×GC analysis and Ref. [18], **Ref. [19], ***Ref. [20]
The data presented in this paper are relevant to fuel/air mixtures in GTE combustors. Typical
gas turbine combustors burn a rich fuel/air mixture in the primary zone to ensure flame stability
and aid in high-altitude relight if necessary. Soot is mostly produced in rich regions, like the
primary zone of GTE combustor, and then is consumed downstream. Thus, the primary zone
governs the soot formation rate, whereas the intermediate and dilution zones determine the soot
oxidation. Consequently, the engine-out soot depends on the balance of these two processes. The
current work is focused on non-premixed and rich-premixed flame conditions in order to simulate
conditions in the primary zone.
2. Methods / Experimental
2.1
Burner and Burner system
A co-annular laminar flame burner has been used in the present work to study the soot
formation under the experimental conditions presented in Table. This burner is similar to the coannular laminar flame burner used by Santoro et al. [21]. The burner consists of two concentric
brass tubes as shown in Figure 1. The inner fuel tube diameter is 11.1 mm. This tube protrudes 4
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114RK-0014 Reaction Kinetics
mm above the plane of the co-flow. The inner tube contains glass beads and screen to condition
the flow. The outer air tube has a 101.6 mm diameter. The annular co-flow region consists of series
of screens, glass beads, and honeycomb to provide a uniform exit velocity profile.
Figure 1: Burner dimensions.
The burner system used is shown in Figure 2. The fuel is stored in a Syringe D500 fuel pump
and delivered through 1/16” tube to the vaporization unit. The vaporization unit consists of a ¼”
brass Swagelok tee filled with fiber glass [22]. The energy for fuel vaporization is provided by
heating tapes that are wrapped around the tubing system and Swagelok assembly. The heating
tapes are wrapped from 30 cm below the mixing chamber to the end of the burner inner tube. A
nitrogen stream is used to carry the vaporized fuel from the mixing chamber to the burner. A 100
micron orifice is installed after the mixing chamber to provide sufficient pressure and residence
time to heat the fuel-nitrogen mixture. For premixed cases, the premixed air inlet is located after
the orifice in the main tubing system. Five K-type thermocouples are placed on the tubing system
to monitor the temperature at critical locations, as shown in Figure 2. Four filters are installed for
nitrogen, fuel, fuel/nitrogen mixture, and air. The flow rate of premixed air and nitrogen is
controlled by mass flow controllers (Brooks Instruments 5850 series). The mass flow controllers
are calibrated using a bubble meter. The co-flow air is set at a constant flow rate of 4 scfm.
The temperature of the heating tapes is maintained at 200ᵒ C in order to vaporize the fuel. The
temperature is also properly maintained to prevent fuel pyrolysis in the tubing system. Gas
chromatography has been used on the fuel-air-nitrogen mixture at the exit of burner tube to ensure
that no fuel pyrolysis has occurred in the tubing system. The iso-octane fuel used in this experiment
is 99.9% pure; the Fisher-Tropsch fuel used is a coal-based Sasol fuel. The nitrogen used was
99.9% pure industry grade and filtered air was supplied from an air compressor.
A brass chimney (400 mm long) with screens on the top is placed around the flame. This
chimney helps to protect the flame from surrounding air-currents and obtain a stable flame. Four
slots are machined at symmetrical locations on the chimney to provide access for the laser beam
and the thermocouple. The burner assembly can be moved in both the horizontal and vertical
direction using stepper motor.
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114RK-0014 Reaction Kinetics
Figure 2: Burner system.
2.2
Diagnostics Method
Soot volume fractions were measured using a laser extinction technique, as shown in Figure 3.
The laser extinction measurements were obtained using a Coherent Innova 70 (2W) argon ion laser
at a 514.5 nm wavelength. The laser input was 0.5 W and the beam was modulated at 1000 Hz
using a mechanical chopper. A beam splitter (30%:70%) was used to deflect and monitor the
incident laser beam (𝐼𝑜 ) by a PIN-10D silicon photodiode. A neutral density filter (NDF) was used
before this photodiode to reduce the beam intensity to levels so that the photodiode operated in its
linear region. A set of convex and concave lens were used to expand the laser beam before the
photodiode measuring, 𝐼𝑜 . The laser beam was focussed on the flame using a 350 mm focal length
lens. The transmitted power, 𝐼, was measured using a similar photodiode fitted on an integrating
sphere. The integrating sphere was used to reduce the beam steering effect as laser beam passed
through the flame.
Figure 3: Optical setup for Laser extinction measurements.
The output signals from both photodiodes were converted to voltages using a trans-impedance
amplifier and then fed into a lock-in amplifier to reduce the noise from surrounding environment.
The line-of-sight measurements were obtained every 0.25 mm and 1 mm in the radial direction
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114RK-0014 Reaction Kinetics
and axially along centerline, respectively. The extinction profiles are deconvoluted using a Fourier
inversion technique [23]. The refractive index of soot was taken as 𝑚
̃ = 1.57 − 0.56𝑖 to be
consistent with the previous published work [24].
Temperature measurements were obtained using 125 micron Pt/Pt-13% Rh fine-wire, uncoated
R-type thermocouples. The thermocouple configuration used is shown in Figure 4. The
thermocouple apparatus consists of a single ceramic tube that was fixed on a horizontal translation
stage. The thermocouple wires pass through the two holes inside the ceramic tube. One side of the
thermocouple wires are affixed to the connector, and at the other end, the wires are bent at 90
degrees to point vertically down approximately 3 mm. Temperature gradients being small in the
axial direction compared to the radial direction helped to reduce the conduction along the wires.
Temperature measurements were obtained every 1 mm in both the radial direction and axially
along centerline from the burner exit by moving the burner in a horizontal or vertical direction. In
regions containing soot, soot particles deposited on the thermocouple junction; the junction was
cleaned by moving it to an oxidizing region of the flame.
Thermocouple measurements have been corrected for radiation losses and heat conduction
along the thermocouple wires has been neglected. The emissivity for Pt/Pt-13% Rh was taken from
Bradley and Entwistle [25]. The conductivity and viscosity of the gas were taken as that of
nitrogen. The bead was considered spherical and the Nusselt number was estimated by a
correlation from Eckert and Drank [26]. The velocities typically ranged from 30-250 cm/sec inside
the flame [27] and a value of 60 cm/sec was considered for the radiation correction. The data for
both laser extinction and temperature measurement were collected by a National Instruments data
acquisition system at a sampling rate of 10 samples/sec for 4 sec.
Figure 4: Thermocouple configuration.
2.3
Experimental Conditions
The flames investigated are non-premixed (equivalence ratio of “infinity”) and rich premixed
(equivalence ratio of 6) in order to have fuel rich conditions similar to those in the primary zone
of an aircraft engine combustor. The flow rate of nitrogen was selected such that it is sufficient to
carry the vaporized fuel to obtain a stable flame. The total carbon flow rate was held constant for
all flames at 0.0111 mole/min. The carbon flow rate was fixed to match carbon flow from the base
flame, a 75% dodecane and 25% m-xylene mixture. The experimental conditions are provided in
Table 2.
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114RK-0014 Reaction Kinetics
Fuel
FischerTropsch
IsoOctane
Table 2. Experimental conditions.
Carbon Flow N2 Flow
Equivalence Fuel flow
Rate
Rate
ratio (phi)
rate (sccm)
(mole/min)
(slpm)
Inf
0.208
0.0111
0.2
6
0.208
0.0111
0.2
Inf
0.230
0.0111
0.2
6
0.230
0.0111
0.2
Mean exit
velocity
(cm/s)
4.33
9.93
4.63
10.22
Co-flow
flow rate
(slpm)
4.0
4.0
4.0
4.0
3. Results and Discussion
3.1
Flame Heights
Figure 5 shows visible flame pictures taken using a commercial camera. The camera settings
(aperture and shutter speed) were adjusted in order to take clear visible flame images at each
condition. This means that the relative intensities of these images should not be compared. These
images indicate that flame heights for both fuels are nearly equal at same equivalence ratio; these
heights are also presented in Table 3. The flame height of the rich-premixed flame is smaller
compared to the non-premixed flame for both fuels, consistent with previous work [28].
Table 3. Flame height comparison.
Phi = Infinite
Flame
FT
iso-octane
FT
Height above burner [mm]
62.2
62.7
47.8
Phi=6
iso-octane
50.0
Figure 5. Flame picture (a) FT- phi=Infinite flame (b) iso-octane - phi=Infinite flame (c)
FT- phi=6 flame (d) iso-octane - phi=6 flame.
3.2
Temperature Distributions
Temperature was measured in the lower part of the flames using a thermocouple. The primary
reason to compare the temperature in lower part of the flame is because this temperature has a
great impact on the soot production [29]. Figure 6 shows a comparison of radial profiles of
temperature for FT fuel and iso-octane at two heights above the burner exit (HAB). The radial
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114RK-0014 Reaction Kinetics
temperature profiles are consistent with the typical shapes for laminar flames [21]. The peak
temperature and radial temperature profiles for both FT flames and iso-octane flames are quite
similar for both phi=infinite and phi=6 flame conditions.
(a)
(b)
(c)
(d)
Figure 6. Comparison of radial profiles of temperature for FT flame and iso-octane flame:
(a) phi=Infinite flame-5mm height above burner (HAB), (b) phi=Infinite flame-10mm
HAB, (c) phi=6 flame-5mm HAB, (d) phi=6 flame, 10mm HAB.
Figure 7 shows the comparison of the axial temperature profile for FT fuel and iso-octane
under both phi=Infinite and phi=6 conditions. The measurements were taken until 20 mm height
above the burner. Temperature measurements above this height were not possible as the flame
shape was significantly altered by the presence of the thermocouple in this region. The temperature
profiles along the centerline of the flame for both premixed and non-premixed conditions are
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114RK-0014 Reaction Kinetics
consistent with previous work [21, 30]. The temperature from the burner exit to approximately 14
mm above the burner for phi=6 is lower compared to non-premixed flames. Further downstream,
the temperature profiles for the phi=6 and phi=Inf flames cross and the phi=6 flames are hotter;
this is due to heat release at inner flame front in phi=6 flame [30]. The temperatures measured
along the centerline at a given equivalence ratio are quite similar for both FT and iso-octane flames.
Figure 7. Comparison of axial profiles of temperature for FT flame and iso-octane flame
for phi=Infinite and phi=6.
3.3
Laser Extinction
Figure 8 shows the comparison of line-of-sight integrated soot volume fraction for both FisherTropsch and iso-octane flames as a function of normalized distance above the burner; distance is
normalized by the flame height in each case. The visible flame widths, obtained using a digital
camera, were used as extinction path lengths for the calculation of soot volume fraction. In general,
the soot profile for the iso-octane flame follows the soot volume fraction of the FT flame in both
the premixed and non-premixed cases. The soot volume fraction increases first in the lower part
of the flame due to soot production and then it decreases due to soot burnout. The figure shows
that the soot volume fraction is higher for non-premixed flames than in premixed flames. The soot
volume fraction peaks earlier at a normalized height of nominally 0.6 for non-premixed flames
compared to a normalized height of 0.66-0.76 for premixed flames.
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114RK-0014 Reaction Kinetics
Figure 8. Line-of-sight soot volume fraction along axial direction for Fisher-Tropsch and
iso-octane fuel under equivalence ratio of Inf and 6.
(a)
(b)
Figure 9. (a) Maximum soot volume fraction and (b) centerline soot volume fraction along
the axial direction for Fisher-Tropsch and iso-octane fuel.
Figure 9(a) shows the variation of maximum soot volume fraction for both fuels as a function
of downstream distance; the radial location of the maximum soot volume fraction at each
downstream location may differ in each flame. The shape of the maximum soot volume fraction
curves for both fuels is quite similar. In the lower part of the flame, the soot volume fraction is
similar in the FT and iso-octane flames for both the phi=Inf and phi=6 conditions. Further
downstream, the maximum soot volume fraction is higher for the iso-octane flame as compared to
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114RK-0014 Reaction Kinetics
the FT flame. The highest magnitude of the maximum soot volume fraction for the iso-octane
flame is roughly 1.4 times that of the FT flame for both the pre-mixed and non-premixed condition.
Figure 9(b) shows the variation of soot volume fraction along the centerline of the flame. The
profiles for centerline soot volume fraction have similar shapes for both fuels and for the nonpremixed and premixed condition. The peak centerline soot volume fraction is higher by 28% and
48% for iso-octane fuel compared to FT fuel for the non-premixed and premixed conditions,
respectively. This could be due to greater surface growth, particle agglomeration, and slower
burnout in the surrogate fuel. However, further investigation of the distribution of large aromatics
and species concentration would be necessary to establish a more detailed explanation.
The profiles of the soot distribution in the radial direction are symmetric about the centerline.
To compare radial profiles of the iso-octane and FT flames, only half-profiles have been plotted
in Figure 10. The left half from r=-6 to 0 mm is the radial profile of soot volume fraction in the
FT flame, while the right half from r=0 to 6 mm is for the iso-octane flame. The soot distribution
pattern in the radial direction has a similar profile to previously reported data [21]. In the lower
region of the flame, the maximum soot volume fraction occurs in the annular region close to the
flame front where temperature is high. At locations farther downstream, the concentration of soot
in the annular region decreases due to soot oxidation. The central region has less soot near the
base, but the soot volume fraction increases with downstream distance to its peak near 30-35 mm
and then decreases due to oxidation.
Figure 10(a) shows a comparison of the radial distribution of the soot volume fraction in the
lower part of the flame for the non-premixed condition. The radial profiles and maximum soot
volume fraction for the iso-octane flame match very well to the FT flame at the base of the flame.
At a height of 30mm to 35mm above the burner in Figure 10(b), the peak soot volume fraction for
both flames occurs but the peak volume fraction of soot in the iso-octane flame is 40% higher than
that in the FT flame. This peak in the iso-octane flame occurs closer to the center (r=2.25 mm)
than the peak in the FT flame (r=2.75 mm). At 40 mm and 45 mm above the burner, shown in
Figure 10(c), the radial profiles match quite well for both fuels but the peak soot volume fraction
for the iso-octane flame is higher (8.4 ppm) as compared to the FT flame (5.46 ppm). Finally, at
downstream locations of 50 mm and 55 mm, also shown in Figure 10(c), the soot volume fraction
in the central region has decreased for the FT fuel due to oxidation but it is still significant for the
iso-octane flame. This is consistent with Figure 8, where the integrated soot volume fraction for
iso-octane is greater than the FT flame for a non-dimensional height greater than 0.8.
Figure 10(d) shows a comparison of radial profiles for both fuels at an equivalence ratio of 6.
The overall profiles are quite similar in terms of their radial distribution. The FT flame has a
slightly higher peak soot volume fraction in a lower part as compared to the iso-octane flame.
Further downstream at 40 mm above the burner, the iso-octane flame has a higher peak soot
volume fraction in the central part of the flame.
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114RK-0014 Reaction Kinetics
Figure 10: Comparison of half profiles for FT vs i-C8 (a) phi=Inf, 15mm, 20mm, 25mm
HAB, (b) phi=Inf, 30mm, 35mm HAB, (c) phi=Inf, 40mm, 45mm, 55mm HAB, (d) phi=6,
all HAB.
3.4
Residence Times
The residence time of soot in the non-premixed and premixed flame was calculated using the
velocity field obtained from solving a Navier-Stokes based , two-dimensional simulation package
known as UNICORN (Unsteady Ignition and Combustion using Reactions) [31-33]. The velocity
along the centerline of the flame as a function of downstream distance for both the non-premixed
and premixed flame is shown in Figure 11. Since the flames are buoyancy driven, the velocity
profiles do not change much due to premixing [27]. The velocity fields were used to track particle
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114RK-0014 Reaction Kinetics
residence time along seven streamlines starting at different radial locations from the centerline of
the tube.
Figure 11: Velocity along centerline for phi=Inf and phi=6.
Figure 12 shows the streamlines originating at these radial locations for a premixed (left) and
non-premixed (right) flame. The streamlines for the non-premixed flame are more curved inside
the flame as compared to the premixed flame. This is because less secondary air is required for the
premixed flame as compared to the non-premixed.
Figure 12: Streamline originating at different radial location for non-premixed flame
(right) and equivalence ratio of 6 (left).
The residence time along the seven streamlines as a function of downstream distance is plotted
in Figure 13(a) and 13(b) from simulation of the premixed and non-premixed cases, respectively.
A total of 1901 and 1471 points were obtained along each streamline for non-premixed and
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114RK-0014 Reaction Kinetics
premixed cases, respectively. The distance between two adjacent points and the velocity from the
closest grid point were used to calculate the residence time between two points.
Figure 13 shows that the total residence time of a particle decreases from the r=0 mm
streamline to the r=4 mm streamline. This trend is driven by the temperature field; the temperature
is lower along the centerline in lower part of the flame, resulting in a longer residence time in the
buoyancy-driven flow. The residence time along the r=6 mm streamline is longer than the time
along the r=5 mm and r=4 mm streamline. The trends in residence time variation for the premixed
flame, in Figure 13(a), are similar to those in the non-premixed flame in Figure 13(b). The
residence time along a particular streamline for the premixed flame is smaller compared to
corresponding streamlines in the non-premixed flame.
(a)
(b)
Figure 13: Variation of residence along the streamlines as a function of downstream
distance (a) phi=6 flame (b) phi=Inf flame
This residence time information can help explain the soot results from the premixed and nonpremixed flames. Soot volume fraction results in Figures 8-10 indicate that premixing has a
significant impact on soot formation. First, oxygen in the premixed mixture could increase the fuel
pyrolysis, thereby increasing soot formation. Simultaneously, soot oxidation also increases in the
presence of oxygen. The overall effect of these two phenomena is reduced soot volume fraction in
a premixed flame [34, 35]. Additionally, the time available for surface growth affects the soot
volume fraction in a flame and could be another reason that the soot volume fraction is less in
premixed flames [36]. The experimental results in Figure 9(b) and Figure 8 shows that for the
premixed flame, soot inception occurs later at a non-dimensioned height of 0.4 compared to nondimensional height of 0.2 for the non-premixed flame. Table 4 quantifies the time required for a
fluid particle to traverse the flame height; it is clear that the time is less for a premixed flame at
any given streamline. As a result, soot in a premixed flame has less residence time available for
surface growth as compared to soot in a non-premixed flame. The soot surface area available,
which depends on soot number density, would also affect the overall growth of the soot. A greater
surface area and higher residence time would result in faster soot growth. In future, the relative
impact of residence time and surface area on soot surface growth needs to be investigated.
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114RK-0014 Reaction Kinetics
Table 4. Time to travel to flame tip for all streamlines for non-premixed and premixed flame.
Time [ms]
Streamline
0
1
2
3
4
5
6
106
102
94
86
80
79
85.6
Phi=Inf
64
63
60
57.5
56
58.7
64.3
Phi=6
4. Conclusions
This paper presents a set of temperature and soot volume fraction data for iso-octane and FT
fuels under non-premixed and rich-premixed conditions. The peak temperatures in the iso-octane
and FT flames are almost the same in the lower part of the flame under non-premixed and premixed
conditions. Also, radial and centerline temperature field are quite similar for both fuels. The
integrated soot volume fraction in the iso-octane flame is similar to that of the FT flame for both
non-premixed and premixed conditions. However, the maximum soot volume fraction for the isooctane flame is 1.4 times that of the FT flame for both the premixed and non-premixed condition.
The soot volume fraction in the premixed flame is small compared to soot volume fraction in nonpremixed flame.
5. Acknowledgements
The authors also wish to acknowledge the support of this work provided by the Strategic
Environmental Research and Development Program (WP-2145) under the direction of Dr. Robin
Nissan and Mr. Bruce Sartwell.
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16
114RK-0014 Reaction Kinetics
7. Supplementary material:
Table 5: FT fuel (coal- Sasol) composition
Number of C
11
10
9
12
13
9
8
11
10
14
9
Number of H
24
22
20
26
28
18
18
24
22
30
20
Class
iso-C11
iso-C10
iso-C09
iso-C12
iso-C13
monocyclo-C09
iso-C08
n-C11
n-C10
iso-C14
n-C09
17
Mole
Fraction
0.316
0.314
0.156
0.116
0.040
0.017
0.010
0.009
0.008
0.008
0.003