AsiaPacific Combustion Institute Sum mer School Author 1 1 Author 2 1 Author 3 1 1 Affiliation 1 2 Affiliation 2 Presented at the 1st AsiaPacific Combustion ID: 816442
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Slide1
Poster for the 1st Asia-Pacific Combustion Institute Sum-
mer School
Author 11 Author 21 Author 31
1 Affiliation 1. 2 Affiliation 2.
Presented at the 1st Asia-Pacific Combustion Institute Summer School in Viña del Mar (Chile) on Thursday 14th November 2019
Currently there is no thorough
numerical
studies of propane
flames
although it is
heavily
used in numerous domestic and industrial processes.
Soot has become a topic of
mayor
interest for scientific community because of its impact in the environment and health, but also because of its influence in industrial processes efficiency.Even though air, which is 21% oxygen, is the most common oxidant used, it is interesting to investigate how the combustion process is affected when the Oxygen Index is altered.
INT
RODUCTION
Study
numerically the soot production from propane laminar coflow diffusion flames us- ing a PAH-based sectional particle dynamics model giving special importance to the surface growth process.
Extend the soot production model to different oxygen concentrations in the oxidant stream, called Oxygen Index (OI).Compare to propane experimental values from Escudero et al. [1].
OBJECTIVES
Numerical
Model
Based on CoFlame [2]Detailed gas-phase chemical kinetic mechanism 94 species and 719 reactions from DLR [3]Fixed sectional soot model: 35 sectionsSoot production mechanisms considered:Nucleation: collision and sticking of gaseous species: BGHIF, BAPYR and BAPYR*S Condensation of PAH: collision and sticking of gaseous species and soot particles Surface growth by HACA mechanism [4]: sensitivity of the steric factorOxidation by O2 and OH Agglomeration and fragmentationSNBCK-based wide-band radiative property model [4]: CO2, CO, H2O and soot
HACA model and Steric Factor αThe Hydrogen-Abstraction-Carbon-Addition model is based in the concept of Armchair Sites in the
particle surface. χCsoot ◦ represents the number of dehydrogenated sites per surface unit and it can be
estimated as [2]:
soot ◦
χC =
(
k1[H] + k2[OH]) χCsoot−Hk−1[H2] + k−2[H2O] + k4[C2H2] + k5[O2] + k1[H] + k2[OH]
(1)
Then, the increase rate of mass due HACA and decrease rate of mass for oxidation are respectively:
2 2,
C H i
I = 2αC
s,i
mass 4 2 2
p
k [C H ]N χ
soot
C ◦
I = 2αC
A A
s,i
Av Av
p
i i
k [O ]N χ
soot
O2,i mass 4 2 C ◦
(2)
Here α is the Steric Factor which is an empirical parameter that represents the surface area "available" for reactions to occur.
Is there a single Steric Factor that can predict soot production for different OI using propane as fuel?
METHODS
f
max
(ppm)
20
22
24
26
OI
(%)
28
30
32
34
0
1
2
3
4
5
6
7
8
9
10
11
Exp
[1]
=
0.25
=
0.30
=
0.35
Maximum
Soot
Volume
Fraction
-
f
max
2
max
(
ppm
cm
)
20
22
24
26
OI
(%)
28
30
32
34
0
0
.
2
0
.
4
0
.
6
0
.
8
1
1
.
2
1
.
4
1
.
6
1
.
8
2
Exp
[1]
=
0.25
=
0.30
=
0.35
Maximum
Integrated
Soot
Volume
Fraction
-
β
max
Integrated
Soot
Profiles
r
(cm)
(
ppm
cm
2
)
0
2
4
6
0
0
.
5
1
1
.
5
OI = 21%, Exp
[1]
OI = 25%, Exp
[1]
OI = 29%, Exp
[1]
OI = 33%, Exp
[1]
OI = 21%, Num.
=
0.25 OI = 25%, Num.
=
0.25 OI = 29%, Num.
=
0.25 OI = 33%, Num.
=
0.25
α
=
0.25
r
(cm)
(
ppm
cm
2
)
0
2
4
6
0
0
.
5
1
1
.
5
OI = 21%, Exp
[1]
OI = 25%, Exp
[1]
OI = 29%, Exp
[1]
OI = 33%, Exp
[1]
OI = 21%, Num.
=
0.30 OI = 25%, Num.
=
0.30 OI = 29%, Num.
=
0.30 OI = 33%, Num.
=
0.30
α
=
0.30
r
(cm)
(
ppm
cm
2
)
0
2
4
6
0
0
.
5
1
1
.
5
OI = 21%, Exp
[1]
OI = 25%, Exp
[1]
OI = 29%, Exp
[1]
OI = 33%, Exp
[1]
OI = 21%, Num.
= 0.35 OI = 25%, Num.
= 0.35 OI = 29%, Num.
= 0.35 OI = 33%, Num.
=
0.35
α
=
0.35
Flame
Height
h
f
(cm)
20 22 24 26
OI
(%)
28
30
32
34
1
2
3
4
Exp
[1]
h
f2
,
=
0.30
Flame Height
-
h
f
OI
HAB
(mm)
d
p
(nm)
exp
α
=
0.25
α
=
0.30
α
=
0.35
21 45 13.7 9.801 10.059 10.107
29 25 20.1 16.345 16.927 17.029
33 25 26.4 12.750 13.622 14.166
PARTICLE
DIAMETER
RESULTS
Calibration
Parameters
A single constant steric
factor
is able to predict the variation of maximum soot
volume
fraction, maximum integrated soot
volume
fraction and
flame
height.
Results
related to soot pro- duction vary
linearly
as the steric
factor
changes.
Predicted integrated soot results presented a slight
overpredic-
tion
of
the
position
of
the
peak
compared
to
experimental
results.
It is concluded that the steric
factor
affects
the
overall
soot pro- duction as it promotes the soot
growth
process, but does not
affect
the
behavior
of soot production along the
flame
height.
Primary
particle
diameter
predicted
exhibit
differences
less
than 30%
for lower
OI compared to mean diameter from TEM mea- surements at a
certain
height at the
flame
centerline.
It is
noteworthy
that the chemical model used presented accu- rate results in
terms
of soot production
even
though it
was
not optimized/validated
for
propane.
Future
work
includes the use of a
different
kinetic-chemical model that adjust to propane coupled with the soot model al- ready
implemented.
DISCUSSION
[
1
] Escudero et al.
Fuel
183 (2016)
668–679.
[
2
]
Eaves
et al.,
Comput.
Phys.
Commun.
207 (2016) 464–477. [
3
]
Dworkin
et al.,
Combust. Flame
158 (9) (2011) 1682–1695. [
4
] Appel et al.,
Combust. Flame
121 (1) (2000)
122–136.
[
5
] Liu et al.,
J. Thermophys. Heat
Tr.
14 (2) (2000)
278–281.
A
c
kn
o
w
ledgments
:
Chilean
C
ONIC
Y
T
PIA/ANILLO
ACT172095.
REFERENCES