The 30th National Conference on Combustion and Energy
April 24, 2020
National Chin-Yi University of Technology
Paper ID: 0XX
Diffusion Effect on Soot Characteristic of Emulsified/Non-Emulsified Fuel’s Droplet
Combustion
Atul Kumar*, Shouyin Yang
Department of Power Mechanical Engineering, National Formosa University
Huwei Township, Yunlin county, 632, Taiwan
*
Corresponding author Email: 10774128@gm.nfu.edu.tw
MOST Project No: MOST 108-3116-F-008-004-CC1 & MOST 109-3116-F-008-008-CC1
Abstract
The present study examined the physics and mechanisms of Micro-explosion in emulsified and Non-emulsified
fuels. Direct and backlight imaging methods were used to perform the experiment. The experiments were conducted
in normal atmospheric conditions and the fuel droplets were glass fiber supported. Experimental result shows the
difference between puffing and explosion. Puffing Is the ejection of the water vapors from the droplet and with the
ejection the small droplets are also produced which are named as daughter droplet. The daughter droplets are
formed in both puffing and explosion process. Explosion is the breakup of the droplet due to the higher vapor
ejection force. So by analyzing the daughter droplet velocity and size, the puffing and explosion can be
characterized. Also the probability of micro-explosion and puffing taking place in emulsified versus non-emulsified
fuels has been analyzed. And the result shows that the non-emulsified fuels are more prone to the explosion or
droplet break-up and emulsified fuels are more prone to the puffing. The break up delay time shows the prominent
decrease with the increment of water content. The emulsified fuels also show higher droplet shape oscillations as
compared with the non-emulsified fuels. The impact factor which is the Factor which describes the impact of The
puffing or explosion on the parent droplet, shows that the emulsion fuel droplet ejection has Higher local impact
factor than the non-emulsified fuel. The daughter droplet production is higher in non-emulsified fuels but the
diameter of the daughter droplet is higher. Which means if the explosion dominates the micro-explosion then the
daughter droplet produced would be bigger in size than produced in emulsified fuels or puffing dominated
combustion.
Keywords: Droplet combustion, Schlieren imaging, Laser extinction imaging, Emulsion and non-emulsion.
1. Introduction
In all liquid fuel based engines, the reactants are
fed into the combustion chamber in the form of finely
divided droplet arrays. The combustion of such arrays
inside the combustion chamber depends on various
parameters. The droplet size, droplet velocity, droplet
size distribution, pressure, temperature and gaseous
compositions inside the combustion devices are few
to mention. These parameters are so closely
interrelated that each plays an important role. So we
are studying droplet combustion of the fuels. Most
experimental campaigns date back to around The
1990s: the shell-like structure of soot, placed between
the flame layer and the droplet surface, was first
observed by Shaw [1]. The reason behind such a
peculiarity was later attributed by Jackson and
Avedisian to the competition between the convective
or Stefan-flow, due to evaporation, and the
thermophoretic flow acting on particles. They
correlated the decrease in the burning rate with
droplet size to soot production because of a
combination of barrier and radiation effect, affecting
the total heat transferred to the droplet [2,3]. The
structure of the flame enclosing the droplet was then
studied by Mikami [4] by using hooked
thermocouples, and showing that the maximum
temperature region, i.e. the reaction zone, is located
outside of the yellow luminous zone, whose color is
due to radiation from soot [4]. The transient evolution
The 30th National Conference on Combustion and Energy
April 24, 2020
of soot volume fractions was quantified in later
works: the maximum values were found to be
between 10 and 100 ppm, i.e. more than one order of
magnitude higher than that observed in gas-phase
diffusion flames with the same fuels [5]. Finally,
experiments on space laboratories allowed an
extensive investigation on large-sized droplets
(super-mill metric), whose combustion dynamics
cannot be followed in drop towers because of their
insufficient length. In this way, light could be shed on
radiative extinction of large droplets and cool flame
burning due to the low-temperature chemistry of nalkanes [6,7,8].
In this study diesel, butanol, 95% diesel +5%
water (emulsion) and 95% butanol with 5% water
(non-emulsion) are used to compare the results.
Butanol does not need emulsion to produce the
mixture with water but diesel does require emulsions
to make diesel and water mixture. So this study also
focuses on the effects of emulsified and nonemulsified mixtures. The soot production is one of the
biggest problems in the internal combustion engines
because it results in increased operation cost [9]. On
the other hand, soot formation is necessary
phenomenon in many industrial operations like soot
particles increases the radiative heat transfer and due
to this it is very important in industrial furnace
applications. So methods must be derived to control
soot production for selective applications. So keeping
this in mind, the objective of this study is to
understand the relations between soot diameter, hot
boundary width and height, soot thickness, Stefan
flow, evaporation and diffusion because these
phenomena mainly contribute in flame and soot. To
understand and relate these phenomena butanol and
diesel are chosen as fuel for this study. Also the
emulsified diesel and water mixture and butanol and
water mixture is also added in this study to create
wider picture to understand and relate. To perform the
experiments schlieren imaging setup and laser
extinction setup were synchronized. The results from
this synchronized setup gives clear information about
all the phenomenon’s mentioned above.
2. Experimental setup
In this study, single droplet combustion was
used and the droplet was suspended on the quartz or
glass fiber. The quartz fiber is single threaded. As
shown in figure 1. The experimental setup comprises
of droplet generator, combustion chamber, biconvex
National Chin-Yi University of Technology
Paper ID: 0XX
lenses, laser light source, condensing lens, pinhole,
knife edge, electronic ignitor, Band-pass filter, LED
light source, high speed camera and color camera.
For this study a syringe was used to generate the
droplets. With the help of the syringe the droplet is
generated on the quartz fiber thread whose diameter
was around 0.012-0.016mm and the diameter of the
droplets generated ranges from 0.7-0.8mm. The
quartz fiber set in combustion chamber. The size of
the combustion chamber is 71 and 80 mm in length
and width. The chamber was isolated with glass to
exclude ambient air, thus preventing the droplet
combustion being affected by external air flows. The
electronics ignitor is used to ignite the fuel droplets
shown in figure 1. For the schlieren imaging
technique setup a condensing lens is set ahead of light
source to focus the light through the pinhole. After
pinhole a pair of biconvex lens is used whose
objective is to straighten the light rays in the space in
between them where the combustion chamber is set
as shown in figure 1. The biconvex lens 2 also works
as condenser and a knife edge is set at the focus of the
biconvex lens 2. The knife edge hast to be set exactly
on the focus of the biconvex lens 2 so it can cut
through the focus and control the brightness. But if
the knife edge is not set on the focus then it would not
give good quality of images. The light source used
here is LED. After the knife edge the high speed
camera was kept as shown in figure 1 [14,15].
#3
#1
#4
#2
Figure 1. Experimental setup
2.1. Laser Extinction Method
Now diagonally the laser extinction setup is
assembled. Biconvex lens 3 is kept ahead of light
source and for laser extinction setup the light source
is 650nm laser. In laser extinction setup pinholes and
knife edge are not used. Only pair of biconvex lens,
focusing lens and band pass filter is used. After
The 30th National Conference on Combustion and Energy
April 24, 2020
biconvex lens 4 the focusing lens is set and the
position of focusing lens depends on the placement
of combustion chamber. At last in front of high
speed camera the 650nm band pass filter is
assembled to the camera as shown in the figure 1.
These two setups are focused at one point that is
droplet and with the help of the measuring scale
these setups are synchronized. When laser light
passes through an absorbing medium, light
extinction occurs which is the sum of absorption and
scattering and, according to Beer–Lambert's law, the
transmittance 𝑇𝜆 is given by
𝐼
𝑇𝜆 = ln ( 𝐼𝑇 ) = −𝑘𝑒𝑥𝑡 𝐿
0
(1)
where 𝐼𝑇 is the transmitted light intensity, I0 the
incident laser beam intensity, L the path length
traveled by the laser beam in the absorbing medium
and 𝑘𝑒𝑥𝑡 the so-called extinction coefficient. The
latter can be expressed as a function of the number
density (i.e., soot particle number per unit volume) n
of particles with a particle diameter probability
distribution function 𝑝(𝐷), and the extinction crosssection 𝐶𝑒𝑥𝑡 for absorption and scattering
∞
(2)
𝑘𝑒𝑥𝑡 = 𝑛 ∫0 𝑝(𝐷) 𝐶𝑒𝑥𝑡 𝑑𝐷
The extinction cross-section 𝐶𝑒𝑥𝑡 is defined as the
product of the extinction efficiency 𝑄𝑒𝑥𝑡 and the
projected area of the particles onto a plane
perpendicular to the light beam axis. Assuming that
all particles are spherical, 𝑘𝑒𝑥𝑡 becomes
𝜋 ∞
𝑘𝑒𝑥𝑡 = 𝑛 ∫ 𝑝(𝐷) 𝐷 2 𝑄𝑒𝑥𝑡 𝑑𝐷
4 0
(3)
The extinction coefficient 𝑄𝑒𝑥𝑡 is a function of the
particle size, the laser beam wavelength and the
complex refractive index of the absorbing particles
and is generally the sum of the absorption and the
scattering components. However, in the Rayleigh
regime of the Mie theory, i.e. when the particle size is
much smaller than the wavelength of the incident
radiation, πD/λ⪡1, as in the case of the soot particle
mean diameter compared to He–Ne laser wavelength,
the scattering efficiency is much smaller than the
absorption efficiency so that the former can be
neglected.
Light extinction is therefore only due to absorption
and, in this case, the extinction coefficient can be
expressed as follows
National Chin-Yi University of Technology
Paper ID: 0XX
𝑘𝑒𝑥𝑡 = 𝑛
∞
𝜋3
𝑚2 −1
𝐼𝑚
(
) ∫ 𝑝(𝐷) 𝐷 3 𝑑𝐷
𝜆
𝑚2 +2 0
(5)
(4)
where m is the complex refractive index. As it can be
seen from Eq. (4), 𝑘𝑒𝑥𝑡 is directly proportional to 𝐷 3
and therefore to the mean particle volume. Given that
the soot volume fraction, 𝑓𝑣 , is defined by
∞
𝑓𝑣 = 𝑛 ∫
0
𝜋𝐷 3
𝑝(𝐷)𝑑𝐷
6
substituting the soot volume fraction into Beer–
Lambert's law equation (Eq. (1)) and taking into
account Eq. (4), the soot volume fraction becomes
𝐿
∫ 𝑓𝑣 𝑑𝑥 =
0
𝜆 ln(𝐼𝑇 ⁄𝐼0 )
6𝜋𝐼𝑚 (𝑚2 − 1)⁄(𝑚2 + 2)
(6)
If the soot distribution is uniform along the light path,
𝑓𝑣 can be obtained from the (𝐼𝑇 /𝐼0 ) ratio as
𝑓𝑣 =
𝜆 𝑙𝑛(𝐼𝑇 ⁄𝐼0 )
6𝜋𝐿𝐼𝑚 (𝑚2 − 1)⁄(𝑚2 + 2)
(7)
Eq. (7) holds based on three major assumptions.
First, the particles are considered spherical. To
this regard, fast sampling studies followed by
microscopy analysis have shown that in the early
stage of soot formation particles are indeed spherical
[11]. In fact, small particles which form during
combustion are highly reactive and therefore when
they collide and coalesce tend to generate new
particles which are also spherical. Also, chain-like
structures observed in diesel engine exhaust are most
likely to form after the end of the combustion event
rather than before or during it [12]. Since this study is
focused on the early stage of soot formation, particles
can be assumed as spherical with good confidence.
The second assumption is made on the validity
of the Rayleigh regime. With respect to this, it has
been reported in the literature that during the early
stage of soot formation soot particles are very big
molecules with diameters less than 2 nm [11], and,
also, that the aggregates which form during the
combustion phase do not exceed the 20–30 nm size
range in diameter [11], [13]. Using a laser source with
632.8 nm wavelength ensures therefore that no
scattering is likely to occur during the measurement.
Finally, in Eq. (7) the refractive index m is
considered constant. Chang and Charampopoulos
[14] estimated the soot complex refractive index
based on dynamic light scattering (DLS) to be 1.8-
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April 24, 2020
i0.58 at 10 mm above the burner surface and 1.62i0.47 at 6 mm with an incident laser light wavelength
of 632.8 nm. Instead, Lee and Tien [15] calculated the
soot refractive index based on a multivariable
dispersion model finding the 1.9-i0.55 value at 650
nm without any significant temperature effect at this
wavelength. In this work, the value suggested by
Chang and Charampopoulos is used and considered
constant with the varying temperature. If the particle
distribution is not homogeneous, the above
relationship represents an average concentration of
the soot volume along the laser beam path. The
cameras were synchronized together to capture the
combustion of the droplet.
National Chin-Yi University of Technology
Paper ID: 0XX
Figure 2. (i). Pure Butanol Droplet combustion, (ii).
Pure Diesel, (iii). 95% Butanol + 5% Water (noemulsion), (iv). 95% Diesel + 5% Water (emulsion),
& a. Laser Extinction results, b. Schlieren Results
3. Results
3.1. Experimental Results
The aspect ratio shows the shape oscillations
and the expansion of the droplet. As shown in figure
3. The figure 3A shows the aspect ratio of emulsified
fuel. The aspect ratio of emulsified fuel has a lot of
expansion and puffing. So the puffing spikes are
present in emulsified fuel. The instant increment in
the aspect ratio is due to the expansion and then the
decrement shows the puffing taking place, so the
spikes are named as Puffing spikes. After the cycles
of puffing ultimately explosion takes place and it is
marked in figure 3.
In the figure 3. the results of direct Imaging for pure
diesel, pure butanol, 95% butanol + 5% water (nonemulsion) and 95% diesel+ 5% water (emulsion) are
shown.
Figure 3. Direct imaging results of a. Pure
butanol, b. Butanol with water, c. Pure Diesel, d.
emulsified water and diesel
In these results it can be observed that when water is
mixed with butanol it makes no effect as the
combustion can be observed stable. But for diesel
water emulsion the phenomenon’s like puffing,
expansion and explosion takes place. And the reason
behind this could be the different boiling and
evaporating temperature of diesel and water. It can
also be observed that the multicomponent fuel has a
special phenomenon i.e. micro-explosion but it does
not take place in homogenous solutions like Butanol
and Water mixture. This means the solutions which
are naturally miscible does go through microexplosions but the solutions in which the solvents are
not miscible or immiscible and we use emulsifiers to
mix them in solution goes through the microexplosions and puffing phenomenon. The reason
behind this is that the emulsifiers are not fully
efficient, they fail to produce 100% homogenous
solution of two immiscible fuels and the result of this
is micro-explosion and puffing. This happens because
both fuels are not thoroughly mixed and they have
different-different boiling temperatures so when we
ignite the emulsified fuel mixture because of the fuel
is not mixed results in bubble formation and bubble
formation results in expansion and then puffing and
puffing results in micro-explosions. So microexplosions do not take place in non-emulsified fuel
solution like Butanol and Water but this phenomenon
The 30th National Conference on Combustion and Energy
April 24, 2020
National Chin-Yi University of Technology
Paper ID: 0XX
can be observed in emulsified Diesel and Water fuel
solution.
3.2. 𝐷 2 -law
The evaporation law is the relation between the
time, droplet diameter and burning rate. In the figure
4. the relation between normalized instantons droplet
diameter and normalized time (𝑡⁄𝑑02 ) is shown for
pure diesel and butanol. The curve is linear that means
these fuels follow 𝐷 2 -law or evaporation law. But
when Butanol-water and Diesel-water is observed,
the effect of addition is minor on the butanol but a
major change can be observed for diesel. The curve
of diesel-water is not-linear is the first observation
and second observation is that the burning time of the
Diesel-water emulsion has rapidly decreased if we
don’t consider the explosion.
Figure 4. Graph between Normalized diameter
square vs Fractional Burning time for fuels
The plot shows that for butanol water addition divide
the curve into two in first phase the burning rate of
butanol-water mixture is lower but in second phase
the burning rate rapidly increases and becomes more
than pure butanol. But the increase and decrease is
very low but the increase of burning rate of the water
added into diesel with emulsion is very high than the
non-emulsion mixture.
3.3. Hot boundary region
Figure 5. Vertical hot boundary and Horizontal hot
boundary
It can be collected for horizontal hot boundary and
vertical hot boundary As it can be observed from
figure 5. That vertical hot boundary is named as ‘D’
and horizontal hot coundary is named as ‘L’
a. Horizontal Hot Boundary
From schlieren results the information about
hot boundary can be observed and the hot boundary
plays a critical role in the area of soot and soot
production. In the figure 6, It can be observed that the
normalized horizontal hot boundary of pure Diesel
and pure Butanol is higher than the water added
emulsified or non-emulsified fuels. So, water reduces
the horizontal hot boundary of diesel and Butanol
whether its emulsified or Non-emulsified. Less hotboundary means low thermal value so water addition
reduces the thermal value for Butanol and Diesel.
And it also shows that emulsified mixture has a little
higher horizontal hot boundary than Non-emulsified
fuel but the difference is very low.
Figure 6. Graph between Normalized horizontal hot
boundary vs Fractional burning time
b. Vertical Hot Boundary
In the figure 7. Normalized vertical hot
boundary is plotted vs fractional burning time. In this
plot it can be observed that the water addition whether
its emulsified or non-emulsified both are affected but the
emulsified one i.e. 95% Diesel + 5% water is affected
more than non-emulsified i.e. 95% butanol =5% water.
The 30th National Conference on Combustion and Energy
April 24, 2020
The effect can be observed that the vertical hot boundary
‘D’ has increased for both but the increase for
emulsified Diesel is very high than the Butanol. This
also explain the increase in Stefan flow in fig 1, so from
this we can relate the Stefan flow area is directly related
to the vertical hot boundary L. It can also be observed
that the differnce between pure diesel and pure Butanol
its quite big. When these results are compared with the
soot thickness values it can be observed that the higher
D value results it better diffusion and reduced soot
thickness values.
Figure 7. Graph between Normalized Vertical hot
boundary vs Fractional burning time
And when figure 6, & figure 7, was compared it gave
relation between vertical Hot boundary ‘L’ and
horizontal hot boundary ‘D’ and the relation comes
out as vertical hot boundary is inversely proportional
to horizontal hot boundary.
𝟏
L∝ 𝐃
3.4. Soot Stand-off Ratio
The soot standoff ratio (SSR) was calculated
for diesel and Diesel-water emulsion. Butanol does
not show any soot so no SSR value for Butanol. The
uncertainty in these measurements is ±5 %. The SSR
is defined as the ratio of the instantons droplet soot
shell diameter to the instantaneous droplet diameter.
As shown in the figure 7, The SSR for diesel and
diesel-water emulsion is plotted vs fractional burning
time. It can be observed that the soot diameter of the
diesel is first higher than diesel emulsion but the soot
diameter of diesel emulsion increase rapidly, and the
reason behind this could be the low thermal value. If
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Paper ID: 0XX
these SSR results are compared with hot boundary
value it can be observed that the temperature effects
the soot production and coagulation process. Lower
horizontal hot boundary lowers the soot diameter and
lower soot diameter means faster coagulation.
The SSR plots for Pure Butanol and Butanol with
5% Water cannot be observed because no soot
production in each of the fuel and also the effect of
water addition is very low cause the percentage is low
but for Diesel or non-emulsified fuels the effect of
producing mixture is very high.
Figure 8. Soot standoff ratio vs Fractional Burning
Time of Diesel and 95% Diesel+5% Water
(emulsion)
3.5. Soot Thickness (KL)
The soot thickness value analyzed from laserextension imaging shown. It’s calculated for diesel
and diesel-water emulsion. And it is calculated at four
places in the flame based on height foe example at 10,
15, 20, 25 at these four locations the soot thickness is
calculated horizontally at every point. And also
compared at three stages those are (i) Developing
flame or start, (ii) Developed flame or mid (iii) Burnout.
(i). Developing Stage
As it is observed from figure 9. that at the
developing stage the flame is unstable and there is not
much difference between the diesel and diesel + water
emulsion. But still the soot area of pure diesel is
higher than the soot area of diesel-water emulsion.
When the average KL value is compared at every
point of line it can be observed that the difference
The 30th National Conference on Combustion and Energy
April 24, 2020
between pure and emulsified at developing stage is
very minute but the emulsified one has lower KL
value than the pure Diesel. When its compared with
these hot boundaries and SSR plot results, it can be
observed that increase in vertical hot boundary
reduces the soot production and soot diameter. The
increase in the vertical hot boundary can be the result
of the micro explosions and puffing.
National Chin-Yi University of Technology
Paper ID: 0XX
Figure 10. KL values vs position at four heights for
i. Diesel and ii. 95%Diesel+5%water at Developed
stage
At the developed stage the clear difference can be
observed. The KL area of pure Diesel is higher than
the 95% diesel +5 water emulsion, and also average
KL value of pure diesel is higher than the 95% diesel
+ 5 water as shown in figure 10.
(iii). Burn-Out
At the burn-out stage again the difference
is very minor. The area of both the soot is same but
the average KL value for diesel is higher than the 95%
diesel + 5% water emulsion as shown in figure 11.
Figure 9. KL values vs position at four heights for i.
Diesel and ii. 95%Diesel+5%water at Developing
stage
(ii). Developed Flame
In figure 10. The KL value graph is shown.
Figure 11. KL values vs position at four heights for
i. Diesel and ii. 95%Diesel+5%water at Burn-out
stage
4. Discussion
All the results are compared and it can be said
that the Stefan flow area affect the Diffusion and Low
diffusion results in higher soot concentrations and it’s
all explained in the Figure 12. As it can be observed
from the figure 12. How the diffusion area gets
affected by Stefan flow? And it has been already
explained how Stefan flow area differs for emulsified
and emulsified fuels. So the Stefan flow area
increases for emulsified fuels due to microexplosions and due to that diffusion area increases
and this all sums up by the reduced KL (sootthickness) value for emulsified fuels.
The 30th National Conference on Combustion and Energy
April 24, 2020
It can also be explained as here are two diffusion
vectors one is Air Diffusion and another is Fuel
Diffusion and the soot characteristics depends on the
domination of these diffusion vectors.
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Paper ID: 0XX
(𝑈)𝑟=𝑅 =
𝐷(𝑑𝑞𝑤 ⁄𝑑𝑟)𝑟=𝑅
⁄𝑞 𝑅
𝑎
= − 𝑀𝐴 ⁄𝑀𝑊 𝐷(𝑑𝑞𝑤 ⁄𝑑𝑟)𝑟=𝑅 ⁄𝑞𝐴 𝑅
𝑀𝐴 and 𝑀𝑊 being the molecular weight of air and
water respectively, it turns out that
𝐹𝑊 ≃ 𝐹0 [1 +
(𝑝𝑤𝑠 + 𝑝𝑤𝑎 )
]
2𝑃
(11)
Since both 𝑝𝑤𝑠 and 𝑝𝑤𝑎 ,the water vapor partial
pressures at the droplet's surface and in the
environment, respectively, are very small with
respect to P, the atmospheric pressure.
5. Conclusions
Figure 12. Effects of Stefan-flow and diffusion area
on soot characteristics.
The domination of these vectors is like when the air
diffusion dominates the total diffusion then vapor
diffusion area diffusion decreases and due to that soot
production increases. And in the other case when the
vapor diffusion domination is higher than the
diffusion area increase and results in good diffusion
and the result of that is lower soot concentration as its
observed in emulsified fuels. It is explained by
Maxwell as shown. Water droplet has been assumed.
(8)
−𝐷(𝑑𝑞𝑤 ⁄𝑑𝑟)𝑟=𝑅
which gives, according to MAXWELL[16], the vapor
flux 𝐹0 (water mass per unit of surface and for unit of
time) at the surface of an evaporating droplet of radius
R, is used for computing Stefan-flow velocity. In the
more rigorous Stefan-Maxwell equation, the water
vapor flux 𝐹𝑤 at the droplet surface is given by
(9)
𝐹𝑤 = −𝐷(𝑑𝑞𝑤 ⁄𝑑𝑟)𝑟=𝑅
The flux is composed of a diffusive and a convective
term which is generally called Stefan flow. It is a
consequence of a velocity 𝑈 ≠ 0 arising in the mass
centre of the fluid with respect to the interface and
directly normally to this. Since the velocity of this
Stefan flow is given at the droplet surface by
(10)
In this study the images obtained from
synchronized schlieren imaging and laser extension
setup were analyzed and examined for finding
establishing relations between soot, burning rate
diffusion characteristics and horizontal and vertical
hot boundary length. The conclusion obtained from
this study are written bellow:
1. The vertical hot boundary and horizontal hot
boundary are related. Vertical hot boundary
is inversely proportional to horizontal hot
boundary.
2. The effects of water addition are more severe
in emulsified mixture so that means
emulsions fail to mix the fuel to 100%
efficiency.
3. Lower burning rate results in increase of
vertical hot boundary (L) and Increase of
vertical hot boundary results in higher Stefan
flow area that results in good evaporation and
diffusion and all this results in lower soot
thickness.
4. The KL value decreases for emulsified 95%
Diesel + 5% water and also the soot thickness
or diameter value decreases. This is because
temperature of the flame affects the soot
Diameter.
5. The comparison between emulsified and nonemulsified multicomponent fuel shows that
the micro explosion is result of the
heterogeneous solution due to the emulsifiers
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April 24, 2020
and no micro explosion in homogenous
solutions like Butanol and Water.
6. Domination of air diffusion and fuel
diffusion affects the soot production. If air
diffusion is dominant, then the Stefan flow
area decreases and soot production increases
and decreases likewise.
Acknowledgment
The authors thank the Ministry of Science
and Technology, Taiwan, for financially supporting
this research under MOST 108-3116-F-008-004-CC1
and MOST 109-3116-F-008-008-CC1.
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National Chin-Yi University of Technology
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