Spray Characteristics of Fuel Mixed with Carbon Dioxide Liquefied
by
H. FUJIMOTO, J. SENDA, D. KAWANO and H. NAGATOMO
Doshisha University
Department of Mechanical Engineering
Kyotanabe, Kyoto 610-0321; Japan
ABSTRACT
The human healthy and the earth environment demand a high-speed diesel engine to apply the severe
regulation against its exhaust emissions now and near future. The conventional technique does not always
suit the regulation, and all the people strongly need the new technique for it. This paper describes the new
concept on the low emissions of diesel combustion. The concept is the usage of the liquid fuel oil mixed
with liquefied carbon dioxide. This kind of mixed fuel forms the two-phase region shown in Figure 1.
When the state of this mixed fuel crosses over this region, the dramatic atomization promotes by the flash
boiling phenomena and the deposition of carbon dioxide and the fine and minute spray is realized. The
experiments were carried out in the non-evaporating atmosphere in a high-pressure vessel and in the
evaporating atmosphere in a rapid compression and expansion machine. The experimental variables are the
molar fraction of carbon dioxide mixed in liquid n-tridecane that is the reference of gas oil used in an actual
high-speed diesel engine, the injection pressure, the temperature of mixed fuel and the ambient
pressure/density. The larger two-phase region is formed when the molar fraction increases. It is the point
that the injection pressure is much lower than that supplied in the actual engine. Figure 2 displays the
non-evaporating spray pattern as functions of molar fraction and ambient pressure. Figure 3 shows the
droplets size distribution of non-evaporating spray. These figures are one of the evidences of the realization
of the fine and minute spray by applying the new concept proposed.
Critical point
Critical pressure
t ur
Sa
d
ate
liq
ur
Sat
l
uid
at
ine
a po
ed v
e
as
ph
o on
w
T egi
r
97
e
r lin
Gas phase region
Critical
temperature
Tc
Temperature T
0
Fig.1 Pressure-temperature diagram
of two conponents solution
5
9
10
8
13
11
Fuel Tank
1
Air
2
Air
N2
Air
6
40
51.7
Liquid phase region
Axial distance from nozzle outlet z [mm]
Pressure p
pc
0
Super critical
region
0
97
0
97
0
52.3
64
0
i) Xco2 = 0.0, Tf = 293 [K]
40
51.7
52.3
64
0
ii) Xco2 = 0.8 , Tf = 383 [K]
(a) Time after injection start t = 2 [ms]
51.7
40
52.3
64
0
i) Xco2 = 0.0, Tf = 293 [K]
51.7
40
0.74
0.74
0.74
Fuel
CO2
3
7
14
4 12
1 Fuel tank
6 5-port solenoid valve 11 Pressure regulator
2 High pressure vessel
7 Pressure regulator
3 Pressure regulator
8 Oil pressure booster 2 13 Gap sensor
4 Oil pressure booster 1 9 Solenoid valve 1
5 Air cylinder
12 Piezo pressure sensor
14 Micro heater
10 Solenoid valve 2
Fig.2 Flow sheet of experimental setup for
non-evaporating spray
97
64
52.3
0
0.74
Radial distance r [mm]
ii) Xco2 = 0.8, Tf = 383 [K]
(b) Time after injection start t = 4 [ms]
Fig.3 Macroscopic and microscopic image
a: 17[kg/m3])
╧
of spray (Pinj: 20[MPa]
1. INTRODUCTION
The regulation for exhaust emissions through a high-speed diesel engine has been much severe in the world in
these twenty years to maintain the earth environment and the human healthy. Examples of countermeasures for
the regulation have been the super high pressure injection accompanying with small hole diameter of an injector,
the timing retard of injection, EGR, HCCI and the others. The standpoint of these is the usage of the
conventional fuel oil like gas oil. However, there is the limit of these countermeasures if much severer
regulations are proposed and it is very necessary for researchers and engineers to propose the new concept. The
authors has presented the new concept, that is, the usage of the fuel mixed with liquefied carbon dioxide, CO2,
for a high-speed diesel engine (1)-(7). The points of this concept are that the atomization progresses are
remarkably improved due to the flash boiling phenomena with lower injection pressure than that applied to
recent engines. As a result, low soot emission is realized due to the minute and fine spray, low NOx emission
takes place due to the effect of the existence of carbon dioxide, in other words, that of the internal EGR in
cylinder. The experiments were carried out in a high-pressure chamber and in a rapid compression and expansion
machine (RCEM) to detect the characteristics of this kind of fuel spray. This paper describes the outline of the
concept, a part of the experimental results.
2. OUTLINE OF CONCEPT
The examples of recent countermeasures against the regulation of emissions exhausted from a high-speed
small diesel engine are the super high-pressure injection through holes with small diameter and HCCI engines.
The former has the demerit, that is, the loss of engine power due to the driving of the system of super
high-pressure injection. The latter has the great question whether the engine can be driven at high load with high
revolution speed or not. However, it is capable of actualizing the minute and fine spray under the condition of
injection pressure around under 20 [Mpa] when the concept is applied to the injection system.
Generally speaking, the relation between the dissolved pressure, pd, and the molar fraction, X, of liquid is
expressed by the following Henry’s law:
pd = HX
(1)
where H is the Henry’s constant. The liquid dissolves more easily when H is smaller. Figure 1 is the
solubility limit of gas in the case of n-tridecane that is the reference fuel of gas oil for a high-speed small diesel
engine. The Henry’s constant of carbon dioxide is much smaller than those of the other gas of oxygen and
nitrogen. As a consequence, the carbon dioxide has the most capability to make realization of the concept.
0.5
0.3
Pd=HX
(Henry's law)
0.2
O2 (H=61.0)
0.1
Pressure p [MPa]
Mole fraction X
0.4
25
CO2
(H=61.0)
15
NH3
10
5
5
10
Dissolved pressure Pd [MPa]
Fig.1 Solubility limit of gas in case of n-tridecane
H2O
20
N2 (H=100)
0
Condition inside injector
0
CO2 Methanol
Methane
N2
200
Condition
in cylinder
Pentane
n-Tridecane
400
600
800
Temperature T [K]
Fig.2 Line of saturated vapor pressure of
some substances and their critical points
Pressure p
pc
Critical point Super critical
Critical pressure
region
Liquid phase region
e
as
ine ph n
l
o
uid Tw egio
r
liq
ed
ine
rat
Critical
u
t
or l
p
a
a
temperature
S
v
d
te
a
r
u
Sat
Gas phase region
0
Fuel pressure pf [MPa]
Figure 2 illustrates the line of saturated vapor pressure of some substances and their critical points. Both
large rounds show the condition in the injector and that in the cylinder during the injection period, respectively.
If the pure substance is selected like n-tridecane, the flash boiling does not surely occur and the fine and minute
spray is not obtained. However, the aspect is much different in the case of the binary solution comparing to the
pure fuel. Figure 3 displays the pressure-temperature diagram of the solution of two components. It is marked
matter that there appears the two-phase region, which does never appear in the case of the pure fuel. The upper
limit of region is the saturated liquid line and the lower one is the saturated vapor line. These two lines are
connected at the critical point. In the two-phase region the liquid and the gas of both substances exist according
to the fraction decided by the pressure and the temperature. If the pressure of liquid reaches and enters this
region, the flash boiling occurs surely. Namely, when the atmospheric pressure, in other words, the pressure of
mixed fuel, reaches the two-phase region, the component with low boiling temperature, that is, with
high-saturated vapor pressure, is vaporized firstly. The vaporization of this component is dominant, although the
other one with high boiling temperature, that is, with low saturated vapor pressure, is vaporizing in the
two-phase region. If the atmospheric pressure crosses over the two-phase region, two components are rapidly
vaporized due to the flash boiling. As a consequence, it is marked matter that it is capable of reforming relatively
the fuel with high boiling temperature to that with low boiling temperature and of vaporizing easily the mixed
fuel including both different boiling temperatures. The other remarkable matter is that the mixed fuel is atomized
much more finely with lower injection pressure not with super high-pressure injection than the pure fuel.
Tc
30
Conditions inside nozzle
XCO2=0.8
XCO2=0.6
0.95
XCO2=0.4
Decompression
at injection
0.99
20
10
Conditions at injection 1
in cylinder
0
100
Temperature T
Fig.3 Pressure-temperature diagram
of two conponents solution
200
0.9
Locus of
critical point
Molar fraction
of CO2 XCO2
0.8
0.7
0.6
Ambient conditions
0.5 in diesel engine
0.4
0.3
0.2
0.1
0
300 400 500 600 700
Fuel temperature Tf[K]
800
Fig.4 Effect of molar fraction on two phase region for
n-Tridecane-CO2
3. USAGE OF LIQUEFIED CARBON DIOXIDE
As shown in Figure 1, the carbon dioxide is one of the hopeful candidate to realize the new concept if the
two-phase region is formed. Figure 4 is the evidence of this concept. The fuel is n-tridecane as the reference of
gas oil and the other component is the liquefied carbon dioxide. It is able to calculate the critical temperature, Tc,
of condensation due to the law of Cueh-Prausnitz (8) and it is capable of estimating the critical pressure, pc, of
condensation by application of the law of Kreglewski-Key (8). The two-phase region is obtained by the equation
of corrected BWR (9), (10). The two-phase region just takes place corresponding to the molar fraction, XCO2, of
carbon dioxide. The critical temperature of carbon dioxide is 304 [K], however, it increase 450 [K] when
n-tridecane whose molar fraction is only 0.1 adds in it. As a consequence, it is able to shift the line of saturated
pressure of liquefied carbon dioxide to the region of higher pressure and lower temperature by adding
n-tridecane with high boiling temperature. The larger the molar fraction of carbon dioxide is, the larger the shift
is. When the sate of this mixed fuel changes from the condition inside the nozzle to that in the cylinder of a
diesel engine, it crosses over the two phase region in the case of the molar fraction of carbon dioxide of 0.4, 0.6
and 0.8. In the two-phase region, the carbon dioxide generates as the vapor and it extracts owing to the Henry’s
law. As a result, it is expected the simultaneous reduction of Nox and soot when this mixed fuel is supplied to a
diesel engine.
The followings are one of merits of the concept proposed:
1. Preservation/increase in thermal efficiency by use of lower injection pressure applied to an old diesel engine
2. Promotion of atomization and vaporization due to flash boiling and extraction of carbon dioxide
(1) Formation of lean mixture with relative homogeneity due to that of fine and minute spray with short
penetration and with wide dispersion
(2) Decrease in formation rate of particulate matters like soot due to combustion of lean and homogeneous
mixture
3. Combustion control through carbon dioxide vaporized and extracted
(1) Decrease in NO and heat loss due to decrease in flame temperature caused by effect of internal EGR
through existence of carbon dioxide
(2) Increase in thermal efficiency due to shortening of combustion duration
4. Promotion of re-burning of soot due to component of heat dissociation of carbon dioxide
5. Avoidance of friction between cylinder liner and piston ring taking place in case of EGR.
4. EXPERIMEMTAL SETUP, PROCEDURE AND CONDITIONS
Fig. 5 displays the flow sheet of experimental setup for the experiments of a non-evaporating spray. The
liquefied carbon dioxide stored in a bomb was supplied to a high pressure vessel [1] whose atmosphere was
pressurized by the nitrogen gas at 10 [MPa] to keep the stable liquid state of carbon dioxide and it was going to
an oil pressure booster 1 [2] with quasi-steady state. The fuel of n-tridecane was also pressurized by the same
system as that of the carbon dioxide. It was able to set the arbitrary ratio of liquefied carbon dioxide to
n-tridecane. A rod was connected with a piston in an air cylinder [4] and it was inserted in the booster [2]. Both
substances were mixed and stirred by the fall and rise movement of a disk installed at the tip of rod in the booster
[2]. The air stored in an air bomb went through a pressure regulator and it drove the booster [2]. A 5-port
solenoid valve [6] controlled the fuel supply and the application of pressure to the fuel. A pressure regulator [7]
managed under control of the injection pressure. The nozzle needle lift was brought under control of the oil
pressure through an oil pressure booster 2 [8]. The injection rate was almost the rectangular during injection
duration. A micro heater [14] of 200 [W] was put around a nozzle holder and it was capable of setting arbitrarily
the fuel temperature. The temperature was watched by a thermocouple of K type with sheath whose diameter
was 0.53 [mm]. The type of the injector was the hole nozzle with a single hole. Its diameter was 0.25 [mm] and
its length was 0.75 [mm]. The injection pressure was changed in the range from 10 [MPa] to 20 [MPa]. The
injection quantity of n-tridecane was kept to be constant, as a result, the injection duration prolonged as the
increase in the molar fraction, XCO2, in both experiments of non-evaporation and evaporation. The range of
fraction was decided by considering the rate of exhaust gas re-circulation in an actual high-speed diesel engine.
The mixed fuel was injected into the quiescent atmosphere with room temperature. The variables were the molar
fraction, XCO2, of carbon dioxide, the injection pressure pinj, the ambient pressure pa and the ambient temperature
Ta. A still camera took the scattering image of spray in some cases through a thin sheet of light (thickness: 0.5
[mm], height: 60 [mm]). The light source was the second harmonic (wave length: 532 [nm]) of an Nd:YAG laser.
In some cases, the transmitted light generated by a micro flash caught the spray. In the other cases, the
shadowgraph of the spray was taken by a high-speed video camera with speed of 9000 [fps]. The measuring
items were the spray pattern, the droplets information and the spray momentum.
5
9
10
8
Connecting
Crank Fly wheel Pulley
13 Injector Piston
rod
11
Fuel Tank
1
Air
2
Air
N2
Air
6
7
CO2
1
3
5
7
9
11
13
Fuel tank
Pressure regulator
Air cylinder
Pressure regulator
Solenoid valve 1
Pressure regulator
Gap sensor
2
4
6
8
10
12
14
12 14
3 4
High pressure vessel
Oil pressure booster 1
5-port solenoid valve
Oil pressure booster 2
Solenoid valve 2
Piezo pressure sensor
Micro heater
Fig.5 Flow sheet of experimental setup for
non-evaporating spray@@
Fuel
Quartz window
Electric clutch
Gear Motor
V-belt
Fig. 6 RCEM for experiments of evaporating spray
The information of an evaporating spray was also detected in RCEM illustrated in Figure 6. Its diameter is 100
[mm] and its stroke is 450 [mm]. The compression ratio was 15, the revolution speed was equivalent to 200
[rpm], and the temperature and the pressure in-cylinder at the injection were 750 [K] and 3.2[MPa], respectively.
The diameter and the length of nozzle used was 0.18 [mm] and 0.85 [mm], respectively. They are much different
from those in non-evaporating spray for avoidance of the adherence of spray on the wall of combustion chamber
due to the short distance. The injection pressure was 16 [MPa] constant. Exciplex technique (11) was applied to
the evaporating spray to separate vapor and liquid phases by mixing naphthalene of 9 [% in mass] and
N.N.N’.N’-tetramethyl –p-phenylenediamine of 1 [% in mass] into n-tridecane.
Axial distance from nozzle outlet z [mm]
5. SPRAY CHARACTERISTICS
XCO2=0.0
0
20
40
60
XCO2=0.2
0
20
40
60
Axial distance from nozzle outlet z [mm]
Axial distance from nozzle outlet z [mm]
0
20
40
60
XCO2=0.4
0
20
40
60
XCO2=0.6
0
20
40
60
0.1
XCO2=0.8
0.3
0.5
0.7
0.9
Ambient pressure pa [MPa]
Fig.7 Spray pattern as functions of molar fraction
and ambient pressure
(pinj:10MPa, ρa:1.5kg/m3,Tf:293K, t:7ms)
0
97
0
97
0
97
0
97
40
51.7
52.3
64
0
i) Xco2 = 0.0, Tf = 293 [K]
40
51.7
52.3
64
0
ii) Xco2 = 0.8 , Tf = 383 [K]
(a) Time after injection start t = 2 [ms]
51.7
40
52.3
64
0
i) Xco2 = 0.0, Tf = 293 [K]
51.7
40
64
0.74
0.74
0.74
52.3
0
0.74
Radial distance r [mm]
ii) Xco2 = 0.8, Tf = 383 [K]
(b) Time after injection start t = 4 [ms]
Fig.8 Macroscopic and microscopic image of spray
(pinj:20[MPa], ρa:17[kg/m3])
Figure 7 displays one of examples of spray pattern taken by the transmitted light. Figure 8 is also one of
examples of the macroscopic and microscopic images of spray. In the case of XCO2 equal to 0.0, i. e., in that
without mixing of liquefied carbon dioxide, there is little change in the spray pattern. The pattern shows the
much large dispersion in the radial direction in the cases of the molar fraction, XCO2, of 0.2 at the ambient
pressure, pa, equal to 0.1 [MPa], XCO2 of 0.4 in that from 0.1 [MPa] to 0.3 [MPa], XCO2 of 0.6 in that from 0.1
[MPa] to 0.5 [MPa] and XCO2 of 0.8 in all the range of pa. Namely, the flash boiling and the deposition of the
carbon dioxide occur and the atomization is promoted dramatically. As shown in Figure 6, the spray tip region
becomes leaner as the molar fraction becomes larger and droplets at the spray periphery in this region show the
smaller diameter. Just the trends are corresponds to those shown in Figure 4, in other words, it is proved that the
concept is hopeful. The atomization promotes more distinguished as the increase in the molar fraction and the
fuel temperature.
40
40
20
0
20
0
pinj=10[MPa]
20
20
10
10
0
0
35
30
0.9Pa]
M
0.4 0.8
XCO2
0.p1 a [
0 .9 P a ]
M
0.1p a [
0
35
30
Distribution of arithmetical mean
Diameter of droplets dn/n [%]
θC [deg.]
θC [deg.]
60
60
35
30
0
0.8
0.4
XCO2
pinj=20[MPa]
0.00
-0.10
8
0.0
14 rom
Tim 2.6 5.2
22 f
of e e afte 7.710.3
30 ance m
t
xpe r st
s
50
rim art s 12.9 90 al di H m
i
e nt
ign
is
d
s
Ra ay ax
ms al
spr
(a) XCO2: 0.0, Tf: 293 [K]
0.40
0.30
0.20
0.10
0.00
-0.10
8
0.0
14 rom
Tim 2.6 5.2
f
22
of e e afte 7.710.3
30 nce m
xpe r st
50 dista
m
12.9
a
rim
r
90 ial
ent t sign
sH
i
d
x
a
s m al
R ay a
s
sp r
(c) XCO2: 0.0, Tf: 373 [K]
0
0
28.2
56.5
88.2
28.2
56.5
88.2
35
30
10
10
0
0
28.2
56.5
88.2 00
Droplet diameter d [µm] Droplet diameter d [µm]
(pa: 1.1[MPa])
(a) XCO2=0.0
(b) XCO2=0.8
Fig.10 Droplets size distribution (pinj:20[MPa],
Tf:n-tridecane293[K],mixed fuel393[K],t:6[ms]
Equivalent spray momentum V
0.10
88.2
20
Equivalent spray momentum V
0.20
Equivalent spray momentum V
Equivalent spray momentum V
0.30
56.5
20
Fig.9 Relation among spray cone angle,molar fraction
and ambient pressure
0.40
28.2
Droplet diameter d [µm] Droplet diameter d [µm]
(pa: 2.9[MPa])
High
0.40
0.30
0.20
0.10
0.00
Low
-0.10
8
0.0
14 rom
Tim 2.6 5.2
22 f
of e e afte 7.710.3
30 ance m
t
xpe r st
s
50
rim art s 12.9 90 al di H m
i
e nt
ign
is
d
s
Ra ay ax
ms al
spr
(b) XCO2: 0.8, Tf: 293 [K]
0.40
High
0.30
0.20
0.10
0.00
-0.10
8
0.0
14 rom
Tim 2.6 5.2
f
22
of e e afte 7.710.3
30 nce m
xpe r st
50 dista
m
12.9
a
rim
r
90 ial
ent t sign
sH
i
d
x
a
s m al
R ay a
s
sp r
(d) XCO2: 0.8, Tf: 373 [K]
Fig.11 Temporal and radial distribution of equivalent momentum of non-evaporating spray
Low
Fig. 9 is the relation among the spray cone angle, the molar fraction and the ambient pressure in both cases of
injection pressure pinj of 10 [MPa] and 20 [MPa], respectively. The angle is measured on a shadow photograph
taken through a thin sheet of laser light. The angle shows the maximum under the conditions of the ambient
pressure pa of 0.1 [MPa] at the molar fraction XCO2 equal to 0.8. As the ambient pressure increases and the molar
fraction decreases, the distribution of the angle becomes broader. The trend is more remarkable in the case of pinj
equal to 20 [MPa] than that equal to 10 [MPa]. At the most distinguished point of the ambient pressure of 0.1
[MPa] at the molar fraction equal to 0.8, the angle shows 53 [deg.] in the former case and it is 35 [deg.] in the
latter one. Figure 10 is one of examples of the droplets size distribution at the given time t equal to 6 [ms] from
the injection start. They are measured on the direct photograph taken by a still camera. The resolution of film
used is 800 [lines/mm], the magnification is 1 on the film, the axial range of photography is from 40 [mm] to 60
[mm] from the nozzle outlet and the radial range is from the spray axis to 35 [mm]. The calibration was
conducted using glass beads whose diameter is accurately known. The left-hand side shows the case of the pure
fuel of n-tridecane and the right hand side is that of the mixed fuel with the molar fraction, XCO2, of 0.8. The
upper is the case of the ambient pressure pa of 2.9 [MPa] and the lower shows that of 1.1 [MPa]. It is marked
matter that the distribution is more uniform in the case of the mixed fuel than that of the pure fuel due to the
flash boiling and the deposition of carbon dioxide. The other distinguished matter is that the droplets only taken
on the film are shown in these figures and n-tridecane vaporized by the effect of the two-phase region is not
detected. As a result, it is able to avoid the generation of the local region of fuel rich.
Axial distance from nozzle outlet [mm]
Figure 11 displays one of examples of temporal and radial distribution of equivalent spray momentum whose
unit is output voltage [V] of the sensor. The cases shown are n-tridecane of XCO2 equal to 0.0 and the mixed fuel
with XCO2 of 0.8. When the molar fraction and the fuel temperature increase, the highest equivalent spray
momentum decreases even at the location very near the nozzle outlet and the slope from zero level to the peak
becomes gentler due to the promotion of the atomization through the flash boiling phenomena and the deposition
of the carbon dioxide.
Fluorescent intensity of liquid phase
Fluorescent intensity of liquid phase
Fluorescent intensity of vapor phase
Fluorescent intensity of vapor phase
-7 0 7 -7 0 7 -7 0 7
Radial distance from spray axis[mm]
-7 0 7 -7 0 7 -7 0 7
Radial distance from spray axis[mm]
t=0.6
t=1.2
t=1.8
Time after injection start t [ms]
t=0.6
t=1.2
t=1.8
Time after injection start t [ms]
(a)XCO2:0.0
Low
(b)XCO2:0.8
High
Figure 12 shows the temporal distribution of both images of liquid and vapor phases by applying the exciples
technique just before the ignition from the time after injection start. They are not the sequential data. The white
zone in the vapor phase is the halation area because the smallest gradation corresponds to the information of the
leanest vapor. It is much clear that the area of liquid phase becomes smaller, that of vapor phase becomes larger
and the leaner part of the vapor phase becomes larger as the increase in the molar fraction.
6. SUMMARY
All the experimental data mentioned above taken by the low techniques proves that the new concept for
realization of the fine and minute spray by mixing the liquid fuel oil with liquefied CO2 gas is very hopeful.
Namely, the area of liquid phase decreases and much leaner area of liquid phase increases as the molar fraction
of CO2 increases although the injection pressure of this case is much smaller than that of an actual high-speed
diesel engine. It is strongly expected to actualize the simultaneous reduction of soot and NOx in this kind of
engine.
ACKNOWLEDGEMENT
The authors express thanks to the Grant-in Aid for Scientific Research (C) (2) of No. 10650227 and No. 1365027
of The Ministry of Education, Sports, Science, Technology and Culture, Japan and the Grant-to RCAST at
Doshisha University from this Ministry for their support for a part of this work. They also wish to thank Mr. I.
Shibata, Mr. K. Matsui and Mr. S. Oshita who were students of Doshisha University for their experimental work.
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(9) Ditto, pp.337-357.
(10) Sato, S., (1987) “Fundamental Estimation of Equilibrium Properties by Means of Statistical Thermodynamics”,
Baifukan, Tokyo, pp.160-175, (in Japanese).
(11) Murray, A. M. and Melton, L. A. (1985), “Fluorescence Methods for Determination of Temperature in Fuel Sprays”,
Applied Optics, Vol. 24, No.17, pp.2783-2787.
(12) Rotunno, A. A., Winter, M., Dobbs, G. M. and Melton, L. A., (1990), “Direct Calibration Procedures for
Exciplex-Based Vapor/Liquid Visualization of Fuel Sprays, Combustion Science and Technology, Vol. 71,
pp.247-261.