energies
Article
The Effect of Elliptical Diesel Nozzles on Spray
Liquid-Phase Penetration under
Evaporative Conditions
Bifeng Yin *, Bin Xu , Hekun Jia and Shenghao Yu
School of Automotive and Traffic Engineering, Jiangsu University, Zhenjiang 212013, China;
2211704049@stmail.ujs.edu.cn (B.X.); human_cm@126.com (H.J.); ysh@ujs.edu.cn (S.Y.)
* Correspondence: ybf@ujs.edu.cn
Received: 7 March 2020; Accepted: 2 April 2020; Published: 3 May 2020
Abstract: Elliptical diesel nozzles affect the fuel–air mixing process, and thus combustion and exhaust
emissions. Experiments were conducted to study biodiesel spray liquid-phase behaviors for elliptical
and circular nozzles through the Mie-scattering method under evaporative conditions. Based on the
measurements, the results show that the elliptical nozzle spray liquid-phase penetration is smaller
than the circular one under steady-state conditions. The deformation and the axis-switching behaviors
of the elliptical jet are helpful in accelerating the breakup of the liquid core. Moreover, the injection
pressure has little impact on the penetration of the liquid-phase spray for either geometrical orifice.
Additionally, increasing the ambient temperature can reduce the penetration of liquid-phase spray,
because an increase in temperature increases the rate of evaporation. The differences in steady
liquid-phase penetration between circular and elliptical sprays decrease as the ambient temperature
increases. Additionally, increasing the backpressure can decrease the liquid-phase penetration.
The differences in steady liquid-phase penetration between circular and elliptical nozzles are reduced
with the increase in backpressure, probably due to the axis-switching and deformation behaviors of
the elliptical jet being restrained under high-backpressure conditions. Finally, the application of an
elliptical orifice is beneficial for decreasing the spray liquid-phase penetration, and thus avoiding the
fuel impingement in small engine combustion chambers. The lower liquid-phase penetration for
elliptical spray indicated higher fuel and air mixture quality, which is helpful for reducing the diesel
engine exhaust soot emissions.
Keywords: diesel nozzle; elliptical orifice; biodiesel; liquid-phase penetration
1. Introduction
Fuel spray evaporation and liquid fuel penetration, before ignition and combustion, are relevant
issues concerning diesel spray behavior subsequent to air–fuel mixing, and is related to combustion
processes and exhaust emissions [1]. In the traditional research related to fuel injection and atomization,
spray and atomization quality is improved by increasing the injection pressure and reducing
the diameter of the nozzle hole [2,3]. However, when blindly increasing the injection pressure,
the penetration of the long spray tip is prone to adverse effects such as wall impingement and
lubricating oil dilution [4,5]. Therefore, people have tried to use orifices with new structures, having
different cross-section shapes, in order to improve the fuel atomization quality. The elliptical orifice
has obvious advantages with respect to improving the fuel–air mixture quality, and it has therefore
become a hot research topic [6,7].
Yu et al. [8–10] compared the spray characteristics of a diesel injector with circular and elliptical
cross-section shapes under room temperature, the results showed that using an elliptical nozzle reduced
Energies 2020, 13, 2234; doi:10.3390/en13092234
www.mdpi.com/journal/energies
Energies 2020, 13, 2234
2 of 14
the spray tip penetration, and the elliptical spray cone angle and the projection area were both higher
than the circular spray, indicating that the application of the elliptical hole nozzle could greatly increase
the air–fuel mixture quality. Ku et al. [11] presented a study of the macro spray characteristics by
using an elliptical hole injector and a conventional circular nozzle under non-evaporative conditions.
The results indicated that the application of the elliptical hole injector sped up the liquid core breakup
progress, resulting in a larger spray cone angle. Matsson et al. [12] presented the impact of the elliptical
hole diesel nozzle on engine exhaust emissions. They found that the diesel nozzle with an elliptical
orifice reduced the NOx emission, while the use of the elliptical nozzle had little effect on the soot
emission. Ho and Gutmark [13] found that the elliptical jet had a better air entrainment ratio than that of
the circular jet. Hong et al. [14,15] also investigated the effects of the non-circular hole on the cavitation
and spray patterns with a large transparent nozzle at room temperature. The results indicated that
when the cavitation appeared in the elliptical hole, the elliptical spray cone angle became larger than
the circular spray. Sharma and Fang [16,17] studied the spray behaviors with various cross-section
hole shapes under non-evaporative conditions. They presented results claiming that the use of the
elliptical orifice reduced the jet breakup length in comparison with the circular orifice. Cung et al. [18]
characterized the effects of non-circular diesel nozzles on diesel spray and combustion characteristics
by a numerical simulation method, and the results revealed that the non-circular nozzle had a larger
spray cone angle and a longer ignition delay than the circular nozzle. Stinivansan and Bowersox [19]
presented the numerical simulation to study the characteristics of the circular and rhomboid jet when
the flow Mach number was 5, and it was found that the rhomboid jet generated a reverse rotating vortex,
which was conducive to strengthening the fuel and air mixing quality. Jadidi et al. [20] investigated
the elliptical jet in low-speed cross flows experimentally, and it was reported that the elliptical spray
liquid penetration height was shorter than the circular injector. Kasyap et al. [21,22] presented a study
analyzing the influence of non-circular diesel nozzles on the jet breakup process under non-evaporative
conditions. The results claimed that the use of an elliptical hole increased the instability of the jet
deformation and thus accelerated the jet fragmentation, which was beneficial to improving the fuel
atomization quality. Morad and Khosrobeygi [23] investigated the elliptical liquid jet under low-speed
crossflow conditions at room temperature, their results illustrated that the elliptical hole with larger
aspect ratio had a shorter liquid breakup length. Molina et al. [24] carried out a computational study in
order to investigate the influence of the use of elliptical orifices on the inner nozzle flow and cavitation
development, and the results showed that elliptical geometries with a vertically oriented major axis
were less prone to cavitation and had a lower discharge coefficient, whereas elliptical geometries
with a horizontally oriented major axis were more prone to cavitation and showed a higher discharge
coefficient. Chiatti et al. [25] investigated the influence of the Slot orifice in diesel common rail nozzles
under transient injection conditions, and their results illustrated that the Slot hole shape exerted a
robust influence on the fuel flow pattern within the nozzle that was weakly reflected by the rate of
injection, but well evidenced by the spray evolution.
Some beneficial innovations and explorations have been carried out with respect to the spray
emerging from non-circular orifices. Preliminary study shows that the spray and atomization quality of
non-circular orifices can be improved effectively when compared to circular orifices. However, previous
research works have been conducted under room temperature conditions (non-evaporative), which
does not adequately represent the high-temperature conditions of a real diesel engine. Additionally,
these existing works do not answer the questions regarding evaporative elliptical spray behaviors at
high ambient temperature; in particular, elliptical spray liquid breakup behaviors under evaporative
conditions are more complex than those under non-evaporative conditions, and more detailed
research work is necessary in order to understand the liquid breakup process for the elliptical
nozzle. Additionally, considering the liquid-phase penetration under evaporative conditions has
major relevance for fuel impingement in small direct injection diesel engines. Therefore, a better
understanding of this phenomenon is important for improving engine performance.
Energies 2020, 13, 2234
3 of 14
Energies 2020, 13, x FOR PEER REVIEW
3 of 14
This study is a contribution to understanding the effects of the elliptical and circular holes
injectors
overfollow-up
the spraytoliquid-phase
penetration
under
evaporative
conditions.
This
study
is
a
follow-up
to
our previous works, which investigated elliptical spray at room temperature (under
our previous
works,conditions).
which investigated
elliptical
spraypresented
at room temperature
non-evaporative
non-evaporative
Consequently,
the study
in this article (under
compares
the spray
conditions).
Consequently,
the study presented
in thisdiesel
article
compares
spray liquid-phase
liquid-phase
breakup characteristics
for non-circular
nozzles
underthe
evaporative
conditions, breakup
by
characteristics
for non-circular
nozzles
evaporative
by using
Mie-scattering
using Mie-scattering
with a diesel
Nd: YAG
laserunder
system,
providing aconditions,
comprehensive
analysis
of the
of variables,
such as
elliptical aand
circular orifices,
injection
(80 MPa,
100 MPa, such
withinfluence
a Nd: YAG
laser system,
providing
comprehensive
analysis
ofpressures
the influence
of variables,
120 MPa),
bulk
temperatures
(600
K, 700 K),
and backpressures
MPa,
2 MPa),
on spray
liquid-phase
as elliptical
and
circular
orifices,
injection
pressures
(80 MPa,(1100
MPa,
120 MPa),
bulk
temperatures
penetration
characteristics.
(600 K, 700 K), and backpressures (1 MPa, 2 MPa), on spray liquid-phase penetration characteristics.
2. Experimental
Method
2. Experimental
Method
2.1. Diesel Nozzle
2.1. Diesel
Nozzle
The experiment was conducted for two different diesel nozzles with different cross-section
The experiment was conducted for two different diesel nozzles with different cross-section shapes:
shapes: circular and elliptical. Figure 1 presents the diesel injector used and the two cross-section
circular
andThe
elliptical.
Figure
1 presents
the
diesel injector
used and
two cross-section
shapes.
shapes.
two nozzles
are both
micro-sac
single-hole
diesel nozzles
with the
the same
exit cross-section
The two
bothgeometric
micro-sacparameters
single-holeare
diesel
withTable
the same
exit cross-section
area, and
area,nozzles
and theareother
keptnozzles
the same.
1 summarizes
the normal
the other
geometric
parameters
are
kept
the
same.
Table
1
summarizes
the
normal
geometric
parameters.
geometric parameters.
Figure
Thediesel
diesel injector
injector with
elliptical
holes.
Figure
1. 1.The
withcircular
circularand
and
elliptical
holes.
Table
different
orifices.
Table1.1.The
The parameters
parameters ofofdifferent
orifices.
Nozzle
Circle
Circle
Elliptical
OrificeOrifice
Major
Minor
CrossHydraulic
Hydraulic
Perimeter
Major Axis
Minor Axis
Cross-Section
Perimeter
Length
Diameter
Length
Axis
Axis
Section Area
[µm]
[µm]
Area [µm2 ][μm] [µm]
Diameter [mm]
[mm]
[mm] [mm]
[μm]
[μm]
[μm2]
160160
160 160 20106.2 20,106.2 205.7 205.7 1.23 1.23
160 160
189.3
135.2 135.2 20106.2 20,106.2 533.0 533.0 1.23 1.23
150.9
189.3
150.9
2.2. Experimental Visualization Work
2.2. Experimental Visualization Work
The Mie-scattering spray test experiment was operated in a high-temperature and high-pressure
The Mie-scattering
spray test
experiment
was
operateddiagram
in a high-temperature
and high-pressure
constant
volume combustion
chamber,
and the
schematic
for this experimental
set up is
constant
volume
combustion
chamber,
and
the
schematic
diagram
for
this
experimental
up is shown
shown in Figure 2. The optical configuration setup is shown in Figure 2a, includingset
a camera
in Figure
2. Thewith
optical
configuration
is shown
in Figure
2a, including
a camera
connected with a
connected
a spike
filter and a setup
Nd: YAG
laser for
the visualization
of the
spray liquid-phase.
the YAG
Nd: YAG
and spray image
system can be found
previously
spikeMore
filterdetails
and aofNd:
laserlaser
for system
the visualization
of thecapture
spray liquid-phase.
Moreindetails
of the Nd:
works
highcapture
bulk temperature
achieved
by previously
setting electrical
resistors
inside
YAGpublished
laser system
and[10,26].
sprayThe
image
system canisbe
found in
published
works
[10,26].
the
bottom
of
the
chamber,
as
shown
in
Figure
2b.
The
heating
system
is
able
to
provide
a
maximum
The high bulk temperature is achieved by setting electrical resistors inside the bottom of the chamber,
bulk temperature
and The
pressure
of 900system
K in theisconstant
chamber,
and thebulk
bulktemperature
temperature and
as shown
in Figure 2b.
heating
able to volume
provide
a maximum
was calibrated with a fluctuation of ±10 K. The chamber has four optical accesses placed orthogonally,
pressure of 900 K in the constant volume chamber, and the bulk temperature was calibrated with a
in order to obtain complete access to the spray domain. The fuel injection system, which consists of a
fluctuation of ±10 K. The chamber has four optical accesses placed orthogonally, in order to obtain
high-pressure pump with an electronic motor, can generate an injection pressure of up to 180 MPa.
complete
access to
spray
domain.
The
injection
system,system,
whichand
consists
of asystem
high-pressure
Additionally,
thethe
fuel
injection
system,
thefuel
spray
image capture
the laser
are
pump
with anby
electronic
motor, can
generate
an injectionofpressure
up tocan
180
Additionally,
controlled
a delay controller,
so accurate
measurement
the spray of
images
beMPa.
achieved.
the fuel injection system, the spray image capture system, and the laser system are controlled by a
delay controller, so accurate measurement of the spray images can be achieved.
Energies 2020, 13, 2234
Energies 2020, 13, x FOR PEER REVIEW
4 of 14
4 of 14
(a)
(b)
Figure 2. Experimental equipment diagram. (a) Mie-scattering test schematic; (b) Constant volume chamber.
Figure 2. Experimental equipment diagram. (a) Mie-scattering test schematic; (b) Constant volume
2.3. Experimental Test Plan
chamber.
The experimental test plan is shown in Table 2. To simulate actual engine operating conditions,
2.3. Experimental
Test Plan
various
high injection
pressures were adopted, and the chamber was filled with nitrogen to provide
different
Considering
the test
was performed
under
evaporative
conditions,
the bulk
The backpressures.
experimental test
plan is shown
in Table
2. To simulate
actual
engine operating
conditions,
temperatures
were set as
600 K and
700adopted,
K. For the
whole
injection test,
injection
durationtotime
was
various high injection
pressures
were
and
the chamber
was the
filled
with nitrogen
provide
fixed
at
2
ms.
The
whole
experiment
was
performed
for
conventional
biodiesel
fuel.
Table
3
illustrates
different backpressures. Considering the test was performed under evaporative conditions, the bulk
the
fuel used and
the
properties
temperatures
were
setphysical
as 600 K
and 700 of
K. biodiesel.
For the whole injection test, the injection duration time
was fixed at 2 ms. The whole experiment was performed for conventional biodiesel fuel. Table 3
Table
2. Spray
visualization
text conditions.
illustrates the fuel used and the
physical
properties
of biodiesel.
Parameter
Value-Type
Table 2. Spray visualization text conditions.
Fuel
Biodiesel
Injection
pressure (Pinj )
80 MPa,
100 MPa, 120 MPa
Parameter
Value-Type
Backpressure
1Biodiesel
MPa, 2 MPa
Fuel(Pback )
Gas property
Nitrogen
Injection pressure (Pinj)
80 MPa, 100 MPa, 120 MPa
Ambient temperature (Tbulk )
600 K, 700 K
Backpressure (Pback)
Gas property
Ambient temperature (Tbulk)
1 MPa, 2 MPa
Nitrogen
600 K, 700 K
Energies 2020, 13, x FOR PEER REVIEW
5 of 14
-Energies 2020, 13, 2234
5 of 14
Table 3. Biodiesel fuel used and its properties.
Table 3. Biodiesel fuel used and its properties.
Physical Properties
Density (kg/m )
3) 2
Density
(kg/m
Kinetic viscosity
(mm
/s)(40 °C)
2
Kinetic viscosity (mm /s)(40 ◦ C)
Surface tension (mN/m)
Surface tension (mN/m)
Flashpoint
temperature
Flashpoint
temperature
(◦ C)(°C)
Physical Properties 3
Biodiesel
Biodiesel
876
876
4.52
4.52
35.2
35.2
169.0
169.0
3. Experimental Procedure
3. Experimental Procedure
Figure 3 presents the development of the spray liquid-phase images at different injection
Figure 3 presents the development of the spray liquid-phase images at different injection pressures,
pressures, with a fixed bulk temperature of 600 K. The present work investigates liquid-phase
with a fixed bulk temperature of 600 K. The present work investigates liquid-phase penetration, and
penetration, and therefore all of the images were captured at the major view planes of the elliptical
therefore all of the images were captured at the major view planes of the elliptical nozzle. Considering
nozzle. Considering the fluctuation in the process of the spray, ten spray images were taken under
the fluctuation in the process of the spray, ten spray images were taken under the respective conditions
the respective conditions for each injection shot. Please note that the spray image presented in Figure
for each injection shot. Please note that the spray image presented in Figure 3 is only one injection
3 is only one injection event. From Figure 3, it can be seen that the spray liquid-phase of the elliptical
event. From Figure 3, it can be seen that the spray liquid-phase of the elliptical nozzle is shorter
nozzle is shorter than the circular spray in the steady state. Additionally, as compared to the circular
than the circular spray in the steady state. Additionally, as compared to the circular nozzle spray,
nozzle spray, the distribution area of the elliptical spray liquid-phase is smaller. In general, lower
the distribution area of the elliptical spray liquid-phase is smaller. In general, lower liquid-phase
liquid-phase penetration and smaller distributions are evidence of faster and better fuel and air
penetration and smaller distributions are evidence of faster and better fuel and air mixture qualities [27].
mixture qualities [27]. Moreover, in the following sections, the influence of the elliptical diesel nozzle,
Moreover, in the following sections, the influence of the elliptical diesel nozzle, the ambient and
the ambient and injection conditions on the liquid-phase penetration will be analyzed in more detail.
injection conditions on the liquid-phase penetration will be analyzed in more detail.
(a)
Figure 3. Cont.
Energies 2020, 13, 2234
Energies 2020, 13, x FOR PEER REVIEW
6 of 14
6 of 14
(b)
(c)
Figure 3. Evolution of liquid mass fraction for various geometrical orifices (Pback = 1 MPa,
Tbulk = 600 MPa). (a) The injection pressure of 120 MPa; (b) The injection pressure of 100 MPa;
Figure 3. Evolution of liquid mass fraction for various geometrical orifices (Pback = 1 MPa, Tbulk = 600
(c) The injection pressure of 80 MPa. The original spray images were obtained using the Mie-scattering
MPa). (a) The injection pressure of 120 MPa; (b) The injection pressure of 100 MPa; (c) The injection
method, and these need to be subtracted from the background image, which were taken before the
pressure of 80 MPa.The original spray images were obtained using the Mie-scattering method, and
injection began. After that, the spray liquid-phase images were distinguished from the background with
these need to be subtracted from the background image, which were taken before the injection began.
an in-house MATLAB code. The spray liquid-phase penetration was identified from the background
After that, the spray liquid-phase images were distinguished from the background with an in-house
with an intensity threshold calculated as suggested in [28,29]. After this, the spray liquid-phase was
MATLAB code. The spray liquid-phase penetration was identified from the background with an
analyzed for each spray image. The spray liquid-phase length is the length between the tip of the
intensity threshold calculated as suggested in [28,29]. After this, the spray liquid-phase was analyzed
spray and the orifice tip. The final liquid-phase length is the average of ten spray images, and the error
for each spray image. The spray liquid-phase length is the length between the tip of the spray and the
analysis for the spray liquid-phase penetration indicated that the difference from the average value
orifice tip. The final liquid-phase length is the average of ten spray images, and the error analysis for
was less than 4.0%.
the spray liquid-phase penetration indicated that the difference from the average value was less than
4.0%.
Energies 2020, 13, 2234
7 of 14
4. Results
Energiesand
2020, Discussion
13, x FOR PEER REVIEW
7 of 14
4. Results
Discussion
4.1. The
Effects and
of Injection
Pressure on the Spray Liquid-Phase Penetration
In
4, the
spray Pressure
liquid-phase
penetration
is depicted
against injection time for orifices
4.1.Figure
The Effects
of Injection
on The Spray
Liquid-Phase
Penetration
with different cross-section shapes under various injection pressure conditions, and a fixed ambient
In Figure 4, the spray liquid-phase penetration is depicted against injection time for orifices with
temperature of 600 K. The time used in the present research work is the time since the start of the
different cross-section shapes under various injection pressure conditions, and a fixed ambient
injection
(ASOI). Based on Figure 4, it can be seen that the elliptical liquid-phase penetration increases
temperature of 600 K. The time used in the present research work is the time since the start of the
during
the
stages
then
toelliptical
remainliquid-phase
steady at the
end of increases
the injection.
injectionearly
(ASOI).
Basedofoninjection,
Figure 4, itand
can be
seentends
that the
penetration
The variation
the same
for the circular
spray
research
Additionally,
during theisearly
stages as
of injection,
and then
tendsin
toprevious
remain steady
at theworks
end of[30,31].
the injection.
The
very early
injection
times,asthe
spray
liquid-phase
was
longerAdditionally,
than the circular
variation
is the same
forelliptical
the circular
spray
in previous penetration
research works
[30,31].
very one.
early injection
times, the elliptical
spray
wasthe
longer
than the
circular
one.
However,
for quasi-stationary
injection,
theliquid-phase
important penetration
finding is that
elliptical
spray
liquid-phase
However,
for
quasi-stationary
injection,
the
important
finding
is
that
the
elliptical
spray
liquid-phase
penetration is shorter than the circular one, indicating that the application of the elliptical hole nozzle is
penetration
is shorter
than the
circular
one, indicating
theinstability
applicationdeformation
of the elliptical
nozzle
helpful
for speeding
up liquid
core
fragmentation
due that
to the
of hole
the asymmetric
is helpful for speeding up liquid core fragmentation due to the instability deformation of the
elliptical jet and the axis-switching phenomenon, as well as the axis-switching behaviors that were
asymmetric elliptical jet and the axis-switching phenomenon, as well as the axis-switching behaviors
found in our previous work [10].
Spray liquid-phase penetration (mm)
that were found in our previous work [10].
40
35
30
25
20
Circular
Elliptical
15
Pinj=120MPa
10
5
Pback=1MPa
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
ASOI (ms)
Spray liquid-phase penetration (mm)
(a)
40
35
30
25
20
Circular
Elliptical
15
Pinj=100MPa
10
5
Pback=1MPa
0.0
0.3
0.6
0.9
1.2
ASOI (ms)
(b)
Figure 4. Cont.
1.5
1.8
2.1
Energies
Energies 2020,
13,2020,
223413, x FOR PEER REVIEW
8 of 14
8 of 14
8 of 14
40
Spray liquid-phase penetration (mm)
Spray liquid-phase penetration (mm)
Energies 2020, 13, x FOR PEER REVIEW
40
35
35
30
30
2525
2020
Circular
Circular
Elliptical
Elliptical
Pinj
=80MPa
P=80MPa
inj
1515
1010
Pback
P =1MPa
=1MPa
back
5 5 0.0 0.3
0.0
0.3
0.6
0.6
0.9
0.9
1.2
1.2
1.5
1.5 1.8
1.8 2.12.1
ASOI (ms)
ASOI (ms)
(c)
(c)
Figure 4. The spray liquid-phase penetration for various injection pressures and the bulk temperature is
Figure
4. The
spray liquid-phase
for various
injection
pressures
and the
fixed at 600 K.
(a)The
injection
pressurepenetration
of 120 MPa;
(b) The
injection
pressure
ofbulk
100 temperature
MPa; (c) The injection
is fixed
atspray
600 K.liquid-phase
(a)The injection
pressure offor
120various
MPa; (b)
The injection
pressure
100bulk
MPa;temperature
(c) The
The
penetration
injection
pressures
andofthe
pressureFigure
of 804.MPa.
injection
of 80
MPa. pressure of 120 MPa; (b) The injection pressure of 100 MPa; (c) The
is fixed
at 600pressure
K. (a)The
injection
injection
pressure
of
80
MPa.
In order toInanalyze
the influence
of of
the
parameters
onlength
the of
length
of the
order to analyze
the influence
theinjection
injection parameters
on the
the stable
spraystable spray
liquid phase,
Figure
5 Figure
shows5 shows
the method
used
the
stabilized
of the
spray liquid-phase
liquid
phase,
the method
usedto
to obtain
obtain the
stabilized
value value
of the spray
liquid-phase
In order to analyze the influence of the injection parameters on the length of the stable spray
penetration.
The red
line window,
which
was used to
the average
of the spray
liquid-phase
penetration.
The
red
line
window,
which
was
tocalculate
calculate
the average
ofspray
the
spray
liquid-phase
liquid
phase,
Figure
shows in
theorder
method
usedused
to
the stabilized
the
liquid-phase
penetration,
was 5selected
to capture
theobtain
stabilized
region for value
circularofand
elliptical
sprays
penetration,
was selected
in window,
order
towhich
capture
stabilized
region
for circular
and
elliptical
sprays
penetration.
The red
line
was the
used
to last
calculate
the in
average
the spray
liquid-phase
under various
injection
conditions.
The average
of the
six values
the laterofstage
of injection
was
penetration,
was
selected
in
order
to
capture
the
stabilized
region
for
circular
and
elliptical
sprays
under various
injection
conditions.
The
average
of
the
last
six
values
in
the
later
stage
of
injection
was
taken as the steady spray liquid-phase penetration.
Spray liquid-phase penetration (mm)
various spray
injection
conditions.
The
average of the last six values in the later stage of injection was
40
taken asunder
the steady
liquid-phase
penetration.
Spray liquid-phase penetration (mm)
taken as the steady spray liquid-phase penetration.
4035
3530
Stability regions
25
30
Stability regions
20
25
Circular
15
Pinj=120MPa
20
Pback=1MPa
10
15
10
5
Circular
0.0
0.3
0.6
0.9
1.2
ASOI (ms)
Pinj=120MPa
1.5P
1.8
=1MPa2.1
back
Figure 5. Spray 5
liquid-phase penetration averaging methodology. The colored area represents the
0.0 has0.3
0.6
0.9
1.2
1.5
1.8
2.1
domain where the average
been calculated.
ASOI (ms)
Figure
5. Spray
liquid-phase
penetrationaveraging
averaging methodology.
TheThe
colored
area represents
the
Figure 5.
Spray
liquid-phase
penetration
methodology.
colored
area represents
the
domain
where
the
average
has
been
calculated.
domain where the average has been calculated.
Figure 6 demonstrates the steady spray liquid-phase penetration for the circular and the elliptical
sprays. As can be seen from Figure 6, the elliptical orifice presents a shorter steady spray liquid-phase
penetration than the circular spray under all injection conditions. In particular, the steady spray
liquid-phase penetration was reduced by 34.5% with the application of the elliptical hole nozzle as
compared to the circular one at the injection pressure of 120 MPa; the results show that the elliptical hole
nozzle effectively accelerates the unstable fracture of the liquid jet, thus decreasing the length of the
spray liquid-phase. Additionally, for the same geometrical orifice, the difference in spray liquid-phase
penetration decreases as the injection pressure increases, and these presented results indicate that the
Steady liquid spray penetration (mm)
Figure 6 demonstrates the steady spray liquid-phase penetration for the circular and the
elliptical sprays. As can be seen from Figure 6, the elliptical orifice presents a shorter steady spray
liquid-phase penetration than the circular spray under all injection conditions. In particular, the
steady spray liquid-phase penetration was reduced by 34.5% with the application of the elliptical
hole nozzle as compared to the circular one at the injection pressure of 120 MPa; the results show that
Energies 2020,
13, 2234 hole nozzle effectively accelerates the unstable fracture of the liquid jet, thus decreasing 9 of 14
the elliptical
the length of the spray liquid-phase. Additionally, for the same geometrical orifice, the difference in
spray liquid-phase penetration decreases as the injection pressure increases, and these presented
injection
pressure
has
little
onpressure
the spray
liquid-phase
penetration
of the penetration
two geometric
results
indicate
that
the effect
injection
has little
effect on the
spray liquid-phase
of the orifices,
as has also
been
reported
previously
for
circular
diesel
nozzles
[32,33].
two geometric orifices, as has also been reported previously for circular diesel nozzles [32,33].
40
Circular
Elliptical
35
30
25
20
15
10
120MPa
100MPa
80MPa
The injection pressure
Figure
6. Steady
spray liquid-phase
penetration
for circular
and elliptical
nozzles
at a temperature
bulk
Figure 6.
Steady
spray liquid-phase
penetration
for circular
and elliptical
nozzles
at a bulk
temperature of 600 K.
of 600 K.
The Effects
of Bulk
Temperature
SprayLiquid-Phase
Liquid-Phase Penetration
4.2. The4.2.
Effects
of Bulk
Temperature
on on
Spray
Penetration
Bulk temperature is one of the most important parameters for analyzing evaporative diesel
Bulk temperature
is one of the most important parameters for analyzing evaporative diesel sprays,
sprays, significantly influencing the spray and combustion characteristics. The effects of different
significantly
influencing the spray and combustion characteristics. The effects of different ambient
ambient temperatures on circular and elliptical spray liquid-phase penetration are presented in
temperatures
circular
and elliptical
spray
liquid-phase
penetration
are presented
Figure 7. For the
Figure on
7. For
the circular
liquid-phase
penetration,
as expected,
the curves
for each in
temperature
circularoverlap
liquid-phase
penetration,
asinjection,
expected,
thefor
curves
for eachspray,
temperature
at the
beginning
at the beginning
of the
while
the elliptical
there wasoverlap
no overlap.
From
Figure
7,
it
can
be
found
that
increasing
the
ambient
temperature
decreases
spray
liquid-phase
of the injection, while for the elliptical spray, there was no overlap. From Figure 7, it can be found
penetration
forambient
both nozzles;
Xu et al. [34]decreases
and Payri etspray
al. [35]liquid-phase
have reported similar
results previously.
that increasing
the
temperature
penetration
for both nozzles;
Additionally, for the same ambient temperature, it is noted that using an elliptical orifice leads to
Xu et al. [34] and Payri et al. [35] have reported similar results previously. Additionally, for the same
shorter liquid-phase penetration, as well as a shorter period of time to achieve a quasi-steady liquid
ambientlength.
temperature,
it is noted
usingorifice
an elliptical
orificeshorten
leads totheshorter
penetration,
The application
of anthat
elliptical
can effectively
length liquid-phase
of the liquid-phase
as wellpenetration
as a shorter
period
of
time
to
achieve
a
quasi-steady
liquid
length.
The
application
and thus avoid the fuel impingement under the realistic diesel engine operating of an
conditions.
Additionally,
theshorten
shorter liquid-phase
for the elliptical
orifice indicated
better
elliptical orifice can effectively
the length penetration
of the liquid-phase
penetration
and thus
avoid the
fuel
and
air
mixture
quality,
which
is
helpful
for
reducing
engine
exhaust
soot
emissions.
fuel impingement under the realistic diesel engine operating conditions. Additionally, the shorter
liquid-phase penetration for the elliptical orifice indicated better fuel and air mixture quality, which is
helpful Energies
for reducing
engine
2020, 13, x FOR
PEERexhaust
REVIEW soot emissions.
10 of 14
Spray liquid-phase penetration (mm)
40
35
30
25
20
Circular-600K
Elliptical-600K
Circular-700K
Elliptical-700K
15
10
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
ASOI (ms)
7. Spray
liquid-phase
penetration
differentbulk
bulk temperatures
temperatures (P(P
inj = 120
MPa,
Pbcak P
= bcak
1 MPa).
Figure Figure
7. Spray
liquid-phase
penetration
forfor
different
MPa,
= 1 MPa).
inj = 120
Figure 8 depicts the steady liquid-phase penetration at various ambient temperatures, indicating
that increasing the ambient temperature reduces the liquid-phase penetration for both nozzles, and
the differences in steady liquid-phase penetration between circular and elliptical orifice decrease with
an increase in ambient temperature. For the ambient temperature of 700 K, in particular, the steady
elliptical spray liquid-phase penetration was 7.9% smaller than that of the circular spray. Otherwise,
Spray liquidEnergies 2020, 13, 2234
20
Circular-600K
Elliptical-600K
Circular-700K
Elliptical-700K
15
10
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
10 of 14
ASOI (ms)
7. Spray
penetration for penetration
different bulk temperatures
inj = 120 MPa, Pbcak = 1 MPa).
Figure Figure
8 depicts
theliquid-phase
steady liquid-phase
at various(Pambient
temperatures, indicating
that increasing
the
ambient
temperature
reduces
the
liquid-phase
penetration
for both nozzles, and
Figure 8 depicts the steady liquid-phase penetration at various ambient temperatures, indicating
the differences
in steady
liquid-phase
penetration
between
circular
and elliptical
orifice
decrease
with
that increasing
the ambient
temperature
reduces the
liquid-phase
penetration
for both
nozzles,
and
an increase
in ambient
temperature.
For
the ambient
temperature
700 K,orifice
in particular,
the steady
the differences
in steady
liquid-phase
penetration
between
circular andof
elliptical
decrease with
anspray
increase
in ambient temperature.
Forwas
the ambient
temperature
of 700ofK,the
in particular,
the steady
elliptical
liquid-phase
penetration
7.9% smaller
than that
circular spray.
Otherwise,
elliptical
spray
liquid-phase
penetration
was
7.9%
smaller
than
that
of
the
circular
spray.
Otherwise,
for an ambient temperature of 700 K, the difference in steady liquid-phase penetration between circular
for an ambient temperature of 700 K, the difference in steady liquid-phase penetration between
and elliptical orifice was 84.8% smaller than the difference for the ambient temperature of 600 K.
circular and elliptical orifice was 84.8% smaller than the difference for the ambient temperature of
The reason
forThe
this
is probably
that
the influence
of temperature
on theon
spray
is greater
thanthan
the impact
600 K.
reason
for this is
probably
that the influence
of temperature
the spray
is greater
of the nozzle
cross-section
shape
on the liquid-phase
penetration,
indicating
that thethat
high
the impact
of the nozzle
cross-section
shape on the liquid-phase
penetration,
indicating
thetemperature
high
reduces
the difference
between
the steadypenetration
liquid-phaseofpenetration
of circular
andsprays.
reducestemperature
the difference
between
the steady
liquid-phase
circular and
elliptical
elliptical sprays.
Steady liquid penetration (mm)
40
Circular
Elliptical
35
30
25
20
15
10
600K
700K
The bulk temperature
8. Steady
spray
liquid-phasepenetration
penetration for
and
elliptical
nozzles
at different
bulk
Figure Figure
8. Steady
spray
liquid-phase
forcircular
circular
and
elliptical
nozzles
at different
bulk
inj = 120 MPa, Pbcak = 1 MPa).
temperatures
temperatures
(Pinj =(P120
MPa, Pbcak = 1 MPa).
4.3. The Effects of Backpressure on Spray Liquid-Phase Penetration
Figure 9 presents the spray liquid-phase penetration against the injection time with different
cross-section shapes at various backpressures; the injection pressure is fixed at 120 MPa and the ambient
temperature is 700 K. From Figure 9, the results show that increasing the backpressure decreases the
liquid-phase penetration for both nozzles; note that Shang et al. [36] and Li et al. [37] observed the
same trend in their experimental results. Because the high ambient pressure can reduce the initial spray
velocity, on the other hand, the high backpressure is beneficial for increasing the spray cone angle,
thus entraining more hot gas in the spray center. Both factors will result in a reduction in liquid-phase
penetration when the backpressure is increased. Interestingly, the difference of the liquid-phase
penetration between the circular and elliptical nozzle decreases with higher backpressure.
In Figure 10, the steady liquid-phase penetration results at different backpressures are plotted.
From Figure 10, the steady liquid-phase penetration reduced as the backpressure increases, but the
differences of the steady liquid-phase penetration for the circular and elliptical orifice are reduced
under the condition of higher ambient density. For the backpressure of 2 MPa, in particular, the steady
liquid penetration of the elliptical spray is only 6% smaller than the circular spray, probably because
under the environment of high backpressure suppresses in axis-switching and deformation behaviors
of the elliptic spray.
decreases the liquid-phase penetration for both nozzles; note that Shang et al. [36] and Li et al. [37]
observed the same trend in their experimental results. Because the high ambient pressure can reduce
the initial spray velocity, on the other hand, the high backpressure is beneficial for increasing the
spray cone angle, thus entraining more hot gas in the spray center. Both factors will result in a
reduction in liquid-phase penetration when the backpressure is increased. Interestingly, the
difference
of the liquid-phase penetration between the circular and elliptical nozzle decreases with 11 of 14
Energies 2020,
13, 2234
higher backpressure.
Spray liquid-phase penetration (mm)
30
25
20
Circular-1MPa
Elliptical-1MPa
Circular-2MPa
Elliptical-2MPa
15
10
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
ASOI (ms)
EnergiesFigure
13,9.xSpray
FOR PEER
REVIEW penetration for different backpressures (Pinj = 120 MPa, Tbulk = 700 K).12 of 14
liquid-phase
Figure
9.2020,
Spray
liquid-phase
penetration for different backpressures (Pinj = 120 MPa, Tbulk = 700 K).
Steady liquid penetration (mm)
In Figure 10, the 30
steady liquid-phase penetration results at different backpressures are plotted.
Circular
From Figure 10, the steady liquid-phase penetration reduced as the backpressure increases, but the
Elliptical
differences of the steady liquid-phase penetration for the circular and elliptical orifice are reduced
under the condition of
25higher ambient density. For the backpressure of 2 MPa, in particular, the
steady liquid penetration of the elliptical spray is only 6% smaller than the circular spray, probably
because under the environment of high backpressure suppresses in axis-switching and deformation
behaviors of the elliptic spray.
20
15
10
1MPa
2MPa
The backpressure
10. Steady
spray
liquid-phase penetration
penetration for
andand
elliptical
nozzles
at different
Figure Figure
10. Steady
spray
liquid-phase
forcircular
circular
elliptical
nozzles
at different
backpressures
(P
inj
=
120
MPa,
T
bulk
=
700
K).
backpressures (Pinj = 120 MPa, Tbulk = 700 K).
5. Conclusions
5. Conclusions
The spray liquid breakup behaviors for diesel nozzles with the application of non-circular crossThe spray
liquid breakup behaviors for diesel nozzles with the application of non-circular
section shapes (elliptical, circular) were studied using the Mie-scattering method under evaporative
cross-section
shapes
(elliptical, circular) were studied using the Mie-scattering method under
conditions. This study provides a comprehensive analysis of the influence of variables such as
evaporative
conditions.
This
studyinjection
provides
a comprehensive
analysis
of MPa),
the influence
of variables such
elliptical
and circular
orifices,
pressures
(80 MPa, 100
MPa, 120
bulk temperatures
as elliptical
and
orifices, injection
pressures
MPa,
100 MPa,penetration
120 MPa),
bulk temperatures
(600 K,
700circular
K), and backpressures
(1 MPa,
2 MPa) on(80
spray
liquid-phase
characteristics.
conclusions can be
(600 K, The
700following
K), and backpressures
(1drawn:
MPa, 2 MPa) on spray liquid-phase penetration characteristics.
(1)
The
elliptical
spray
liquid
length
The following conclusions can be drawn: increased in the early stages of injection, and tended to be
steady then. The elliptical spray liquid-phase penetration was smaller than the circular spray at the
(1) The elliptical spray liquid length increased in the early stages of injection, and tended to be
end of the injection, due to the deformation and the axis-switching behaviors both being helpful for
steady then.
The elliptical
spray
was smaller than the circular spray at the
accelerating
the breakup
of theliquid-phase
elliptical liquidpenetration
core.
end of the injection,
duespray
to the
deformation
and the
axis-switching
both being
helpful for
(2) The steady
liquid-phase
penetration
of the
elliptical dieselbehaviors
nozzle was 34.5%
lower than
accelerating
the breakup
of thethat
elliptical
liquid
core. orifice nozzle can effectively shorten the liquidthe circular
one, indicating
the use of
an elliptical
the same
geometricalpenetration
orifice, the differences
in the spray
liquid-phase
(2)phase
The length.
steadyFor
spray
liquid-phase
of the elliptical
diesel
nozzle penetration
was 34.5% lower
were
reduced
with
an
increase
in
injection
pressure,
suggesting
that
injection
has little shorten
than the circular one, indicating that the use of an elliptical orifice nozzle pressure
can effectively
impact on the spray liquid-phase penetration for either geometrical orifice.
the liquid-phase length. For the same geometrical orifice, the differences in the spray liquid-phase
(3) Increasing the ambient temperature is able to reduce the spray liquid-phase penetration for
penetration
reduced
with an increase
injection pressure,
suggesting
that injection
pressure has
both were
orifices.
The differences
in steady in
liquid-phase
penetration
between circular
and elliptical
little impact
onwere
the spray
liquid-phase
penetration
for either
geometrical
orifice. temperature
nozzles
reduced
with an increase
in ambient
temperature.
Under high-bulk
conditions of 700 K, the steady elliptical spray liquid-phase penetration was 7.9% lower than the
circular spray.
(4) Increasing the backpressure is able to lower the liquid-phase penetration for both orifices,
because higher ambient gas density consumes the momentum of the spray. With the increase of the
backpressure, the differences in the steady liquid-phase penetration between circular and elliptical
orifices were reduced, probably due to the axis-switching and deformation behaviors of the elliptical
jet being restrained under high-backpressure conditions.
Energies 2020, 13, 2234
12 of 14
(3) Increasing the ambient temperature is able to reduce the spray liquid-phase penetration for
both orifices. The differences in steady liquid-phase penetration between circular and elliptical nozzles
were reduced with an increase in ambient temperature. Under high-bulk temperature conditions of
700 K, the steady elliptical spray liquid-phase penetration was 7.9% lower than the circular spray.
(4) Increasing the backpressure is able to lower the liquid-phase penetration for both orifices,
because higher ambient gas density consumes the momentum of the spray. With the increase of the
backpressure, the differences in the steady liquid-phase penetration between circular and elliptical
orifices were reduced, probably due to the axis-switching and deformation behaviors of the elliptical
jet being restrained under high-backpressure conditions.
(5) With the application of the elliptical orifice, which can effectively decrease the liquid-phase
penetration, it can be inferred that for small cylinder size diesel engines, the use of elliptical holes
can effectively avoid fuel impingement. Additionally, the lower liquid-phase penetration for the
elliptical orifice indicated better and faster fuel and air mixture quality, which is helpful for reducing
engine emissions.
Author Contributions: B.X. and B.Y. designed research; B.X. and S.Y. performed research, analyzed data, and
wrote the paper; H.J. supervised research and reviewed the paper. All authors have read and agreed to the
published version of the manuscript.
Funding: Graduate Student Innovation Fund Project of Jiangsu Province [KYCX17_1778]; Science and Technology
on Scramjet Laboratory Project of China [STS/MY-KFKT-2017001]; Jiangsu Province Post-Doctoral Fund
[2018K031B].
Acknowledgments: This work was supported by the contribution of Graduate Student Innovation Fund
Project of Jiangsu Province [KYCX17_1778]; Science and Technology on Scramjet Laboratory Project of China
[STS/MY-KFKT-2017001]; Jiangsu Province Post-Doctoral Fund [2018K031B]; The Priority Academic Program
Development of Jiangsu Higher Education Institutions [PAPD].
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
Wang, Z.; Shi, S.; Huang, S.; Tang, J.; Du, T.; Cheng, X.; Huang, R.; Chen, J.-Y. Effects of water content on
evaporation and combustion characteristics of water emulsified diesel spray. Appl. Energy 2018, 226, 397–407.
[CrossRef]
Tian, J.; Zhao, M.; Long, W.; Nishida, K.; Fujikawa, T.; Zhang, W. Experimental study on spray characteristics
under ultra-high injection pressure for DISI engines. Fuel 2016, 186, 365–374. [CrossRef]
Nishida, K.; Zhu, J.; Leng, X.; He, Z. Effects of micro-hole nozzle and ultra-high injection pressure on air
entrainment, liquid penetration, flame lift-off and soot formation of diesel spray flame. Int. J. Engine Res.
2017, 18, 51–65. [CrossRef]
Kiplimo, R.; Tomita, E.; Kawahara, N.; Yokobe, S. Effects of spray impingement, injection parameters, and
EGR on the combustion and emission characteristics of a PCCI diesel engine. Appl. Therm. Eng. 2012, 37,
165–175. [CrossRef]
Ge, M.; Liang, X.; Yu, H.; Wang, Y.; Zhang, H. Effect of Lube Oil Film Thickness on Spray/Wall Impingement with
Diesel, M20 and E20 Fuels; SAE Technical Paper Series; SAE International: Warrendale, PA, USA, 2017; 01-0847.
Yu, S.; Yin, B.; Deng, W.; Jia, H.; Ye, Z.; Xu, B.; Xu, H. Experimental study on the diesel and biodiesel spray
characteristics emerging from equilateral triangular orifice under real diesel engine operation conditions.
Fuel 2018, 224, 357–365. [CrossRef]
Yunyi, G.; Changwen, L.; Yezhou, H.; Zhijun, P. An Experimental Study on Droplet Size Characteristics and Air
Entrainment of Elliptic Sprays; SAE Technical Paper Series; SAE International: Warrendale, PA, USA, 1998.
Yu, S.; Yin, B.; Deng, W.; Jia, H.; Ye, Z.; Xu, B.; Xu, H. Experimental study on the spray characteristics
discharging from elliptical diesel nozzle at typical diesel engine conditions. Fuel 2018, 221, 28–34. [CrossRef]
Yu, S.; Yin, B.; Deng, W.; Jia, H.; Ye, Z.; Xu, B.; Xu, H. Internal flow and spray characteristics for elliptical orifice
with large aspect ratio under typical diesel engine operation conditions. Fuel 2018, 228, 62–73. [CrossRef]
Energies 2020, 13, 2234
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
13 of 14
Yu, S.; Yin, B.; Deng, W.; Jia, H.; Ye, Z.; Xu, B.; Xu, H. An experimental comparison of the elliptical and circular
nozzles spray and mixing characteristics under different injection pressures. Fuel 2019, 236, 1474–1482.
[CrossRef]
Ku, K.-W.; Lee, Y.-J.; Kim, I.-S.; Lee, C.-W. Experimental study of the effects of nozzle hole geometry for di
diesel engine. J. ILASS-Korea 2007, 12, 154–159.
Matsson, A.; Jacobsson, L.; Andersson, S. The Effect of Elliptical Nozzle Holes on Combustion and Emission
Formation in a Heavy Duty Diesel Engine; SAE Technical Paper Series; SAE International: Warrendale, PA,
USA, 2000; 01-1251.
Ho, C.-M.; Gutmark, E. Vortex induction and mass entrainment in a small-aspect-ratio elliptic jet. J. Fluid Mech.
1987, 179, 383–405. [CrossRef]
Hong, J.G.; Ku, K.W.; Kim, S.R.; Lee, C.W. Effect of cavitation in circular nozzle and elliptical nozzles on the
spray characteristic. At. Sprays 2010, 20, 877–886. [CrossRef]
Hong, J.G.; Ku, K.W.; Lee, C.-W. Numerical simulation of the cavitating flow in an elliptical nozzle. At. Sprays
2011, 21, 237–248. [CrossRef]
Sharma, P.; Fang, T. Spray and atomization of a common rail fuel injector with non-circular orifices. Fuel
2015, 153, 416–430. [CrossRef]
Sharma, P.; Fang, T. Breakup of liquid jets from non-circular orifices. Exp. Fluids 2014, 55. [CrossRef]
Cung, K.; Moiz, A.A.; Shah, B.; Kalaskar, V.; Miwa, J.; Abidin, Z. Evaluation of Diesel Spray with Non-Circular
Nozzle—Part I: Inert Spray; SAE Technical Paper Series; SAE International: Warrendale, PA, USA, 2019; 01-0065.
Srinivasan, R.; Bowersox, R.D.W. Transverse Injection through Diamond and Circular Ports into a Mach 5.0
Freestream. AIAA J. 2008, 46, 1944–1962. [CrossRef]
Jadidi, M.; Sreekumar, V.; Dolatabadi, A. Breakup of elliptical liquid jets in gaseous crossflows at low Weber
numbers. J. Vis. 2018, 22, 259–271. [CrossRef]
Kasyap, T.V.; Sivakumar, D.; Raghunandan, B.N. Breakup of liquid jets emanating from elliptical orifices at
low flow conditions. At. Sprays 2008, 18, 645–668. [CrossRef]
Kasyap, T.; Sivakumar, D.; Raghunandan, B. Flow and breakup characteristics of elliptical liquid jets. Int. J.
Multiph. Flow 2009, 35, 8–19. [CrossRef]
Morad, M.R.; Khosrobeygi, H. Penetration of Elliptical Liquid Jets in Low-Speed Crossflow. J. Fluids Eng.
2018, 141, 011301. [CrossRef]
Molina, S.; Salvador, F.; Carreres, M.; Jaramillo, D.; Rubio, F.J.S. A computational investigation on the
influence of the use of elliptical orifices on the inner nozzle flow and cavitation development in diesel injector
nozzles. Energy Convers. Manag. 2014, 79, 114–127. [CrossRef]
Chiatti, G.; Chiavola, O.; Palmieri, F.; Pompei, R. On the Influence of the Slot Orifice in Diesel Common Rail
Nozzle. Open Fuels Energy Sci. J. 2018, 11, 55–69. [CrossRef]
Yu, S.; Yin, B.; Deng, W.; Jia, H.; Ye, Z.; Xu, B.; Xu, H. Experimental study on the spray and mixing
characteristics for equilateral triangular and circular nozzles with diesel and biodiesel under high injection
pressures. Fuel 2019, 239, 97–107. [CrossRef]
Payri, R.; Salvador, F.; Gimeno, J.; Zapata, L.; Rubio, F.J.S. Diesel nozzle geometry influence on spray
liquid-phase fuel penetration in evaporative conditions. Fuel 2008, 87, 1165–1176. [CrossRef]
Pastor, J.V.; Arrègle, J.; Palomares, A. Diesel spray image segmentation with a likelihood ratio test. Appl. Opt.
2001, 40, 2876–2885. [CrossRef]
Pastor, J.V.; Arrègle, J.; García, J.M.; Zapata, L.D. Segmentation of diesel spray images with log-likelihood
ratio test algorithm for non-Gaussian distributions. Appl. Opt. 2007, 46, 888–899. [CrossRef]
Zheng, L.; Ma, X.; Wang, Z.; Wang, J. An optical study on liquid-phase penetration, flame lift-off location
and soot volume fraction distribution of gasoline–diesel blends in a constant volume vessel. Fuel 2015, 139,
365–373. [CrossRef]
Payri, R.; Giraldo, J.S.; Ayyapureddi, S.; Versey, Z. Experimental and analytical study on vapor phase and
liquid penetration for a high pressure diesel injector. Appl. Therm. Eng. 2018, 137, 721–728. [CrossRef]
Martínez-Martínez, S.; Sánchez-Cruz, F.; Riesco-Ávila, J.; Gallegos, A.; Aceves, S. Liquid penetration length
in direct diesel fuel injection. Appl. Therm. Eng. 2008, 28, 1756–1762. [CrossRef]
Kook, S.; Pickett, L.M. Liquid length and vapor penetration of conventional, Fischer–Tropsch, coal-derived,
and surrogate fuel sprays at high-temperature and high-pressure ambient conditions. Fuel 2012, 93, 539–548.
[CrossRef]
Energies 2020, 13, 2234
34.
35.
36.
37.
14 of 14
Xu, M.; Cui, Y.; Deng, K. One-dimensional model on liquid-phase fuel penetration in diesel sprays. J. Energy Inst.
2016, 89, 138–149. [CrossRef]
Payri, R.; Gimeno, J.; Bardi, M.; Plazas, A.H. Study liquid length penetration results obtained with a direct
acting piezo electric injector. Appl. Energy 2013, 106, 152–162. [CrossRef]
Shang, W.; He, Z.; Wang, Q.; Cao, J.; Li, B.; Leng, X.; Tamilselvan, P.; Li, D. Experimental and analytical study
on capture spray liquid penetration and combustion characteristics simultaneously with Hydrogenated
Catalytic Biodiesel/Diesel blended fuel. Appl. Energy 2018, 226, 947–956. [CrossRef]
Li, D.; He, Z.; Xuan, T.; Zhong, W.; Cao, J.; Wang, Q.; Wang, P. Simultaneous capture of liquid length of
spray and flame lift-off length for second-generation biodiesel/diesel blended fuel in a constant volume
combustion chamber. Fuel 2017, 189, 260–269. [CrossRef]
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).