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SAE TECHNICAL
PAPER SERIES 2002-01-0495

Optical Investigation of the Effect of Fuel Jet

Wall Impact Position on Soot Emissions
in a Single Cylinder Common Rail Direct
Injection Diesel Engine
Nicolas Docquier
IFP Powertrain Engineering, France

Reprinted From: Diesel Fuel Injection and Sprays 2002

(SP–1696)

SAE 2002 World Congress

Detroit, Michigan
March 4-7, 2002

400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760
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2002-01-0495

Optical Investigation of the Effect of Fuel Jet Wall Impact

Position on Soot Emissions in a Single Cylinder Common Rail
Direct Injection Diesel Engine
Nicolas Docquier
IFP Powertrain Engineering, France

Copyright © 2002 Society of Automotive Engineers, Inc.

ABSTRACT combustion mechanisms within the combustion chamber

will help to design more efficient and cleaner DI Diesel
This study is dealing with optical experiments in a engines. This experimental study is dealing with these
common rail DI Diesel small-bore automotive engine. Its aspects and is related to optical investigations in a small-
purpose is to investigate the influence on soot emissions bore, common rail DI Diesel engine. Its purpose is to
of the location of the point of impact of the fuel jet on the investigate the influence on soot emissions of the
piston bowl walls. The experiments are carried out in a location of the point of impact of the fuel jets on the
single cylinder, 4 valves Diesel engine equipped with a piston bowl walls. This location is characterized by the
common rail injector and a bowl shaped piston. A classic Jet Wall Impact (JWI) parameter as defined in Figure 1.
extended piston with piston-crown quartz window It is the distance between the top surface of the piston
provides a first optical access to the combustion head and the theoretical impact location of the fuel jets
chamber. A transparent quartz cylinder also provides a on the piston bowl walls.
second access to the chamber. Liquid and vapor phases
of the fuel were visualized using Exciplex laser induced
fluorescence while combustion and soot images were
recorded with an intensified CCD camera by direct light
emission monitoring. Soot emissions were also analyzed
in the exhaust pipe with a standard smoke meter.
Experiments carried out for several vertical positions of
the injector show that smoke emissions are strongly
affected by the fuel jets point of impact in the piston
Figure 1 : Definition of Jet Wall Impact (JWI) position.
bowl. The analysis of the fuel and combustion
visualizations presented in this article shows that this
phenomenon is related to distribution of the vapor fuel in It has been noticed with production engines that soot
the combustion chamber between squish area and emissions in the exhaust pipe were greatly influenced by
piston bowl. this JWI parameter. The purpose of this study is to
investigate the reasons for this behavior. The
experiments are carried out in single cylinder, 4 valves
INTRODUCTION
Diesel engine equipped with a common rail injector and
a bowl shaped piston whose geometry is given in Figure
Within the last few years, common rail Direct Injection
1. Optical access to the combustion chamber is provided
(DI) has widely spread to production automotive Diesel
by a piston-crown quartz window and a transparent
engines as this technology allows highly flexible engine
quartz liner. It is first checked that the optical engine
management and leads among other things, to a large
reproduces well the behavior of production engines with
reduction in noise and fuel consumption. Although this
regard to JWI. Liquid and vapor phases of the fuel are
technology is mature, due to growing environmental
then visualized using Laser Induced Exciplex
concern and more and more stringent regulations,
Fluorescence (LIEF) while combustion and soot images
reducing pollutant emissions from DI Diesel engine
are recorded with an intensified CCD camera by direct
needs further research efforts. While post treatment
light emission monitoring. Accordingly, a mechanism is
techniques such as particulate filters or catalytic
proposed and discussed to explain the influence of JWI
converters may provide a solution to this major problem,
on soot emissions.
better understanding of fuel injection as well as

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EXPERIMENTAL It has to be noted that the measured compression ratio

is slightly lower than the geometric volumetric ratio
OPTICAL ENGINE essentially due to small air leaks typically encountered in
optical engines at the piston rings as well as between
Experiments were carried out with a 4-stroke, single cylinder head and combustion liner.
cylinder, Direct Injection Diesel (DID) engine based on a
DW10 (PSA) motor. It is equipped with a production OPERATING CONDITIONS
cylinder head and several optical access depending on
the experiment type : a piston quartz window and a The optical engine was operated at 1200 rpm by an
transparent quartz liner. Ganser Hydromag provided the electrical dyno system to ensure synchronization with the
injector unit and its electronics. It consists in a central 10 Hz repetition rate Nd:YAG laser system. Except for
common rail injector operated by a hydro-pneumatic experiments where exhaust gases where sampled and
pump. A 5 hole nozzle with nominal hole diameter/length cylinder pressure was recorded to perform combustion
of 0.148 mm/1 mm was used. A picture of the engine analysis, the engine was fired every 10th engine cycle - at
setup is presented in Figure 2 while the optical access to which time data were acquired - to minimize the rate of
the combustion chamber is illustrated in the data window fouling. Finally, fuel injection started at 356.6
acquisition section. To avoid damages to the optical CAD (360 Crank Angle Degree corresponds to top dead
engine, its volumetric ratio normally set to 17.2 was center - TDC) and fuel pressure was maintained at
reduced to 15.2 during operation with the quartz liner in 850 bar, while air was supplied to the engine at ambient
order to lower the stress encountered by the cylinder. conditions, respectively 25 °C and 1 bar. These
This was realized by increasing the squish area conditions are given in Table 3. The events taking place
thickness. Table 1 and Table 2 respectively summarize during an engine cycle were synchronized using a BEI
the specifications of the engine and the fuel injector. M25 optical absolute angular coder (0.1 CAD resolution).

Engine speed 1200 rpm

Intake air temperature 25 °C
Intake air pressure 1 bar
Start of injection 356.6 CAD
Injection pressure 850 bar
Skip fire mode 1 inj./10 cycles
Table 3 : Engine operating conditions with combustion.

FUEL JET WALL IMPACT POSITION (JWI)

The location of the impact of

the fuel jets on the piston bowl
walls (JWI parameter) defined
Figure 2 : Single cylinder Direct Injection Diesel engine. in Figure 1 was varied from
5.5 mm to 7.5 mm by vertically
Engine base type PSA DW10, DI Diesel moving the fuel injector while
Cycle 4-stroke keeping constant all other
Number of cylinders 1 parameters as illustrated on
Number of valves 2 intake + 2 exhaust the right hand side figure.
Bore 85 mm
Stroke 88 mm LASER INDUCED EXCIPLEX FLUORESCENCE
Displacement volume 0.5 l
Combustion chamber diameter 40.7 mm The Laser Induced Exciplex Fluorescence (LIEF)
Squish area thickness 1 mm 1.94 mm technique was used to visualize the liquid and vapor
Volumetric ratio (VR) 17.2 15.2 phases of the fuel jets. This technique was first
Compression ratio (CR) 15.6 13.9 described by Melton [1] and has been successfully
Table 1 : Specifications of the optical engine. applied in optical engines (see e.g. [2-8]) and
pressurized bombs (see e.g. [9,10]). In this technique,
Type Ganser Hydromag the base fuel is doped with a small quantity of organic
Angle of fuel jet axis (from vertical) 72° dopants. After excitation with a laser, the dopants
Number of holes 5, uniformly spaced fluoresce at different wavelengths depending whether
Hole diameter 0.148 mm they exist in the liquid or vapor phases. In this work, the
Hole length 1 mm base fuel (solvent) was dodecane employed with a
dopant mixture of α-methyl-naphtalene (partner) and
Table 2 : Specifications of the fuel injector.
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tetramethyl-phenylene diamine (TMPD, fluorescent Element % by weight Boiling Point Cetane #.

monomer). In the vapor phase, the TMPD molecule can Dodecane 89.64 214.5 °C 80
be elevated to an excited state by absorption of UV α-methyl-naphtalene 9.96 244.8 °C 0
radiation. It returns to ground state by collision with a TMPD 0.40 260.0 °C /
quenching molecule or by fluorescence emission. The
Table 4 : Fuel properties
spectrum of this emission peaks around 380 nm (Figure
4, mixture 1). In the liquid phase, TMPD binds with α-
Although very attractive, this LIEF technique suffers from
methyl-naphtalene to form an excited complex (exciplex)
two major drawbacks. On the one hand, oxygen
which returns to ground state principally by fluorescent
quenches quite effectively the excited species (collision
emission in which the spectrum is red-shifted from that of
de-excitation). This poses a severe problem for exciplex
the excited TMPD monomer. The emission spectrum of
studies of the vapor phase dispersed in air, where
the excited complex peaks near 470 nm (Figure 4,
quenching collisions with oxygen molecules are frequent.
mixtures 2 and 3). This mechanism is depicted in Figure
Therefore, although the liquid phase reaction is
3.
somewhat less affected due to the low concentration of
dissolved oxygen in the liquid phase fuel, the
visualizations of the fuel jets were carried out in an
oxygen-free nitrogen environment to ensure sufficient
vapor phase emission intensity.

On the other hand, to discriminate the vapor and liquid

phases, appropriate interference filters should be used
to collect the fluorescence signal emitted either around
370 nm (vapor) or 480 nm (liquid). However, Figure 4
shows that whatever the concentration of the partner,
some residual fluorescence signal is emitted by the liquid
phase in the 370 nm region. Therefore, as the liquid
phase is about 50 times denser than the vapor phase,
vapor visualizations will strongly be affected by the liquid
phase. As a result, the interpretation of the fuel vapor
images given by LIEF will be hazardous whenever
Figure 3 : Laser Induced Exciplex Fluorescence (LIEF). doped liquid fuel is located in the vicinity of the probed
region. The vapor phase should ideally be studied with
It is shown in Figure 4 that by proper selection of the LIEF when all the liquid is vaporized.
dopant concentrations, it is possible to arrange for the
monomer to be the dominant emitter in the vapor phase Although quantitative data may be obtained with the
while the excited complex dominates in the liquid phase LIEF technique under certain circumstances (see
emission. [3,9,11] for a detailed discussion), the corresponding
conditions are quite difficult to achieve in the optical
engine due among others things, to temperature and
incident light and signal absorption effects (O2 quenching
as well if air was supplied to the engine). Therefore, the
technique was used in this study only to provide
qualitative information about fuel spray penetration and
vaporization within the combustion chamber.

DATA ACQUISITION

Cylinder Pressure - Cylinder pressure was recorded at

0.1 CAD increments for each operating condition with a
Kistler 6053C60 sensor and ensemble-averaged over 50
engine cycles.

Figure 4 : Emission spectra of various fuel/dopant mixtures LIEF - The setup used to visualize liquid and vapor
excited at 355 nm (adapted from [9]). Do, A and D respectively phases of the fuel jets through the piston quartz window
refer to dodecane, α-methyl-naphtalene and TMPD. is presented in Figure 5. Using a divergent spherical lens
(f=35 mm), the combustion chamber was globally
The third mixture was selected for this study. Its main illuminated with a frequency tripled Nd:YAG laser at
properties are given in Table 4. 355 nm. The fluorescence signal was collected

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backward using a Xybion ISG 250 intensified CCD video These results clearly indicate that soot emissions
camera equipped with a 105 mm UV Nikon objective. observed in the exhaust pipe increase with JWI for the
The camera was associated to a high-pass Melles Griot two VR considered here, therefore reproducing the
3FCG065 filter for liquid phase monitoring (λ>500 nm) or production engine behavior (not shown here). Thus, the
a band-pass Corion 040 S25-400-S filter for vapor phase optical engine may be used to investigate this
monitoring (λnom=400 nm). Images presented in this study phenomenon.
are ensemble-averaged over 50 engine cycles.
LIEF VISUALIZATIONS OF THE FUEL JETS
Combustion Imaging - The light emitted by the
combustion was directly monitored with the CCD camera PISTON BOWL INVESTIGATIONS
previously presented, without any filter this time. Apart
from the early stages of combustion where The influence of JWI on the fuel jets was first studied
chemiluminescence may be dominant - during and a few using LIEF applied through the piston quartz window
CAD after auto-ignition [12] - the light emitted by the (40.5 mm diameter) according to the setup described in
flame is largely dominated by the black-body radiation Figure 5.
from hot soot. Therefore, direct combustion visualization
gives qualitative indications on flame propagation and CAD Liquid Phase Vapor Phase CAD
soot location. Images presented in this study are
ensemble-averaged over 50 engine cycles.

SOI 359

357 360

Figure 5 : Setup for LIEF visualizations in the piston bowl.

PRELIMINARY RESULTS 358 361

It was first checked that the tendencies observed on the

production engine could be reproduced by the optical
engine setup. For this purpose, soot emissions of the
optical engine were measured by sampling the exhaust
gases using a standard AVL 415 smoke meter. Results
gathered for the two volumetric ratios (VR) set in this
study, are presented in Figure 6 as a function of the jet 359 362
wall impact position parameter JWI.

360 363

Figure 7 : Averaged images of the liquid (left) and vapor (right)

Figure 6 : Soot index as a function of JWI. phases of the fuel jets. Temporal sequence at JWI=6.51 mm.

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Start of injection (SOI) 356.6 CAD All other parameters being constant this trend may be
Injected fuel quantity (Q) 31.4 mm3/injection interpreted as shown by Figure 9. As JWI increases, the
Volumetric ratio (VR) 17.2 jets impinge deeper in the piston bowl so that due to the
Skip fire mode 1 injection/cyle shape of the reentrant, a larger fraction of the vapor is
Chamber atmosphere Nitrogen likely diverted to the bottom of the chamber, resulting in
more vapor in this region. As the chamber is illuminated
Table 5 : Operating conditions corresponding to Figure 7.
from the bottom, this implies a fluorescence signal
Injection is started at 356.6 CAD, and detected at the growth in the vicinity of the bowl walls that can actually
same angle in this sequence due to small uncertainties be noticed in Figure 8.
(0.1 to 0.2 CAD) in the angular coding system. No
fluorescence signal could be detected before this stage. Conversely, if JWI decreases, more vapor fuel should be
Then, one notices that the liquid core of the fuel jets available in the squish area. This point is investigated in
does not impinge on the piston bowl walls. the following section.

To avoid misinterpretation, vapor images are not shown SQUISH AREA INVESTIGATIONS
before 359 CAD. Indeed, at this crank angle, the
progression of the liquid phase has stopped and it is To verify that this mechanism really applies to our
therefore possible to analyze the vapor signal beyond engine, the visualization of the fuel vapor phase was
the tip of the liquid spray. As an example, Figure 7 conducted in the squish area. For this purpose, the
shows that the vapor reaches the bowl walls around experimental setup was modified as shown in Figure 10.
359 CAD, rebounds on the reentrant (see e.g. upper left
jet at 361 CAD) and finally spreads all over the chamber.
It is also interesting to note that the vapor is affected by
the aerodynamics of the chamber. A clockwise deviation
of the jets due to the swirl motion is clearly detected from
359 to 361 CAD.

Whereas the influence of JWI on the liquid phase could

not be detected, the vapor phase is somewhat affected
by this parameter. As an example, Figure 8 presents the
vapor phase images of the jets at 361 CAD for three
different JWI parameters.
Figure 10 : Setup for LIEF visualizations in the squish area.
JWI=5.51 mm JWI=6.51 mm JWI=7.61 mm
The 355 nm laser beam of the YAG laser (approximately
7 mm in diameter) was horizontally directed, without any
optics, across the quartz liner through one of the five fuel
jets. The intensified CCD camera was set at 90° with
respect to the laser beam to capture the squish area
from the injector axis to the liner. Due to the small
thickness of the squish area, measurements were
Figure 8 : Averaged images of the vapor phase. Influence of JWI carried out for angles greater than 370 CAD only.
at 361 CAD. Operating conditions are given in Table 5.
Visualizations of the fuel vapor phase were carried out
As JWI increases, this figure indicates that the intensity for three different JWI, 5.57, 6.67 and 7.07 mm. A
of the fluorescence signal raises in the vicinity of the temporal sequence of the jets penetration in the squish
piston bowl walls. area at JWI=5.57 mm is presented in Figure 11. Except
for the volumetric ratio that was reduced to 15.2 to avoid
Low JWI High JWI
breaking the quartz liner, the corresponding operating
conditions were similar to those given in Table 5.

On these images the laser beam propagates towards the

left and the dark zone on the upper-left corner of each
image corresponds to the common rail injector nozzle.

Figure 9 : Influence of JWI on vapor phase fluorescence signal.

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CAD Vapor Phase One clearly notes that intensity increases with crank
angle, and rises at a given angle as JWI is diminished.
375

380

385

390

Figure 11 : Averaged images of the vapor phase in the squish

area. Temporal sequence at JWI=5.57 mm.
Figure 13 : Evolution of fuel vapor fluorescence intensity as a
To study the influence of JWI, the intensity of the images function of crank angle and different JWI parameters.
obtained at different JWI and CAD has been spatially
integrated perpendicularly to the laser beam axis, and Although the quantitative interpretation of the images is
these data have been corrected for the camera subject to caution due to pressure and temperature drop
intensifier gain which was adjusted all along the as the engine cycle proceeds after TDC, these results
experiments. The corresponding fluorescence intensity however indicate that more fuel vapor propagates to the
profiles along the beam axis have been first used to squish area as JWI decreases, as suggested by the
determine the vapor penetration in the squish area as a analysis of the images acquired through the piston
function of the crank angle. These results are presented quartz window.
for the three JWI parameters in Figure 12.
FUEL VAPOR DISTRIBUTION AND SOOT EMISSIONS

The LIEF visualizations have shown that more fuel vapor

is available in the squish area as the jet wall impact
distance diminishes. Although these results were
obtained with fuel injection in nitrogen, they indicate that
the fuel distribution in this zone is sensitive to the vertical
position of the injector.

As shown later, the auto-ignition of the fuel/air mixture

occurs around 361 CAD. As a result, later stages of the
fuel vapor propagation certainly differ from what has
been shown here but the trend should be preserved.

Therefore, as a fraction of the air supplied to the

chamber is entrapped in the squish area during fuel
injection and the early stages of combustion, reducing
Figure 12 : Fuel vapor penetration in the squish area as a function JWI likely allows to consume this fuel earlier in the cycle.
of crank angle and different JWI parameters.
Indeed, it is directly in contact with air whereas at higher
JWI, it should propagate in the bowl back to the squish
From this graph, one notes that the penetration distance
area. This mechanism might allow either more time for
increases with crank angle, as already shown by the
soot post-oxidation or locally leaner combustion,
sequence in Figure 11, and that the influence of JWI is
probably both, and would therefore result in lower
weak, except at 375 CAD where penetration increases
tailpipe soot emissions when JWI decreases.
for small JWI.
In the next section, combustion has been investigated in
The fluorescence intensity profiles previously calculated
the piston bowl as well as in the squish area to confirm
were also spatially integrated along the beam axis to
this interpretation.
study the evolution of the images global intensity. These
data are given in Figure 13 as a function of crank angle.
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COMBUSTION VISUALIZATION

PISTON BOWL INVESTIGATIONS

Combustion was investigated first in the piston bowl

through the piston quartz window by direct monitoring
with the intensified CCD camera. A temporal sequence
at JWI=6.51 mm is presented in Figure 17. The
corresponding operating conditions are given in Table 6.

Start of injection (SOI) 356.6 CAD

Injected fuel quantity (Q) 25 mm3/injection
Volumetric ratio (VR) 17.2
Skip fire mode 1 injection/10 cycles
Chamber atmosphere Air
Figure 15 : Burnt fraction at different JWI. VR=17.2.
Table 6 : Operating conditions corresponding to Figure 17 :
Averaged combustion images in the piston bowl. Temporal SQUISH AREA INVESTIGATIONS
sequence at JWI=6.51 mm. VR=17.2..
The analysis of the LIEF images has already shown the
The first appearance of auto-ignition (AI) sites was importance of the squish area with respect to this study.
detected at 360.6 CAD, 4 degrees after the start of This region was therefore specifically investigated to
injection. After this stage, combustion spreads in the check if combustion and any influence of JWI could be
vapor phase (361 CAD), reaches the bowl walls (362 detected there. Accordingly, combustion was monitored
and 363 CAD) and bounces back to the center of the with the intensified CCD camera through the quartz liner.
chamber (365 and following CAD). One also notes the
effect of the swirl motion in the chamber that causes a Once again, the volumetric ratio was reduced to 15.2
clockwise rotation of the burning jets. These while other parameters were identical to those given in
measurements were repeated for the two other JWI Table 6. It was first checked that this decrease of the VR
parameters, 5.5 and 7.61 mm, but differences could did not affect the tendencies observed in the previous
hardly be noticed in the images. However, the analysis section. Figure 6 already shown that soot emissions also
of the corresponding pressure signals presented in grow at VR=15.2 when JWI is increased, although
Figure 14 gives interesting results. weaker in quantity. Figure 16 shows that auto-ignition
occurs approximately 2 CAD later in the cycle.
Accordingly, the premixed phase of the combustion,
which likely produces less soot than the combustion of
the fuel jets in the diffusion mode, is probably more
important at VR=15.2. This might be an element that
explains the decrease in soot emissions observed in
Figure 6.

Figure 14 : Pressure signals at different JWI. VR=17.2.

Indeed, one notes that pressure gets slightly higher at

low JWI. Burnt fractions were then calculated using a 0-
D thermodynamic analysis similar to that presented in
Ref. [13]. Corresponding results are presented in Figure
15 and indicate that combustion significantly improves as
JWI diminishes from 7.61 to 5.51 mm. This reveals a
Figure 16 : Burnt fraction at different JWI. VR=15.2.
faster and more efficient combustion process in
agreement with the decrease of the soot emissions It is also observed in this figure that the conclusions
observed at low JWI. drawn from Figure 15 still apply. As a result, one might
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expect a similar behavior of the optical engine at one of the fuel jets, on the left side of the images.
VR=15.2 with regard to the influence of JWI. Therefore, Therefore, the information found on the right side of
Figure 18 and Figure 19 present a temporal sequence of these images corresponds to combustion zones located
the combustion images in the squish area respectively at in front and behind the camera focus plane. Accordingly,
JWI=5.57 mm and JWI=7.07 mm. these zones seem to be tilted towards the axis of the
chamber. Taking this remark into account, one notes
from Figure 18 and Figure 19 that combustion actually
takes place in the squish area. As no light could be
detected in the vicinity of the reentrant, the combustion
365 process seems to evolve simultaneously in the bowl and
AI
CAD the squish area. Therefore, if more fuel is supplied and
burnt in this zone when JWI is decreased, the
combustion process is probably accelerated. This
mechanism might explain why combustion luminosity is
still large at 380 CAD in Figure 19 while it has almost
disappeared at the same crank angle for a lower JWI in
Figure 18.
361 370
CAD CAD CONCLUSION

The aim of this experimental study was to explain the

behavior of small-bore direct injection Diesel (DID)
engines with respect to the vertical position of the
common rail injector. For this purpose, optical
362 380 investigations were carried out in a single cylinder
CAD CAD common rail DID engine with optical access to the
combustion chamber and the squish area.

The parameter JWI (Jet Wall Impact) was defined to

characterize the position of the impact of the fuel jets in
the piston bowl. As these jets impact deeper in the bowl,
JWI increases. It was shown, as measured in production
363 390 engines, that soot emissions in the exhaust pipe of the
CAD CAD optical engine grow up as JWI is increased. Experiments
were carried out to understand this trend. They
essentially consisted of Laser Induced Exciplex
Fluorescence (LIEF) visualizations of liquid and vapor
phases of the fuel jets, as well as direct visualizations of
Figure 17 : Averaged combustion images in the piston bowl.
Temporal sequence at JWI=6.51 mm. VR=17.2. the combustion.

365 From the LIEF images, it was concluded that more vapor
fuel is directed to the squish area as JWI is decreased.
370 Moreover combustion images have indicated that the
375 squish area actively takes part to the combustion
380 process. In addition, the analysis of the pressure curves
acquired for the investigated combinations of JWI and
Figure 18 : Averaged combustion images in the squish area. volumetric ratios clearly show that combustion
Temporal sequence at JWI=5.57 mm. VR=15.2. completeness improves with decreasing JWI. This result
was in agreement with images of the combustion in the
370 squish area that suggested that combustion ends faster
375 when JWI is decreased.
380
It was therefore concluded that when fuel jets impact
Figure 19 : Averaged combustion images in the squish area. higher in the bowl, soot emissions might be reduced due
Temporal sequence at JWI=7.07 mm. VR=15.2. to locally leaner early stages of the combustion process
and/or better soot post-oxidation related to the
To analyze these images, one should remember that simultaneous combustion of fuel in the squish area and
combustion luminosity is integrated along the line of the piston bowl.
sight. The camera axis was set to be perpendicular to
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Finally, it has been shown in this study that the optical Visualization in a Transparent Model Diesel Engine,"
engine was a useful tool to investigate the behavior of SAE paper 1999-01-3648, 1999.
Direct Injection Diesel engines in relation to soot 8. Mokkadem, K., Bruneaux, G., and Baritaud, T.,
emissions and common rail injector position. In addition, "Liquid and Vapor Phase Penetration in a DI
JWI influences engine performances and should be Common Rail Diesel Engine Equipped with an
carefully tuned to avoid large soot emissions. inclined injector," 4th International Symposium on
Internal Combustion Diagnostics, Baden Baden,
ACKNOWLEDGMENTS Germany, 2000.
9. Bruneaux, G., "Liquid and Vapor Spray Structure in
This study was carried out in the framework of the High Pressure Common Rail Diesel Injection,"
Groupement Scientifique Moteurs (IFP, PSA and Atomization and Spray, vol 5, 2001.
Renault) which also provided the financial support. The 10. Le Coz, J.F. and Hermant, L., "Quantification of Fuel
technical expertise of Patrice Lessart is gratefully Concentrations and Estimation of Liquid/Vapor
acknowledged and the author would also like to thank Ratios in Direct Injection Gasoline Sprays by Laser-
Gilles Bruneaux for his helpful advises. Induced Fluorescence," SAE paper 2001-01-0916,
2001.
REFERENCES 11. Rotunno, A.A., Winter, M.A., Dobbs, G.M., and
Melton, L.A., "Direct Calibration Procedures for
1. Melton, L.A. and Verdieck, J.F., "Vapor/Liquid Exciplex Based Vapor/Liquid Visualization of Fuel
Visualization for Fuel Sprays," Comb. Sci. & Tech., Sprays," Comb. Sci. & Tech., 71:247, 1990.
42:217, 1985. 12. Dec, J. and Espey, C., "Chemiluminescence Imaging
2. Hodges, J.T., Baritaud, T.A., and Heinze, T.A., of Autoignition in a DI Diesel Engine," SAE paper
"Planar Liquid and Gas Fuel and Droplet Size 982685, 1998.
Visualization in a DI Diesel engine," SAE paper 13. Heywood, J.B., "Internal Combustion Engine
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