1. 1
CFD Evaluation of Fuel Injection Techniques in a DI Diesel
Engine to Control Emissions
Rahul Surianarayanan
Kettering University
Abstract
The various effects of different fuel injection
strategies/methods with EGR in a DI Diesel
Engine have been studied and evaluated using
CFD. These strategies aim towards enhanced
air-fuel mixing in order to minimize the peak
temperatures that leads to NOx formation.
EGR is used to help reduce peak in-cylinder
temperatures. The strategies used in this study
are the spilt injection and staggered injection
with small nozzle orifice diameters and high
injection pressures. The fuel is injected 10
degrees before TDC with 70% of fuel injected
first followed by the remaining 30% in the
second pulse. Results showed that a retarded
parallel injection reduces NOx emissions by
reducing the in-cylinder temperature. Also,
retarded injection reduces the ignition delay of
the first injection which causes the combustion
to begin close to TDC. An advanced injection
timing of 20 degrees BTDC with similar initial
conditions as the retarded injection was
simulated to improve peak pressure. A 78%
increase in NOx was noticed compare to
retarded injection due to an increase in peak
temperature. Thermal Efficiency is higher when
injecting 20 degrees BTDC compared to 10
degrees BTDC. An equal distribution of fuel
injected spatially across the cylinder showed
that there was much better mixing of air and
fuel in the available volume. Results showed
that peak pressure and temperature are higher
when fuel is injected early. This paper focuses
on optimizing these strategies for best results.
Introduction
Conventional diesel engines are overall lean-
burn systems; however the classical
heterogeneous nature of the high temperature
combustion (HTC) presents numerous
challenges regarding nitrogen oxides (NOx)
and particulate matter (PM) emissions. In such
diesel engines, the flames tend to initialize in
and propagate to regions where the air/fuel
ratios are near-stoichiometric, thus resulting in
an inherent NOx-PM trade off.
To meet the strict emission standards, modern
diesel engines utilize a range of advanced
combustion strategies such as splitting the
heat release into multi-events or shifting the
heat release away from the TDC.
As mentioned earlier when the primary focus
is on NOx emissions, the use of exhaust gas
recirculation (EGR) or retarded injection timing
has been proved effective. EGR replaces the
inlet charge of air with carbon dioxide and
water vapor from the exhaust that have high
specific heat capacities. The gases inside the
cylinder end up spending shorter periods of
time at high temperatures leading to lower NOx
formation. Gas temperatures within the cylinder
are reduced and oxygen concentration also
drops. The drop in oxygen concentration
impairs the oxidation process of soot.
Furthermore, retarding the injection timing also
tends to increase soot formation because of
decreasing temperatures during the expansion
stroke.
The fuel and air have less time to mix when
the ignition delay is small causing lower
combustion temperatures compared to an
advanced injection method.
This paper focuses on enhancing the air-fuel
mixing inside the sector geometry to achieve a
more uniform temperature distribution, hence
reducing the peak temperature and using an

2. 2
advanced injection timing to improve the peak
pressure for lower Brake Specific Fuel
Consumption(BSFC). Advanced injection
timing has a negative effect on NOx which
increases considerably. But soot reduces. In
order to lower emissions but also maintain the
peak pressure to achieve higher thermal
efficiency and Brake Specific Fuel
Consumption (BSFC), Exhaust Gas
Recirculation (EGR) is used. In addition to this,
a small nozzle hole diameter and high injector
velocity is used to accelerate the evaporation
of the fuel droplets. The nozzle orifice diameter
is varied from 0.12mm to 0.09mm. The
advantage of a smaller orifice is that the fuel
droplets are smaller and penetrate a shorter
distance. Reducing the injection velocity also
reduces the penetration distance. This means
that there are very less chances of the fuel
impinging the walls of the piston especially
when the injection timing is advanced. The
overall pressure inside the cylinder is less
when the fuel is injected 20 Degrees BTDC
compared to 10 Degrees BTDC, hence lower
pressures do not facilitate in faster evaporation
of fuel droplets because of lesser aerodynamic
drag on the droplet. To validate the use of a
small nozzle orifice diameter and high injection
velocity, a number of cases with varying orifice
diameter are run and compared. The injection
velocity is fixed at 550 m/s.
CFD Code and Initial Conditions
The computational mesh was created using
pointwise and used in AVL Fire. Due to the
symmetrical location of the injector at the
center of the combustion chamber, the
simulations are performed on 600 sector
meshes. The simulation starts from Intake
Valve Closure (IVC) to Exhaust Valve Opening
(EVO). The total number of cells at BDC add to
87540.
Figure 1: Computational Mesh modeled in
Pointwise.
The Combustion Model
The combustion model is based on the
Coherent Flame Model. The ECFM-3Z model
distinguishes between all three main regimes
relevant in diesel combustion, namely auto-
ignition, premixed flame and non-premixed, i.e.
diffusion combustion. The auto-ignition pre-
reactions are calculated within the premixed
charge of fuel and air, with the ignition delay
governed by the local temperature, pressure,
fuel/air equivalence ratio and the amount of
residual gas. Local auto-ignition is followed by
premixed combustion in the fuel/air/residual
gas mixture formed during the time period
between start of injection and auto-ignition
onset within the ECFM-3Z modeled according
to a flame propagation process. The third
regime is the one of diffusion combustion
where the reaction takes place in a thin zone
separates fuel and oxidizer.
The Turbulent mixing and spray
model
The amount of mixing is computed with a
characteristic time scale based on the k-e
model. For a diesel spray the fuel droplets are
very close to each other and are located in a
region essentially made of fuel. After the
evaporation of the fuel, an adequate time is
needed for the mixing from the nearly pure fuel

3. 3
region with the ambient air. In this case the
mixing of fuel with air is modeled by initially
placing the fuel into the pure fuel zone of the
ECFM-3Z model.
The Pollutant models
The Extended Zeldovich Mechanism was used
to predict NO formation in the CFD code. It is
well known that the formation of NO depends
mainly on three different processes, the
thermal NO, the prompt NO and the fuel
mechanism. Usually in automotive diesel
engine applications the third one can be
neglected because there is no significant
amount of nitrogen in the fuel. The two other
mechanisms can contribute to the NO
formation in engines, where mainly thermal NO
is formed, but also some amount of prompt NO
can appear. The model used for this work,
covers these two contributions.
The Hiroyasu model was also used to
anticipate the soot formation. Soot is generally
formed depending on the fuel composition, in-
cylinder gas pressure, in-cylinder gas
temperature and local fuel and oxygen
concentrations. The soot formation model used
is based upon a combination of suitably
extended and adapted joint chemical/physical
rate expressions for the representation of the
processes of particle nucleation, surface
growth and oxidation.
Initial Conditions
The specifications of the engine and initial
conditions that were used to run the simulation
are displayed below.
Bore (cm) 9.5
Stroke (cm) 10.5
Compression Ratio 16.72:1
Displacement (cm^3) 744.2629
Connecting Rod Length
(cm) 19.8
Squish Clearance (mm) 1.499
Table 2: Engine Specifications
Pressure (bar) 1.18
Density (kg/m^3) 1.31
Temperature (K) 314
Turbulent Kinetic Energy
(m^2/s^2) 35
Turbulent Length Scale (m) 0.005
Turbulent Dissipation Rate
(m^2/s^3) 6804.78
Swirl/Tumble (rpm) 3150
Engine RPM 1500
Stoichiometric Air-Fuel Ratio 14.45
Air-Fuel Ratio 21
EGR (%) 40
Table 2: Initial Conditions for AVL Fire
Injector Velocity (m/s) 550, 350
Beginning of Injection (CA
BTDC)
9 and 20
degrees
Spray Angle 1 145, 140, 130
Spray Angle 2 -15
Spray Cone Angle (Half
outer) 7
Injector Protrusion (mm) 1.5, 2
Injector Hole Size (mm)
0.12, 0.10,
0.09
Number of Holes 6, 12
Fuel Injected at 40% EGR
(mg) 4.85473
Table 3: Injector Specifications for AVL fire
Results obtained from CFD
1. Effects of EGR on
Combustions and Emissions
Using the meshed sector geometry a series of
cases were run all having the same initial and
injector specifications. The injection timing was
set to 700 to 708 degrees CA and method of
injection was an equally spilt injection. EGR
was varied from 10% to 40%.

4. 4
Figure 2: Mean Pressure (Pa) vs. Crank Angle
Pressure plots show a decrease in peak in-
cylinder pressure when EGR is used and
increased. For 40% EGR the peak pressure is
99.44 bar. As EGR is increased, the inlet
charge of air is replaced with carbon dioxide
and water vapor, hence the combustion
pressures are lower because. Achieving the
higher peak pressures is crucial for better
thermal efficiency and lower Brake Specific
Fuel Consumption (BSFC).
Figure 3: Mean Temperature (K) vs. Crank Angle
From the graph above it is clear that EGR by
itself is capable of reducing in-cylinder
temperatures from 2500K (0%EGR) to around
1600K (40%EGR). As EGR increases the
mean temperature drops. Lower peak
temperatures can be favorable for NOx
emission reduction but can impair soot
oxidation which we will see in the graph below.
Figure 4: Mass Fraction NOx at Exhaust Valve Open
(EVO)
For 0% EGR NOx emissions are 3897 ppm.
With 20% EGR it drops to 2863 ppm and the
least at 65 ppm at 40% EGR. With increase in
EGR there is an increase in ignition delay and
shift in the location of the whole combustion
process further towards the expansion stroke.
The gases spend lesser time in high
temperature regions leading to lower thermal
NOx.
Figure 5: Mass Fraction of Soot at Exhaust Valve
Open (EVO)
Use of EGR has a negative effect on soot
emissions. There is almost a linear increase in
soot emissions with increase in EGR. The
main reason for this is the reduction in the
amount of oxygen available to oxidize the
0.00
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10000000.00
12000000.00
14000000.00
16000000.00
500 600 700 800 900 1000
MeanPressure(Pa)
Crank Angle (Degrees)
Mean Pressure vs. CA
0% EGR 20%EGR 30%EGR 40%EGR
0
500
1000
1500
2000
2500
500 600 700 800 900 1000
MeanTemperature(K)
Crank Angle (Degrees)
Mean Temperature vs. CA
0% EGR 20%EGR 30%EGR 40%EGR
0
0.001
0.002
0.003
0.004
0%EGR 20%EGR 30%EGR 40%EGR
NOxMassFraction
%EGR
NOx Mass Fraction vs. %EGR
0.00E+00
1.00E-06
2.00E-06
3.00E-06
4.00E-06
5.00E-06
6.00E-06
7.00E-06
0% EGR 20%EGR 30%EGR 40%EGR
SootMassFraction
EGR %
Soot Mass Fraction vs. %EGR

5. 5
unburnt hydrocarbons. There is a reduction in
the equivalence ratio as EGR is increased.
2. Effect of Nozzle Orifice
Diameter on Emissions
A comparison of 3 nozzle orifice diameters
against emissions were tabulated. All these
cases were run 20 degrees BTDC.
Figure 6: NOx Mass Fraction vs. Crank Angle
It is understood that a nozzle orifice diameter
of 0.10 mm shows better reduction in NOx than
0.12 and 0.09 mm. The reason for this is,
beyond 0.10 mm the smaller orifice produces
even smaller droplets and results in faster
mixing of air and fuel. The improved mixing
yields a more rapid start of combustion, hence
a shorter ignition occurs. A shorter ignition
delay leads to higher temperatures and thus
higher NOx.
Figure 7: Soot Mass Fraction vs. Crank Angle
The soot emissions for an orifice diameter of
0.12mm is the lowest compared to 0.10 and
0.09 mm. Better air entrainment into the spray
cone for the smaller diameters and earlier
mixing of burned fuel-air elements with air
which leads to better soot oxidation. Also, for
smaller nozzle diameters (0.09 and 0.10mm)
the fuel penetration distance is shorter and can
also lead to a negative utilization of air
available. This leads to a rich local mixture
which is a source of CO and soot emissions.
Hence, the 0.12mm diameter works best for
this piston bowl geometry. This also proves
that there is a strong trade-off between piston
bowl design and orifice diameter.
Nozzle Orifice
Diameter
(mm)
Tailpipe NOx
Emissions
(ppm)
Tailpipe Soot
Emissions
(ppm)
0.12 65.3 6
0.1 53.7 7
0.09 60 6.52
Table 4: NOx and Soot for Different Nozzle Orifice
Diameters.
0
0.00001
0.00002
0.00003
0.00004
0.00005
0.00006
0.00007
500 600 700 800 900 1000
NOxMassFraction
Crank Angle (Degrees)
NOx Mass Fraction vs. CA
Nozzle Orifice Diameter:0.12mm
Nozzle Orifice Diameter:0.1mm
Nozzle Orifice Diameter:0.09mm
0
0.000002
0.000004
0.000006
0.000008
0.00001
0.000012
500 600 700 800 900
SootMssFraction
Crank Angle (Degrees)
Soot Mass Fraction vs. CA
Nozzle Dia -0.12mm Nozzle Dia -0.10mm
Nozzle Dia -0.09mm

6. 6
Figure 8: CO Mass Fraction vs. Crank Angle.
Carbon Monoxide (CO) emissions as expected
are higher for nozzle orifice size of 0.1mm and
0.09mm compared to 0.12mm due to shorter
penetration distance and bad utilization of air.
3. Effects of Injection Timing
 Parallel Spilt Injection
Injection timing is beneficial to study in order to
improve the efficiency of a diesel engine.
Increasing the injection timing improves the
indicated efficiency by increasing the mean
pressure and temperature inside the cylinder.
But it has a negative effect on NOx emissions
(increases) and positive effect on soot
(decreases).
In this study both advanced and retarded
injection timing have been tested. The method
of injection is a parallel injection method.
Figure 9: Peak Pressure vs. Injection Timing.
The retarded injection timing (9 degrees
BTDC) has a maximum pressure of 9274560
Pa, 4.8 degrees ATDC compared to 11129200
Pa, 2.2 degrees ATDC from an advanced
injection timing (20 degrees BTDC). The
combustion for the retarded injection starts at
TDC whereas for the advanced injection it
begins 3 degrees BTDC. Hence the gases
spend more time in high temperatures for the
advanced injection resulting in higher pressure
values.
Figure 10: Peak Temperature vs. Injection Timing.
Peak pressures and peak temperatures are co-
related to each other. This is why the retarded
injection timing (9 degrees BTDC) has a peak
temperature of 1535.38 K and the advanced
injection timing has 1771.5 K peak
temperature. Higher peak temperatures are
more favorable to NOx formation.
Figure 11: NOx Mass Fraction vs. Crank Angle.
To significantly reduce BSFC, we must
advance the injection timing up to a certain
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
600 700 800 900 1000
COMassFraction
Crank Angle (Degrees)
CO Mass Fraction vs. CA
Nozzle Orifice Diameter: 0.12mm -
Nozzle Orifice Diameter: 0.1mm
Nozzle Orifice Diameter: 0.09mm -
8000000.00
9000000.00
10000000.00
11000000.00
12000000.00
Pressure(Pa)
Peak Pressure vs. Injection Timing
Retarted Injection Timing Advanced Injection Timing
1400
1600
1800
PeakTemperature(K)
Peak Temperature vs. Injection
Timing
Retarded Injection Advanced Injection
0
0.00005
0.0001
0.00015
0.0002
0.00025
500 600 700 800 900 1000
MassFractionNOx
Crank Angle (degrees)
NOx Mass Fraction vs. CA
Retarded Injection Advanced Injection

7. 7
point. The increase in cylinder pressure and
temperature has a negative effect on NOx
emissions. The NOx tailpipe emission value for
an advanced injection timing is 236 ppm.
Whereas for the retarded injection it is 27 ppm.
Figure 12: Soot Mass Fraction vs. Crank Angle.
Soot tailpipe emissions for retarded injection is
16 ppm and 6 ppm for advanced injection. As
mentioned above the advanced injection timing
has a negative effect on NOx emissions but a
positive effect on Soot emissions. There are
possibilities that the fuel and air do not have
the time to mix thoroughly when the injection is
retarded because of a shorter ignition delay.
This is essentially bad utilization of air available
and results in rich zones of fuel which lead to
higher soot. In the advanced injection, fuel and
air have ample time to mix uniformly so the
burnt fuel is oxidized well. Over mixing of the
fuel and air can result in lean mixture formation
that favors NOx emissions. Hence, along with
an optimized injection timing, fuel injecting
methods have to be optimized too.
After these analysis it was concluded that to
obtain high pressure and low emissions, the
parallel spilt injection with advanced injection
timing is not the best combination. Although
the BSFC would be significantly less, the high
temperature leads to high thermal NOx.
The next set of results is from an injection
method of spraying equal amount of fuel
across the horizontal plane of the sector
geometry. This type of injection technique is
believed to result in much better air-fuel mixing
compared to the parallel injection because the
fuel is spread across a wider area.
Table 5: Comparison of Retarded and Advanced
Injection Timing in a Parallel Spilt Injection.
Figure 13: Parallel Spilt injection at Spray Angle 140
degrees.
Figure 14: Parallel Spilt injection at Spray Angle 130
degrees.
0
0.000002
0.000004
0.000006
0.000008
0.00001
0.000012
0.000014
0.000016
0.000018
0.00002
500 600 700 800 900 1000
SootMassFraction
Crank Angle (Degrees)
Soot Mass Fraction vs. CA
Retarded Injection Advacned Injection
Advanced Injection
Peak Pressure (Pa)
Peak Temperature (K)
Tailpipe NOx
Emissions (PPM)
Tailpipe Soot
Emissions (PPM)
Parallel Spilt Injection
1771.5, 3.8 degrees
ATDC
1535.38, 10
degrees ATDC
27 236
616
Retarded Injection
9274560, 4.8
degrees ATDC
11129200, 2.2
degrees ATDC

8. 8
Figure 15: Fuel Impingement at a Higher Spray
Angle (145 degrees) at a Retarded Timing.
Figure 16: Fuel Mass Fraction for Parallel Spilt
Injection (Front View of the sector).
 Equally Spilt Injection Method
Figure 17: Mean Pressure vs. Crank Angle.
The peak pressure for the advanced injection
is 10491400 Pa 1.6 degrees ATDC. The peak
pressure for the retarded injection is 9407410
Pa 6.7 degrees ATDC. Compared to the
parallel spilt injection, the peak pressure for
advanced injection timing is lesser for the
equally spilt injection.
Figure 18: Mean Temperature vs. Crank Angle.
As expected the peak temperature for the
advanced injection method is higher than the
retarded injection method. The temperature at
TDC for retarded injection is 816.63 K and
1615.44 K for advanced injection. There is
once again a drop in temperature by employing
the equally spilt injection method compared to
parallel injection method.
Figure 19: NOx Mass Fraction vs. Crank Angle.
Here although the retarded injection timing has
34.4 ppm of tailpipe NOx emissions compared
to 70 ppm from the advanced injection, it is
important to recollect that for the parallel spilt
0
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MeanPressure(Pa)
Crank Angle (degrees)
Mean Pressure vs. CA
Retarded injection Advanced Injection
0
200
400
600
800
1000
1200
1400
1600
1800
500 600 700 800 900 1000
MeanTemperature(K)
Crank Angle (Degrees)
Mean Temperature vs. CA
Retarded Injection Advanced Injection
0
0.00001
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0.00003
0.00004
0.00005
0.00006
0.00007
0.00008
500 600 700 800 900 1000
NOxMassFraction
Crank Angle (Degrees)
NOx Mass Fraction vs. CA
Retarded Injection - Advanced Injection -

9. 9
injection method with advanced injection timing
produced 236 ppm of tailpipe NOx. Hence, it
can be confidently said that the equally spilt
injection method helps reduce peak
temperatures and NOx.
Figure 20: Soot Mass Fraction vs. Crank Angle.
The tailpipe soot emissions for advanced
injection is higher (10 ppm) than for retarded
injection timing (7ppm). This pattern is
contradicting to the soot emissions in a parallel
spilt injection method. In that case the
advanced injection timing read a lower soot
value (6 ppm) than the retarded injection (17
ppm). This behavior could be again attributed
to the air-fuel mixing parameter. When equally
spilt at a retarded injection time the fuel is
mixing better with the air in the time available
and oxidizes better than when it is spilt by
parallel injection.
Table 6: Comparison of Retarded and Advanced
injection timing in an Equally Spilt Injection.
Figure 20: Equally Spilt Injection (Top view of the
sector).
Figure 21: Fuel Mass Fraction Formation for an
Equally Spilt Injection.
 Staggered Injection:
The last method of injection used in this study
is the staggered injection. This injection
technique is by again splitting the main
0
0.000002
0.000004
0.000006
0.000008
0.00001
0.000012
0.000014
0.000016
0.000018
500 600 700 800 900 1000
SootMassFraction
Crank Angle (Degrees)
Soot Mass Fraction vs. CA
Retarded Injection - Advanced Injection -
Retarded Injection Advanced Injection
Peak Pressure (Pa)
Peak Temperature (K)
Tailpipe NOx
Emissions (PPM)
Tailpipe Soot
Emissions (PPM)
7034.4
7 10
Equally Spilt Injection
1600.81, 9 degrees
ATDC
1647.72, 3.6 degrees
ATDC
10496700, 1.6
degrees ATDC
9407410, 6.7
degrees ATDC

10. 10
injection into two pulses, typically sprayed at
the same crank angle with equal amount of fuel
in each pulse. To achieve a better mixing of air
and fuel in the upper region and lower region of
the sector geometry the injectors are located at
different heights and sprayed at different
angles. One higher than the other. Since an
advanced injection timing is used to achieve
better thermal efficiency and lower BSFC, the
same injection timing is used in this case.
Results for staggered injection
Figure 22: Mean Pressure vs. Crank Angle.
Figure 23: Mean Temperature vs. Crank Angle.
Figure 24: NOx Mass Fraction vs. Crank Angle.
Figure 25: Soot Mass Fraction vs. Crank Angle.
The peak pressure was 10436200 Pa and
peak temperature 1636.5 K. NOx emissions
are 70 ppm followed by soot with 10 ppm.
These results are very close to the results
obtained from the equally spilt injection with
advanced injection timing. Therefore, it is
understood that the staggered injection
technique does not in any way improve the
peak pressure and give lower emissions
compared to the equally spilt injection method.
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690 740 790 840 890 940
MeanPressure(Pa)
Crank Angle (Degrees)
Mean Pressure vs. CA
0
200
400
600
800
1000
1200
1400
1600
1800
690 740 790 840 890 940
MeanTemperature(K)
Crank Angle (Degrees)
Mean Temperature vs. CA
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NOxMassFraction
Crank Angle (Degrees)
NOx Mass Fraction vs. CA
0
0.000005
0.00001
0.000015
0.00002
690 740 790 840 890 940
SootMassFraction
Crank Angle (Degrees)
Soot Mass Fraction vs. CA

11. 11
Conclusion:
This paper focuses on improving the
combustions and emissions in a DI diesel
engine by controlling the various parameters
that influence air-fuel mixing inside the
cylinder. Since a significant portion of the
combustion process in DI diesel engines takes
place in diffusion flames, the rates of chemical
reaction and of heat release are controlled by
the rates of air-fuel mixing. The method of fuel
injection and injection timing is also very
important to achieve a high peak pressure and
low temperatures to control the emissions.
Higher peak pressures are beneficial for higher
thermal efficiency and lower Brake Specific
Fuel Consumption (BSFC).
 A small nozzle orifice diameter produces
smaller droplets of fuel which evaporate
and mix faster with the air. However, the
The penetration distance also reduces
with reducing the orifice diameter hence
could result in bad utilization of air. This
impairs the soot oxidation process. A
nozzle orifice diameter of 0.10 mm
produced the least NOx compared to
0.12 and 0.09 mm. In the case of soot
0.12 mm had the best result compared
to 0.10 and 0.09mm.
 The effect of spray angle for better air-
fuel mixing is significant. Higher spray
angles result in fuel-wall impingement
which can lead to reduced fuel economy
and higher emissions of unburnt
hydrocarbons. Typically, when there is
fuel-wall interaction the fuel sticks to the
walls of the cylinder for a few
milliseconds until it completely
evaporates and burns. During that time,
the process of evaporation is slow and
leads to high possibilities of rich zones.
This rich zone can cause the formation
of soot in that zone when the fuel in
burnt. The same effect is noticed when
the spray angle is very low. The spray
angles used for this study are 145, 140
and 130 degrees.
 Injection timing is the next important
parameter to optimize for lower
emissions and higher peak pressures.
Ab advanced injection timing (20
degrees BTDC) can result in higher
peak pressures but also higher
emissions. A retarded injection timing (9
degrees BTDC) results in lower
emissions but also lower peak
pressures. To get the best of both, the
direction of fuel sprayed must be
observed and corrected since it can
directly influence how uniform of an air-
fuel mixture is achievable. This along
with a smaller orifice diameter and
higher injection velocity can accelerate
the process of air-fuel mixing.
 The parallel spilt injection method
proved effective for achieving higher
peak pressures when injected early but
lead to very high NOx emissions.
Hence, the equally spilt injection method
was used to achieve both high peak
pressures and low emissions. The best
emission result for this method was 53.5
ppm of NOx and 7 ppm of Soot. The
peak pressure was 10032800 Pa and
peak Temperature was 1597K. Beyond
1600K, it is noted that NOx emissions
significantly rise. Hence, in this study
the peak temperatures are aimed to
maintain under 1600K.
 The staggered injection method did not
prove to improve the emission results or
peak pressure any better than the
equally spilt injection method.
 EGR is very useful tool for reducing in-
cylinder temperatures and NOx.
 A lot more of research involving the
various combustion models, emission
models, engine loads, EGR, air-fuel
ratio, equivalence ratio, injection
methods and strategies along with
detailed CFD are need to further reduce
the NOx emissions.

12. 12
Acknowledgments:
I would like to whole heartedly thank Dr.
Bassem Ramadan for giving me this chance to
perform this study.
References:
1. Bae, M.-w. (1999). A Study on the Effects of
Recirculated Exhaust Gas Upon NOx and Soot
Emissions in Diesel Engines with Scrubber EGR
System. SAE Technical Paper Series (p. 12).
SAE International.
2. 2. Berstrand, P., & Denbratt, I. (2001). Diesel
Combustion with Reduced Nozzle Orifice
Diameter. SAE Technical Paper Series (p. 12).
Sweden: SAE International.
3. 3. Boot, M., Rijk, E., Luijten, C., Somers, B., &
Albercht, B. (2010). Spray Impingement in the
Early Direct Diesel Injection Premixed Charge
Compression Ignition Regime. SAE Technical
Paper Series (p. 12). SAE International.
4. 4. Deshpande, J. S. (2005). Effect of Injection
Timing Retard on Emissions and Performance of
a Pongamia Oil Methyl Ester Fuelled CI Engine.
SAE International, (p. 15). Nagpur.
5. 5. Dodge, L. G., Simescu, S., Neely, G. D.,
Dickey, M. J., & Saonen, C. L. (2002). Effects of
Small Holes and High injection Pressures on
Diesel Engine Combustion. SAE Technical
Paper Series (p. 8). SAE International .
6. 6. G, B. A. (2001). Control of Diesel Engine
Pollutants by Spilt Injection Method using
Multizone Model. (p. 5). SAE International.
7. 7. Hountalas, D. A., Binder, K. B., & Schnabel,
A. R. (2001). Using Advanced Injection Timing
and EGR to Improve DI Diesel Engine Efficiency
at Acceptable NO and Soot Levels. SAE
Technical Paper Series (p. 16). SAE
International.
8. 8. Peng, R. M., & Mirsalim, S. M. (2011). CFD
Evaluation of Effects of Spilt Injection on
Combustion and Emissions in a DI Diesel
Engine. SAE Technical Paper Series (p. 12).
SAE International.
9. 9. Ramadan, B. H., Charles L. Gray, J.,
Hamady, F. J., Squibb, C., & Schock, H. J.
(2011). The Effect of Piston Bol Geometry and
Spray Configuration on Diesel Combustions and
Emissions. ASME Internal Combustion Engine
Division, (p. 15). West Virginia.
10. 10. Ramadan, B., & Wadkar, C. (2016). A
Numerical Study on the Effect of Enhanced
Mixing on Combustions and Emissions on
Diesel Engines., (p. 14).
11. 11. Usman Asad, M. Z. (2008). Fuel Injection
Strategies to Improve Emissions and Efficiency
of High Compression Ration Diesel Engines.
SAE Technical Series Paper (p. 14). University
of Windsor: SAE International.
CONTACT INFORMATION:
Rahul Surianarayanan
2026 Monteith St.
Flint, Michigan – 48504, USA.
Phone: 810-814-7013
E-mail: suri5832@kettering.edu
ABBREVIATIONS USED:
CA – Crank Angle
ATDC – After Top Dead Center
BTDC- Before Top Dead Center
EVO – Exhaust Valve Open
IVC – Intake Valve Closure
EGR – Exhaust Gas Recirculation
BSFC – Brake Specific Fuel Consumption