Theoretical Study of the Effect of Injection Timing Malfunction on DI Diesel Engine Performance and Combustion Characteristics

Abstract

In the present study a theoretical investigation was performed relative to the effect of fuel injection timing malfunction, which was considered as retardation compared to the nominal value at a certain operating point, on the performance and combustion characteristics of a single-cylinder high-speed direct injection (DI) diesel engine. The examination of fuel injection timing retardation on DI diesel engine performance and combustion characteristics was based on the use of a closed cycle engine simulation model and of a cylinder pressure processing and combustion analysis model. The engine simulation model was used to generate cylinder pressure profiles for four different values of fuel injection timing. The cylinder pressure profiles were supplied to a combustion analysis model developed under a diploma thesis conducted in Hellenic Naval Academy. The combustion analysis model provided results for various performance characteristics and combustion characteristics. The examination of the combustion analysis model results showed that the retardation of injection timing results in considerable deterioration of diesel engine performance parameters and combustion characteristics and thus, it can be considered as an engine malfunction, which require specific maintenance actions.

Full text

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Theoretical Study of the Effect of Injection
Timing Malfunction on DI Diesel Engine
Performance and Combustion
Characteristics
T.C. Zannis1, M. Kourampas1, E.A. Yfantis2, J.S. Katsanis1, E.G. Pariotis1, R.G. Papagiannakis3
1 Section of Naval Architecture and Marine Engineering, Hellenic Naval Academy, Piraeus, Greece
2 College of Engineering, University of Nicosia, Nicosia, Cyprus
3 Section of Thermodynamics and Propulsion Systems, Hellenic Air Force Academy, Dekelia, Greece
ABSTRACT
In the present study a theoretical investigation was performed relative to the effect of fuel injection timing malfunction, which was considered
as retardation compared to the nominal value at a certain operating point, on the performance and combustion characteristics of a single-cylinder
high-speed direct injection (DI) diesel engine. The examination of fuel injection timing retardation on DI diesel engine performance and combustion
characteristics was based on the use of a closed cycle engine simulation model and of a cylinder pressure processing and combustion analysis model.
The engine simulation model was used to generate cylinder pressure profiles for four different values of fuel injection timing. The cylinder pressure
profiles were supplied to a combustion analysis model developed under a diploma thesis conducted in Hellenic Naval Academy. The combustion
analysis model provided results for various performance characteristics and combustion characteristics. The examination of the combustion analysis
model results showed that the retardation of injection timing results in considerable deterioration of diesel engine performance parameters and
combustion characteristics and thus, it can be considered as an engine malfunction, which require specific maintenance actions.
INTRODUCTION
Diesel engine is widely known for its high thermal efficiency, which is superior compared to the efficiencies of spark-
ignition engines, gas turbines and steam turbines (Heywood,1988). Specifically, the thermal efficiency of modern four-
stroke (4-S) diesel engines is close to 50% whereas the thermal efficiency of two-stroke diesel engines is close to 55%.
Diesel engines indicate also very high availability; high reliability and low maintenance needs and for this reason and also
due to their high thermal efficiency are selected as prime movers in most of the land-based and marine transport
applications. However, diesel engine parts have a certain operational life and, depending on engine use and efficient
maintenance, diesel engines may encounter specific malfunctions, which if not identified on time and treated efficiently may
lead to severe engine failures (Greuter and Zima,2012). According to Greuter and Zima (2012) the higher proportion of
diesel engine malfunctions and failures are related to the in-cylinder physical and chemical processes. Fuel injection process
has a direct and determinant influence on in-cylinder processes and thus, it affects directly diesel combustion mechanism
and through this, it controls diesel engine performance and combustion characteristics and also in-cylinder pollutant
formation (Dec,1997;Heywood,1988). Consequently, diesel injection system malfunctions such as excessive fuel pump
blow-by losses and loss of injection pressure, fuel injector tip blocking and injector needle lift retardation have a direct
detrimental influence on diesel engine performance and combustion parameters since they alter significantly all in-cylinder
physical and chemical processes having thus, a profound negative effect on diesel combustion mechanism. Especially, fuel
injection timing determines the initiation of in-cylinder fuel injection, atomization and vaporization and thus, it controls
diesel combustion mechanism. Studies conducted in the past have considered the use of injection timing advancement as a
mean for increasing diesel engine indicated power and thermal efficiency and combined injection timing advancement with
other technologies such as exhaust gas recirculation (EGR) for controlling diesel emitted pollutants (Hountalas et

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al.,2005;Hountalas,2000;Kouremenos et al.,2001). However, there is a lack of information regarding the effect of fuel
injection timing retardation as a result of needle lifts retardation on direct injection (DI) diesel engine combustion
mechanism and its main characteristics. For this reason, in the present study a theoretical investigation is performed to
assess the influence of fuel injection timing retardation, which is considered as engine malfunction, on the performance and
combustion characteristics of a single-cylinder high-speed 4-S DI diesel engine. Specifically, a close cycle engine simulation
model, based on a multi-zone combustion model, is used upon experimental validation for generating cylinder pressure
profiles for a nominal injection timing (i.e. 15 degCA BTDC) value at 2500 rpm and at 80% of full load and three retarded
injection timings (i.e. 14, 13 and 12 degCA BTDC) compared to the nominal value. Afterwards, the cylinder pressure
profiles are supplied to a cylinder pressure processing and combustion analysis model, which was developed in Hellenic
Naval Academy under a diploma thesis. The processing of cylinder pressure profiles result in the production of theoretical
results for main engine performance parameters such as indicated power, indicate mean effective pressure (IMEP) and
indicated specific fuel consumption (ISFC) and for combustion characteristics such as ignition angle, ignition delay and the
combustion durations of individual phases of diesel combustion mechanism. The examination of the theoretical results for
engine performance and combustion parameters showed that the retardation of injection timing affects negatively the diesel
combustion mechanism resulting in reduction of diesel engine power and thermal efficiency through shifting of diesel
combustion towards expansion stroke.
DESCRIPTION OF ENGINE SIMULATION AND COMBUSTION ANALYSIS MODELS
Brief Description of the Closed Diesel Engine Simulation Model
In the present study a closed cycle diesel engine simulation model based on a two-dimensional multi-zone combustion
model was properly modified and used for generating in-cylinder pressure profiles for all examined injection timing values
(Rakopoulos et al.,2004;Zannis,2006;Zannis and Hountalas,2004). The specific closed cycle engine simulation model was
developed at the past in the Internal Combustion Engines Laboratory of National Technical University of Athens under a
Phd thesis (Zannis,2006). According to the multi-zone combustion model concept, fuel jet is divided during in-cyinder
injection process into discrete control volumes called “zones” (Jung and Assanis,2001;Zannis,2006). Each fuel jet zone is
treated as an open thermodynamic system, which exchanges energy and mass with its in-cylinder surroundings. Fuel jet
discretization into “zones” allows the prediction of zone temperature and chemical composition at each crank angle degree
step. In Figure 1 is shown a representative schematic view of the fuel jet distribution into zones at the axial and the radial
direction inside the cylinder as well as the effect of swirled intake air movement on fuel jet formulation (Rakopoulos et
al.,2004;Zannis,2006;Zannis and Hountalas,2004).
Figure 1 Schematic View of the Intake Air Flow Field and one of the Fuel Jets in a Plane Perpendicular to the Cylinder Axis
(Zannis, 2006)

The thermodynamic conditions inside each fuel jet zone are predicted using the first law of thermodynamics and the
mass and momentum conservation laws in differential forms whereas the in-cylinder pressure is considered to be uniform

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at each crank angle degree step. Jet zone temperature variation rate depends directly to the energy released inside the jet
zone due to induction of vaporized fuel mass and of swirled air mass, to instantaneous zone heat losses, to the variation of
zone gas mixture internal energy and to the elementary technical work. A first-order ordinary differential equation (ODE) is
generated by combining equations for first law of thermodynamics and in-cylinder gas equation of state. Also a number for
first-order ODEs are formulated for all considered fuel jet zones using the energy, mass and momentum conservation laws
in differential forms. Hence, a set of first-order ODEs is developed, which is numerically solved using a non-stiff predictor
– corrector method, providing thus predictions for each zone temperature and in-cylinder pressure at each crank angle
degree step. The specific closed cycle engine simulation model contains also detailed physical and chemical models for fuel
injection process, fuel jet development and atomization, fuel vaporization, ignition delay, combustion rate, chemical
equilibrium and in-cylinder soot and NO formation. More detailed descriptions of the aforementioned closed cycle diesel
engine simulation model can be retrieved from the following references (Rakopoulos et al.,2004;Zannis,2006;Zannis and
Hountalas,2004).
Brief Description of the Diesel Engine Performance and Combustion Analysis Model
A diesel engine experimental data processing and performance and combustion analysis model was developed under a
diploma thesis in Hellenic Naval Academy (Kourampas,2018). The specific model receives as input raw experimental data
of cylinder pressure, fuel injection pressure and TDC position, which have been obtained from a diesel engine cylinder over
many consecutive cycles. Usually cylinder pressure is measured in internal combustion engines using a piezoelectric
transducer whereas a piezoelectric transducer is usually used for fuel injection pressure recording at the high pressure
pipeline connecting the fuel injection pump with the fuel injector (Bueno et al.,2009;Bueno et al.,2011;Bueno et al.,2012). A
problem raised with cylinder pressure and injection pressure measurements is that each cylinder and injection pressure
should be matched with a corresponding crank angle for generating a cylinder pressure – crank angle and an injection
pressure – crank angle profile for each measured engine cycle (Hountals and Anestis,1998). Hence, the developed
performance and combustion analysis model is generating cylinder pressure and injection pressure profiles for each
measured cycle and also mean cylinder pressure and injection pressure profiles over all measured cycles by correlating
cylinder pressure and injection pressure data with TDC position data (Ding et al.,2011;Roth et al.,2002;Stas,1996). The
mean cylinder pressure and injection pressure profiles obtained at each engine operating point are then used for the
calculation of engine performance characteristics such as indicated work/power, brake work/power, ISFC, IMEP, indicated
and brake efficiency and dynamic injection timing. The combustion analysis model is also using the mean cylinder pressure
profile at each operating case for performing a heat release rate analysis. Specifically, the differential expression of the first
law of thermodynamics and ideal gas equation of state during closed engine cycle provides the two following equations:
bl
V
dQ dQ dV dT
pmc
dd d djj j j
-= + (1)
dV dp dT
pV mR
dd djj j
+= (2)
In Eq. (1) the term b
dQ
djis called gross heat release rate whereas the difference bl
dQ dQ
ddjj
- is called net heat release rate and
it can be determined from the following differential equation (Kourampas,2018;Heywood,1988):
(1 )
net b l V V
dQ dQ dQ c c
dV dp
pV
ddd RdRdjjj j j
=-=+ + (3)
The term l
dQ
djin Eqs (1) and (3) corresponds to the instantaneous heat losses of the in-cylinder gas mixture, which are

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transferred to the cylinder walls and to the cylinder head through mainly convection and flame radiation. For this reason, in
the present analysis the instantaneous heat flux from the cylinder gas mixture to the cylinder walls and to the cylinder head
is calculated using Annand’s semi-empirical model, which takes into account both cylinder gas convection and flame
radiation (Annand,1963;Heywood,1988):
0.7 4 4
Re ( ) ( )
g
cgwgw
qa TT c T
D
ls=-+T-
 (4)
where:
 Tg is the in-cylinder bulk gas temperature at each crank angle, which is calculated through ideal gas equation of state
using instantaneous cylinder pressure and instantaneous cylinder volume.
 Tw is the mean temperature of cylinder walls and the corresponding mean temperature of the cylinder head.
 σ Stephan- Boltzmann radiation constant (5.67x108 W/m2K4).
 λg is the in-cylinder gas thermal conductivity, which is calculated using a polynomial expression of the in-cylinder gas
temperature.
 Re is the dimensionless Reynolds number, which is equal to Dsn/30νg, where D is the cylinder bore, s is the piston
stroke and νg is the in-cylinder gas kinematic viscosity.
Hence the aforementioned heat release rate analysis of the cylinder pressure profile at each operating point can derive
results for the instantaneous gross and net heat release rate, the cumulative gross and net heat release rate, the ignition
angle, the ignition delay and also the combustion duration of 5%, 25%, 50% and 90% of total injected fuel mass per engine
cycle.
DIESEL ENGINE AND FUEL DESCRIPTION
The diesel engine examined in the present study is the “Lister LV1” test engine, which was installed in the Internal
Combustion Engines Laboratory of National Technical University of Athens, Greece. The specific engine is four stroke,
direct injection, and single cylinder, naturally aspirated and bowl-in-piston diesel engine. Its cylinder bore is equal to 85.73
mm and its piston stroke is equal to 82.55 mm. The specific diesel engine was connected to a hydraulic brake for power
absorption. “Lister LV1” engine was equipped with a conventional high pressure reciprocating fuel pump, which was
connected with engine’s camshaft whereas dynamic injection timing variation in the specific engine can be attained through
variation of static injection timing. The specific engine was equipped with a piezoelectric transducer placed on the cylinder
head for recording in-cylinder pressure, with a piezoelectric transducer for recording fuel injection pressure and a magnetic
pick-up placed on the engine’s flywheel for recording TDC position signal. Cylinder pressure, injection pressure and TDC
position signals are transferred to amplifiers and then were collected to a personal computer through a fast acquisition
multi-channel card. The diesel oil considered in the present analysis is a Finnish summer grade city diesel, which was
prepared along with other 12 fuels under a European research project aiming to the identification of the effect of fuel
composition and properties on DI diesel engine performance characteristics and pollutant emissions (NEDENEF,2003).
The specific fuel was used as basis for the preparation of all the other fuels and for this reason was called “D1 – Base fuel”.
The “base fuel” has lower heating value (LHV) equal to 43.03 MJ/kg and its Cetane number is equal to 53.3. More details
about the chemical composition and the physical and chemical properties of the specific diesel oil can be found in
references (NEDENEF,2003;Rakopoulos et al.,2004;Zannis,2006;Zannis and Hountalas,2004).
RESULTS AND DISCUSSION
Experimental Validation of Engine Simulation Model Predictions for In-Cylinder Pressure
Before performing the theoretical examination of the effect of injection timing retardation on the combustion
characteristics of the single-cylinder high-speed DI diesel engine “Lister LV1” at 2500 rpm, it is of utmost importance to

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validate the predictive ability of the close cycle diesel engine simulation. Specifically, it should be assessed whether the
engine simulation model predicts in-cylinder pressure during the entire diesel engine closed cycle with sufficient accuracy.
This should be done to ensure that in-cylinder pressure profile predictions for all examined injection timing values are
accurate and reliable. For this reason in Figure 2 is shown a comparison of predicted and experimental results for in-
cylinder pressure of the “Lister LV1” diesel engine at 2500 rpm and at 80% of full engine load. In-cylinder pressure
predictions shown in Figure 2 were generated using the closed cycle engine simulation model for mean injection pressure
equal to 238 bar, fuel consumption rate equal to 1.19 kg/h, fuel injection timing 165 degCA after BDC (15 degCA BTDC)
and compression ratio equal to 17.1:1. Experimental in-cylinder pressure profile shown in Figure 2 corresponds to the mean
cylinder profile, which was calculated from processing of experimental data for cylinder pressure obtained over many
concecutive engine cycles during a detailed experimental investigation performed in the past with various test fuels
(NEDENEF,2003;Rakopoulos et al.,2004;Zannis,2006;Zannis and Hountalas,2004). According to Figure 2, it is observed
that the closed cycle engine simulation model predicts with sufficient accuracy the in-cylinder pressure either during
compression stroke both during combustion and expansion stroke. Hence, the main thermodynamic parameter (i.e., in-
cylinder pressure) characterizing in-cylinder phenomena evolution during closed engine cycle is accurately predicted by the
engine simulation model. Consequently, the specific engine simulation model can reliably be used for generating close cycle
in-cylinder pressure profiles for all values of injection timing variation considered in this study allowing thus, through their
processing, the assessment of injection timing influence on diesel engine combustion mechanism and its relative
characteristics.
Figure 2. Comparison of Theoretical and Experimental Values of In-Cylinder Pressure. Modeling and Experimental Results are
given for Single-Cylinder High-Speed DI Diesel Engine “Lister LV1” at 2500 rpm and 80% of full load.
Effect of Injection Timing Retardation on DI Diesel Engine Performance and Combustion Characteristics
Having examined and secured that the closed cycle engine simulation model predicts with sufficient accuracy the
variation of in-cylinder pressure with crank angle during all phases of a closed engine cycle, a theoretical investigation of the
effect of injection timing retardation on the performance parameters and the combustion characteristics of the 4-S high-
speed single-cylinder DI diesel engine “Lister LV1” using the fuel D1-base. Specifically, it is examined the influence of fuel
injection timing retardation (late start of injection) compared to the nominal value of injection timing at 2500 rpm and at
80% of full load of “Lister LV1” engine on the indicated power, the ISFC, the instantaneous net heat release rate, the
cumulative net heat release rate, the ignition angle, the ignition delay and the combustion durations of 5%, 25%, 50% and
90% of total fuel injected mass per engine cycle. The values of fuel injection timing examined in this theoretical
examination are: 165 degCA ABDC (15 degCA BTDC – Nominal value of injection timing at 2500 rpm and at 80% of full
load), 166 degCA ABDC (14 degCA BTDC), 167 degCA ABDC (13 degCA BTDC) and 168 degCA ABDC (12 degCA
BTDC).
In Figure 3 is shown the effect of injection timing retardation on in-cylinder pressure predictions of “Lister LV1”,
which were generated using the closed cycle engine simulation model. Simulations were performed considering the chemical
composition and the chemical and physical properties of the base diesel fuel and cylinder pressure predictions were
produced for four injection timings namely 15 degCA (Nominal value at 2500 rpm and at 80% of full load), 14 degCA, 13

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degCA and 12 degCA. According to Figure 3, the retardation of fuel injection timing results in the considerable reduction
of in-cylinder pressure during combustion phase around TDC providing thus, a noticeable reduction of maximum
combustion pressure. The higher reduction of cylinder pressure during combustion phase is observed in the case of 12
degCA. The reduction of cylinder pressure during combustion phase with retarded injection timing is closely related, as will
be evidenced more clearly below, with the retardation of combustion initiation. It should be mentioned here that the
cylinder pressure variations caused by the delay in the start of injection will result in small variations in engine load and
rotational speed. It should be also commented that the delay in the start of injection does not bring noticeable variations in
cylinder pressure during late expansion stroke just before exhaust valve opening.
Figure 3. Effect of Injection Timing Retardation on Cylinder Pressure Predictions of ‘Lister LV1” DI Diesel Engine. Theoretical
Results for Cylinder Pressure are given at 15 degCA BTDC (Nominal Value at 2500 rpm and at 80% of full load), 14 degCA
BTDC, 13 degCA BTDC and 12 degCA BTDC.

In Figure 4 is shown the effect of injection timing retardation on the instantaneous net heat release rate (Figure 4(a)),
on the cumulative net heat release rate (Figure 4(b)) and the instantaneous in-cylinder bulk gas temperature (Figure 4(c)). All
theoretical results shown in Figure 4 were generated with the cylinder pressure processing and combustion analysis model
for four injection timings namely 15 degCA BTDC (Nominal value at 2500 rpm and at 80% load), 14 degCA BTDC, 13
degCA BTDC and 12 degCA BTDC of “Lister LV1” test engine. As observed from Figure 4(a), the retardation of injection
timing results in combustion initiation delay and to the suppression of premixed combustion phase intensification, which
eventually results in reduction of peak net heat release values during premixed combustion period. In other words, injection
timing retardation results in less reactive premixed combustion phase and in reduced peak combustion-released energy
values. On the other hand, the delay in start of injection results in the intensification of combustion energy released during
diffusion-controlled combustion phase. Hence, the delay in in-cylinder injection process commencement leads to a lower
injected fuel mass proportion burned in a premixed-controlled mode and a higher fuel mass proportion burned in a
diffusion-controlled mode. This observation means that the retardation of injection process initiation results in a diesel
combustion shift to the expansion stroke enhancing thus, the combustion-released energy rate during downward piston
movement from BDC to TDC. The effects of the delay in in-cylinder fuel injection process commencement on
instantaneous net heat release rate evidenced in Figure 4(a) are reflected also in the the cumulative net heat release rate
values shown in Figure 4(b). Specifically, according to Figure 4(b), the retardation of injection timing by 3 degrees
compared to the nominal value reduces significantly the cumulative combustion-released energy during the initial stages of
combustion, where in-cylinder physically and chemically prepared mixture is burned homogeneouslyw whereas promotes
the pertinent mixture-burning energy during the expansion stroke, where the in-cylinder combustion rate is governed by the
amount of vaporized fuel entrained the combustion zones. Finally, as witnessed from Figure 4(c), the delay in injection
process initiation results in delayed in-cylinder bulk gas temperature elevation due to combustion and in the curtailment on
bulk gas temperarure rise during premixed combustion phase. Oppositely, according to Figure 4(c), the retardation of
injection timing results in higher in-cylinder gas temperatures during expansiojn stroke, where in-cylinder flame propagation
is governed by diffusion. Consequently, the delay of in-cylinder fuel injection process commencement results in the increase
of exhaust gas temperature just before exhaust valve opening due to combustion shift towards expansion. This is a strongly

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undesirable phenomenon for engine operational integrity since high exhaust gas temperatures can result in considerable
thermal loading of exhaust valves and also can result in fire initiation in the exhaust outlet possibly due to lubricant oil
ignition.
(a) (b)
(c)
Figure 4. Effect of Injection Timing Retardation on (a) Instantaneous Net Heat Release Rate, (b) Cumulative Net Heat Release
Rate and (c) In-Cylinder Bulk Gas Temperature. Results of the Combustion Analysis Model are given for the Single-Cylinder
High-Speed DI Diesel Engine ‘Lister LV1’ at 15 degCA BTDC (Nominal Value at 2500 rpm and at 80% of full load), 14 degCA
BTDC, 13 degCA BTDC and 12 degCA BTDC.

In Figure 5 is shown the influence of injection timing retardation on the indicated power (Figure 5(a)), the ISFC
(Figure 5(b)) and peak cylinder pressure (Figure 5(c)). All theoretical results shown in Figure 5 were generated with the
cylinder pressure processing and combustion analysis model for four injection timings namely 15 degCA BTDC (Nominal
value at 2500 rpm and at 80% load), 14 degCA BTDC, 13 degCA BTDC and 12 degCA BTDC of “Lister LV1” test engine.
As observed from Figure 5(a), the delay in the start of injection result in small reduction of the examined diesel engine
indicated power due to reduction of the fuel injected mass percentage burned in premixed combustion phase and due to the
consequent increase of the fuel injected mass proportion burned in diffusion combustion phase during expansion stroke.
According to Figure 5(b) the retardation of fuel injection timing results in small increase of ISFC due to the shift of diesel
combustion towards the expansion stroke. Hence, the injection commencement delay is directly related to diesel engine
efficiency deterioration, which is a strongly undesirable phenomenon since the major asset of diesel engines is their high
thermal efficiency. Finally, as witnessed from Figure 5(c), the injection commencement delay results in significant reduction
of maximum combustion pressure, which is up to 7 bar when injection timing is delayed by 3 degrees compared to the
nominal value. The reduction of maximum cylinder pressure with injection timing retardation is associated explicitly with
the reduction of premixed combustion phase intense.

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(a) (b)

(c)
Figure 5. Effect of Injection Timing (i.e., Start of Injection) Retardation on (a) Indicated Engine Power, (b) Indicated Specific
Fuel Consumption (ISFC) and (c) Peak Cylinder Pressure. Results of the Combustion Analysis Model are given for the Single-
Cylinder High-Speed DI Diesel Engine ‘Lister LV1’ at 15 degCA BTDC (Nominal Value at 2500 rpm and at 80% of full load), 14
degCA BTDC, 13 degCA BTDC and 12 degCA BTDC.

Figure 6 depicts the impact of injection timing retardation on the ignition angle (Figure 6(a)) and on the ignition delay
(Figure 6(b)). According to Figure 6(a) it can be observed that the injection initiation delay results in reduction of ignition
angle (expressed in crank angle degrees from TDC) or in other words, results in delay of combustion commencement. On
the other hand, according to Figure 6(b), the reduction of injection timing (expressed in crank angle degrees from TDC)
results in insignificant variations of ignition delay due to the fact that the ignition angle is varying as much as injection
timing and thus their difference remains almost the same. On a fundamental basis, the variation of injection timing does not
affect directly the fuel physical and the chemical preparation period (i.e., ignition delay), which is primarily related to the in-
cylinder gas phase pressure and temperature at the end of compression stroke, the fuel ignition quality (i.e. fuel Cetane
number) and the local fuel/air equivalence ratio (Heywood,1988).

(a) (b)
Figure 6. Effect of Injection Timing (i.e., Start of Injection) Retardation on (a) Ignition Angle and (b) Ignition Delay. Results of
the Combustion Analysis Model are given for the Single-Cylinder High-Speed DI Diesel Engine ‘Lister LV1’ at 15 degCA BTDC
(Nominal Value at 2500 rpm and at 80% of full load), 14 degCA BTDC, 13 degCA BTDC and 12 degCA BTDC.

In Figure 7 is shown the effect of injection timing retardation on the combustion duration of the 5% (Figure 7(a)), the

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25% (Figure 7(b)), the 50% (Figure 7(c)) and the 90% (Figure 7(d)) of the total injected fuel mass per cycle. As evidenced
from Figures 7(a)-(d) the retardation of injection timing by 3 degrees compared to the nominal value results in the increase
of all individual combustion durations. Hence, the delay in the start of injection results in the deterioration of the diesel
engine combustion efficiency since a higher combustion period expressed in crank angle degrees is required for the
combustion of same fuel quantity per engine cycle either on premixed mode both on diffusion mode.

(a) (b)
(c) (d)
Figure 7. Effect of Injection Timing (i.e., Start of Injection) Retardation on (a) 5%, (b) 25%, (c) 50% and (d) 90% Burnt of the
Total Injected Fuel Mass per Engine Cycle. Results of the Combustion Analysis Model are given for the Single-Cylinder High-
Speed DI Diesel Engine ‘Lister LV1’ at 15 degCA BTDC (Nominal Value at 2500 rpm and at 80% of full load), 14 degCA
BTDC, 13 degCA BTDC and 12 degCA BTDC.
CONCLUSION
A theoretical examination was performed in the present study to investigate the effect of fuel injection timing
malfunction (i.e. retardation compared to the nominal value) to a single cylinder high speed DI diesel engine performance
and combustion characteristics. A closed cycle engine simulation model was used to generate cylinder pressure profiles for
four different values of fuel injection timing i.e. 15 degCA BTDC (Nominal value at 2500 rpm and at 80% load), 14 degCA,
13 degCA and 12 degCA BTDC. The generated cylinder pressure profiles were supplied to a performance and combustion
analysis model developed under a diploma thesis in Hellenic Naval Academy. The combustion analysis model produced
theoretical results for main performance characteristics and for specific combustion characteristics such as instantaneous
and cumulative net heat release rates, ignition angle, ignition delay and individual combustions durations. From the
assessment of the performance and combustion analysis model results examined in this study it can be concluded that the
retardation of fuel injection timing results in:
 Reduction of the intensity of the premixed combustion phase and enhancement of the intensity of the diffusion-
controlled combustion phase.
 Increase increase of exhast gas temperature at exhaust valve opening.
 Reduction of indicated power and increase of ISFC and thus, reduction of engine indicated efficiency.
 Considerable reduction of peak cylinder pressure
 Reduction of ignition angle

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 Increase of 5%, 25%, 50% and 90% combustion durations of the total fuel injected mass per engince cycle revealing
thus, a deterioration of premixed-controlled and diffusion-controlled combustion efficiencies.
Overall, it can be stated that the fuel injection timing malfunction is an undesirable phenomenon since it can be led to high
exhaust gas temperatures at the exhaust outlet, reduced diesel engine power and thermal and combustion efficiencies.
Hence, the retardation of injection timing when applied in diesel engines (for example in the case NOx reduction is
required) it should be accompanied by recording of engine performance and combustion characteristics in order not to
result in their serious deterioration.
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