5. Editorial Board
Mehdi Ahmadian, USA
Rehan Ahmed, UK
Muhammad T. Akhtar, Japan
Nacim Alilat, France
M. Affan Badar, USA
Luis Baeza, Spain
R. Balachandran, UK
Adib Becker, UK
Filippo Berto, Italy
No¨el Bruneti`ere, France
Mustafa Canakci, Turkey
Marco Ceccarelli, Italy
Fakher Chaari, Tunisia
Chin-Lung Chen, Taiwan
Lingen Chen, China
Qizhi Chen, Australia
Long Cheng, China
Kai Cheng, UK
Hyung H. Cho, Republic of Korea
Seung-Bok Choi, Korea
Ahmet S. Dalkilic, Turkey
J. Paulo Davim, Portugal
Kangyao Deng, China
Francisco D. Denia, Spain
T. S. Dhanasekaran, USA
Nihad Dukhan, USA
Farzad Ebrahimi, Iran
Ali Fatemi, USA
Mario L. Ferrari, Italy
Lu´ıs Godinho, Portugal
Rahmi Guclu, Turkey
Tian Han, China
Ishak Hashim, Malaysia
Davood Jalali-Vahid, Iran
Jiin Y. Jang, Taiwan
Xiaodong Jing, China
Mitjan Kalin, Slovenia
S.-W. Kang, Republic of Korea
Michal Kuciej, Poland
Yaguo Lei, China
Zili Li, The Netherlands
Yangmin Li, Macau
Jun Li, China
Zhijun Li, China
Jianguo Lin, UK
Cheng-Xian Lin, USA
Jian Liu, China
Chen-Chi M. Ma, Taiwan
Seyed N. Mahmoodi, USA
Oronzio Manca, Italy
Ramiro Martins, Portugal
Francesco Massi, Italy
Hua Meng, China
Roslinda Nazar, Malaysia
T. H. New, Singapore
Cong T. Nguyen, Canada
Hirosi Noguchi, Japan
Takahito Ono, Japan
Hakan F. Oztop, Turkey
Duc T. Pham, UK
Ioan Pop, Romania
Jurij Prezelj, Slovenia
Xiaotun Qiu, USA
Pascal Ray, France
Robert L. Reuben, UK
Pedro A. R. Rosa, Portugal
Elsa de S´a Caetano, Portugal
David R. Salgado, Spain
Mohammad R. Salimpour, Iran
Sunetra Sarkar, India
Pietro Scandura, Italy
A. S. Sekhar, India
Liyuan Sheng, China
Xi Shi, China
Seiichi Shiga, Japan
Chow-Shing Shin, Taiwan
Andrea Spagnoli, Italy
Anand Thite, UK
Shan-Tung Tu, China
Sandra Velarde-Surez, Spain
Junwu Wang, China
Moran Wang, China
Jia-Jang Wu, Taiwan
Hongwei Wu, UK
Gongnan Xie, China
Hui Xie, China
Ruey-Jen Yang, Taiwan
Jianqiao Ye, UK
Chun-Liang Yeh, Taiwan
Boming Yu, China
Bo Yu, China
Jianbo Yu, China
Yufeng Zhang, China
Min Zhang, China
Ling Zheng, China
Zhaowei Zhong, Singapore
6. Contents
Recent Trends in Internal Combustion Engines, Halit Yas¸ar, Hakan Serhad Soyhan, Adnan Parlak,
and Nadir Yılmaz
Volume 2014, Article ID 143160, 1 page
Design and Implementation of the Control System of an Internal Combustion Engine Test Unit,
Tufan Koc¸, Durmus¸ Karayel, Barıs¸ Boru, Vezir Ayhan, ˙Idris Cesur, and Adnan Parlak
Volume 2014, Article ID 914876, 9 pages
Trends of Syngas as a Fuel in Internal Combustion Engines, Ftwi Yohaness Hagos, A. Rashid A. Aziz,
and Shaharin Anwar Sulaiman
Volume 2014, Article ID 401587, 10 pages
Simulation Analysis of Combustion Parameters and Emission Characteristics of CNG Fueled HCCI
Engine, P. M. Diaz, N. Austin, K. Maniysundar, D. S. Manoj Abraham, and K. Palanikumar
Volume 2013, Article ID 541249, 10 pages
Calibration and Validation of a Mean Value Model for Turbocharged Diesel Engine, Ruixue Li,
Ying Huang, Gang Li, Kai Han, and He Song
Volume 2013, Article ID 579503, 11 pages
Fuzzy Sets Method of Reliability Prediction and Its Application to a Turbocharger of Diesel Engines,
Yan-Feng Li and Hong-Zhong Huang
Volume 2013, Article ID 216192, 7 pages
9. 2 Advances in Mechanical Engineering
test units, exhaust emission analysis has statistical and sys-
tematic errors. By using PC-controlled engine test and con-
trol unit some simulation procedures could be created and
performed. This is very accurate and robust way for emission
analysis [3–5].
Bunker et al. [6] have been designed a control unit in
order to provide the control of an engine test unit and dyna-
mometer. The diesel engine has been tested at the designed
control unit. As a result of experimental study successful
results were obtained. Gubeli and Dorey [7] have designed
an interface to control dynamometer at the engine test unit.
Designed system can be made automatical according to dif-
ferent working conditions.
Feng et al. [8] have designed an interface at the LabVIEW
program to conduct engine test. The experiments have been
carried out on a SI engine. The system consists of the engine
control unit, DAQ card, computer, and some additional elec-
tronic circuits as hardware. The system has tested basically
three functions: ignition control, stepper motor control, and
throttle position control. As a result of the engine tests the
engine that is designed is more reliable and accurate data have
been obtained from experiments.
Hafner et al. [9] have developed a software/hardware
environment for engine control systems. This dynamic engine
test stand has been qualified to perform functions such as
design and tests for new control. The desired control settings
have been calculated by using the developed engine manage-
ment system and developed optimization strategies by means
of adequate models of the engine behavior with fast neural
networks. Benito et al. [10] have aimed to improve the real-
time performance of some optimization algorithms used in
engineering control units. A genetic algorithm (GA) has been
used to optimize the working parameters of a spark ignition
reciprocating engine. They have tried to find out the values
of some engine control parameters such as intake pressure,
intake pipe length, intake valve closing angle, and spark
timing that yield the requested engine power while requiring
minimum specific fuel consumption. Wang et al. [11] have
designed and developed a diagnostic tool based on Kingtec
Standard Diagnostic Protocol. A physical connection and
level translation between personal computer (PC) and elec-
tronic control unit (ECU) have been realized by using devel-
oped special communication module. The system consists
of guidance service suggestion (GSS) function module and
fundamental function module which have been designed
with Visual C++ and LabVIEW languages. They have showed
that the developed system could realize accurate and quick
data communication, online diagnostic management, real-
time and dynamic measuring data refreshment, online pro-
gramming data, and practical GSS.
Cerri et al. [12] have attempted to achieve high levels of
specific power output and efficiency and so, they have carried
out an experimental activity to understand how each fuel
sample could improve the performance of a modern naturally
aspirated SI (spark ignition) engine for passenger cars. This
experimental campaign has consisted in measurements of
the maximum brake torque (MBT) curve up to knock onset
and the corresponding knock intensity, at wide open throttle
(WOT) and partial load operating conditions, for each tested
gasoline sample. Gonz´alez et al. [13] have studied the simula-
tion design of an engine control unit (ECU) for an Otto cycle
engine with electronic fuel injection (EFI) using Simulink
and Stateflow. Their simulation includes a model for the ECU
as well as physical parameters of the engine, which allows
closed-loop control and monitoring of various systems. The
study allows controlling of various parameters of the ECU
using an open-loop control. They have used this simulation
for gas emission, fuel economy, and engine performance
improvement purposes. Antonopoulos et al. [14] have real-
ized an experimental investigation on a single cylinder diesel
test engine to identify the aforementioned problem. They
have recorded cylinder pressure and instantaneous speed
during the tests. The comparison of the two cylinder pressure
traces and the thermodynamic parameters derived from
them reveals the introduction of an error which depends on
engine load and speed. Taglialatela et al. [15] have proposed
the use of a multilayer perceptron neural network to model
the relationship between the engine crankshaft speed and
some parameters derived from the in-cylinder pressure cycle.
They have demonstrated an application of neural network
model on a single-cylinder spark ignition engine tested in
a wide range of speeds and loads and have confirmed that
a good estimation of some combustion pressure parame-
ters can be obtained by means of a suitable processing of
crankshaft speed signal.
Scattolini et al. [16] have presented a model and a simula-
tion environment in order to characterize new throttle bodies
and to design the associated control algorithms. Thus, they
can properly regulate the additional air flow provided to the
engine in idle speed conditions. Isermann and M¨uller [17]
have explained the structure of a rapid control prototyping
(RCP) system, which allows for fast measurement signal
evaluation and rapid prototyping of advanced engine control
algorithms. Providing efficient engine models for the pro-
posed development tools, a dynamic local linear neural net-
work approach has been explained and applied for modelling
the NOx emission characteristics of a direct injection diesel
engine. Finally, they have presented the simulation results
for a 40-ton truck. Chung et al. [18] have proposed a real-
time estimation algorithm of combustion parameters. The
proposed estimation algorithm uses the difference pressure
only instead of the in-cylinder pressure for calculation of the
combustion parameters and it requires only 51% of the execu-
tion time to calculate the combustion parameters compared
to the conventional method. They have validated the pro-
posed estimation algorithm with an engine experiment under
131 operating conditions that showed high linear correlation
with the original combustion parameters.
Franco et al. [19] have presented a real-time engine brake
torque estimation model where the instantaneous measured
engine speed serves as the model input. The engine brake
torque estimation has been separated into two parts: steady
state and transient in their study. They have provided valida-
tion of the engine brake torque model using a computational
engine model for a 6-cylinder heavy duty diesel engine.
Mart´ınez-Morales et al. [20] have presented a neural network
model of internal combustion engine in their work. At first,
they have collected data of a 1.6 L gasoline engine which has
10. Advances in Mechanical Engineering 3
been used for deriving an engine neural model. Three inputs
such as engine speed, injection angle, and the amount of
injected fuel have been included to the system into a specific
value range and then emissions have been measured. The
results obtained showed the effectiveness of the proposed
approach in modeling the studied gasoline engine.
Here, we have tried to choose the most relevant ones to
our study of studies. Almost, all of the studies are original
and also they provide significant contribution to the world
of science. However, each of them is focused on one or
a few parameters. Also, they have a rigid structure and
to use them for other parameters on similar researches is
difficult. However, our available study has a flexible structure
completely. The desired parameter can be added and removed
very easily. Therefore, the developed system can be adapted
to all engine tests with only a few arrangements. In this
respect, this system can also be used for educational purposes,
including distance education, as well as professional engine
tests. In other words, the system has a universal structure and
is suitable for both testing and control. This case is distinctive
feature of this study.
This study is organized as follows: at first, an introduction
and literature review are presented. Section 2 gives mate-
rial and methods. Section 3 illustrates experimental studies.
Section 4 presents the results and discussion, and section five
describes the conclusions of the study and future works.
2. Materials and Methods
Framework and mechanical equipment of the test stand
of which the control system will be developed are already
available. The developed control system has been adapted to
this current mechanical system. LabVIEW software has been
used to design the control system. It is a highly productive
development environment and is very suitable for real-time
control applications. The engine operating data such as load,
temperature, speed, and instantaneous fuel consumption
have been transferred to a computer by using data acquisition
card in real time. At the same time, the engine throttle control
has been controlled by a servomotor and also the load of
the dynamometer has been controlled by applying voltage to
the setting input. These controls are real-time processes too.
The USB-6251 DAQ card which produced by the National
Instruments company has been used in the control system.
The 6251 DAQ card has been preferred because it has the
analog/digital input and output channels and provides the
required specifications. Data to be read from the engine
have been received by means of analog/digital inputs of the
data acquisition card and then the parameters needed to be
adjusted have been controlled by using analog/digital outputs.
The overview of the designed engine test stand in Figure 1 and
its block diagram in Figure 2 have been given respectively.
The prepared interface and program have been developed
using national instruments “LabVIEW” software. LabVIEW
software has a high capability for real-time data acquisition
operations and can operate fully compatible with the data
acquisition card and so it has been preferred for this study.
Inlet and outlet temperatures of the engine coolant,
engine oil temperature, and atmosphere temperatures have
Figure 1: Experimental setup.
been measured by NTC type thermistors. NTC thermis-
tor’s resistance changes negatively according to temperature
increase. Practically thermistor resistance value was mea-
sured as analog voltage using a reference serial resistor. In
this study, NTC thermistors are read by DAQ card analog
inputs. Measured voltage converted the temperature by using
formula (1):
𝑇 = [
1
𝑇𝑅
+
1
𝛽
ln (
𝑉
(𝑉𝑖 − 𝑉)
)]
−1
, (1)
where 𝛽 is the gain coefficient of thermistor (fixed), 𝑇𝑅 is the
reference temperature (kelvin), 𝑇 is actual thermistor temper-
ature (kelvin), 𝑉 is thermistor voltage, 𝑉𝑖 is Input reference
voltage.
Exhaust temperature is extremely high. Therefore, a ther-
mocouple with a maximum range of 1200∘
C is used to mea-
sure exhaust temperature. Thermocouple produces a voltage
output according to temperature. But this voltage should be
filtered and linearized. Therefore, in this study, a control
device (EMKO ESM-4400) is used. This device produces 0–
10 V linear voltage output for measuring range of thermo-
couple. Measured voltage for thermocouple converted the
temperature by using formula (2):
𝑇 =
𝑉read
0.0083
, (2)
where 𝑇 is thermocouple temperature (celsius) and 𝑉read is
thermocouple control device output voltage.
The engine speed has been read from the counter inlet of
the DAQ card by means of encoder. The encoder measures
the output pulse intervals from outlet of channel Z. Channel
Z of the encoder gives a pulse for every 3600. Hence, the
interval between the two pulses taken consecutively from
the Z channel of the encoder represents the period taken to
complete a cycle. Therefore, counter inlet of the DAQ card
and the Z channel pulse interval have been measured in
seconds. The measured cycle time is divided by 60 and so it is
converted to rev/min. Load of the motor has been measured
with a load cell connected to the dynamometer force arm.
The fuel consumption in mass has been measured by
using the load cell that has 0.1 g accuracy and connected to the
fuel tank. The mass of the fuel tank during the test has been
11. 4 Advances in Mechanical Engineering
Water tank
Engine
Emission
device
Dynamometer
Dynamometer
control
panel
Computer
(labVIEW software)
Precision scale
Fuel tank
DAQ card
Encoder
Thermocouple
Thermocouple control device
Thermistor 1
Thermistor 3
Thermistor 4
Thermistor 2
Water inlet temperature
Water outlet temperature
Atmosphere temperature
Exhaust
USB 2.0
RS-232
RS-232
RS-232
Measuring
Dynamometer
Shaft
Water inlet
Water outlet
Servo motor
Throttle control
Oil temperature
load amount
load setting
temperature
Figure 2: Experimental setup block diagram.
read at the beginning of the experiment and at the end of the
experiment and then the difference has been divided by total
test time and so the instantaneous mass fuel consumption has
been measured as g/s.
The throttle control has been controlled by the servomo-
tor and the servomotor has been controlled by using digital
outputs of the data acquisition card too. This digital output
produces a PWM signal for servomotor driving. The PWM
signal is produced by hardware timer module of DAQ card.
The control of motor load has been achieved by changing
the voltage value of the electric dynamometer. These voltage
values have been controlled by using the analog outputs of
the data acquisition card through the interface. The minimum
and maximum voltage values of the dynamometer panel have
been determined and these values have been entered to the
interface as the lower and upper limits. The interface can real-
ize load control of the dynamometer by voltage control of the
lower and upper limits. Ranges and tolerance of measuring
devices used in this study are given in Table 1.
In the experiments, an emission device branded BILSA
has been used to measure emissions. This device can com-
municate with the designed interface by means of serial port
(RS-232) in real time. The resulting emissions are recorded
as log file. This electronically controlled test system provides
that the engine test steps are automated, the measured values
can be seen on the interface, and the test results are recorded.
Designed interface can be used for both modes as manual
control and full-load test mode.
After preparing experimental setup and LabVIEW pro-
grams for measurement, systematic errors have been calcu-
lated and are given in Table 2.
2.1. Manuel Control Mode. In the manual control mode,
the test unit is controlled by the user manually. Position
of the throttle control and the voltage value applied to the
dynamometer can be controlled by the user in real time while
the program is in manual control mode. Whereby, adjusting
precisely the required speed and load can be possible. Fur-
thermore, after setting the required speed and/or load, the
data are recorded to the computer as log file through “Import
data” button situated at the interface. Designed interface can
be operated into the two modes including manual control
and a full-load test mode. Also, in manual control mode, to
perform partial load tests is aimed. In this mode, the system
has opportunity to perform experiments in the partial load
because load and speed are controlled by user.
2.2. Full-Load Test Mode. In full-load test mode, the control
of the system is taken from the user and all of the activities are
controlled by the designed interface. In this mode, the desired
engine speed is entered into the interface of the system and
then the start button is pressed and so the designed interface
controls the throttle control in its initial state. At the same
time, the voltage value at ends of dynamometer is increased
and so reaching to maximum motor speed is prevented. After
the throttle control arrives at the full throttle position, value
of the voltage applied to the dynamometer is changed by
the program until the desired speed is achieved. When the
desired motor speed is achieved by means of the program,
the system waits to remain constant the exhaust temperature
data and the data are saved to the computer as log file when
the temperature reaches a constant value.
If a full-load test is required, after the mode is selected, it
is sufficient that the user only enters the desired speed value.
12. Advances in Mechanical Engineering 5
Table 1: Sensor measuring ranges and tolerances.
Device Brand Range Tolerance
Thermocouple EMKO Max. 1200∘
C ±2∘
C
Thermocouple control devices EMKO ESM-4400 0–10 V ±0.016 V
Thermistor ENDA −50∘
C–110∘
C ±1∘
C
Precision scales DIKOMSAN Max. 3000 g 0.01 g
Load cell ESIT S Type Max. 50 kg % ±0.05
Incremental encoder Heidenhain ROD-426 3600 pulse/tour 1/20
Table 2: Systematic errors.
Parameters Systematic errors, ±
Load, (𝑁) 0.1
Speed, (d/d) 1.0
Time, (s) 0.1
Temperature, (∘
C) 1
Fuel consumption, (g) 0.01
NO 𝑥, (ppm) 5
CO, (%) 0.06
HC, (ppm) 12
CO2, (%) 0.5
Desired test conditions can be accomplished by obtaining
the desired speed value as a result of the load control. The
operating principle of the full-load test mode is presented as
the block diagram in Figure 3.
In full-load test mode, a closed-loop control system has
been prepared to control the engine speed using the dyna-
mometer load voltage. For the designed controller, the pro-
portional control structure has been preferred. As is known,
the response times of engine and dynamometer vary for dif-
ferent combinations of load and motor speed. Therefore, the
adaptation of time-dependent structures such as PD (propor-
tional derivative) or PID (proportional integral derivative)
controllers to this system is highly difficult while they can
quickly reach stability state. The proportional controller has
been used because the accuracy is more important than the
operational time to create desired experimental conditions.
The proportional controller has been used because the accu-
racy is more important than the operational time to create the
desired experimental conditions.
3. Experimental Studies
The experimental study has been performed on a two-
cylinder and water cooled Lombardini SI engine. Engine test
stand has been prepared with measurement devices men-
tioned above according to software and interface design. The
characteristics of the engine used in the experiment have been
presented in Table 3.
In this study, full-load test has been preferred as the first
experiment and so the speed has only been entered in the
user interface and then all of the procedures took place
automatically without any user interaction. In this mode,
the designed program switches throttle control and the
Table 3: The Characteristics of the engine used in the experiment.
Engine type Lombardini
Piston diameter (mm) 72
Stroke (mm) 62
Number of cylinders 2
Stroke volume (dm3
) 0.505
Power (kW) 15
Compression ratio 10.7
Cooling type Water
Injectıon type Direct injection
dynamometer load to passive mode and does not allow user
to interact. By entering speed value, the program sets to the
desired speed value of the engine by itself. The program trans-
fers the measured data to the computer when the exhaust
temperature arrives to a constant value. The interface of the
system during a test step has been presented in Figure 4.
The experiments have been realized (carried out) in the
engine speed range from 1600 rpm to 3600 rpm. The recorded
data have been also transferred to excel program. The screen
output in excel program of the obtained data for full-load tests
has been shown in Table 4.
The partial load tests have been performed at the manual
control mode. In partial load tests, the throttle control and
the dynamometer load are controlled by the user and the
desired speed and/or the dynamometer load adjusted by the
user. Data import process is realized by pressing the data
acquisition button when the engine speed and/or the load
reaches the desired values, if it is demanded by the user. The
partial load tests have been also realized in the engine speed
range from 1600 rpm to 3600 rpm and the system has received
data at the beginning of each increase of 400 rpm as was done
in the full-load test mode. Also, in this mode, the recorded
experimental engine speed data can be transferred to excel
program as in the full-load mode.
4. Results and Discussion
A gasoline engine is used in the experiment. The full-load
limit is point that consisted of knocking. After the engine is
worked at the WOT (wide open throttle), the throttle is fixed.
Full-load test is made by changing the setting of the load on
the control dynamometer. In this case, the load dynamometer
control system is working to stabilize the cycles. Several tests
13. 6 Advances in Mechanical Engineering
Table4:Thedataobtainedfromfull-loadtests.
Speed
(rpm)
Load
(kg)
Fuel
consumption(g)
InstantaneousFuel
consumption(g/s)
Water
inlet(∘
C)
Water
outlet(∘
C)
Oil
(∘
C)
Atmosphere
(∘
C)
Exhaust
(∘
C)
O2
(%)
HC
(ppm)
CO
(%)
CO2
(%)
NO𝑥
(ppm)
SO2
(%)
Torque
(Nm)
Effective
power
(kW)
Specificfuel
consumption
1605.327.948.310.403526165283763.073771.4211.6217530.029.449624.948228293.1959
2005.158.161.200.510556471.2284561.983561.2512.5121961.130.195186.337134289.7209
2403.178.573.600.613576775284902.503021.5612.1422321.231.68637.970112276.8844
2806.238.486.740.723607179.9295222.612871.4811.9823991.231.313529.197368282.994
3204.788.2100.100.834627385295322.732811.6211.8624271.430.5679610.25352292.8165
3606.127.8118.180.985677796305481.682864.0210.9913431.529.0768410.97478323.1045
14. Advances in Mechanical Engineering 7
Encoder
CounterPID
controller
Analog
Charging
voltage
output
Requested
speed (rpm)
Engine
Dynamometer
control panel
Servomotor
Timer
Requested throttle level position
−+
Figure 3: Block diagram of full-load test.
Figure 4: The output of the interface taken during full-load test.
have been performed for verification performance of the con-
trol system developed in this study. As a result of experiments,
the engine speed has been fixed as error range of ±6 speed.
For verification, experiments are done with/without the
engine control system in the same situations and results are
compared. Also, torque, instantaneous fuel consumption, and
effective power graphics have been drawn in excel. It has
been shown that the engine performance curves are correct
according to the graphs and so the developed system has been
verified. Some of the performance and emission curves have
been presented in Figure 5.
5. Conclusions
In this study, the design of the control system of an inter-
nal combustion engine test unit has been developed and
implemented. The developed data acquisition and control
system have been successfully integrated with the mechanical
structure of the available test stand. Finally, the verification
tests have been realized by using the reference data proven
to be true their results. The experiment results have showed
that the designed system has a good performance to meet
the expected requirement. The conclusions drawn from this
study can be summarized as follows.
(i) Thanks to the developed system, researchers have
regained modern experimental environment. Hence-
forth, all processes of the manual engine test bench
can be realized by the aid of computer in real time.
(ii) Engine performance parameters can be monitored
and analyzed on the computer screen in real time by
using the developed system.
(iii) The new system has superior properties such as the
higher measurement accuracy, reliability, and the
shorter measurement period according to the classi-
cal system. Also, the measurement errors are reduced.
(iv) Thanks to the user interface, testing and control oper-
ations have become easier so that even a person alone
can perform all the experiments.
(v) In addition to scientific studies, it will contribute to
education and training activities especially in distance
education because it has rich visuals. It is usually diffi-
cult to teach students who do not have an automation
and engine background. However, to use this system
will help students in understanding important test
functions.
(vi) The measurements can be recorded easily, and so the
relations between the different parameters can be
observed more easily.
(vii) The cost of the system is very low according to its
commercial competitive products which have similar
characteristics.
(viii) Remote measurement capability of the system pro-
vides noiseless and safer working environment to the
test personnel.
We hope that the developed system will provide an impor-
tant contribution for researchers, employees and education-
training activities. The research results provided a foundation
for the further study. Future step based upon this work will
be on the internal combustion engine tests using artificial
intelligence technologies as control algorithm.
Nomenclature
DAQ: Data acquisition
I/O: Input/output
SI: Spark ignition
NTC: Negative temperature coefficient
PWM: Pulse-width modulation
RS-232: Serial communication port
PD: Proportional derivative
PID: Proportional integral derivative
RPM: Revolutions per minute
WOT: Wide open throttle.
15. 8 Advances in Mechanical Engineering
10.00
10.50
11.00
11.50
12.00
12.50
13.00
1600 2000 2400 2800 3200 3600
Engine speed (rpm)
STD
CO2(%)
(a)
STD
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
1600 2000 2400 2800 3200 3600
Engine speed (rpm)
CO(%)
(b)
STD
25
26
27
28
29
30
31
32
33
1600 2000 2400 2800 3200 3600
Engine speed (rpm)
Torque(Nm)
(c)
STD
2
3
4
5
6
7
8
9
10
11
12
1600 2000 2400 2800 3200 3600
Engine speed (rpm)
Pe(kW)
(d)
STD
0
50
100
150
200
250
300
350
400
450
1600 2000 2400 2800 3200 3600
Engine speed (rpm)
HC(ppm)
(e)
0
500
1000
1500
2000
2500
3000
1600 2000 2400 2800 3200 3600
Engine speed (rpm)
STD
NOx(ppm)
(f)
Figure 5: Some of the performance and emission curves.
Conflict of Interests
The authors declare that there is no conflict of interests
regarding the publication of this paper.
Acknowledgments
This study was supported through the interdisciplinary
project numbered 2012-05-04-012 by Sakarya University,
Head of Scientific Research Commission. The authors grate-
fully acknowledge the sponsoring of this work by Sakarya
University, Commission for Scientific Research Projects.
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18. 2 Advances in Mechanical Engineering
times in the past such as town gas, water gas, producer gas,
and blast furnace gas [3].
The gasifying agent is the most significant parameter that
affects the yield from the thermochemical conversion process
[2]. The main gasifying agents used in the process are oxygen,
steam, and air. Syngas produced using steam or oxygen
as a gasifying agent is called medium calorific value syngas
(simply syngas) with its heating value range of 10–28 MJ/Nm3
[2]. On the other hand, syngas produced using air as a gasify-
ing agent is called lower calorific value gas or “producer gas”
and its heating value ranges from 4 to 7 MJ/Nm3
[2]. Syngas
can be used as a standalone fuel for power production or as
an intermediate product in chemical industry for the pro-
duction of synthetic natural gas, synthetic liquid petroleum,
ammonia, and methanol [4].
A majority of research in the field of syngas utilization
have been focused on its use as a direct fuel in integrated
gasification combined cycle (IGCC) [4–10] and in the fuel and
chemical production, where syngas is used as an intermediate
product [4]. However, internal combustion engine (ICE) is
the most vital technological advancement, playing a major
role in the distributed energy power generation for a variable
power output requirement. It has very flexible application in
moving and stationary machineries. Compared to other types
of combustion technologies, ICE is believed to have benefits
like low capital cost, reliability, good part-load performance,
high operating efficiency, and modularity and is quite safe to
use. Because of this, utilization of syngas in these engines is
noteworthy; yet research in this area has been very limited
[4, 11]. The constituent of syngas that comes from gasification
lacks consistency. Besides, there were misconceptions about
syngas autoignition tendency at higher compression ratios
and power derating which later were explained elsewhere
[11, 12]. These were the two reasons for the lack of adequate
research in the area.
2. Technological Development
The era of using oils (such as olive, sesame, nut fish, whale,
and beeswax) for lighting was transformed into gas lighting
at the end of 18th century. Initially streets used to get light
from the hanging of door lamps facing the street. The idea
of public street lighting was initiated after the discovery of
flammable gas from coal by William Murdoch, who first used
it to light his house in 1792. This was further strengthened
by Frederick Albert Winsor, who got first patent in coal gas
lighting in 1804 [17]. In 1799, a French engineer and chemist,
Philippe Lebon patented his “thermolamp” which burned a
distilled gas from wood [18]. This was the cornerstone for
technological development of gasification and application of
its products for lighting. This technology was later expanded
to elsewhere to the Westminster Bridge (London) in 1813 and
the city of Baltimore, MD, in the USA in 1816. It was further
spread into major industries for lighting so that productivity
could be stretched into the night shift [3].
The application of this gas in automotive technology
was possible in the 1920s. In 1923, for instance, a French
inventor Georges Imbert (1884–1950) developed a wood gas
generator for mobile application [19]. Up to 9,000 vehicles
were produced with Imbert technology until the end of 1930s
[20]. In the later years, mass production of automobiles with
this technology continued including companies like General
Motors, Ford, and Mercedes-Benz.
World War II led to the shortage of gasoline and as a
result development of wood gas vehicles expanded all over the
world, which saw production of more than a million of such
vehicles [20]. The number of cars running on producer gas at
the time of WW II was estimated at 7 million [21]. Germany
was leading with over 500,000 vehicles on the ground.
Countries like Sweden, France, Denmark, Austria, Norway,
and Switzerland were also on the list [20].
Petrol domination at the end of 1940s led to a quick exit
of these Imbert-technology engines from the market. Since
then, application of syngas shifted into integrated gasification
combined cycle as a stationary power generation system.
However, even at the moment, certain countries have not
totally given up on the use of such fuel in mobile engine appli-
cations. USA is promoting the application of this technology
as a backup energy supply source in the event the country
faces petroleum crisis [22].
3. Syngas in Stationary Power Plant
Since the end of World War II, research and development on
syngas application have shifted focus into stationary power
generation. On top of this, coal, which is a prime fuel for
steam and gas power plants, has been branded the most envi-
ronmentally pollutant fuel. This has forced countries to draw
stringent regulations on direct firing of coal and other solid
fuels [2]. These two factors led to research into upgrading of
solid fuels. Besides reducing pollutant emissions, the upgrad-
ing process of solid fuels through the gasification process
has other advantages such as easy handling and flexibility
of feedstock ranging from agricultural residue to municipal
waste. The earlier versions of gas turbines were primarily
fuelled on natural gas. However, since the oil crisis of 1970s
there have been many commercial installations of syngas
fuelled integrated gasification combined cycle and gasifica-
tion cofiring plants globally. The feedstock for most of them
was coal and petroleum coke. There are also some installa-
tions with biomass and solid waste as feedstock. General Elec-
tric (GE) has led in the technology development of syngas and
other lower calorific value gas turbine technology in the last
20 years. Up to 2007, GE was operating gas turbines with a
total capacity of more than 3 GW in 15 plants (25 turbines)
installed in USA, Canada, Singapore, Germany, Italy, The
Netherlands, and Czech Republic [23].
Gas turbine burners have been designed for monocompo-
nent gaseous fuels (such as compressed natural gas (CNG))
and as a result fuelling of syngas in such burners would
lead to problems. The problems are associated with varied
composition of component gases, high hydrogen content,
and high volume flow rate requirements to maintain com-
parable gas turbine efficiency [9, 24]. These issues, in turn,
lead to flashback, flame oscillation under lean operation,
autoignition of hydrogen at higher temperature and pressure,
19. Advances in Mechanical Engineering 3
component overheating, handling problem of high flow rate
fuel in the combustor, and compressor instability. Summary
of these problems are explained elsewhere [24]. Besides, there
is risk of high nitrogen oxides (NOx) emission consequent
to high reactivity of hydrogen component of the fuel. Many
research efforts have been undertaken globally to tackle the
aforementioned problems [8, 9, 23, 25].
Direct coupling of gas production and power generation
plants such as gas turbine or ICE have technical and economi-
cal drawbacks. The gasifier must be sized to fit the syngas end-
use (gas turbine or ICE) [26]. Besides, such direct coupling
lacks the flexibility to run the two plants separately. Therefore,
introduction of syngas storage will enable utility stations to
operate their power plant during peak demand while running
the gas production syngas as per production schedule. There
are few researches on the introduction of a syngas storage
system in an integrated gasification combined cycle and small
scale gasification plants, in which, gas production and power
generation work separately and independently [26–28]. Yang
et al. [29] reported that syngas can be stored with no effect
on the chemical composition under temperature range of
−15∘
C to 45∘
C and pressure up to 83 bar [29]. Introduction of
storage has both technical and economic advantage according
to a study by the National Energy Technology Laboratory
(NETL) [26]. In comparison with other storage mechanisms,
the study by the National Energy Technology Laboratory also
emphasized that storage through compressed gas technology
has some advantages such as its large-scale applicability and
the fact that is less expensive than other methods.
4. Syngas in Internal Combustion Engine
Engines are divided into mobile and stationary types depend-
ing on their applications. The engines used in stationary
applications are of both internal and external combustion
types while mobile type engines are only of internal combus-
tion types. ICE is the most vital technological advancement,
playing a major role in distributed energy power generation
especially when there is a need for a variable power output.
They have very flexible application in moving and nonmoving
machineries. ICE is believed to have benefits like low capital
cost, reliability, good part-load performance, high operating
efficiency, and modularity and are quite safe to use as com-
pared to other types of combustion technologies [4].
The prospect of syngas as a fuel in ICE is believed to be
very promising and cost competitive when compared with
natural gas [4]. ICE is more tolerant towards contaminants as
compared to gas turbines. Even though they are not signif-
icant in number like in the area of IGCC, there are some
research works in the area of syngas utilization in ICE.
These researches can be categorized into spark-ignition (SI)
application specifically in the naturally aspirated carbureted
and port injection type and dual-fuel compression ignition
(CI) engines. Carbureted and port injection engines mix
the fuel and air prior to the combustion chamber and the
volumetric efficiency of the engine drops at the cost of the
voluminous syngas displacing air. Furthermore, they have
higher pumping and heat losses as compared to direct
injection (DI) SI engines, resulting in high fuel consumption
[30]. Consequently, the theoretical power output of syngas-
fuelled carbureted and port-injection engines is lower than
those of gasoline and CNG. In DI systems, fuel is mixed with
air in the combustion chamber and there is no restriction
to the amount of air aspirated into the chamber. Apart from
other engine operating parameters, syngas-fuelled engine
with a DI system is expected to have better engine power
output. However, based on an extended literature survey on
DI SI fueled with syngas has never been studied.
4.1. Syngas as a Dual Fuel in CI Engine. Stringent regulations
towards the emissions from diesel engines are restricting
development of the most efficient ICE. Application of syngas
in diesel engines is considered to be a viable alternative both
for the emissions and energy crises. However, syngas has high
self-ignition temperature (typically above 500∘
C) and as a
result, it cannot be ignited by compression ignition in a diesel
engine. A possible way of utilizing syngas in the CI engine is
through dual fuelling, where diesel is injected as a pilot fuel to
initiate the ignition while syngas injected into the induction
system. The main motivation in using syngas and other
gaseous fuels in diesel engine is as a substitute to diesel as this
can consequently reduce cost, minimize emissions (NOx and
particulate matters), and increase the engine performance.
There are many reports on research regarding syngas dual
fuelling in CI engine. Azimov et al. [31] investigated the effect
of H2 and CO2 contents in syngas on the performance and
emission of a four-stroke single cylinder engine [31]. Diesel
was used to assist the autoignition of syngas in a pilot-fuel
mode under lean condition for a wide range of equivalence
ratio (𝜙). The engine was supercharged and operated in a
premixed mixture ignition in the end-gas region (PREMIER).
PREMIER combustion was observed for all syngas fuels,
mainly when the pilot fuel used is very small. This combus-
tion was observed enhancing the performance and increasing
the efficiency of dual fuelling. Furthermore, they reported
that an increase in hydrogen composition in syngas short-
ened the main combustion duration and thereby causing an
increasing in the mean combustion temperature, indicated
mean effective pressure (IMEP), and efficiency. However,
neither diesel could be completely substituted nor could
syngas stand alone as a fuel in a diesel engine in the study.
Sahoo et al. [32] investigated the second law analysis of
a single cylinder DI CI engine fuelled with syngas under a
dual fuel mode, in which diesel served as a pilot fuel [32]. The
effect of H2/CO ratio on the dual fuel engine performance
and thermomechanical availability of the engine was studied.
The imitation syngas was composed of H2 and CO mixed
in a gas mixer and was charged into the gas carburetor.
The experiment was conducted at different load conditions
ranging from 20 to 100% with a 20% interval. They reported
that the syngas dual fuel had a better work availability at
higher loads as compared to diesel fuelling. Besides, an
increase in the content of hydrogen in syngas improved the
work availability of the dual fuelling. In a separate study, the
same researchers [14] investigated the effect of H2/CO ratio
on the performance of a dual fuel engine under the same
20. 4 Advances in Mechanical Engineering
test conditions. The performance parameters examined in the
study [14] were brake thermal efficiency, diesel substitution,
pressure profile, maximum cylinder pressure, and exhaust gas
temperature. In addition, the resulting emissions like CO,
NOx, and hydrocarbon (HC) were also investigated. The
syngas H2 and CO composition were 50 : 50, 75 : 25, and 100%
in volume percentage. They observed that an increase in H2
in the syngas results in an increase in the brake thermal effi-
ciency. The highest diesel replacement with syngas and max-
imum in-cylinder pressure was observed at 80% load with
100% H2. On emissions, NOx was observed to increase with
H2 content in syngas. As anticipated, the CO emission was
directly related to the CO content in syngas. The HC emission
was found to be minimum with 100% H2 [14].
Wagemakers and Leermakers [33] reviewed the effect of
dual fuelling of diesel and different gaseous fuels on perfor-
mance and emission [33]. CNG, liquid petroleum gas (LPG),
syngas, and hydrogen were some of the gaseous fuels con-
sidered in their review. They reported that all gaseous fuels,
when applied in diesel fuel combustion as dual fuel, could
decrease soot emissions except for syngas. Reduction in
NOx was reported when both CNG and LPG were used as
primary fuels. However, combustion of syngas and hydrogen
increased the NOx level as compared to diesel. Unburned
hydrocarbons and CO emissions increased with dual fuelling
of all the gaseous fuels as compared to diesel alone. With
regard to the effect of these fuels on efficiency, hydrogen
and LPG affected positively while syngas and CNG affected
negatively [33].
The performance of a dual fuel mode compression igni-
tion engine fueled by syngas with a composition of 10% H2,
25% CO, 4% CH4, 12% CO2, and 49% N2 and diesel (as pilot
fuel) was compared with that of methane under the same
duel fuel arrangement [34]. For both two fuel mixtures, a
shift from diffusion flame combustion to propagation flame
combustion was reported with reduction of the pilot diesel
fuel. Overall, methane was shown to perform better as
compared to syngas in the duel fuelling mode for diesel
substitution [34].
In summary, a complete replacement of diesel fuel with
syngas could not be possible. Besides, the performance of
such dual-fuelling of syngas and diesel was poorer as com-
pared to dual-fuelling of CNG and diesel. Therefore, syngas
cannot be a reliable substitute to diesel fuel in CI engines.
However, it can be used as a supplementary fuel to reduce
cost and emissions of NOx and particulate matter.
4.2. Syngas Combustion in Carbureted and Port Injection
SI Engines. The research and development of wood gas
automotive technology have taken place since the last 100
years. However, there are still key technoeconomic barriers
that hinder its commercialization [35]. To date, research
in this category has been more or less a continuation of
the World War II wood gas engine development. There are
many researches on both experimental and numerical inves-
tigations of fuelling syngas in naturally aspirated carbureted
and port injection engines. The research works can be
broadly classified into comparison of syngas and CNG [36]
and comparison of syngas and diesel [21] more specifically
to the study of overall energy balance of syngas fuelling,
performance, and emission studies. The fuelling setup used
was a direct coupling of gasification with a carburetion system
of the engine with a subsequent cleaning and cooling sys-
tem integrated. Most of the studies used the conventional
carburetor. However, Sridhar et al. [12, 15, 21] used a locally
manufactured carburetor in their investigation to address
the high volume flow rate of gaseous fuel [12, 15, 21]. They
modified a diesel engine into spark-ignition configuration to
obtain a higher compression ratio SI engine suitable for syn-
gas combustion. The latest research studies on utilization of
syngas (including producer gas and medium calorific value
syngas) in carbureted and port injection SI engine are
summarized here.
Sridhar [15] studied utilization of biomass derived pro-
ducer gas in a high compression SI engine experimentally and
numerically/analytically [15]. In their experimental investi-
gation, they optimized the compression ratio for maximum
brake power and efficiency by varying the compression ratios
to 11.5 : 1, 13.5 : 1, 14.5 : 1, and 17 : 1. Besides, they analyzed the
overall energy balance and the emission levels of CO and
NO. The syngas used in their study was a producer gas with
gas composition of 19 ± 1% H2, 19 ± 1% CO, 2% CH4,
12 ± 1% CO2, 2 ± 0.5% H2O, and rest N2 and calorific value
of 4.65 ± 0.15 MJ/Nm3
, respectively. They observed a smooth
combustion process with a very low cyclic pressure variation.
The producer gas experienced a short combustion duration
prompting a retardation of ignition timing. With respect
to power and efficiency, it was compared with diesel and
reported with a power drop of 16% and 32%, respectively. Fur-
thermore, a higher overall heat loss was reported for producer
gas. NO emission was dependent on the compression ratio
and ignition timing. Maximum NO emission was observed at
the highest compression ratio and advanced ignition timing.
On the contrary, minimum CO emission was observed at the
highest compression ratio. The main attribute of the emission
results was high temperature due to high compression ratio.
This experimental work was also reported elsewhere [12, 21].
Even though the study clarified the misconceptions about the
autoignition of producer gas, it was restricted to naturally
aspirated carburetor engines. The study was also limited only
to lower calorific value syngas (producer gas) [12, 15, 21].
Ahrenfeldt [37] studied the fuelling of biomass producer
gas on a combined heat and power (CHP) engine and its long-
term effect [37]. Emission, performance, efficiency, and other
operating parameters were investigated when producer gas
produced from three different gasification plants with their
lower heating values 5.5, 6, and 12.1 MJ/Nm3
were engaged
in the combined heat and power operations. Based on the
performance study, it was reported that producer gas is an
excellent fuel for lean burn application; its lean limit was close
to an excess air ratio (𝜆) of 3.00. There was no effect of
variation of ignition timing on the power and efficiency.
However, ignition timing was observed to affect the emission
level of NOx. The emission level of NOx was reported to be
low. On the other hand, CO emission was observed to be
very high due to the higher content of CO in the fuel. On
21. Advances in Mechanical Engineering 5
the combustion study, the coefficient of variation (COV) of
the IMEP and mass fraction burn (MFB) remained constant
for the producer gas even when 𝜆 increased.
Mustafi et al. [38] investigated performance and emission
of power gas in a variable compression ratio SI engine and
further compared it with that of gasoline and CNG. The
composition of power gas was mainly H2, CO, and CO2 sim-
ilar to that of medium calorific value syngas produced from
the gasification of solid fuels. However, the production of
this fuel was through Aqua-fuel process. The molar ratio of
the fuel investigated was 0.52, 0.44, and 0.04 for CO, H2
and N2, respectively. The lower heating value of the gas was
15.3 MJ/kg. The stoichiometric air-fuel ratio of the gas was
observed to be 4.2 as compared to 14.6 and 15.5 for gasoline
and CNG, respectively. A Ricardo single cylinder SI engine
with a variable compression ratio was modified to accompany
a gas mixer, gas regulator, and needle valve setting to accom-
modate the fuel-air blending before the cylinder. On their
comparison of power output of this gas at different compres-
sion ratios, an improvement of 22% was reported by increas-
ing the compression ratio from 8 : 1 to 11 : 1. The power output
of this gas, gasoline and CNG was compared at constant
speed of 1500 rev/min. It was reported that the brake torque
of power gas was 30% and 23% lower than that of gasoline,
and CNG, respectively. The fuel consumption was also
compared and power gas was requiring 2.7 and 3.4 times
more than that of gasoline and CNG, respectively. However,
consumption was not affected with the change in compres-
sion ratio. Emissions of total hydrocarbon (THC) and CO of
power gas were observed lower than for gasoline and CNG.
However, CO2 and NOx emissions were higher than all
these fuels. These experimental results were compared with
simulation model and were found to be consistent at all
conditions [38].
Papagiannakis et al. [39] have numerically modeled the
combustion process of a four-stroke, turbocharged, water-
cooled, multicylinder SI GE Jenbacher 320 engine fuelled
with syngas [39]. The fuel is a product of gasification of wood
with a volume percentage composition of 19% H2, 29% CO,
6% CH4, 8% CO2, and 38% N2. The two-zone model
predicted in-cylinder pressure profile, heat release rate, nitric
oxide (NO), and CO concentrations. The model results were
validated by the experimental results from the same engine
operated at constant speed of 1500 rev/min at four conditions
of 40, 65, 85, and 100% of full load. Their observation mainly
focused on the validation of the numerical model. Moreover,
they discussed the combustion, performance, and emission
characteristics of syngas in comparison with CNG. However,
the study was more focused on the numerical model vali-
dation than the effect of fuel property on the combustion,
performance, and emissions. Similar reports on syngas with
their main intention on predictive model validation could be
found elsewhere [40–42].
A small-scale naturally aspirated single cylinder SI engine
with compression ratio of 9.4 and 11.9 was used to test the per-
formance of low-BTU gases produced from gasification and a
two-step pyrolysis/reforming process. The gas produced from
gasification was hydrogen rich with a lower calorific value
(LCV) of 3.83 MJ/Nm3
while from the two-step pyrolysis was
methane rich with LCV of 4.2 MJ/Nm3
. The carburetor in the
fuelling system was replaced with a gas mixer to adjust the
air-fuel ratio. They reported that the two fuels had registered
a similar thermal efficiency compared to CNG. Besides, the
hydrogen-rich gas produced from gasification was reported
with a wider stable engine operation 𝜆 up to 2.00. Compared
to both CNG and the methane-rich pyrolysis gas, NOx and
HC emissions were quite low with the hydrogen-rich gas.
With the methane-rich gas, NOx was reported quite low too.
There was no information about BSFC performance of the
two fuels [43]. The study was limited to low-BTU gases only.
Shah et al. [44] have investigated the performance of
a naturally aspirated, single-cylinder, four-stroke, SI engine
with a capacity of 5.5 kW fuelled with syngas [44]. This
fuel composition was 16.2–24.2% CO, 13–19.4% H2, 1.2–6.4%
CH4, 9.3–13.8% CO2, and balance N2 with a lower heating
value of 5.79 MJ/Nm3
. It was compressed to a pressure of
15 bar and stored in LPG tank before fueled in the engine.
The performance parameters used in this study were power
output, overall efficiency, and run duration of the engine by
syngas. Emissions such as CO, CO2, HC, and NOx were also
investigated. The overall efficiency of both syngas and gaso-
line was reported to be similar at their respective maximum
power output (1.392 kW for syngas and 2.451 kW for gaso-
line). On the exhaust emissions side, CO was observed to
be 30–96% lower with syngas compared to gasoline at each
operation. This was attributed to the higher carbon content
and rich operation in gasoline. For syngas, the CO emission
was observed to increase with an increase in flow rate. The
CO2 concentration was reported to be 33–167% higher with
syngas compared to gasoline operation. This was attributed to
the CO2 presence in syngas and the conversion of CO content
in the fuel upon combustion. The CO2 concentration was
observed to increase with an increase in flow rate of syngas.
The hydrocarbon concentration of exhaust emission of syngas
was less than 40 ppm in all operations. This negligible content
was attributed to the limited presence of HC in syngas. NOx
emission in syngas operation was reported to be 54–94%
lower compared to gasoline operation. This was attributed to
lower cylinder temperature as a result of lower heating value
of syngas. The NOx concentration versus flow rate profile
was similar to that of power output curve. In this study,
comparison was made only to gasoline. CNG was not con-
sidered. However, comparison of gaseous fuel with liquid
fuel in internal combustion has its own constraints as per
Sridhar and Yarasu [45]. Combustion characteristics were not
investigated in the study. Besides, effects of ignition timing
and air-fuel ratio on the combustion, performance, and
emissions were not properly addressed.
Bika [46] studied varied ratios of H2/CO syngas in a port
injection SI engine and variable compression (4 : 1–18 : 1) for
their combustion characteristics and knock limit [46]. The
fuel was injected at 4 cms from the intake port. The fuels
investigated are pure H2, 75% H2/25% CO, and 50% H2/50%
CO. The study was limited to 𝜙 = 0.6–0.8 and compression
ratios of 6 : 1 to 10 : 1. It was reported that an increase
in percentage of CO increased the knock limit of syngas.
22. 6 Advances in Mechanical Engineering
The study also indicated that the increase in CO percentage
has advanced the ignition timing of MBT. Maximum heat
release rate was observed with pure hydrogen. The peak
pressure was, however, observed to be more influenced by
the compression ratio rather than by the CO percentage. The
MFB was also observed broader with an increase with CO
percentage. The overall conclusion of the study was that there
was an increase in combustion duration with an increase in
CO percentage. A maximum indicated thermal efficiency of
32% was reported with 50% H2/50% CO at 𝜙 = 0.6 and com-
pression ratio of 10 : 1. The study was limited to combustion
only. Performance and emissions of these fuels were not
investigated.
In summary, reduction of torque was reported in most of
the researches with syngas as compared to their fossil-based
counterparts. This was more pronounced with the lower
colorific value syngases (producer gases) as it demands higher
volume of gas to produce equal amount of power produced
from higher calorific value gases such as CNG and gasoline.
Besides other combustion parameters, the main attribute to
such power reduction was the volumetric efficiency penalty.
An appreciable amount of air gets displaced by the lower
calorific value syngas.
5. Current Engine Technologies
Over the years, ICE has passed through a lot of technological
advancements. The engine fuelling system was among other
parts which had huge attention. Early engines were fueled
with a surface carburetion system where air passes over a
stored fuel picking some from the surface [47]. Through
the inspiration of this technology, other carburetion systems
came to light over the years. In 1875, Siegfried Marcus
invented a rotary-brush atomizer that operates through drop-
ping of fuel in the air suction as a result of brush rotation over
the fuel storage surface. Even though this technology was
better at atomizing the fuel, the fuel entered into the com-
bustion chamber without evaporation. This shortcoming was
addressed through the invention of wick carburetor by Fred-
erick William Lanchester in 1896. A wick was extended from
fuel storage chamber to the air passage chamber. As a result,
fuel passed from the bottom of the wick into the upper
chamber where it evaporated. The incoming air in the upper
chamber mixed with the evaporated fuel and sucked into the
combustion chamber [48]. The introduction of float type car-
buretors by Wilhelm Maybach and Gottlieb Daimler as cited
in Barach [48].
The float type carburetor, also called simply carburetor,
was dominant technology over 90 years up to 1980s with
a continuous upgrading over the years. This technology
became very complex as it had to include many circuits to
accommodate the demands of high efficiency and low emis-
sions. Even though it is still the cheapest fuelling technology,
it has been phased out and replaced with other technologies
due to its inefficiency and lack of attaining the current emis-
sion standards. However, it is still operational in countries
where emission regulation is weak [49].
After the era of carburetor, fuel injection systems became
the primary technology to deliver fuel into the chamber. In
this technology, atomization of the fuel is done by forcing the
fuel through a narrow nozzle with the help of high pumping
pressure. The early fuel injection system was a throttle
body fuel injection system where an electronically controlled
injection system was added to the throttle body. This design
was later modified into port injection system where every
cylinder was equipped with fuel injectors that spray fuel near
the inlet valve. Even though the multipoint/port injection is
by far better technology than the carburetor in fuel metering,
it still needs more time to completely mix fuel and air before
entering the combustion chamber [50]. This further impinges
negatively on the fuel efficiency of the engine. Such limitation
has prompted for the adaptation of DI technology from diesel
engines. In the DI SI engine, high-pressure fuel is delivered
into a common rail, from where it is injected direct into
the cylinder via fuel injectors. Due to the high pressure and
injector nozzle interaction, the fuel is atomized in the cylinder
with a varied degree of penetration depending on the angle of
the injectors. This technology is fuel efficient, allowing precise
control system that puts century-old ICE still in a better
position compared to hybrid and electric vehicles.
With the emergence of DI application in SI engines, lean
combustion strategy has become a means for the reduction
of greenhouse gas emissions and an increase in thermal
efficiency [30, 51–53]. This strategy is mainly accompanied
with fuel stratification so that variable air-fuel ratio occurred
around the combustion chamber. The stratification provides
a relatively rich mixture near the igniter and a uniformly
mixed ultralean mixture all over the cylinder [30]. Engine
performance reduction due to volumetric efficiency drop can
also be overcome by injecting the fuel very late after inlet valve
closes (IVC). However, this may lead to insufficient time for
fuel-air mixing and slow combustion rate. For the fast burn-
ing type fuels, this is the type of fuel injection strategy that
has been adopted and it has attracted much attention these
days.
CNG DI had been under intensified research and devel-
opment since the 1970s. Previous research and development
of natural gas vehicles (NGV) was focusing on modification
of the existing petrol engines. However, currently there is
an increasing trend on the application of original equipment
manufacturer (OEM) vehicles for natural gas vehicle (NGV)
with DI technology getting mature and the demand of
NGV increasing [54]. Currently, the global NGV vehicle is
estimated at 20.21 million with 21,400 refueling stations [55].
However, syngas-fuelled DI engine has not been investigated
before.
6. Potential of Syngas in Current
Engine Technologies
The success of syngas reported in old ICE needs to be
investigated for the reinstatement of the fuel in the current
engine technology. Syngas produced from gasification of
biomass lacks consistency in the percentage composition of
constituent gases [21]. There are many varieties of syngas
23. Advances in Mechanical Engineering 7
Table 1: Supplied syngas composition.
Component Syn1 (V%) Syn2 (V%) Syn3 (V%)
Hydrogen 50 40 19.16
Carbon monoxide 50 40 29.60
Methane 0 20 5.27
Carbon dioxide 0 0 5.41
Nitrogen 0 0 40.56
products stated in the literature. The quality of syngas
produced from gasification is mainly dependent on the
gasifying agent used in the process. A low calorific value
syngas (producer gas) of H2, CO, CH4, CO2, and N2 of varied
proportion as constituent gases are generated if air is used
as gasifying agent. If steam or oxygen is used instead of
air, a medium calorific value syngas with H2, CO, and CH4
of varied proportions as constituent gases are produced
[2]. In order to understand the suitability of syngas in the
current engine technologies, representative of the abovemen-
tioned category of syngases, various compositions of syngases
should be investigated for their combustion characteristics.
Table 1 shows three different syngases selected from the lower
and medium calorific value syngases for a case study.
Detailed knowledge of the properties of fuels helps selec-
tion of appropriate operating parameters for an internal com-
bustion engines. In this section, properties of three different
types of syngases were investigated for their properties. CNG
and hydrogen two major gaseous fuels with their combustion
and performance in the current engine technologies were
widely investigated. Their potential and foreseeable chal-
lenges have been studied by different researchers [30, 56–60].
The combustion of CNG is less complete resulting in lower
performance coupled with higher CO and THC emissions.
They are attributed to the lower laminar flame velocity,
narrow combustible range, high ignition energy requirement,
and higher self-ignition temperature [30]. Even with such
shortcomings, this fuel is currently serving its purpose as
stated in Section 5. On the other hand, hydrogen has greater
advantage with the greenhouse gas emission due to its clean
combustion. However, usage of this fuel is hindered due to
its high production cost, difficulty in its storage, high flame
speed, and high flame temperature leading to unstable com-
bustion and knock [58]. The properties of these syngases were
compared with those of CNG and hydrogen to assess the
suitability of this fuel in the current engine technologies.
Table 2 shows the detailed comparison of properties of three
syngases, CNG, and hydrogen.
The fuel properties for the three syngases listed in Table 2
are mostly calculated based on their species except for the
laminar flame velocity and autoignition temperature. The
hydrogen-to-carbon ratio (H/C) is the main factor in the
production of the greenhouse gas emissions from the com-
bustion of fuels [30]. An increase in H/C leads to reduced
production of CO2 and increased production of H2O in the
combustion products. To this end, hydrogen is free of
greenhouse gas emissions. H/C of gasoline, CNG, Syn1, Syn2,
and Syn3 are calculated to be 1.85, 4, 2, 2.67, and 1.45, respec-
tively. Syn1 and Syn2 have better greenhouse gas emission
performance as compared to gasoline. Besides, syngases are
considered to be carbon neutral fuels especially if they are
produced from biomass and solid waste gasification. Syngases
are also oxygenated fuels resulting in a clean burning and an
improved power and efficiency.
Syngases have lower calorific value compared to CNG.
However, all syngases have better stoichiometric mixture
energy density as compared to CNG in an air aspirating
(direct-injection) engines as shown in Table 2. The energy
obtained from the combustion chamber is more influenced
by the mixture energy density than by the lower calorific
value of the fuel [13]. Therefore, the performance of a direct-
injection syngas powered engine is expected to be improved
as compared to the naturally aspirated carbureted and port
injection engines.
Syngases have also wider flammability range as compared
to CNG. This property is responsible for COV of the IMEP of
the combustion of the fuel. It is a measure of the extent of mis-
firing of the combustion. Therefore, syngases are expected to
have lower COV. Additionally, syngases have higher autoigni-
tion temperature as compared to hydrogen and CNG. This
will make them favorable for high compression engine appli-
cation with no incident of knock. Similar observation was
reported by Sridhar et al. [21]. The moderate laminar flame
velocity of syngases improves the slow combustion reported
with CNG and the unstable combustion reported with
hydrogen.
Syngases, especially the medium calorific value syngases,
have an adiabatic flame temperature close to that of hydrogen
leading to higher NOx emissions. Moreover, syngases have
extremely low stoichiometric air-fuel ratio as compared to
CNG and H2. This could result in high brake specific fuel con-
sumption (BSFC). These fuels cannot be operated near stoi-
chiometry as it is impossible to completely inject the amount
of fuel that makes stoichiometric air-fuel ratio especially for
fuels similar to Syn3. A lean charge direct-injection needs to
be adapted to avoid the high NOx emissions and the higher
BSFC of such fuels. However, the mixture energy density
of a lean homogenous mixture of syngases will be very low
leading to misfiring and demanding higher ignition energy.
A charge stratification strategy can be followed to reduce the
combustion misfiring. Such fuel stratification can only be
attained through late injection of the charge after the inlet
valve closes in the direct-injection spark-ignition engines.
Nevertheless, late injection of syngases with low and medium
calorific value leads to limitation of injection duration
thereby limiting power output. Only the medium calorific
value syngases (similar to Syn1 and Syn2) can deliver com-
parable power and torque output to their CNG counterparts.
The lower calorific value syngases (similar to Syn3) may be
feasible in older engines such as the naturally aspirated carbu-
reted and port injection engines. However, their demand for
longer injection duration in direct-injection engines and their
associated lower mixture energy density at lean operation
makes them less favorable in current engine technology.
24. 8 Advances in Mechanical Engineering
Table 2: Properties of different syngases and their comparison to CNG and H2.
Properties
Syngases
CNG H2
Syn1 Syn2 Syn3
Composition, weight %
Carbon 40.0 47.37 21.15 75.0 0.0
Hydrogen 6.67 10.53 2.56 25.0 100
Oxygen 53.3 42.1 28.3 0.0 0.0
Nitrogen 0.0 0.0 48.5 0.0 0.0
Molecular weight (g/mol) 15.0 15.2 23.2 16.04 2.02
Density at 0∘
C and 1 atm (kg/m3
) 0.67 0.68 1.04 0.75 0.09
Specific gravity at 0∘
C and 1 atm 0.52 0.53 0.8 0.58 0.07
Stoichiometric air-fuel ratio
Molar basis 2.38 3.81 1.66 9.7 2.38
Mass basis 4.58 7.23 2.07 17.2 34.3
Stoichiometric volume occupation in cylinder, % 29.6 20.8 37.6 9.35 29.6
Lower calorific value
MJ/Nm3
11.65 16.48 7.67 38.0 10.7
MJ/kg 17.54 24.4 7.47 47.1 120.2
Stoichiometric Mixture Energy density (MJ/Nm3
)
Mixture aspirated 3.3 3.25 2.73 2.9 [13] 3.2 [13]
Air Aspirated 4.45 3.92 4.19 3.60 [13] 4.54 [13]
Flammability limit, % vol. of fuel in air
Lower 6.06 5.8 13.4 5.3 4.0
Higher 74.2 41.4 57.9 15.0 74.2
Laminar flame velocity (cm/s) 180 [14] N/A 50 [15] 30 210
Adiabatic flame temperature, K 2385 2400 2200 2220 2383
Autoignition temperature, K 873–923 873–923 898 813 [16] 858 [16]
7. Conclusions
(i) The direct-injection fuelling system technology and
high compression ratio of the latest spark-ignition
engines, improvement in conversion efficiency, and
advancement in the cleaning process of gasification,
the introduction of syngas storage, and thereby sepa-
ration of gas production and power generation are the
motivating factors for syngas to be a fuel in current
engine technologies.
(ii) Stratified lean charge combustion is an effective way
of powering syngas in the current engine technology
to address the problems of stoichiometric charge
application caused due to very small stoichiometric
air-fuel ratio. However, care should be taken to
the limitation on the power caused due to limited
injection duration. Further investigation of the opti-
mization of injection timing, fuel composition, air-
fuel ratio, and ignition advance needs to be done for
better performance and emissions.
(iii) The problem associated with the higher BSFC of
syngases need to be addressed mainly on the design of
storage systems. The calorific value of CNG is three to
ten times that of syngases. This has huge implication
on the storage system in order to have the same
driving range to CNG counterpart.
Conflict of Interests
The authors declare that there is no conflict of interests
regarding the publication of this paper.
Acknowledgments
This work was supported by the Centre for Automo-
tive Research and Electric Mobility (CAREM), Universiti
Teknologi PETRONAS, and Educational Sponsorship Unit,
PETRONAS Carigali Sdn Bhd.
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