ii
STUDY OF SEQUENTIAL MULTIPOINT INJECTION NOZZLE
EFFECT OF COMPRESSED NATURAL GAS ENGINE
MOHD ADIB BIN ALIAS
A report submitted in partial fulfillment of the requirement for the
award of the Bachelor of Mechanical Engineering with
Automotive Engineering
Faculty of Mechanical Engineering
Universiti Malaysia Pahang
NOVEMBER 2008
v
ABSTRACT
The research and development of injection system has always been influenced by the
availability and the form of fuel. In this project is about the study of the injection nozzle effect of
compressed natural gas engine. This project study and simulate twenty types of sequential
injection nozzle with different geometries using SolidWork and Cosmos FloWork software to
find the best air and fuel mixing in the combustion chamber of the engine. The other effect of the
modified injection nozzle is the velocities of the fuel in combustion chamber that can be
determine using the software. The length of bore and stroke of the engine is base on the actual
diesel engine and been model using SolidWork. As the result, the best injection nozzle is 10
degree nozzle. The air and fuel mixing is very good and better compare with the original
injection nozzle. The velocity of fuel in combustion chamber is the highest compare with other
design.
vi
ABSTRAK
Penyelidikan dan pembangunan system suntikan selalunya dipengaruhi oleh ketersediaan
dan jenis bahan api itu. Projek ini adalah kajian tentang pengaruh muncung suntikan terhadap
enjin gas asli termampat. Di dalam projek ini ada mengkaji dan membuat simulasi dua puluh
jenis penyuntik dengan berlainan bentuk menggunakan perisian SolidWork dan Cosmos
FloWork untuk mencari campuran udara dan bahan api yang terbaik di dalam ruang pembakaran
pada enjin. Pengaruh lain perubahan muncung penyuntik adalah halaju bahan api itu di dalam
ruang pembakaran yang dapat ditentukan menggunakan perisian tersebut. Ukuran diameter dan
tinggi ruang pembakaran adalah berdasarkan enjin diesel yang sebenar dan dimodelkan
menggunakan SolidWork. Keputusannya, muncung suntikan terbaik ialah 10 darjah kecerunan
muncung itu. Udara dan bahan api bercampur dengan baik berbanding dengan muncung suntikan
yang asal. Halaju bahan api di dalam ruang pembakaran adalah yang tertinggi berbanding
muncung suntikan yang lain.
vii
TABLE OF CONTENTS
Pages
TITLE PAGE i
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF FIGURES x
LIST OF ABBREVIATIONS xiv
CHAPTER 1 INTRODUCTION
1.1 Introduction 1
1.2 Background 2
1.3 Problem statement 2
1.4 Project objective 3
1.5 Project scope 3
1.6 Thesis structure 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 4
2.2 Internal combustion engine 4
2.3 Four stroke engine 5
2.4 Spark-ignition engine operation 6
viii
2.5 Compressed natural gas 6
2.6 Compressed natural gas engine 7
2.7 Injection nozzle operation 7
CHAPTER 3 METHODOLOGY
3.1 Introduction 9
3.2 Overview of methodology 9
3.3 Project of methodology 10
3.4 Description of the methodology 11
3.4.1 Injection nozzle 11
3.4.2 Compressed natural gas engine model 14
3.4.3 Preparation of simulation 15
3.4.4 Boundary condition 17
3.4.5 Running the simulation 21
3.4.6 Collecting data 22
CHAPTER 4 RESULT AND DISCUSSION
4.1 Introduction 23
4.2 Air fuel mixing 24
4.2.1 Original injection nozzle 24
4.2.2 Other design of injection nozzles 26
4.3 Velocity 33
4.3.1 Original injection nozzle 33
4.3.2 Other design of injection nozzles 37
4.4 Overall data for injection nozzle of 10 degree Nozzle 38
ix
4.4.1 Air fuel mixing 38
4.4.2 Velocity 40
4.4.3 Pressure 42
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Introduction 44
5.2 Conclusion of the project 44
5.3 Recommendation of future work 45
REFERENCES 46
APPENDICES 48
A Gantt chart final year project 48
B Dimension of the injection nozzle 50
x
LIST OF FIGURES
Figure No. Page
2.1 Starting position, intake stroke, and compression stroke. 5
2.2 Ignition of fuel, power stroke, and exhaust stroke. 5
3.1 Flowchart of final year project 10
3.2 Original Injection Nozzle 11
3.3 Modified Injection Nozzles from SolidWork 2008 12
3.4 Modified Injection Nozzles from Microsoft Visio 2007 13
3.5 CNG Engine Model 14
3.6 How to Create the Wizard 17
3.7 Air Flow Inlet 18
3.8 Fuel Flow Inlet 19
3.9 Environment Pressure 20
xi
3.10 Run Simulation 21
3.11 Data Collection 22
4.1 Air fuel mixing using original injection nozzle 24
4.2 Mixing of air and fuel with different valve lift 26
4.3 Air fuel mixing for injection nozzle with 2 holes with diameter 1.50 mm 27
4.4 Air fuel mixing for injection nozzle with 3 holes with diameter 1.35 mm 27
4.5 Air fuel mixing for injection nozzle with 4 holes with diameter 1.25 mm 27
4.6 Air fuel mixing for injection nozzle with 5 holes with diameter 1.00 mm 28
4.7 Air fuel mixing for injection nozzle with 10 degree Nozzle 28
4.8 Air fuel mixing for injection nozzle with 10 degree Diffuser 28
4.9 Air fuel mixing for injection nozzle with 15 degree Nozzle 29
4.10 Air fuel mixing for injection nozzle with 15 degree Diffuser 29
4.11 Air fuel mixing for injection nozzle with 20 degree Nozzle 29
4.12 Air fuel mixing for injection nozzle with 20 degree Diffuser 30
xii
4.13 Air fuel mixing for injection nozzle with 25 degree Nozzle 30
4.14 Air fuel mixing for injection nozzle with 25 degree Diffuser 30
4.15 Air fuel mixing for injection nozzle with 30 degree Nozzle 31
4.16 Air fuel mixing for injection nozzle with 30 degree Diffuser 31
4.17 Air fuel mixing for injection nozzle with diameter 1.0 mm 31
4.18 Air fuel mixing for injection nozzle with diameter 1.5 mm 32
4.19 Air fuel mixing for injection nozzle with diameter 2 mm 32
4.20 Air fuel mixing for injection nozzle with diameter 2.5 mm 32
4.21 Air fuel mixing for injection nozzle with diameter 3 mm 33
4.22 Velocity of air and fuel flow 34
4.23 Graph velocity versus curve length for fuel 35
4.24 Graph velocity versus curve length for air 36
4.25 The dimension of injection nozzle with 10 degree of the angle 38
xiii
4.26 Mixing of air and fuel with different valve lift 39
4.27 Velocity of air and fuel flow 40
4.28 Graph velocity versus curve length for fuel 41
4.29 Pressure of air and fuel flow 42
4.30 Graph pressure versus curve length for air 43
4.31 Graph pressure versus curve length for fuel 43
xiv
LIST OF ABBREVIATIONS
CAD Computer-aided drafting
CFD Computational fluid dynamics
CNG Compressed natural gas
GGE Gallon of Gas Equivalent
ICE Internal combustion engine
LPG Liquefied petroleum gas
SAE Society of Automotive Engineers
SI Spark Ignition
TDC Top dead center
xv
CHAPTER 1
INTRODUCTION
1.1 Introduction
Natural gas is one of the most widely used forms of energy today. It is commonly used to
heat and cool homes and businesses nationwide. In addition, more than 85,000 compressed
natural gas (CNG) vehicles, including one out of every five transit buses, are operating
successfully today. CNG’s popularity stems, in part, from its clean-burning properties. In many
cases, CNG vehicles generate fewer exhaust and greenhouse gas emissions than their gasoline-
or diesel-powered counterparts.
CNG is odorless, colorless, and tasteless. It consists mostly of methane and is drawn from
gas wells or in conjunction with crude oil production. CNG vehicles store natural gas in high-
pressure fuel cylinders at 3,000 to 3,600 pounds per square inch. An odorant is normally added
to CNG for safety reasons. Small compressors connected directly to the home’s natural gas
supply.
Nowadays, most of the engines are using fuel from petroleum. Fuel from petroleum
becomes less and engineers work hard to find the alternative fuel for the engine. Natural gas is
one of the alternative fuels that have potential to replace the petroleum fuel. This project will
investigate about the injection nozzle effect for compressed natural gas engine. The injector will
be simulated by Cosmos FlowWork software.
1
xvi
1.2 Background
In the internal combustion engines, there are any gasoline engines and diesel engines
were used to generate the power in industries and transportations. The great problems of the
world in the internal combustion engines usage until today are focuses on environment
protection and economically fuel consumption. The problems need the new design, research and
technology to find the new engines or its components so its can use of the alternative fuels
another gasoline and diesel fuel, protect and friendly with the environment, high power and
efficient in fuel consumption.
Some engine designers and researchers have been did any new design, new concepts and
new ideas to found the new better engines, have a high power, friendly with the environment and
efficient on fuel consumption using alternative fuel. The first choice of alternative fuel is
compressed natural gas. By using compressed natural gas (CNG) as an alternative fuel for
internal combustion engine will be reduce the engine performance, but the exhaust gas emission
and economic operational by using compressed natural gas (CNG) as a fuel is lower than diesel
fuel and gasoline fuel. This study will concentrate on enhance dedicated compressed natural gas
(CNG) engine development based on computation and experimental. The project is to design and
development of sequential injection dedicated CNG engine spark ignition based from four stroke
direct injection diesel engine.
1.3 Problem Statement
The main problem of this project is in CNG engine that has low performance. The
alternative fuel for the engine is low energy density and because of that, the performance of
engine is low. Engine volumetric efficiency is also low because it is the gaseous fuel. The
optimum air–fuel ratio changes with fuel properties. The problem will be low air fuel mixing.
2
xvii
1.4 Project Objective
Study about sequential multipoint injection nozzle effect in CNG engine performance. Do
the computational model of sequential multipoint injection nozzle CNG engine flow and study.
1.5 Project Scope
The scope of this project is on design several types of injection nozzles for better air fuel
mixing and the velocity of the fuel flow in combustion chamber. The computational design was
using SolidWork and Cosmos FloWork. This project is studies and analyzes the effect of
injection nozzle in CNG engine performance by using simulation.
1.6 Thesis Structure
This project is belonging to design and simulate the new improvement and development
of the future design of the injection nozzle.
First chapter explains about the background of the study, problem statement, objective
and scope of the project.
Second chapter is about the review of internal combustion engine in CNG, injection
nozzle operation and importance process in the combustion engine which taken from the
reference books and other related resources.
Third chapter explains on the concept and method being used for this project. It explain
and show how to run the simulation of the project.
Fourth chapter shows the result of the project and discussion about the result. The result
of the project is base on the simulation by Cosmos FloWork.
Fifth chapter is conclusions about the project that had been done and recommendation for
future work.
3
xviii
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This chapter is about the review of internal combustion engine in CNG, injection nozzle
operation, part with new improvement and importance process in the combustion engine which
taken from the reference books and other related resources.
2.2 Internal combustion engine
The internal combustion engine is an engine in which the combustion of fuel and an
oxidizer (typically air) occurs in a confined space called a combustion chamber. This exothermic
reaction creates gases at high temperature and pressure, which are permitted to expand. Internal
combustion engines are defined by the useful work that is performed by the expanding hot gases
acting directly to cause the movement of solid parts of the engine [6] [7].
The term Internal Combustion Engine (ICE) is often used to refer to an engine in which
combustion is intermittent, such as a Wankel engine or a reciprocating piston engine in which
there is controlled movement of pistons, cranks, cams, or rods [6] [9].
Internal combustion engines are also an important source of noise [1]. There are several
source of engine noise: the exhaust system, the intake system, the fan used for cooling, and the
engine block surface [1]. The noise may be generated by aerodynamic effect, may be due to
4
xix
forces that result from the combustion process, or may result from mechanical excitation by
rotating or reciprocating engine components [1] [5].
The motion of internal combustion engines is usually performed by the controlled
movement of pistons, cranks, rods, rotors, or even the entire engine itself [6] [9].
2.3 Four stroke engine
The four strokes refer to intake, compression, combustion (power) and exhaust strokes.
The cycle begins at top dead center (TDC), when the piston is furthest away from the axis of the
crankshaft. On the intake or induction stroke of the piston, the piston descends from the top of
the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air is forced (by
atmospheric or greater pressure) into the cylinder through the intake (inlet) port. The intake
(inlet) valve (or valves) then close(s), and the compression stroke compresses the fuel–air
mixture [1] [11].
Figure 2.1: Starting position, intake stroke, and compression stroke.
Figure 2.2: Ignition of fuel, power stroke, and exhaust stroke.
5
xx
2.4 Spark-ignition engine operation
In spark-ignition (SI) engines, the air and fuel are usually mixed together in the intake
system prior to entry to the engine cylinder, using a carburetor of fuel-injection system [1] [5].
The term spark-ignition engine is normally used to refer to internal combustion engines where
the fuel-air mixture is ignited with a spark. The term contrasts with compression-ignition
engines, where the heat from compression alone ignites the mixture [12]. Spark-ignition engines
can be either two-stroke or four-stroke, and are commonly referred to as "gasoline engines" in
America and "petrol engines" in Britain. However, these terms are not preferred, since spark-
ignition engines can (and increasingly are) run on fuels other than gasoline, such as liquefied
petroleum gas (LPG), methanol, ethanol, compressed natural gas, hydrogen, and (in drag racing)
nitro methane [12]. A four-stroke spark-ignition (SI) engine is an Otto cycle engine [1] [12].
2.5 Compressed natural gas
Compressed Natural Gas is a fossil fuel substitute for gasoline (petrol), diesel, or propane
fuel. Although its combustion does produce greenhouse gases, it is a more environmentally clean
alternative to those fuels, and it is much safer than other fuels in the event of a spill [3] [8].
CNG is made by compressing natural gas (which is mainly composed of methane [CH4]),
to less than 1% of its volume at standard atmospheric pressure. It is stored and distributed in hard
containers, at a normal pressure of 200–220 bar (2900–3200 psi), usually in cylindrical or
spherical shapes [8].
The main component in CNG fuel is methane gaseous, about 75% methane. The
chemical reaction of CNG fuel is therefore given by:
CH4 + 2O2 CO2 + 2H2O
6
xxi
2.6 Compressed natural gas engine
Compressed natural gas can be used in Otto-cycle (gasoline) and modified Diesel cycle
engines. The equipment required for CNG to be delivered to an Otto-cycle engine includes a
pressure regulator (a device that converts the natural gas from storage pressure to metering
pressure) and a gas mixer or gas injectors (fuel metering devices). Often assisting the gas mixer
was a metering valve actuated by a stepper motor relying on feedback from an exhaust gas
oxygen sensor. Newer CNG conversion kits feature electronic multi-point gas injection, similar
to petrol injection systems found in most of today's cars [8].
Compressed natural gas engine require a greater amount of space for fuel storage than
convention gasoline power vehicles. Since it is a compressed gas, rather than a liquid like
gasoline, CNG takes up more space for each Gallon of Gas Equivalent (GGE). Therefore, the
tanks used to store the CNG usually take up additional space in the trunk of a car or bed of a
pickup truck which runs on CNG [8].
This project investigate about internal combustion engine using compressed natural gas
as an alternative fuel to reduce the pollution from exhaust gas emission and the operation cost of
the engine [3].
To improve of compressed natural gas (CNG) nozzle holes geometries and understand of
the processes in the engine combustion is a challenge because the compression-ignition
combustion process is unsteady, heterogeneous, turbulent and three dimensional, very complex
and the nozzle fuel injector hole is can be variation with any hole geometry [10].
2.7 Injection nozzle operation
In sequential injection compressed natural gas (CNG) engines, natural gas fuel is injected
by fuel nozzle injector via intake port into combustion chamber and mixing with air must occur
before ignition of the gas fuel. Once ignition occurs, there is a rapid energy release resulting
from the combustion of the fuel mixed during the ignition delay followed by a slower energy
release limited by the availability of gaseous fuel and its mixing rate with air [1].
7
xxii
To improve the perfect of mixing process of compressed natural gas (CNG) fuel and air
in combustion chamber, for example with arranging of nozzle hole geometry, modification of
piston head, arranging of piston top clearance, letting the air intake in the form of turbulent and
changing the compressed natural gas (CNG) fuel angle of spray [10]. The compressed natural
gas (CNG) fuel spraying nozzle is the level of earning variation so that can be done by research
experiment and computational of engine power, cylinder pressure, specific fuel consumption and
exhaust gas emissions which also the variation of them have been researched the sequential
injection of compressed natural gas (CNG) offers several advantages to increase the compressed
natural gas (CNG) engines performance [8] [10].
8
xxiii
CHAPTER 3
METHODOLOGY
3.1 Introduction
This chapter will explain on the concept and method being used for this project. For that,
an overall structure of methodology has been illustrated in a flow chart.
3.2 Overview of the methodology
The project started with the objectives and problem statement that had been defined. The
project cannot be done if the knowledge regarding on the topic itself is not adequate. First of all,
the concepts regarding the project must be clear. This can be done by searching related
information through the journals in the net, reference book, etc. With the information acquired
from the literature review, a clear concept and idea should already in mind. Hence, the next
process which is design and modeling are carryout. In this process, computer-aided drafting
(CAD) software, Solidworks used for design the multi holes injection nozzle while the flow
motion modeling of the injector done by computational fluid dynamics (CFD) software, Cosmos
FloWork.
9
xxiv
3.3 Project Methodology
Figure 3.1: Flowchart of final year project
Collecting Data and Literature Review
Sketch and design the injection nozzles in SolidWork
Sketch the model of the engine
Preparation the simulation in the Cosmos FloWork
Running the simulation Unsatisfied
Data collection
Conclusion
End
Start
10
xxv
3.4 Description of the methodology
3.4.1 Injection nozzles
The beginning of this final year project, literature review were collected from book,
journal and other references to understand about the project. After that, the original injector was
designed by SolidWork 2005.
Figure 3.2: Original Injection Nozzle
11
xxvi
The main purpose of this project is to design the injection nozzle and analyze the flow at
maximum valve lift before ignite. The figures below are the modified injection nozzles that used
in this project.
Figure 3.3: Modified Injection Nozzles from SolidWork 2008
To find the best design, nozzle must be create in different size, degree and number of
nozzles. So that, the best design can be choose after simulate the flow of the nozzle in CNG
engine using Cosmos FloWork software. In this project use 20 types of injection nozzles in
difference diameters, angel of nozzle and sum of holes. Then, analyze each of the injection
nozzles using the CNG engine SolidWork model. The figure below is the detail design.
12
xxvii
Figure 3.4: Modified Injection Nozzles from Microsoft Visio 2007
13
xxviii
3.4.2 Compressed natural gas engine model
The model of the CNG engine in figure below is base on the actual engine in term of
bore, stroke and intake valve. The diameter of the bore is 86 mm and the length of the stroke is
70 mm. The valve lift is 7.11 mm. The injection nozzle is at the intake manifold.
Figure 3.5: CNG Engine Model
14