EFFECTS OF PREMIXING INJECTOR CONFIGURATION AND BIODIESEL ...eprints.uthm.edu.my/9098/1/Latip_Lambosi.pdf · ketara panjang api dan pelepasan yang disebabkan oleh kandungan air yang

EFFECTS OF PREMIXING INJECTOR CONFIGURATION AND

BIODIESEL BLENDS ON SPRAY AND FLAME CHARACTERISTIC IN A

COMBUSTION BURNER

LATIP BIN LAMBOSI

UNIVERSITI TUN HUSSEIN ONN MALAYSIA

This thesis has been examined on date 24 August 2015

and is sufficient in fulfilling the scope and quality for the purpose of awarding the

Degree of Master of Mechanical Engineering

Chairperson:

Dr Al Emran Bin Ismail

Faculty of Mechanical and Manufacturing

Universiti Tun Hussein Onn Malaysia

Examiners:

Dr Mas Fawzi Bin Mohd Ali

Faculty of Mechanical and Manufacturing


Dr. Mohamad Yusof Idroas

School of Mechanical Engineering

Universiti Sains Malaysia

EFFECTS OF PREMIXING INJECTOR CONFIGURATION AND BIODIESEL

BLENDS ON SPRAY AND FLAME CHARACTERISTIC IN A COMBUSTION

BURNER

LATIP BIN LAMBOSI

A thesis submitted in

fulfilment of the requirement for the award of the

Degree of Master of Mechanical Engineering

Faculty of Mechanical and Manufacturing Engineering


JANUARY 2016

iii

ACKNOWLEDGEMENT

I am grateful to the Allah for the good health and wellbeing that were necessary to

complete this thesis. I wish to express my sincere thanks to Prof. Madya Dr. Amir Bin

Khalid my supervisor for providing me with all the sincere and valuable guidance and

encouragement extended to me. I am also grateful to the lecturer, in the Department of

Plants and Automotive Engineering, Mr Farid Sies and Mr. Shahrin Hisham

Amirnordin. I am extremely thankful and indebted to them for sharing expertise and

knowledge. I take this opportunity to express gratitude to all of the department faculty

members for their help and support. I also thank my parents and families for the

unceasing encouragement, support and attention. I also place on record, my sense of

gratitude to one and all, who directly or indirectly, have lent their hand in this venture.

Finally I wish to thank the financial support of the New External Combustion Regimes

- Exploration on the New Concept of Rapid fuel-water-air Premixing Injector in

Burner System for Small and Medium Enterprises in Malaysia (UTHM) (C010) grant

that funded this project.

iv

ABSTRACT

The emission that are released from the combustion of biodiesel either in internal

combustion engine or external burner system can cause an environmental and health

problem. Thus, the premix concept from biodiesel and water were studied with

focusing in controlling of combustion process in order to minimize the harmful

emission. The main purpose of this research is to investigate the effects of biodiesel-

water premix spray characteristic, burning process and flame characteristic. The

studied parameters include the nozzle characteristic in term of nozzle angle,

equivalence ratio, and water content directly introduced into the into the burner and

spray characteristics such as spray penetration length, spray angle and spray area.

Based on the obtained results, different water content showed there was no substantial

effect on the spray characteristic. However, there were significant reduction of flame

length and emission caused by the increasing water content during the combustion.

Other than that, water addition leads a significant difference in emissions between the

fuels. The highest reduction of NOx up to 58% experienced by diesel produced by

W15. It is also causes the reduction of CO emission is experienced by B5 with the

percentage of the difference up to 55%. For HC emission, B15 produce the highest

emission reduction at 83%. Meanwhile for the effects of nozzle characteristic, the

nozzle with 45˚ angle produced the largest spray angle which is around 29˚. This

produced the shortest spray penetration which is approximately 94 mm. Larger nozzle

angle produced higher amount of NOx. Nozzle 30˚ produce 55.22% less NOx emission

and nozzle 40˚ produce 50.75% less compare to 45˚ nozzle. As nozzle angle increase,

the CO emission increase. This shows that nozzle 45˚ promoted more complete

combustion compare to the other two nozzle.

v

ABSTRAK

Pelepasan yang dikeluarkan daripada pembakaran biodiesel sama ada dalam enjin

pembakaran dalaman atau sistem pembakar luaran boleh menyebabkan masalah alam

sekitar dan kesihatan. Oleh itu, konsep pra-campuran dari biodiesel dan air telah dikaji

dengan memberi tumpuan dalam mengawal proses pembakaran untuk mengurangkan

pelepasan berbahaya. Tujuan utama kajian ini adalah untuk mengkaji kesan premix

biodiesel air ciri semburan, proses pembakaran dan ciri-ciri api. Parameter yang dikaji

termasuk ciri muncung dari segi sudut muncung, nisbah kesetaraan, dan kandungan

air terus diperkenalkan ke dalam ke dalam pembakar dan semburan ciri-ciri seperti

panjang penembusan semburan, sudut semburan dan kawasan semburan. Berdasarkan

keputusan yang diperolehi, kandungan air yang berbeza menunjukkan tiada kesan

yang ketara kepada ciri semburan. Walau bagaimanapun, terdapat pengurangan yang

ketara panjang api dan pelepasan yang disebabkan oleh kandungan air yang semakin

meningkat semasa pembakaran. Selain itu, penambahan air membawa perbezaan yang

signifikan dalam pelepasan antara bahan api. Pengurangan tertinggi NOx sehingga

58% dialami oleh diesel yang dihasilkan oleh W15. Ia juga menyebabkan pengurangan

pelepasan CO dialami oleh B5 dengan peratusan perbezaan sehingga 55%. Akhir

sekali untuk HC pelepasan, B15 menghasilkan pengurangan pelepasan tertinggi iaitu

83%. Sementara itu, bagi kesan ciri muncung, muncung penyuntik yang bersudut 45˚

menghasilkan sudut semburan terbesar iaitu kira-kira 30˚. Ini menghasilkan semburan

penembusan terpendek iaitu kira-kira 94 mm. Akhir sekali untuk HC pelepasan, B15

menghasilkan pengurangan pelepasan tertinggi iaitu 83%. Sudut muncung yang lebih

besar menghasilkan jumlah yang lebih tinggi NOx. Muncung 30˚ dan 40˚ masing-

masing menghasilkan 55.22% dan 50.75% pelepasan NOx kurang berbanding dengan

muncung 45˚. Apabila sudut muncung meningkat, pelepasan CO berkurangan. Ini

menunjukkan bahawa muncung 45˚ menggalakkan pembakaran yang lebih lengkap

berbanding dengan dua muncung lain.

vi

TABLE OF CONTENTS

TITLE i

DECLARATION ii

ACKNOWLEDGEMENT iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF TABLES ix

LIST OF FIGURE xii

LIST OF SYMBOLS AND ABBREVIATIONS xv

LIST OF APPENDICES xvii

1.0 INTRODUCTION 1

1.1 Research background 1

1.2 Problem statement 3

1.3 Objectives of study 3

1.4 Scope of study 4

1.5 Thesis outline 4

2.0 LITERATURE REVIEW 5

2.1 Introduction 5

2.2 Burner system 5

2.3 Fuel spray and flame characteristic 6

2.3.1 Spray penetration 7

2.3.2 Spray angle 7

2.3.3 Spray area density 8

2.3.4 Stoichiometric 8

2.3.5 Equivalence ratio, 9

2.3.6 Flame length 9

2.4 Emission gas pollution of burner 10

vii

2.4.1 Carbon monoxide – CO 10

2.4.2 Unburned hydrocarbon – HC 10

2.4.3 Nitrogen Oxide – NOx 11

2.4.4 Carbon dioxide – CO₂ 11

2.5 Biodiesel as alternative fuel source 12

2.5.1 Biodiesel properties 13

2.5.2 Biodiesel flame 16

2.5.3 Emission of biodiesel 18

2.5.4 Previous studies on performance and emissions of

biodiesel

21

2.6 Nozzle characteristic 24

2.6.1 Previous studies on nozzles characteristic 25

2.7 Water in biodiesel combustion 29

2.7.1 Effects of water to biodiesel combustion 29

2.7.2 Water and oil emulsion disadvantages 33

2.8 Summary of literature reviews. 34

3.0 METHODOLOGY 35

3.1 Introduction 35

3.2 Palm oil as a biodiesel source 35

3.3 Biodiesel blending 36

3.3.1 Molecular equation biodiesel blends 38

3.3.2 Calculation of molecular equation of biodiesel fuel 38

3.5 Flow rates calculation 39

3.6 Experimental setup 41

3.7 Instrumentations 42

3.7.1 Measurement of fuel supply 43

3.7.2 Measurement of water supply 44

3.7.3 Direct photography apparatus 44

3.7.4 Measurement of exhaust gas emission 45

3.8 Experimental procedures and acquisition of data 45

3.8.1 Capturing image of spray 46

3.8.2 Capturing image of flame 47

3.8.3 Direct photography image analysis 47

viii

3.8.4 Emission measurement 49

3.9 Summary of research methodology 49

4.0 RESULT AND DISSCUSSION 50

4.1 Introduction 50

4.2 Spray characteristic of biodiesel-water-air premixing 50

4.3 Flame characteristic of biodiesel-water-air premixing 55

4.4 Emission of biodiesel-water-air premixing 60

4.5 Effect of biodiesel on spray characteristic, flame

characteristic and emission

66

4.6 Effect of water content on spray characteristic, flame


68

4.7 Effect of nozzle angle on spray characteristic, flame


70

4.8 Determining an optimum premixing injector configuration

and biodiesel blends on spray and flame characteristic in a

combustion burner

74

5.0 CONCLUSION AND RECOMENDATION 75

5.1 Conclusion 75

5.2 Recommendation 76

REFERENCES 79

APPENDICES 83

ix

LIST OF TABLES

TABLE TITLE PAGE

2.1 Comparison of density and kinematic viscosity for various

types of biodiesel [9], [34], [35], [38], [62], [69], [70]

14

2.2 Different standards and specifications for palm biodiesel

[33]

14

2.3 Summary of current research on biodiesel by various

researchers

22

2.4 Summary of current research on nozzle characteristic by

various researchers

26

3.1 Physical properties of biodiesel fuel blended 38

3.2 Molecule equation 38

3.3 Air flow rate data 41

3.4 Mass flow rate of fuel 41

3.5 Mass flow rate of water 42

3.6 Specifications of Testo 350 Portable Gas analyser (Reproduce

from Testo 350 · Combustion & Emission Analyser Instruction

manual)

46

4.1 Flame image of the four types of fuel flames with water

content 0%, 5%, 10%, and 15% at equivalence ratio, ø

=1.4; θ=45˚

68

4.2 The percentage of the difference on emission between the

tested fuels relative to the W0

70

4.3 Comparison of flame image for Diesel and B5 at three

different angle (0% water content, W0; equivalence ratio,

ø = 1.4)

72

4.4 The percentage of the difference on emission between the

tested fuels relative to the 45˚ nozzle

73

x

B1 Spray formation of diesel at different water content for 45˚

nozzle

87

B2 Spray formation of B5 at different water content for 45˚

nozzle

88


nozzle

89


nozzle

90


nozzle

91


nozzle

92


nozzle

93


nozzle

94


nozzle

95


nozzle

96


nozzle

97


nozzle

98

B13 Spray characteristic of diesel and biodiesel at different

water content for 45˚ nozzle

99

B14 Spray characteristic of diesel and biodiesel different water

content for 40˚ nozzle

100

B15 Spray characteristic of diesel and biodiesel at different


101

C1 Flame development of diesel at different water content for

45˚ nozzle

103

xi

C2 Flame development of B5 at different water content for 45˚

nozzle

104

C3 Flame development of B10 at different water content for

45˚ nozzle

105


45˚ nozzle

106

C5 Flame development of diesel at different water content for

40˚ nozzle

107

C6 Flame development of B5 at different water content for 40˚

nozzle

108


40˚ nozzle

109


40˚ nozzle

110

C9 Flame development of diesel and biodiesel at different


111

C10 Flame development of diesel and biodiesel at different


112

D1 Emission of diesel at different water content for 45˚ nozzle 114

D2 Emission of B5 at different water content for 45˚ nozzle 114



D5 Emission of diesel at different water content for 40˚ nozzle 116




xii

LIST OF FIGURE

FIGURE TITLE PAGE

2.1 Spray Formation by hollow cone nozzle [21] 7

2.2 Density, Kinematic viscosity vs Biodiesel ratio for

RBDPO [38], Soy methyl [70] and Palm oil [62]

15

2.3 Variation of blend density with temperature [34] 16

2.4 Relation between density and fuel temperature of diesel,

biodiesel, and blended fuels (B20–B80) [35]

16

2.5 Combustion flame of (a)biodiesel, (b)diesel [36] 17

2.6 Flame evolutions at various Jatropha oil temperatures

[37]

17

2.7 Micro-explosion sequences at various Jatropha oil

temperatures [37]

18

2.8 Changes in NOx concentration profile on the jet axis for

the time after the start of injection [43]

19

2.9 Percentage of CO2 emission reduction due to the

presence of biodiesel [39]

20

2.10 Comparison of average percentage change in CO with

different biodiesel wrt diesel [65]

20

2.11 The nozzle geometry (a) Orifice Diameter (b)

Length (c) Angle [27]

24

2.12 Formation of the oil membrane in the atomization process

after fuel injection in the cylinder [41].

29

2.13 Regular fuel oil combustion [59] 30

2.14 Emulsified fuel combustion [59] 31

2.15 Density and heating value of pine and forest residue

pyrolysis bio-fuel as a function of water content [32]

32

xiii

2.16 Viscosity of pyrolysis bio-fuel from pine and forest

residue as a function of water content [32]

32

2.17 Comparison of emissions between two types of injector;

(a) Fuel soybean without water; (b): Fuel soybean with

water-mixing or water-emulsified water 50% [14]

33

3.1 Block Flow Diagram of Biodiesel Production in UTHM 36

3.2 Biodiesel blending machine schematic diagram 37

3.3 Biodiesel blending process flow 37

3.4 Parts of premixing injector 39

3.5 Premixing injector nozzle angle. 40

3.6 Flows direction for water, fuel, and air in into mixing

chamber

40

3.7 Schematic diagram of premixing injector 43

3.8 Mass flow meter 44

3.9 Dwyer water flow meter 44

3.10 DSLR camera for fuel spray and flame image capturing 45

3.11 Testo 350 Portable Gas analyser 45

3.12 (a) spray penetration, (b) spray area, (c) spray angle 48

3.13 (a) flame length, (b) flame area, (c) flame angle 48

4.1 Effect of water content on spray characteristic for

different type of fuel at nozzle angle, θ=45˚; (a) Diesel;

(b) B5; (c) B10; (d) B15

51


different type of fuel at nozzle angle, θ=40˚; (a) Diesel:

(b) B5; (c) B10; (d) B15

53


different type of fuel at nozzle angle, θ=30˚; (a) Diesel:

(b) B5; (c) B10; (d) B15

54

4.4 Effect of water content on flame development for

different type of fuel at nozzle angle, θ=45˚; (a) Diesel;

(b) B5; (c) B10; (d) B15

57

xiv

4.5 Effect of water content on flame development for

different type of fuel at nozzle angle, θ=40⁰; (a) Diesel;

(b) B5; (c) B10; (d) B15

59

4.6 Effect of water content on burner emission for different

type of fuel at nozzle angle, θ=45⁰; (a) Diesel; (b) B5; (c)

B10; (d) B15

62

4.7 Effect of water content on burner emission for different

type of fuel at nozzle angle, θ=40⁰; (a) Diesel; (b) B5; (c)

B10; (d) B15

64

4.8 (a) Spray characteristic of biodiesel; (b) Flame

propagation of biodiesel; (θ = 45⁰, 0% water content, W0)

66

4.9 Effect of biodiesel on emission at nozzle angle (θ = 45⁰,

0% water content, W0)

67

4.10 Effect of water on emission of biodiesel burner; (θ = 45˚;

equivalence ratio, ø = 1.4)

69

4.11 Effect of nozzle characteristic on spray characteristic at

zero percent water content, W0; (a) Diesel; (b) B5

71

4.12 Effect of nozzle angle on burner emission (0% water

content, W0; equivalence ratio, ø = 1.4)

73

xv

LIST OF SYMBOLS AND ABBREVIATIONS

ρ - Density

(AF)act - Actual air-fuel ratio

(AF)stoich - Stoichiometric air-fuel ratio

(FA)act - Actual fuel-air ratio

(FA)stoich - Stoichiometric fuel-air ratio

ṁ𝑓 - Fuel flow rate

A - Area

AF - Air-fuel ratio

C - Carbon

CaOME - Canola Oil Methyl Ester

CO - Carbon monoxide

CO₂ - Carbon dioxide

COME - Corn Oil Methyl Ester

CPO - Crude Palm oil

CSOME - Cotton Seed Oil Methyl Ester

DSLR - Digital Single-Lens Reflex

FA - Fuel-air ratio

FAME - Fatty Acid Methyl Ester

GO - Soy bean oil

GOME - Grapeseed Oil Methyl Ester

H2 - Hydrogen

H2O - Water

ṁ - Mass flow rate

ma - Air flow rate

mf - Fuel flow rate

MFOME - Menhaden Fish Oil Methyl Ester

xvi

MOME - Mahua Oil Methyl Ester

MWa - Air molecular weight

MWf - Diesel molecular weight

MWw - Water molecular weight

N2 - Nitrogen

NOx - Nitrogen oxides

ø - Equivalence ratio

O₂ - Oxygen

OOME - Olive Oil Methyl Ester

P - Pressure

PM - Particulate matter

POB - Palm Oil Biodiesel

POME - Palm Oil Methyl Ester

Q2 - Flow rate of secondary air

Qa - Flow rate at nozzle

Qt - Total air flow rate

RME - Rapeseed Methyl Ester

ROME - Rice Bran Oil Methyl Ester

RSOME - Rapeseed Oil Methyl Ester

SBOME - Soy Bean Oil Methyl Ester

SFOME - Sun Flower Oil Methyl Ester

SOME2 - Sun Flower Oil Methyl Ester

V - Velocity

W0 - 0% water content in fuel




WCOB - Waste Cooking Oil Biodiesel

WCOME - Waste Cooking Oil Methyl Ester

WFOME - Waste Frying Oils Methyl Ester

xvii

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Project scheduling

84

B Spray formation of diesel and biodiesel image

86

C Flame development of diesel and biodiesel image

102

D Emission of diesel and biodiesel data

113

E Sample of calculation

118

CHAPTER 1

INTRODUCTION

1.1 Research background

Shortage in hydrocarbon fuel sources, energy preservation and future stringent

emission regulations have been a formidable challenge. Therefore, the alternative

source of fuel is receiving a lot of attention, especially in the application of renewable

energy. One of the most promising sources of alternative energy right now is biodiesel.

Biodiesel is composed of methyl esters of fatty acids derived from the trans-

esterification of alcohols with vegetable oils or animal fats [1]–[4].

Biodiesel has about 90 percent of the energy content of conventional diesel,

but the fuel economies of both are comparable. Biodiesel’s higher oxygen content aids

in achieving complete fuel combustion, thereby reducing emissions of particulate air

pollutants, carbon monoxide, and hydrocarbons. It is generally used in a 5 percent

blend in conventional diesel (B5) and it can be used in blends of up to 20 percent (B20)

in standard diesel engines and as pure biodiesel (B100) in modified engines [5].

Malaysia is currently one of the largest palm oil producers and crude palm oil

(CPO) is the most preferable feedstock to be converted into biodiesel. Malaysia had

implemented B5 on March 2014 in Peninsular Malaysia and will start the B7 program

in the first quarter of 2015. Consequently, it is important to study the effect of various

biodiesel blends because in the future, biodiesel will be the main fuel source replacing

conventional fuel. Biodiesel may be transformed for use in engines or used directly as

fuels in burners. When used as fuels in burners they have certain advantages such as:

i) requiring no specific alteration processes, such that they may be obtained reasonably

price. ii) less rigorous specifications when used in burners than when used in engines.

2

iii) a broader range of technologies related to burners than to heat engines. iv) burners

have a wider range of regulation concerning fuel than heat engines [6].

However, it is estimated that the burning of neat biodiesel would produce

approximately 10% more NOx than that of petroleum-based diesel, mainly due to the

high oxygen content of the neat biodiesel [7]–[9]. This causes health and

environmental problems such as causing or worsen respiratory diseases and global

warming. Reduction of toxic emission is a key to the simultaneous solution of energy

and environmental problems. Water-emulsification has been well known as one of the

easiest and low cost solution of toxic emission in burner combustion [10]–[14].

Nonetheless, water-emulsification needs surfactant to avoid separation of fuel and

water. Water-emulsified fuel has a disadvantage in temporal stability as fuel [9], [15]–

[17]. Hence, it is necessary to find out the effective usage of water in combustion

without involving emulsification.

To further improve the combustion of biodiesel one must be able to control the

combustion process. One of the methods to control combustion in burner system is by

selecting the suitable nozzle. The functions of a nozzle are to atomize the fuel, or break

it up into tiny droplets which can be vaporized in a much shorter period of time when

exposed to high temperatures. A nozzle with a proper characteristic can improve the

spray quality and will affect the air fuel mixing. This leads to a better combustion

process that results in higher performance, nonetheless it will also modifies pollutant

emissions [18].

The aim of this research is to study whether the different characteristics of a

nozzle has a correlation effect with different nozzle angles on the spray characteristic,

flame characteristics and the emission produce from an injector that can use water

directly in combustion field will be investigated in detail. The injector used is a type

of fuel-water internally rapid mixing. Fuel is mixed with water inside of the injector

supported by atomizing air. After mixing, the mixture is injected to the outside. In this

way, water is introduced directly into combustion field and the utilization of water is

consider as independent of emulsification.

3

1.2 Problem statement

Biodiesel is a promising alternative fuel to petroleum diesel because it had comparable

properties to the common diesel, and has an advantage of being renewable because of

its biomass origin. On the other hand, the biodiesel has also the same problem of

exhaust emissions. NOx and Particulate Matter (PM) are released from the combustion

of biodiesel either in internal combustion engine or external burner system will cause

environmental and health problem. Introducing water into the combustion process

through direct premixing method and choosing the suitable nozzle characteristic is an

effective way to encounter this problem. However, there are still barriers of

implementation such as:

a) The effect of controlling parameters that involved during the combustion

process.

b) The effect of direct water premixing in the combustion process on spray

characteristic and flame characteristics.

c) Most fuel injector has curved spray boundaries. The different nozzle holes

angle will produce different spray characteristics hence causing varying

emissions results.

Therefore, in this research an injector that will internally premix the biodiesel-water

mixture with three different angle nozzle were used and the study of the spray

characteristic and flame characteristics of the combination of premixing injector and

diesel-water mixtures is an important process in order to reduce the emission problems.

1.3 Objectives of study

The objectives of these projects are as follows:

a) To determine the spray penetration, spray angle and spray area of diesel by

using different water content and equivalence ratio.

b) To observe how the parameters of the injector such as angle of nozzle,

equivalence ratio, water contents influence the spray formation and flame

characteristics.

c) To determine the emission from the combustion.

4

1.4 Scope of study

This research is done based on the scope identified. The scopes of this study are:

a) The fuel to be tested on injector is biodiesel B5, B10 and B15 and diesel as

base line fuel.

b) The equivalence ratios to be set as in the range of 0.6 to 1.4.

c) The water-fuel ratio will be tested were 5% to 15%. The water content start

with 5% is because we want to know the minimal amount of water that can be

introduced to combustion.

d) Injector with nozzle holes angle 45o, 40o and 35o.

e) The emission of CO, CO₂, HC, NOx, O₂ and flue temperature will be

measured.

1.5 Thesis outline

The current thesis consists of five chapters. Chapter One is the introduction in which

the problem statement, objectives and scope of research, contribute to the knowledge

in research work are presented. The literature review is presented in Chapter Two and

it covers topics from of the fundamental of biodiesel, the performances and emission

characteristics biodiesel in burner system and related information on techniques of

engine diversification.

In Chapter Three, detail description of the experimental setup, procedures and

techniques, of the premixing injector used and calculation for the fuel flow rate and

gas employed in the research are presented. All the experimental results are presented

and discussed with supporting evidence to support them are presented in Chapter Four.

Lastly, in Chapter Five provides conclusions drawn from the research work conducted

are presented.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

In this part of the chapter, it will review the current status of the several studies that

had been carried out on the emission and performance characteristic of biodiesel

burners in term of the specific fuel type that could be used, type of emissions such as

NOx, CO, CO₂, mixing characteristic, spray characteristic and others operating

conditions that can be used to optimize the performance of the biodiesel burner system

and other relevant information of the study were being taken as references.

2.2 Burner system

Generally a function of burner is to provide a stable operation and acceptable flame

pattern over a specific set of operating condition. One of the operating conditions of a

burner is to use a specific type of fuels. This is important because that the fuel used

should match the burner. Using fuels with improved characteristics do not certainly

increase burner performance. The fuel characteristics would depend on burner type,

size, design and operating conditions [19], [20]. In contrast, using fuels with

characteristics below the minimum burner requirements can cause rough burner

operation.

There are a few types of burner which are classified based on its fuel type and

one of them is oil burner. The oil burner is a combustion furnace to blending warming

oil with air, then blowing and igniting this mixture in a boilers fire port. Fuel oil cannot

burn in its liquid state, it must first be atomized even though oil is regarded as

inflammable.

6

Fuel spray or fuel atomization is a process of breaking up bulk liquid into many

small droplets. In order to have good combustion, fuel and air must mix well. A bulk

liquid has a limited surface area to contact with the air. This is the reason that liquid

fuel, or specifically, fuel oil, requires atomization before burning. Atomization

increases the liquid surface area, which results in an increase of the fuel evaporation

rate and fuel-air mixing rate. [21]. If the oil is transformed into vapour or atomize

rapidly the chances of clean and effective combustion are increased.

To help in better understanding of the research work presented, the next section

will discuss and define the relevant terms and concepts. The following material is not

intended as a complete review of the reacting flow and the systems theory, but only as

a partial list of definitions and concepts, which shall be referred throughout this work.

2.3 Fuel spray and flame characteristic

There are few physical characteristics and parameters of spray that were explained in

next section. It will generally highlight the interaction of the control volume where the

fuel is injected and mixed. These characteristics will be used as the parameters to help

in analysing the fuel spray in macroscopic point of view. Spray characteristics depend

on the type of liquids, pressure, density, temperature, and the design of injector. The

basic function of spray are to generate surface area for evaporation or combustion (heat

and mass transfer), and transfer momentum to a surface or a gas. Figure 2.1 shows

spray formation using a hollow cone nozzle. Figure 2.1(a) is hollow-cone spray. α is

the initial spray cone angle. The spray angle is the angle between the lines drawn on

the edge of different contrast, and D is the diameter of nozzle hole. S is spray

penetration.

7

Figure 2.1: Spray Formation by hollow cone nozzle [21]

2.3.1 Spray penetration

Penetration of spray may be defined as the maximum distance it reaches when injected

into the stagnant air. This continues until the liquid phase region penetrates to a point

where the total fuel evaporation rate in the spray equals the fuel injection rate. When

this condition occurs, the tip of the liquid region stops penetrating and begins

fluctuating about a mean axial location (defined as the liquid length). The energy for

vaporizing the fuel comes mainly from air entrained into the spray, and not energy

released by combustion. The location of the tip of the liquid phase fuel depends on

injector parameters, ambient gas conditions, fuel properties. [22].

2.3.2 Spray angle

Most of the sprays have a conical shape and the spray angle is defined as the angle

formed by two straight lines that start from the exit orifice of the nozzle and tangent to

the spray outline (sprays morphology) in a determined distance. The angle in a diesel

spray is formed by two straight lines that are in contact with the spray’s outline. Many

practical systems require atomizers that distribute the fuel in the form of a less

concentrated and lower penetrating spray. An appropriate spray angle is the key

(a)Hollow-cone spray.

Example: outwardly opening

nozzle

(b): Image of spray formation

using a hollow cone Nozzle

Sowing sheet breakup

8

element to maintaining a stable oil flame. If the spray angle is too narrow, the

recirculation vortex is too small to bring the high temperature flue gas back to the oil

gun tip resulting in a lift-off flame[23].

2.3.3 Spray area density

The spray area density is the product of the spray drop surface area and the number of

drops per unit volume. The surface area density is important in evaporation and

combustion applications since the local evaporation rate is highly correlated to the

surface spray area. The extinction of light caused by the drops within a spray is also

directly proportion to the surface area density. The two most widely used methods of

measuring the surface area density are Laser Sheet Imaging and Statistical Extinction

Tomography[23].

2.3.4 Stoichiometric

Stoichiometric reaction is a unique reaction in which all the reactants are consumed.

This means that the amount of oxidant present in the reaction is just enough to

completely burn the fuel. This ideal mixture approximately yields the maximum flame

temperature, as all the energy released from combustion is used to heat the products.

Assuming that air consists of 21% oxygen and 79% nitrogen by volume it can be

written in chemical equation[24]:

CaHb + (a +b

4 ) (O₂ + 3.773N2) = aCO₂ +

b

2H2O + 3.773 (a +

b

4 ) N2 (2.1)

Above chemical equation is overall complete combustion equation for a general

hydrocarbon fuel of average molecular composition CaHb with air.

9

2.3.5 Equivalence ratio, ø

The fuel-air ratio is one of the most important parameters for combustion analysis and

is normally reported in terms of a non-dimensional variable called equivalence ratio ø,

which is the actual fuel-air ratio normalized by the stoichiometric fuel-air ratio[24]:

ø =(FA)act

(FA)stoich=

(AF)stoich

(AF)act (2.2)

Where, FA = Fuel-air ratio

AF = Air-fuel ratio

FA = 1

AF (2.3)

Besides that, we can use lambda value, λ instead of equivalence value:

λ = 1

ø=

(FA)stoich

(FA)act=

(AF)act

(AF)stoich (2.4)

ø = 1.0 is defined as stoichiometric condition. Conditions where there is an excess of

oxidant present in the mixture are “lean”, ø < 1.0. Similarly, mixtures with an excess

of fuel are “rich”, ø > 1.0.

2.3.6 Flame length

Typical specifications for flames include maximum flame lengths and widths. The

number, heat release, and layout of the burners in the furnace are designed to provide

the proper heat transfer pattern. Flame length is referenced to the leading edge mainly

because it then follows the streamlines in the flame. It has also been defined

alternatively as the cord length from the tip of the flame to a point along the base of

the flame midway between the leading and trailing edge.

The flame dimensions for oil or gas firings be influenced by on its applications.

Some applications would like short flames and some prefer long flames. The flame

length is primarily determined by the burner design. During operation, flame length

would vary with heat releases and O₂ levels. Normally, flame length is estimated by

the length per unit heat release. However, different O₂ levels would affect this

estimation. The lower the O₂ level, the longer the flame length. The flame dimensions

10

are important to ensure that there is proper heat distribution in the combustion and that

the flames do not impinge undesirably on anything in the combustor

2.4 Emission gas pollution of burner

Combustion products cause harm at a wide range of scales. Until this day, there had

been an increasing interest in reducing pollutant emissions of all types from all

combustion processes. Efforts are ongoing from a broad cross section of organizations

to improve existing techniques and to develop new techniques for minimizing

pollution[25].

This research has particularly focused on biodiesel burner, where the exhaust

emissions include a wide range of gaseous and particulate organic and inorganic

compounds. However, these exhaust gas emissions are dependent on the fuel

composition. The biodiesel burner pollutants can be classified into four main groups

consisting of carbon monoxide (CO), hydrocarbon (HC), nitrogen oxides (NOx) and

carbon dioxide (CO₂).

2.4.1 Carbon monoxide – CO

CO is generally produced in trace quantities in many combustion processes as a

product of incomplete combustion. CO is a flammable gas, which is non-irritating,

colourless, odourless, tasteless, and normally noncorrosive. It is highly toxic and acts

as a chemical asphyxiant by combining with haemoglobin in the blood that normally

transports oxygen inside the body. CO is generally produced by the incomplete

combustion of a carbon-containing fuel. Normally, a combustion system is operated

slightly fuel lean (excess O₂) to ensure complete combustion and to minimize CO

emissions[26].

2.4.2 Unburned hydrocarbon – HC

Unburned hydrocarbons (HC) is a term describing any fuel or partially oxidized

hydrocarbon species that exit the stack of a furnace. The cause for these emissions is

11

typically due to incomplete combustion of the fuel from poor mixing or low furnace

temperature. A low-temperature environment can be created by operating the furnace

at a reduced firing rate or turndown[26]. HC emissions constitute compounds of

hydrogen, carbon and occasionally, oxygen. HC emission have a very similar trend as

CO since both are intermediate species during combustion processes HC can cause

respiratory problems and is known to be carcinogenic.

2.4.3 Nitrogen Oxide – NOx

NOx refers to oxides of nitrogen. These generally include nitrogen monoxide, also

known as nitric oxide (NO), and nitrogen dioxide (NO₂). In most high temperature

heating applications, the majority of the NOx exiting the exhaust stack is in the form

of nitric oxide (NO). NO is a colourless gas that rapidly combines with O₂ in the

atmosphere to form NO₂. NO is poisonous to humans and can cause irritation of the

eyes and throat, tight- ness of the chest, nausea, headache, and gradual loss of strength

[27], [28].

Ideally, NOx is produced from burning hydrocarbon fuels with oxygen during

the combustion process with a high combustion temperature of about 1800K. NO is

not irritant, but the effects are similar to CO emissions. A wide range of health and

welfare effects is caused by NOx emissions such as the irritation of the lungs, which

can lower resistance to respiratory infections. Acid rain is also caused by NOx

emissions, which possess a hazardous risk to the ecosystem by increasing irritation

and toxic algal blooms and reduces sun light penetration resulting in losses of

submerged aquatic vegetation.

2.4.4 Carbon dioxide – CO₂

Carbon dioxide (CO₂) is a colourless, odourless, inert gas that does not support life

since it can displace oxygen and act as an asphyxiant. It is found naturally in the

atmosphere at concentrations averaging 0.03% or 300 ppmv. Concentrations of 3% –

6% can cause headaches, dyspnea, and perspiration. Concentrations of 6% – 10% can

cause headaches, tremors, visual disturbance, and unconsciousness[25].

12

There are a number of different anthropogenic sources of CO₂ emissions.

Predominately, the emissions are from the combustion of fossil fuels. CO₂ is produced

when a fuel containing carbon is combusted.

2.5 Biodiesel as alternative fuel source

As stated in the section 2.2, fuel plays an important role in controlling the efficiency

and performance of the burner. Among the types of fuel that is increasingly gaining

attention these days is biodiesel. Currently, petroleum diesel is widely being used in

all over the world. Petroleum diesel is a major crude oil for world market demand in

the automotive industry, heavy manufacturing industry and even in light industry.

Petroleum diesel fuel is also known as petrodiesel, or fossil diesel is produced from

petroleum and hydrocarbon mixture, obtained from petroleum refining fractional.

Because of the depletion of fossil fuel, many researchers have been are focusing on

biodiesel. This is because biodiesel is an attractive renewable resource that have

similar characteristic to the diesel.

The biodiesel derived from different plant oils will have slightly different

molecular structures such as carbon-chain lengths, hydrogen-carbon ratio and oxygen

content due to the difference in the degree of unsaturation of the fatty acids in different

sources [29], [30]. In Europe, biodiesel is widely available in both features in the form

of 100% biodiesel (known as B100) and in the form of a mixture of petroleum diesel

range together. European biodiesel produced from rapeseed oil of canola oil family.

While in the United States, an initial interest in producing and using biodiesel has

focused on the use of soybean oil as the main fuel in the country with the largest

production of soybean oil in the world [31].

However, Malaysia Crude Palm Oil (CPO) is the most preferable feedstock to

be converted into biodiesel because Malaysia is presently one of the main palm oil

producers in the world. Furthermore, there are many encouragements from the

government to conduct research on palm oil regarding the feasibility and capability of

the oil towards biofuel production.

13

2.5.1 Biodiesel properties

Different applications of combustion processes pose different requirements on

combustion characteristics. For example, density, viscosity and surface tension are

vital parameters in the fuel combustion as they, for instance, influence pump and

channel line plan. Be that as it may, above all, they have a huge impact on the

atomization nature of the spray injectors, with resulting effects on the productivity of

the combustion and emissions. This is on account of these parameters basically focus

the droplet measurement dispersion issuing from the injector nozzle, and hence affect

the vaporization, ignition and combustion of the droplets. The droplet size from the

spray increases with the viscosity, surface tension and density of the fluid [32].

Table 2.1 shows a comparison of density and kinematic viscosity for 8 various

types of biodiesel. Various types of biodiesel (B100) have different values of densities

and kinematic viscosities at test temperature of 30˚C and 40˚C respectively. For

example, maximum and minimum values of density are 897 kg/m3 for biodiesel from

waste cooking oil and 882.1 kg/m3 for biodiesel from rapeseed oil methyl ester

(GOME) and soybean. This is showing that different feedstock will produce different

fuel properties.

Table 2.2 shows the Malaysian palm oil biodiesel specifications and Malaysian

petroleum diesel standards obtained from studies conducted by Abdullah et al. [33].

From the table it shows the kinematic viscosity of biodiesel range at 40oC and density

range at 15˚C are within the range of 3.3 to 5.0 mm2/s and 860 to 900 kg/m3

respectively. The density and viscosity of B100 are much higher compared to the

regular diesel used in oil burner which is ranging from 2.5 to 3.5 mm2/s and 827 to 845

kg/m3 respectively. Even though the biodiesel fuel can be used in its pure form, more

common use of it is seen as biodiesel blends or blended with petroleum fuel. Because

the use of biodiesel as the sole fuel requires the burner system modification as it tends

to cause the clogging on fuel filters and injector holes and also the formation of carbon

deposits inside the combustion chamber. The most common mix or biodiesel fuel

blends are referred to as "B20" containing 20% biodiesel by volume, and 80%

petroleum.

14

However, even after blending with regular diesel, biodiesel blends such as B5, B10,

B15, and B20 still have different values of density and kinematic viscosity. This is

shown in Figure 2.2. B0 stands for diesel fuel and B100 for pure biodiesel. B5 is 5%

biodiesel and 95% diesel fuel, B20 is 20% biodiesel and 80% diesel. Refined, Bleached

Table 2.1: Comparison of density and kinematic viscosity for various types of

biodiesel [9], [34], [35], [38], [62], [69], [70]

Types of biodieselChemical

formula

Test

method

Kinematic

viscosity at 40˚C

(mm2/s)

Test methodDensity

(kg/m3)

Test method

Sun flower oil methyl ester (SOME2) CH1.82 O0.11 Calculation 5.8 ASTM D445 893.4 @60˚C ASTM D1298

Corn oil methyl ester (COME) CH1.84 O0.11 Calculation 5.5 ASTM D445 884 @60˚C ASTM D1298

Rice bran oil methyl ester (ROME) CH1.85 O0.11 Calculation 6 ASTM D445 889.5 @60˚C ASTM D1298

Olive oil methyl ester (OOME) CH1.87 O0.11 Calculation 5.3 ASTM D445 887.6@60˚C ASTM D1298

Grapeseed oil methyl ester (GOME) CH1.83 O0.11 Calculation 5.2 ASTM D445 882.1 @60˚C ASTM D1298

Rapeseed methyl ester (RME) - - 4.478 ASTM D445 883.7@15˚C ASTM D4052

Soybean - - 5.8 ASTM D445 882.1 @60˚C ASTM D1298

C14-C24

methyl esters

C15-25H28-48 O2

Palm oil biodiesel (PBO) - - 4.71 ASTM D445 864.4 @25˚C ASTM D1298

Palm biodiesel (palm methyl ester) - - 4.5 - 855 @40˚C -

Waste cooking oil biodiesel - - 5.3 - 897 @17˚C -

Soy bean crude oil - - 5.2 - 870 @20˚C -

Waste cooking oil - - 4.56 ASTM D445 866 @60˚C ASTM D1298

Animal’s fats C53H102O6 - 6 - 870 @60˚C -

Fatty acid m(ester (FAME) 3.3-5.2 EN 14214860 -894

@15˚CEN 14214

Table 2.2: Different standards and specifications for palm biodiesel [33]

Property Unit

EN14214 ASTM D6751 Normal point Low pour point PLPO/PD B5a MS123: 1993b

Ester content % (m/m) 96.5> - 98.50 99.5 - -

Density at 15˚C Kg/m3860-900 - 878.3 870-890 841.9-845.9 -

Viscosity at 40˚C mm3/s 3.5-5.0 1.9-6.0 4.415 4 to 5 4.136- 4.549 1.5-5.8

Flash Point ˚C 120< 130.0 182 150-200 75-81 60<

Cloud point ˚C Report 15.2 -18 to 0 14-16 18

Pour point ˚C 15 -21 to 0 15

Carbon residue (on 10% distilation residue) % (m/m) 0.3> 0.50> 0.02 0.02-0.03 0.2 0.2

Acid Value mg KOH/g 0.5> 0.80> 0.08 0.3> - -

Cetane index - 51< 47< 58.3 53.0-59.0 51-57 47<

Sulphur content % (m/m) 0.001> 0.0015> 0.001> 0.001> 0.00017-0.00018 0.005

Sulphated ash content % (m/m) 0.02> 0.020> 0.01 0.01> - -

Water content mg /kg 0.05> 0.05> 0.05> 0.05> 0.001 0.001>

PLPO/PD B5: 5% processed liquid palm oil (PLPO) +95% petrolium diesel (PD)

MS123: 1993: Malaysian Standard for Diesel Fuel (Malaysia Biodiesel Standard, 2007)

The cloud point of biodiesel is generally higher than petroleum based diesel and should be taken into consideration when blending

Biodiesel standard Palm biodiesel

15

and Deodorized Palm Oil (RBDPO) has high value of the density at 40oC as compared

with soy methyl and palm oil, nonetheless lower value of kinematic viscosity.

To overcome the biodiesel density and viscosity problem, the fuel temperature can be

raised and controlled beforehand for fuel atomization process. P. Benjumea et al. [34]

studied the basic properties of several palm oil biodiesel–diesel fuel blends according

to the corresponding ASTM standards. Figure 2.3 shows the effect of temperature on

density (ρ) for pure fuels and B5 and B20 blends [34]. If the temperature increases, the

density of fuel will decrease. Similar finding had been discovered by Yoon et al. [35].

They had investigated the fuel density of diesel and biodiesel fuel in the temperature

range from 0 to 200 °C. Test fuels used are conventional diesel, neat biodiesel (100%

methyl ester of soybean oil), and their blends with blending ratios of 20%, 40%, 60%,

and 80% [35]. Figure 2.4 showed the density of diesel, biodiesel, and blended fuels

(B20–B80) decreases when fuel temperature is increased.

Figure 2.2: Density, Kinematic viscosity vs Biodiesel ratio for RBDPO [38], Soy

methyl [70] and Palm oil [62]

16

2.5.2 Biodiesel flame characteristic

When firing burners on a wide variety of fuels, flame characteristics and flame

dimensions can change, depending on the fuel fired, the operating fuel pressure, and

the heat release, because the mixing energy available can significantly affect the

volume or shape of a flame. According to Souza et.al [36], the flame of the diesel is

shorter and wider than biodiesel flame. Figure 2.5 is the formation of the flame of the

biodiesel and the diesel and both combustions is at the same pressure. The temperature

that around the injector nozzle will be higher compare to another diesel flame. Besides

Figure 2.3: Variation of blend density with temperature [34]

Figure 2.4: Relation between density and fuel temperature of diesel, biodiesel,

and blended fuels (B20–B80) [35]

17

that, when undergoes combustion process, the higher heat transfer rate of diesel oil

compare to biodiesel.

Wardana et al.[37] has performed a study on the combustion of Jatropha biodiesel. The

combustion of Jatropha biodiesel is done at different temperature as shown in Figure

2.6. The photo is taken every 0.04s. During combustion, micro-explosion occurred

causing the changes of flame geometry. Figure 2.7 shows the sequence of micro-

explosion at various temperatures. The micro-explosion cannot view clearly at room

temperature during flame evolution. As the oil temperature increased, the micro-

explosion can be seen clearly. The micro-explosion is bulge at low temperature. As

the temperature increase, it lengthen the flame height become a spike.

Figure 2.5: Combustion flame of (a)biodiesel, (b)diesel [36]

(a) (b)

Figure 2.6: Flame evolutions at various Jatropha oil temperatures [37]

18

2.5.3 Emission of biodiesel

Most of the biodiesels emit more NOx than diesel although there are cases where the

opposite occurs. The amount of NOx produced would depend on the nitrogen and

oxygen content in the biodiesels as well as the combustion dynamics, which can be

influenced by the adiabatic flame temperature, duration of high burning gas

temperature and sprays characteristics. Blends of biodiesels can alter the NOx

emissions [38]–[40]. The increasing of biodiesel proportion will increase NOx due to

the difference in physical and chemical properties of diesel and biodiesel. Biodiesel

has significant oxygen content compared to diesel and higher proportion of oxygen to

fuel in combustion chamber which leads to more complete combustion to produce

higher temperature and more NOx formation. Besides that biodiesel has higher fuel

density and iodine number in biodiesel such as Palm Oil Methyl Ester (POME) which

leads to increases of NOx [41], [42].

Figure 2.8 shows a comparison of NOx emissions obtained for biodiesel and

ethanol with those of natural gas, fuel oil #1 and fuel oil #2 obtained from the study

performed by Kaneko et al. [43]. As can be seen in the figure, the biodiesel and ethanol

emissions are similar to those attained from natural gas and fuel oil #1 and are lower

than the NOx emissions obtained from fuel oil #2 which contained certain fuel bound

nitrogen. This was achieved by using Lean, Premixed, Pre-vaporized (LPP)

Figure 2.7: Micro-explosion sequences at various Jatropha oil temperatures [37]

19

combustion technology has been developed that converts liquid biofuels, such as

biodiesel and ethanol, into a synthetic natural gas.

Hess et al. [44] claimed that biodiesel is carbon neutral and that the combustion

of this fuel does not contribute CO₂ emission to the atmosphere because the carbon

released is equal to the carbon absorbed by plants and also have the potential to reduce

substantial amount of CO₂ emission. This claim is supported by Sann et al. [39] where

they had executed a study of CO₂ emission during the combustion of biodiesel and

distillate blends to explore potential of biodiesel as gas turbine fuel. The result of the

study is shown in Figure 2.9 and the findings are biodiesel has the potential to reduce

CO₂ emission and increase the combustion efficiency compared to the usage of normal

diesel. However, users would need to evaluate the main priority in the system, whether

they would compromise for the efficiency or the CO₂ emission.

CO is one of the consequences of incomplete fuel combustion. Less CO is

generated with biodiesels than diesel. Concentration of oxygen during combustion

would enhance the oxidation rate of CO and lead to less CO formation. This is a major

advantage of oxygenated fuels like biodiesel. It should be noted that the carbon

contents of different biodiesels are not the same and most biodiesels have less carbon

content than diesel. This could also affect the percentage change in CO emission.

Figure 2.10 shows the average percentage change in CO for different biodiesels after

the burners were switched from diesel to operate on the biodiesels.

Figure 2.8: Changes in NOx concentration profile on the jet axis for the time after

the start of injection [43]

1 2 3 4 5 6

0.0

0.2

0.4

0.6

0.8

1.0

NO

x -

pp

mv

d (

at1

5%

O2

)

Exhaust Temperature (0C)

X Axis Title

CENTAUR 50 DATA (1ATM)

X Axis Title

X Axis Title

X Axis Title

X Axis Title

50

30

20

40

10

0800 850 900 950 1000 1050 1100

Fuel Oil #1

Natural Gas

Fuel Oil #2

Biodiesel B100 (SME)

Ethanol (ASTM D-4806)

Fuel Oil #2

Fuel Oil #1

Natural Gas

Biodiesel B100 (SME)

Ethanol (ASTM D-4806)

q

x

20

Figure 2.9: Percentage of CO2 emission reduction due to the presence of biodiesel

[39]

4.32

15.76

17.28

15.76

39.3534

0

5

10

15

20

25

30

35

40

45

BD50BD20

Percentage of CO2 and Combustion Efficiency

Per

centa

ge

(%)

Type of Fuel

Combustion Efficiency

Percentage of CO2 Reduction Due to Use of Distillate

Percentage of CO2 Reduction Due to Use of Biodiesel

-80

-70

-60

-50

-40

-30

-20

-10

0

RS

OM

E (

Wu

et

al.

, 2009)

RS

OM

E (

Celi

kte

n e

t al.

, 2010)

RS

O (

Bu

yu

kk

aya,

2010)

CaO

ME

(O

zse

zen

et

al.

, 2010)

SB

OM

E (

Wu

et

al.

, 2009)

SB

OM

E (

Celi

kte

n e

t al.

, 2010)

SB

OM

E (

Qi

et

al.

, 2009)

PO

ME

(W

u e

t al.

, 2009)

PO

ME

(M

asj

uk

i et

al.

, 1997)

SF

OM

E (

Ilk

ilic

et

al.

, 2005)

MO

ME

R

(Rah

em

an

et

al.

, 2007)

CS

OM

E (

Wu

et

al.

, 2009)

CS

OM

E (

Ayd

in e

t al.

, 2010)

WC

OM

E (

Wu

et

al.

, 2009)

WC

OB

Li

& L

i 2009)

WF

OM

E (

Palm

) (O

zse

zen

et

…

MF

OM

E (

Lin

& L

i, 2

009)

% c

ha

ng

e i

n C

O w

rt

die

sel

Figure 2.10: Comparison of average percentage change in CO with different

biodiesel wrt diesel [65]

21

2.5.4 Previous studies on performance and emissions of biodiesel

This section summarizes the findings from previous studies on biodiesel and its

potential as an alternative fuel source substituting petroleum diesel, as well as studies

on biodiesel properties that aim to produce the optimum performance and lower

emission concentrations. The findings from the previous literatures are summarized as

in Table 2.3.

Table 2.3: Summary of current research on biodiesel by various researchers

Researcher Focused area Research finding

San José et al.

2015 [45]

Determine the fatty acid composition of four vegetable

oils (virgin soybean, virgin rapeseed, refined sunflower,

and refined mixture-seed oils) and to study their

relationship with energy efficiency and gas emissions in

a combustion process.

The experimental results prove the fatty acid profile and specially the content

of linolenic acid appear to have a significant incidence in the burner´s operating

conditions, description of fuels used for heating purposes should be performed

taking into account the chemical composition.

Daho et al. 2014

[46]

Assess the ability of a modified burner for vegetable oils

to achieve the required spray conditions of atomization

and to verify the quality of the combustion, at the same

thermal power output.

This study revealed the possibility of using pure cottonseed oil in an adapted

burner which sustained appropriate adjustments. In the case of this burner, the

proper fuel pressure is 28 bars and the minimum temperature for preheating

cottonseed oil is 125˚C.

Chong &

Hochgreb 2014

[47]

The spray combustion characteristics of rapeseed methyl

esters (RME) were compared to Jet-A1 fuel using a gas

turbine type combustor.

RME exhibits spray characteristics similar to Jet-A1 but with droplet

concentration and volume fluxes four times higher, consistent with the expected

longer droplet evaporation timescale. The flow field characteristics for both

RME and Jet-A1 spray flames are very similar despite the significantly different

visible characteristics of the flame reaction zones.

San José Alonso

et al. 2012 [6]

The present work highlights the possibility of burning

the biofuels (WVO, Soya, Rapeseed, and Sunflower)

that exist on the market using available technologies

without the need to make large investments.

The criterion used to select the burner based on the pulverisation of the fuel and

its stability depending on the density and viscosity of the fuel can be considered

acceptable for oils but not for fats due to problems of flame stability and particle

emissions.

Table 2.3: (Continued)

Researcher Focused area Research finding

José et al. 2011

[48]

The work is divided into two sections. The first deals

with the characteristics of biodiesel as a heating fuel; the

characteristics of heating fuel; the characteristics of the

mixtures of biodiesel and heating fuel, thus enabling an

estimation of the theoretical combustion results.

The tests carried out on the power use of sunflower oil biodiesel and diesel

mixtures for heating purposes allow us to conclude that: The use of the mixtures

tested does not entail any need to alter conventional facilities fired with diesel.

de Souza et al.

2009 [36]

A theoretical and experimental study of the biodiesel

from waste vegetable oil performance in a flame tube

furnace.

The diesel oil showed a higher heat transfer rate in most parts exposed to the

flame. In the region where the body of the flame is not present, the heat transfer

of biodiesel becomes higher

Tashtoush et al.

2003 [49]

The combustion behaviour and the aspects of heat

transfer and emissions of biodiesel produced from waste

vegetable oil and were used in liquid burners such as in

residential diesel heating boilers was studied.

The ethyl ester of waste vegetable oils (biodiesel) is a potential candidate as fuel

for furnaces and boiler combustors. In addition to being available locally,

renewable and cheap, biodiesel can make a good substitute for diesel fuel in

those application

24

2.6 Nozzle characteristic

One of the effective methods for cleaner combustion is by choosing the right nozzle

characteristic. The nozzle selection is very important because it determine the quality

of fuel atomization. An improvement in the air fuel mixing leads to a better combustion

process that results in higher performance, but also reduces pollutant emissions.

The spray characteristics are strongly influenced by the nature of the flow inside

the injection nozzle hole [18]. Also, studies that start with different nozzle geometries

and try to understand the whole process from nozzle flow up to the combustion and

formation of pollutants through the air-fuel mixing and vaporization are very limited

[20]. The nozzle characteristic can be describe as the physical geometry of the nozzle

such as that can influence the spray characteristic. Figure 2.11 show the nozzle

geometry.

Figure 2.11: The nozzle geometry (a)Orifice Diameter (b) Length (c) Angle [27]

In controlling the emission discharge during combustion process, analyzing

quality play an important role in it. The parameter that will determine the spray quality

are the droplets of spray, spray penetration, spray angle, breakup length. The main

purpose is to produce fine droplets and this improves the fuel and air atomization,

hence the soot and Hydrocarbon (HC) emission is decreases [50], [51].

78

REFERENCES

[1] M. Balat, “Potential alternatives to edible oils for biodiesel production : A

review of current work,” Energy Convers. Manag., vol. 52, no. 2, pp. 1479–

1492, 2011.

[2] K. Bozbas, “Biodiesel as an alternative motor fuel: Production and policies in

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