DESIGN OF AUTOMATIC CONTROL SYSTEM TO CONTROL THE FLOW OF

BIOGAS FUEL INTO INTERNAL COMBUSTION SYSTEM

MOHAMAD SAUFI BIN AYOB

Thesis submitted in fulfillment of the requirements

For the award of the degree of

Bachelor of Mechanical Engineering with Automotive Engineering

Faculty of Mechanical Engineering

UNIVERSITI MALAYSIA PAHANG

6 DECEMBER 2010

iv

SUPERVISOR’S DECLARATION

I hereby declare that I have checked this project and in my opinion, this project is

adequate in terms of scope and quality for the award of the degree of Bachelor of

Mechanical Engineering with Automotive Engineering.

Signature : …………………………………

Name of Supervisor : DR. MAISARA MOHYELDIN GASIM MOHAMED

Position : LECTURER

Date : 6 DECEMBER 2010

v

STUDENT’S DECLARATION

I hereby declare that the work in this project is my own except for quotations and

summaries which have been duly acknowledged. The project has not been accepted

for any degree and is not concurrently submitted for award of other degree.

Signature : ……………………………….

Name : MOHAMAD SAUFI BIN AYOB

ID Number : MH07059

Date : 6 DECEMBER 2010

vii

ACKNOWLEDGEMENTS

I am grateful and would like to express my sincere gratitude to my supervisor

Dr. Maisara Mohyeldin Gasim Mohamed for his germinal ideas, invaluable guidance,

continuous encouragement and constant support in making this research possible. I

appreciate his consistent support from the first day I applied to graduate program to

these concluding moments. I am truly grateful for his progressive vision about my

training in science, his tolerance of my naive mistakes, and his commitment to my

future career. I also sincerely thanks for the time spent proofreading and correcting

my many mistakes.

My sincere thanks go to all my friends and members of the staff of the Mechanical

Engineering Department, UMP, who helped me in many ways and made my stay at

UMP pleasant and unforgettable. Many special thanks go to member engine research

group for their excellent co-operation, inspirations and supports during this study.

I acknowledge my sincere indebtedness and gratitude to my parents for their love,

dream and sacrifice throughout my life. I cannot find the appropriate words that could

properly describe my appreciation for their devotion, support and faith in my ability to

attain my goals. Special thanks should be given to my committee members. I would

like to acknowledge their comments and suggestions, which was crucial for the

successful completion of this study.

viii

ABSTRACT

This work is to analyze the parameter and variables that used to design an automatic

control system to control biogas fuel in internal combustion engine. The objective of

this thesis is to design the automatic control system. It shows that for governed

engines, the governor maintains constant engine rpm by moving the throttle to control

fuel supply to the engine and match power output to the engine load. The function of

the mechanical governor is to adjust the fuel valve angle so the load on the engine will

maintain the desired engine rpm at the horsepower setting selected. Performance of

the designed automatic control system was investigated and the effect of the

automatic control system to the internal combustion engine predicted. System analysis

for the project were done by using manual calculation to set the displacement and

force affected by the governor and the size opening of the valve and also using

FORTRAN code to analyze the speed and position of the mechanical governor by

using certain input speed that have been decided. In conclusion, this thesis aim to

explain the significant of the automatic control system that have been designed and

describe how the system can manage to maintain the optimum speed during steady

state and transient condition.

ix

ABSTRAK

Projek ini adalah tentang kajian parameter dan pembolehubah dalam sistem kawalan

automatik untuk mengawal penghantaran bahan bakar biogas kepada enjin

pembakaran dalaman. Objektif laporan ini adalah untuk menentukan parameter dan

pembolehubah dalam merancang sistem kawalan automatik. Tesis ini menunjukkan

bahawa pada proses telah ditetapkan, pengawal kelajuan mekanikal akan menetapkan

kelajuan mesin malar dengan cara mengawal sudut bukaan pendikit supaya bekalan

bahan bakar ke enjin dapat dikawal dan disesuaikan dengan kuasa pada beban. Fungsi

pengawal kelajuan mekanikal adalah untuk menyesuaikan sudut injap sehingga beban

pada enjin akan dapat ditetapkan pada kelajuan yang dikehendaki. Di dalam tesis ini,

keupayaan sistem kawalan automatik yang telah dirancang akan dikaji dan kesan

daripada sistem kawalan automatik pada enjin pembakaran dalaman diramal. Analisis

sistem dilakukan dengan menggunakan perhitungan manual untuk mencari perubahan

jarak dan saiz pembukaan injap yang dipengaruhi oleh pengawal kelajuan. Selain itu,

tesis ini juga menggunakan kod FORTRAN untuk menganalisa kelajuan dan

kedudukan pengawal kelajuan mekanikal dengan menggunakan input kelajuan

tertentu yang telah ditetapkan. Kesimpulannya, laporan ni bertujuan untuk

menjelaskan kepentingan sistem kawalan automatik dan menerangkan bagaimana ia

dapat mengawal kelajuan untuk sentiasa pada keaadaan terbaik.

x

TABLE OF CONTENTS

Page

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES ix

LIST OF FIGURES xvi

LIST OF SYMBOLS xvii

LIST OF ABBREVIATIONS xviii

CHAPTER 1 INTRODUCTION

1.1

1.2

1.3

1.4

Background

1.1.1 Introduction of Automatic Control System Operation

1.1.2 Introduction Internal combustion for biogas fuel

Problem Statements

Objective

Scopes

1

1

2

2

2

3

CHAPTER 2 LITERATURE REVIEW

2.1

2.2

2.2

2.3

2.4

Automatic Control

Error Detector

Error detector

Governor Lever / Output Element

Governor

2.4.1 Governor Types

4

4

4

5

5

6

xi

2.5

2.6

2.7

Biogas

2.5.1 Present Fuels and Limitations

2.5.2 Component of Biogas

2.5.3 Properties of Bio-Gas

2.5.4 Advantages of Biogas

BIOGAS IN INTERNAL COMBUSTION ENGINE

2.6.1 S.I. Engine

2.6.2 C.I. Engine

2.6.3 Performance

2.6.4 Exhaust emissions

Introduction Of Fortran

2.7.1 FORTRAN programming

2.7.2 FORTRAN Mathematical Analysis

8

8

9

10

10

11

11

11

11

12

13

14

15

CHAPTER 3 METHODOLOGY

3.1

3.2

3.3

3.4

3.5

Introduction

Step in sizing of valve

Selecting a valve type

Designing the Opening of the Valve.

FORTRAN Programming

3.5.1 FOTRAN explanation

16

16

17

18

22

23

CHAPTER 4 RESULTS AND DISCUSSION

4.1

4.2

4.3

4.4

4.5

4.6

Introduction

Manual calculation

Governor

Determine the displacement of the governor XG

Result from Governor Equilibrium

FORTRAN discussion.

25

26

27

28

29

30

xii

CHAPTER 5 CONCLUSION AND RECOMMENDATIONS

5.1 Automatic Control System Operations.

5.1.1 on speed

5.1.2 over speed

5.1.3 under speed

32

33

33

33

REFERENCES 34

APPENDICES 36

A

B

C

D

E

F

Gantt chart

Figure 5.1: Automatic Control System

FORTRAN Mechanical Program

Table 5.1: Valve selection table

Table 5.2: Program input transient condition

Table 5.3: Program output transient condition

36

37

38

40

41

42

xiii

LIST OF TABLES

Table No

Title Page

2.1

Component of Biogas 9

2.2

Comparison of Exhaust Emission 12

3.1

Opening Area of valve data 20

3.2

Governor mechanical 21

3.3

Program input for FORTRAN 22

4.1

Valve displacement 26

4.2

Governor force 27

4.3

Governor displacement 28

4.4 Program output 29

xiv

LIST OF FIGURES

Figure No

Title Page

3.1

Define the angle and size opening of the valve.

18

3.2

4.1

4.2

Governor mechanical

Force versus governor position

Governor speed versus governor position

21

31

32

xv

LIST OF SYMBOLS

A Area of the fuel valve (m2)

b Small radius ellipse (m).

c Constant of the system.

d Ball arm finger length (mm)

D Diameter of the fuel valve (m).

f Friction coefficient (Ns/m)

FR Friction coefficient (Ns/m)

G specific gravity relative to water

itr Transmission ratio ( – )

IGOV Transmission ratio between governor axis–crankshaft

k Sensing element spring stiffness (N/m)

l Ball arm length (mm)

L Dimensions (mm)

N Engine speed (rpm) or Force (N)

NFW Number of flyweights

NGOV Type of governor

mc Mass of center lever

MFW Mass of flyweights (kg)

MGOV Mass of governor clutch (kg)

SPEED0 Initial speed (rpm)

r0 Initial radius of gyration of flyweights (mm)

T Time (s)

Q Design flow rate (gpm)

xvi

XG Governor displacement.

Y Governor setting (prior spring strain) (mm)

z Sensing element current position (mm)

ZMAX Maximum spring deformation (mm)

ω Angular velocity (rads-1

)

Ø The angle of fuel valve.

∆P Allowable pressure drop across wide open valve.

xvii

LIST OF ABBREVIATIONS

0 Initial conditions rest

A ellipse Ellipse area

C.I. Engine Compression ignition engine

CH4 Methane

CO2 Carbon monoxide

H2 Hydrogen

H2S Hydrogen Sulphide

I.C. Engines Internal combustion engine

LPG Liquefied petroleum gas

N2 Nitrogen

O2 Oxygen

rpm Revolutions per minute

Se Sensing element supporting

S.I. engine Spark ignition engine

1

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

Nowadays the world economics depends to on the increasing transportation.

The depleted oil reserves and the increasing demand in cheaper energy source have

changed the interest of scientist and research to work towards alternative fuels. Viable

substitute for fuel are gaseous hydrocarbons, hydrogen gas, alcohol and electricity

that run on hydrocarbon gas and electricity are still in the experimental stage

The use of methane separated from biogas as a fuel will substantially reduce

harmful engine emission and will help to keep the environment clean. Biogas consists

of approximately 55-60 % of methane. An automatic control system is importance for

engine steady-state and transient conditions to achieve the optimum performance and

the best response of the mechanical governed biogas engine and also to reduce

pollutant-emission.

1.1.1 Introduction of Automatic Control System Operation

The automatic control system operations are start from the sensing element of

the governor that linked mechanically to the engine gears, through a hollow drive gear

shaft. The center mass, actuated by the centrifugal force of a flying ball developed by

the speed of the rotation, will control the valve mechanism to cover or uncover fuel

line. The system consists of three major parts that is governor, valve and the engine

itself.

2

1.1.2 Introduction Internal combustion for biogas fuel

Biogas typically refers to gas produced by the biological breakdown of an

organic matter in the absence of oxygen. The internal combustion engine is an engine

in which the combustion of a fuel biogas fuel occurs with an oxidizer (usually air) in

the combustion chamber. Biogas is slow burning fuel. Hence in order to get optimum

engine performance, spark timing will maintain, and the combustion must continue in

the expansion stroke.

1.2 PROBLEM STATEMENT

Biogas engine speed is controlled solely by the amount of fuel injected into

the engine by the injectors. This is because a biogas engine is not self-speed- limiting,

it requires not only controlling the changing engine speed but also mechanism to

maintain the optimum speed. The governor provides the engine with the feedback

mechanism to change speed as needed and to maintain the optimum speed of the

engine.

The study is will use manual calculation and FORTRAN simulation to analyze

the function of the governor in automatic control system. The output will determine

the optimum condition in maintaining the engine speed.

1.3 OBJECTIVE

The objective of this project as listed as following;

To analyze system operation system of automatic control and determine all

parameters including the size opening of the valve and the speed in designing

the system.

To produced for the analytical simulation of the governor under both steady-

state and transient conditions of an automatic control system mechanism.

3

1.4 SCOPES

Study the mechanism of automatic control system for valve opening using

governor watt and explain the system effect to the internal combustion engine.

Study of governor force, limit of governor control, system governor operation

and method of speed control at different speed.

Analyze and discuss all parameters in the automatic control system

mechanism using FORTRAN

4

CHAPTER 2

LITERATURE REVIEW

2.1 AUTOMATIC CONTROL

An automatic control system consists of a few elements that are error detector,

controller, and output element. In the first element, spring restoring force act as an

error detector, a device that includes monitoring a series of outputs from the engine

and detecting an error in the process.

In the second element are the governor spring, a device that includes a same

output counter and a detector controller. The same output counter is operable to store

the outputs comprising a same value received from the engine. The detector controller

is a system using FORTRAN code to detect a failure in the engine based on the data

stored in the output counter.

Output element, are the displacement of the governor lever that will act as a

speed controller by controlling the angle of fuel valve to open or close the fuel

opening.

2.2 ERROR DETECTOR

Spring restoring force is a device that act as error detector that can detect error

from the speed in an internal combustion engine, and with such detection it can ensure

that malfunctions of the engine are easily detected and it can gave an output which

indicates whether speed increasing or decreasing in the engine.

5

2.3 GOVERNOR LEVER/ OUTPUT ELEMENT

Governor lever is the beam that controls the angle of the valve opening. The

lever will move and transmit the correction force from the engine that so that it can

control the opening area for biogas fuel intake.

2.4 GOVERNOR

A governor is a device that is found in many machines that need to control the

mechanism of the intake fuel valve. There are many methods to achieve this control.

In this thesis, mechanical governor is used. Mechanical governor comprise a

movement vertical shaft which has two hinged arms connected near the top.

At the end of each arm is a ball of a given mass which is free to swing in a

vertical plane. The speed of the governor’s rotating shaft is directly linked to the

speed of the engine. An increase or decrease in rotational speed causes the arms to

swing up or down respectively, thus changing the angle they make with the vertical

axis. Connecting the arms with a throttle or brake control will allow the governor to

control the engine speed.

6

2.4.1 Governor Types

Types of Governors used on biogas engines are dependent upon the

application required. The six basic types of governors are as follows:

Mechanical centrifugal flyweight style that relies on a set of rotating

flyweights and a control spring; used since the inception of the biogas engine

to control its speed.

Power-assisted servomechanical style that operates similar to the mechanical

centrifugal flyweight but it uses engine oil under pressure to move the

operating linkage.

Hydraulic governor that relies on the movement of a pilot valve plunger to

control pressurized oil flow to a power piston, which, in turn, moves the fuel

control mechanism.

Pneumatic governor that is responsive to the air flow (vacuum) in the intake

manifold of an engine. A diaphragm within the governor housing is

connected to the fuel control linkage

that changes its setting with increases or decreases in the vacuum.

Electromechanical governor uses a magnetic speed pickup sensor on an

engine-driven component to monitor the rpm of the engine. The sensor sends a

voltage signal to an electronic control unit that controls the current flow to a

mechanical actuator connected to the fuel linkage.

Electronic governor uses magnetic speed sensor to monitor the rpm of the

engine. The sensor continuously feeds information back to the electronic

control module. The electronic control module then computes all the

information sent from all other engine sensors, such as the throttle position

sensor, turbocharger-boost sensor, engine oil pressure and temperature sensor,

engine coolant sensor, and fuel temperature to limit engine speed.

7

The governors, used on heavy-duty truck applications and construction

equipment, fall into one of two basic categories:

Limiting-speed governors sometimes referred to as minimum/maximum

models since they are intended to control the idle and maximum speed settings

of the engine. Normally there is no governor control in the intermediate range,

being regulated by the position of the throttle linkage.

Variable-speed or all range governors that are designed to control the speed of

the engine regardless of the throttle setting.

Other types of governors used on biogas engines are as follows:

Constant-speed, intended to maintain the engine at a single speed from no

load to full load.

Load limiting, to limit the load applied to the engine at any

give speed. Prevents overloading the engine at whatever speed it may be

running.

Load-control, used for adjusting to the amount of load applied at the engine to

suit the speed at which it is set to run.

Pressure regulating, used on an engine driving a pump to maintain a constant

inlet or outlet pressure on the pump. At this time on heavy-duty truck and

construction equipment applications, straight mechanically designed units

dominate the governor used on nonelectronic fuel injection systems.

8

2.5 BIOGAS

Gaseous hydrocarbons seem to be the best immediate option presently

available to prevent the dependent to other type of hydrocarbon fuel. The use of

methane separated from biogas as a fuel will substantially reduce harmful engine

emission and will help to keep the environment clean. Biogas consists of

approximately 55-60 % of methane.

2.5.1 Present Fuels and Limitations

There are so many fuels used in I.C. Engines, but they have certain physical

and chemical properties. In other words, fuels used in I.C. Engine designed to satisfy

the performance requirements of engine system. The limitations of fuels that are used

presently are as follows:

Gasoline contains many impurities. It has low octane number. All petroleum fuels

oxidize slowly in the presence of air. The oxidation of unsaturated hydrocarbons

result in formation of resinous materials called gum and reduces its quality and

tends to form sludge and warmish on piston and rings. It has less knock resistance

as well as energy per unit mass. It has less efficiency compared to other fuels. It

has high cost.

In LPG, it reduces volumetric efficiency due to its high heat of vaporization. The

road sensitivity is very high. It is very corrosive. Response to blending is very

poor. It has higher cost of transportation. It has higher cost for conversion kit,

installation of extensive.

In electricity, they use in initially generated power stations that use fossil fuel of

nuclear power. There are other problems too. The problem is with batteries in

these vehicles. These batteries are quite heavy and life of these is also low. Cost of

replacing these batteries is high.

9

The 2.1 stated the composition of biogas fuel in its pure state. The composition is

depending on the environment and temperature on its original state.

Table 2.1: Component of Biogas

Gaseous Composition by volume

Methane(CH4) 50-68% Carbon monoxide (CO2) 25-35%

Hydrogen(H2) 1-5% Nitrogen (N2) 2-7% Oxygen (O2) 0-.1%

Hydrogen Sulphide (H2S) Rare

Out of these gaseous, CO2 is the only one that does not help in combustion

process but reduce the calorific value of biogas. H2S is in minor quantity but it has

corrosive action on combustion chamber and also reduces calorific value of biogas.

So harmful gradients are removed and use only methane as a fuel.

2.5.2 Properties of Bio-Gas

In its pure state, it is color less, odorless, tasteless. For safety reason, an

odorant is added so that any leak can be easily detected because of typical smell. The

composition of bio gas is never constant.

Methane is by far the largest component, its presence accounting for about

95% of the total volume. Methane is a simple hydrocarbon, a substance consisting of

carbon and hydrogen. There are many of these compounds each has its own carbon

and hydrogen atoms joined together to form a particular hydrocarbon gas as fuel gas.

Methane is very light fuel gas. If we increase the number of hydrogen and carbon

atoms, we have got progressively heavier gases, releasing more heat, therefore more

energy, when ignited.

Specific gravity of methane is 0.55 which is less than petrol and LPG that is

between to 0.60 - 0.70. It does not contain any toxic component; therefore there is no

health hazard when handling it. The stoichiometric air fuel ratio by volume for

complete combustion of this fuel is 9.5:1 to 10:1.

10

Biogas has a very slow flame velocity, only 0.290 m/s. at its maximum. The

range of flammability is from 4 to 14% which can give good combustion efficiency.

Biogas has very high octane number approximately at 130. By comparison, gasoline

has octane number between 90 and 94 and alcohol is best at 105. This means that a

higher compression ratio engine can be used for biogas fuel. Hence, cylinder head of

the engine is faced so that clearance volume will be reduced and compression ratio

can sufficiently increase. Thus volumetric efficiency and power output can be

increased. The boiling point of biogas is above 300 degree Celsius while the calorific

value is 35.390 MJ/m3

One of the promising renewable energy sources is biogas, which is natural gas

consisting mainly of methane (CH4) and carbon dioxide (CO2). It is normally formed

with the decomposition of organic substances. Because of its low energy density, the

gas is generally stored in high-pressure gas bomb. Biogas can also store methane in

the form of clathrate. The clathration of methane requires normally high pressure and

low temperature environment. If the clathration of biogas and methane could be

achieved under the normal pressure and temperature, this would make the gases to be

a very useful energy source.

2.5.3 Advantages of Biogas

Biogas is a light fuel gas compare to other types fuel. It also can easily mixes

when reacted to oxygen. Biogas have highly knock resistance due to higher uniform

distribution thermal efficiency. Biogas has a high octane number that can reduces

pollution. Biogas also have higher compression ratio can be used with biogas.