experiment and analysis of motorcycle exhaust design … · and this result can be applied to...
TRANSCRIPT
EXPERIMENT AND ANALYSIS OF MOTORCYCLE EXHAUST DESIGN
ABDUL MUIZ BIN JAAFAR
Report submitted in partial fulfilment of the requirementfor the award of the degree of
Bachelor of Mechanical Engineering with Automotive Engineering
Faculty of Mechanical Engineering
UNIVERSITI MALAYSIA PAHANG
JUNE 2013
vii
ABSTRACT
Internal combustion engine is one of beautiful engineering knowledge in engineeringscope. Internal combustion consists of two type categories which are Spark Ignition (SI)and Compression Ignition (CI). Based on internal combustion engine, a lot of researchcan be done to improve the performance of engine, fuel consumption, and emission.One of the researches is Experiment and Analysis for Motorcycle Exhaust Design. Themain objective is to study the variable design length to increase the performance of theengine. The second is to obtain high power and torque at low speed of engine (rpm)based on the change of exhaust parameter. The experiment is handle by utilize the EddyCurrent Dynamometer 15kW. There are two difference length of exhaust pipeline whichis 570mm and 1140mm. The length that change are from manifold until before thesilencer. Before undergo the experiment, test rig of the engine need to fabricate becausethe engine that use is difference from previous experiment of dynamometer. Tofabricate the test rig, four elements involve which are sketching, designing, analysis,and fabrication. These experiments consist of three different result which is baselinegraph, length of exhaust 570mm and length of exhaust 1140mm. The graphs are plot forpower and torque graph versus speed of engine. When there are changes of the length ofthe exhaust the torque graph will be change according to the difference length. Theshorter the length, the result of torque and power graph will be more improve. But thereare limit to make sure the exhaust pipe length not give bad impact to the engine. Theresult conclude that, the better length of exhaust pipe is the shorter one which is 570mmand this result can be applied to student formula race.
viii
ABSTRAK
Enjin pembakaran dalaman adalah salah satu daripada pengetahuan kejuruteraan yangindah. Pembakaran dalaman terdiri daripada dua kategori salah satunya adalah “SparkIgnition” (SI) dan “Compression Ignition” (CI). Banyak penyelidikan yang bolehdilakukan untuk meningkatkan prestasi enjin, penggunaan bahan api dan pelepasanbahan pembakaran. Salah satu daripada kajian tersebut ialah Eksperimen dan Analisisuntuk rekabentuk ekzos motosikal. Objektif utama projrk ini ialah untuk mengkajipanjang ekzos yang pelbagai untuk meningkatkan prestasi enjin. Yang kedua adalahuntuk mendapatkan kuasa dan tork yang tinggi pada kelajuan enjin (rpm) yang rendahberdasarkan perubahan ekzos parameter. Eksperimen ini menggunakan mesinDynamometer 15kW. Terdapat dua jenis panjang ekzos yang akan di kaji iaitu 570mmdan 1140mm. Panjang ini diukur dari manifold sehingga sebelum penyerap bunyi.Sebelum menjalani eksperimen, tapak enjin untuk di ujikaji perlu dibina kerana enjinyang digunakan adalah perbezaan dari eksperimen sebelumnya. Untuk pembinaan tapakenjin, empat elemen terlibatkan secara langsung ialah lakaran, reka bentuk, analisis, danfabrikasi. Daripada eksperimen yang dibuat terdapat tiga graf yang berbeza mengikutjenis-jenis ekzos pertama ialah graf asas, kedua ialah graf utk panjang ekzos 570mmdan panjang ekzos 1140mm. Graf ini ialah untuk graf kuasa dan graf tork berdasaekankelajuan enjin. Jika terdapat perubahan panjang ekzos,graf tork akan berubah mengikutpanjang perbezaan. Ekzos yang pendek akan menghasil bacaan graf tork dan graf kuasalebih baik jika dibandingkan dengan yang asal. Tetapi ada had untuk memastikanpanjang paip ekzos tidak memberi kesan buruk kepada enjin. Secara konklusi nya,ekzos yang terbaik bagi meningkatkan prestasi enjin GT128 ialah ekzos 570mm dankeputusan ini boleh digunakan untuk perlumbaan formula pelajar.
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TABLE OF CONTENTS
Page
SUPERVISOR’S DECLARATION ii
STUDENT’S DECLARATION iii
DEDICATION iv
ACKNOWLEDGEMENTS v
ABSTARCT vi
TABLE OF CONTENTS ix
LIST OF TABLES xii
LIST OF FIGURES xiii
LIST OF SYSTEM xv
LIST OF ABBREVIATION xvi
CHAPTER 1 INTRODUCTION
1.1 Project Background 1
1.2 Problem Statement 2
1.3 Project Objective 3
1.4 Scope of Project 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 4
2.2 Exhaust Design for Engine Scavenging Performance 5
2.3 Exhaust Pipe Length 8
2.4 Intake and Exhaust Tuning 9
2.5 Exhaust Megaphone 11
2.6 Noise and Silencer 13
x
CHAPTER 3 METHODOLOGY
3.1 Introduction 15
3.2 Designing the Test Rig for Four Stroke Engine 17
3.2.1 Analysis of Test Rig by FEA 22
3.2.2 Fabrication of Test Rig GT128 26
3.3 Engine Specification 28
3.4 Exhaust Design 29
3.5 Experimental Study of Dynamometer 31
3.5.1 Test Rig Preparation 31
3.5.2 Experiment Procedure of Dynamometer 34
CHAPTER 4 RESULT AND DISCUSSION
4.1 Experiment Result 38
4.1.1 Baseline Result of Engine GT128 with Standard Exhaust 38
4.1.2 Result for Exhaust Length of 570mm 39
4.1.3 Result for Exhaust Length of 1140mm 40
4.1.4 Result Comparison of Baseline Graph with Difference
Length of Exhaust 41
4.2 Discussions 42
4.2.1 Backpressure 42
CHAPTER 5 CONCLUSION
5.1 Conclusion 44
5.2 Recommendation 45
REFERENCES 46
xi
APPENDIX 48
A1 Engineering Drawing of Test Rig 48
A2 Raw Data of Experiment 51
xii
LIST OF TABLE
Table No. Title Page
1.1 Population of Motorcycle in January 2012 1
2.1 Intake and Exhaust Configuration 9
3.1 List of material to fabricate Test Rig 19
3.2 Material Properties of AISI 1005 Steel 22
3.3 Tool used for Fabrication 26
3.4 Engine Specification 28
3.5 Engine Transmission 28
3.6 Example data recorded 37
xiii
LIST OF FIGURE
Figure Title Page
2.1 Valve timing event showing valve overlap Valve Guide 5
2.2 Tuned engine ingest exhaust gas into the cylinder
during the overlap 5
2.3 Reflection of rarefaction wave at exhaust pipe end which
returns to the exhaust valve 6
2.4 Variation of volumetric efficiency with intake and
exhaust length 7
2.5 Measured and calculated power and torque when
change exhaust length 8
2.6 Torque Curve for Intake and Exhaust Tuning 10
2.7 Power Curve for Intake and Exhaust Tuning 10
2.8 Exhaust Diffuser/Megaphone 11
2.9 Horsepower for Exhaust Megaphone 12
2.10 Torque for Exhaust Megaphone 12
2.11 Power curve for silencer 13
2.12 Noise level for silencer 14
3.1 Flow Chart of Methodology 16
3.2 Previous test Rig for FZ150 17
3.3 Flow Chart of Designing New Test Rig 18
3.4 Isometric View of GT128 Test Rig 20
3.5 Drawing of the Test Rig 21
3.6 Boundary Condition and Force Applied to the Test Rid 23
3.7 Result of Stress von Mises 24
3.8 Result of Strain von Mises 24
3.9 Displacement of Y Component 25
3.10 Test Rig that Finish 27
3.11 Left view of Test Rig 27
3.12 Exhaust Pipe Length of 570mm 30
3.13 Exhaust Pipe Length of 1140mm 30
3.14 Test Rig of FZ150 31
xiv
3.15 Test Rig of GT128 32
3.16 Connector of Input and Output Shaft 32
3.17 Cooling Tank for Dynamometer 34
3.18 Indicator of Dynamometer is Ready to Use 35
3.19 Control Panel of Speed, Torque and Button type of Experiment 35
3.20 Throttle Lever Controller 36
3.21 Engine Speed Reader 36
3.22 Torque Reading on the Main Control Panel 37
4.1 Graph of Torque and Power versus Speed 38
4.2 Graph of Torque and Power versus Speed 39
4.3 Graph of Torque and Power versus Speed 40
4.4 Graph comparison between baseline parameter and difference
length of pipe length 41
xv
LIST OF SYMBOLS
D Diameter of exhaust pipe
ET Exhaust valve duration
Li Intake length
Le Exhaust length
kW Kilowatt
L Length
mm milimeter
rpm Rotational per minute
xvi
LIST OF ABBREVIATIONS
1D One Dimensional
CC Centimeter Cubic
CI Compression Ignition
CO2 Carbon Dioxide
FEA Finite Element Analysis
MAI Malaysia Automotive Institute
NOx Nitrogen Oxide
SAE Society Automotive Engineering
SI Spark Ignition
SOHC Single Overhead Camp
CHAPTER 1
INTRODUCTION
1.1 INTRODUCTION
Motorcycles are two-wheel vehicle that powered by internal combustion engine
either two-stroke or four-stroke. According to the latest statistics in Table 1.1,
motorcycles population has increase about 11.6% from 54,619 units in January 2011 to
60,956 units in January 2012.
Table 1.1: Population of Motorcycle in January 2012
Engine Capacity (cc) Units
50 cc or under 7076
51 – 125 1817
126 – 250 8086
Over 250 43977
Source: Malaysia Automotive Institute (MAI), 2012
These populations show that many people in Malaysia usually use motorcycle as
their transportation. A power source for motorcycle is internal combustion engine.
Internal combustion engine is combustion that occur in the combustion chamber by
ignite the mixture of compress of air and fuel. The combustion produce power can move
the motorcycle from one place to another.
2
Other than produce power as a power source to move the motorcycle, it is also
produce emission of NOx and CO2 gas that dangerous to humankind and environment.
All manufacture of engine especially automotive engineer in this world doing research
on improvement of internal combustion engine for both CI and SI engine. Their
researches focus on the improvement power of the engine, decrease emission of NOx
and CO2 gas and fuel consumptions.
There are many parameters that can increase the power of the engine such as
change the size of the bore of the cylinder block and change the cylinder head to
performance standard. Nowadays, researcher want to increase the performance the
engine without change the bore size, but change other parameter that have relation
before the combustion chamber and after it. The important variables that can increase
the performance of the engine are gas flow through the four-stroke engine, and
discharge coefficients of flow within four stroke engine (Blair, 1999).
Gas flow through four-stroke engine is process of into, through, and out of an
engine. The gas involve is unsteady which the pressure, temperature, and gas particle
velocity in a duct are variable with time. In the case of exhaust flow, the unsteady gas
flow behavior is produced because the cylinder pressure falls with the rapid opening of
the exhaust valve or valves. This gives an exhaust pipe pressure that change with time.
In the case of induction flow into the cylinder through an intake valve whose area
change with time, the intake pipe pressure alters because the cylinder pressure is
affected by the piston motion causing volumetric change within that space.
1.2 PROBLEM STATEMENT
In performance of racing engine, each parameter is very important to get the best
engine performance. Investigations of the engine performance characteristics, especially
for power and torque need to considered. The characteristic are gas flow through and
discharge coefficient of flow in four-stroke engine. There are two parameters that
usually involve in the gas flow thought engine, intake and exhaust valve.
3
1.3 PROJECT OBJECTIVE
a) To study the effect of the variable exhaust design length to the performance of
the engine.
b) To obtain high power and torque at low speed of engine (rpm) based on the
change of exhaust parameter.
1.4 SCOPE OF PROJECT
a) Literature review on the performance of 200cc engine and below based on the
exhaust parameter change.
b) Design and fabricate variable exhaust length for engine Modenas GT128.
c) Test the engine performance by utilizing engine dynamometer.
d) Plot graph of the engine performance.
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
Quality design of an exhaust system requires an understanding of its contribution
to both the overall power output of an engine and to noise attenuation (Blair, 2009).
Good design of exhaust is to increase the performance of engine without unharmed to
human kind and environment. A well designed exhaust system is one of the cheapest
ways of increasing engine efficiency, and then increasing engine power. In a four stroke
cycle engine, only one stroke out of the four does useful work which is the power
stroke. The other three strokes which are intake, compression and exhaust will absorb
some of the power that was produced during the power stroke. If the amount of power
that is lost by these idle strokes can be minimized, more power will be available to drive
the wheels, which is what the engine is supposed to be doing (Mohideen, 2008).
It is also important to understand the mechanisms that enable these contributions
as well as their significance. A wide variety of sources were studied to determine
current exhaust theories, design and analysis methods as well as to better understand the
restrictions imposed by SAE noise regulations.
2.2 EXHAUST DESIGN FOR ENGINE SCAVENGING PERFORMANCE
Performance considerations of exhaust design are a result of the nature of the
gas exchange process in a four stroke engine (Blair, 2009). This process includes a
period of valve overlap where both the intake and exhaust valves are open
simultaneously as seen in Figure 2.1. Without due regard by the designer this period
could see the induction of exhaust gases into the cylinder as shown in Figure 2.2 ,
effectively reducing the amount of fresh combustibles ingested and therefore overall
power.
Figure 2.1: Valve timing event showing valve overlap
Source: Blair, 1999
Figure 2.2: Tuned engine ingest exhaust gas into the cylinder during the overlap
Source: Blair, 1999
Exhaust Valve
TDC
Ovelap Period
Intake Valve
Valv
e Li
ft
⁰Crank
EVO IVO EVC IVC
Power Stroke Exhaust Stroke Intake Stroke Compression Stroke
TDC BDC TDC BDC
Closing exhaust Valve
Opening Intake valve
Piston Descending at Start of induction stroke
5
Performance aspects of exhaust design are concerned with minimizing residual
quantities or otherwise maximizing scavenging efficiency of the engine. To achieve the
maximum efficiency, the pressure of exhaust valve must reduce during valve overlap
such as to bias this exchange process to achieve this scavenge. Exhaust scavenging is
achieved via two methods. Firstly, scavenging is achieved through techniques wave
tuning and inertial scavenging depending on which of these mechanisms that utilize.
The aim of wave tuning is to tuned exhaust pipe harnesses the pressure wave
motion of the exhaust process to extract a greater mass of exhaust gas from the cylinder
during the exhaust stroke and initiate the induction process during the valve overlap
period. This scavenging effect is possible if a pressure wave originating from the
exhaust valve travel at the local acoustic velocity, over a tuned length such that it is
reflected back to the valve face as a rarefaction wave, as seen in Figure 2.3, in time to
assist the gas exchange process during valve overlap.
Figure 2.3: Reflection of rarefaction wave at exhaust pipe end which returns to the
exhaust valve
Source: Morrison, 2009
Another perspective of the priorities of exhaust system design is provided by a
parameter (Sammut and Alkidas, 2007). This study utilizes the engine simulation
software Ricardo WAVE to quantify the effects of and interactions between exhaust,
intake and valve timing parameters. For a constant valve timing and engine speed,
6
shows a comparison of the scavenging effect of the intake and exhaust measured in
volumetric efficiency.
Figure 2.4: Variation of volumetric efficiency with intake and exhaust length
Sources: Sammut and Alkidas, 2007
The data presented firstly shows that the individual contributions of the intake
and exhaust are independent as the contribution made by the exhaust is relatively
constant for any intake length. All data presented here in illustrating variation in
scavenging as a function of tuned length is obtained for constant valve timing. Variation
in valve timing would inevitably change the characteristics of the overlap period and
therefore the action of exhaust scavenging. Secondly, data presented in Figure 2.4 also
concludes that the effect of exhaust tuning is relatively small compared to the benefits
of intake tuning.
As a consequence of the diminishing significance of exhaust scavenging
benefits, minimizing the losses conceded to increased pumping losses whilst achieving
sufficient noise attenuation becomes of relatively high importance if a maximum
amount of power is to be derived from the engine.
7
2.3 EXHAUST PIPE LENGTH
According to 1D-Simulation method, the output power and pressure in the
intake-exhaust system can be calculated. Engine that use for dynamometer are 150cc
with air-cooled system. The parameters for tested are refer to pipe length exhaust. The
parameter that changes is pipe length before the catalyst (Horikawa et al., 2010).
Figure 2.5 show the measured and calculated output power for this type of
engine that tested using dynamometer. Those graphs indicate that when the length of the
piping system is change the performance of the engine for torque and speed also
change. The measured result indicates that output power increases at low engine speeds
and decreases at high engine speeds when the exhaust pipe becomes longer, and the
opposite when the exhaust pipe becomes shorter. A similar trend is found in calculation,
and the rate of output power change is also close to the measurement (Horikawa et al,
2010).
Figure 2.5: Measured and calculated power and torque when change exhaustlength
Sources: Horikawa et al., 2010
7
2.3 EXHAUST PIPE LENGTH
According to 1D-Simulation method, the output power and pressure in the
intake-exhaust system can be calculated. Engine that use for dynamometer are 150cc
with air-cooled system. The parameters for tested are refer to pipe length exhaust. The
parameter that changes is pipe length before the catalyst (Horikawa et al., 2010).
Figure 2.5 show the measured and calculated output power for this type of
engine that tested using dynamometer. Those graphs indicate that when the length of the
piping system is change the performance of the engine for torque and speed also
change. The measured result indicates that output power increases at low engine speeds
and decreases at high engine speeds when the exhaust pipe becomes longer, and the
opposite when the exhaust pipe becomes shorter. A similar trend is found in calculation,
and the rate of output power change is also close to the measurement (Horikawa et al,
2010).
Figure 2.5: Measured and calculated power and torque when change exhaustlength
Sources: Horikawa et al., 2010
7
2.3 EXHAUST PIPE LENGTH
According to 1D-Simulation method, the output power and pressure in the
intake-exhaust system can be calculated. Engine that use for dynamometer are 150cc
with air-cooled system. The parameters for tested are refer to pipe length exhaust. The
parameter that changes is pipe length before the catalyst (Horikawa et al., 2010).
Figure 2.5 show the measured and calculated output power for this type of
engine that tested using dynamometer. Those graphs indicate that when the length of the
piping system is change the performance of the engine for torque and speed also
change. The measured result indicates that output power increases at low engine speeds
and decreases at high engine speeds when the exhaust pipe becomes longer, and the
opposite when the exhaust pipe becomes shorter. A similar trend is found in calculation,
and the rate of output power change is also close to the measurement (Horikawa et al,
2010).
Figure 2.5: Measured and calculated power and torque when change exhaustlength
Sources: Horikawa et al., 2010
8
2.4 INTAKE AND EXHAUST TUNING
It is important to understand that the resonant length of the intake and exhaust
systems should be tuned separately. It is suggested that the intake system be tuned for
the desired speed range and then the exhaust system should be adjusted to compliment
the intake system (Blair, 1999).
An experiments were executed with the variables intake primary length (Li) and
exhaust length (Le) using 450cc by 1-Dimensional Simulation (Correia, 2009). Results
from three of the most outstanding instances are presented. The three configurations of
intake and exhaust system settings are indicated in table 2.1.
Table 2.1: Intake and Exhaust Configuration
Li(mm) Le(mm)
Config 1 198 660
Config 2 254 1194
Config 3 198 381
Source: Correia, 2009
Figure 2.6 and 2.7 shows that the configuration 2 has the longest intake and
exhaust lengths and exhibits a wider spread of torque from 4500rpm onwards.
Configurations 1 and 3 both have the same intake primary length to highlight the effect
of exhaust tuning on performance.
9
Figure 2.6: Torque Curve for Intake and Exhaust Tuning
Source: Correia, 2009
Figure 2.7: Power Curve for Intake and Exhaust Tuning
Source: Correia, 2009
0
5
10
15
20
25
30
35
40
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
1000
0
Configuration1Configuration2Configuration3
Engine Speed(rpm)
Torq
ue(N
.m)
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Series1
Series2
Series3
Engine Speed(rpm)
Pow
er(k
W)
10
2.5 EXHAUST MEGAPHONE
Exhaust diffusers (also referred to as megaphones) are sometimes used on highly
tuned four stroke engines (Blair, 1999). There are analogy between the wave
phenomenon active with an exhaust megaphone and the behavior of ocean waves as
they approach the beach. As ocean waves approach the beach and water depth becomes
shallow, the conservation of wave energy forces the waves to increase in amplitude. In a
similar fashion, as reflected exhaust pulses travel back along the megaphone the
amplitude of these pressure waves increase as the cross section of the duct decreases
progressively.
The advantage of an exhaust megaphone is evaluated by modeling it to the
optimize horsepower from 6,000 to 10,000rpm. According to the Figure 2.8 the factors
that adjusted were the secondary length Le2, and the secondary diameter De2 of the
exhaust megaphone in addition to the exhaust primary length Le1. The final values
chosen were Le1 = 510mm, Le2 = 770mm and De2 = 150mm.
Figure 2.8: Exhaust Diffuser/Megaphone
Source: Correia, 2009
198mm Ø41mm
Le1
3.5L
Ø36mm
Le2
11
The Figure 2.9 and 2.10 show the resulting performance trends offered from an
exhaust diffuser. Configuration 3 has length of exhaust 381mm. According to the graph
both systems offer high peak horsepower numbers compared to configurations 1 and 2.
However the exhaust diffuser delivers about 3% more power between 7,500 and
8,500rpm, whilst output remains virtually comparable onwards (Correia, 2009).
Figure 2.9: Horsepower for Exhaust Megaphone
Source: Correia, 2009
Figure 2.10: Torque for Exhaust Megaphone
Source: Correia, 2009
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Exhaust megaphone Configuration 3
Engine Speed (rpm)
Pow
er(k
W)
05
10152025303540
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Exhaust megaphone Configuration 3
Engine Speed(rpm)
Torq
ue(N
.m)
12
2.6 NOISE AND SILENCER
Noise can be describe as unwanted sound, but in producing exhaust noise cannot
be remove but can only reducing the noise from the exhaust. When tuning race engines,
silencer design or selection is often not considered a priority, though it is an integral
part of tuning the exhaust system (Blair, 1999).
Formula SAE requires cars to be tested for noise at an angle of 45 degrees and
0.5m away from the silencer outlet. The noise level must not exceed 110dB (A scale) at
any time during the noise test. A car will not be allowed to compete unless it passes the
noise test. A simulated version of the Formula SAE noise test was setup in WAVE and
two silencer designs were compared along with the scenario of not fitting a silencer to
the exhaust. The simulation was conducted from 5500rpm upwards as it is time
intensive and it was expected that the greatest noise intensity would occur at the higher
speeds (Correia, 2009).
Figure 2.11 and 2.12 compares the engine performance change from fitting of
the silencers. The two silencers have similar output with the absorption model
outperforming the two-box design marginally from about 7,000 to 8,000rpm. The un-
silenced power curve is different in nature likely due to fact that the silencers affect
exhaust tuning.
Figure 2.11: Power curve for silencer
Source: Correia, 2009
0
10
20
30
40
50
60
Two box
Absorbtion
Engine Speed(rpm)
Pow
er(k
W)