Investigate Blade Failure In Axial Compressor.
INVESTIGATE BLADE FAILURE
IN AXIAL COMPRESSOR
MOHAMMAD ASYRAF B OMAR
This Report Is Submitted In
Partial Fullfillment of Requirements For the
Barchelor Degree of Mechanical Engineering (Structural & Material)
Fakulti Kejuruteraan Mekanikal
Universiti Teknikal Malaysia Melaka
APRIL 2009
ii
DECLARATION
I hereby declare that this project report entitled
INVESTIGATE BLADE FAILURE IN AXIAL COMPRESSOR
is written by me and is my own effort except the ideas and summaries which I have
clarified their sources.
Signature
:…………………………………
Author
:…………………………………
Date
: ………………………………...
i
VERIFICATION
“I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in
terms of scope and quality for the award of degree of Bachelor Mechanical Engineering
(Structure & Material)”
Signature
:…………………………………
Supervisor’s Name
:…………………………………
Date
: ………………………………...
iii
ACKNOWLEGEMENT
Thanks to Allah, for giving me permission to complete this project. In here I
would like to record my graceful thank to all the support, encouragement and
inspirations that I have received during completing this project.
I also would like to express greatest thankfulness and appreciation to my
supervising lecturer, Mr. Nazri b. Md Daud of which we had a good working
relationship, and who had offered me a wonderful help and encouragement. He also
gives me full of support and advice.
Special thanks to Mr. Razmi b. A. Razak who has given me information about
the blade of axial compressor for this project.
All the Lecturers and Technicians of Faculty of Mechanical Engineering, I would
like to acknowledge and express my gratitude for giving me their cooperation and help
in order to complete this project.
Last but not least to my family and all my fellow friends, for their concern,
encouragement and understanding.
iv
ABSTRACT
This project presents the analysis blade of the axial compressor by using the
Finite Element Method (FEM). The axial compressor is one of the important devices
that always use in industry. The maintenance for the compressor and its parts is
necessary in order to ensure that the compressor perform well. This need to be done for
certain period that had been set. Sometimes, the compressor will have a problem or fail
to perform well. There are many factors that cause the failure of this compressor. The
one of the factor that may cause the failure is the damage of the component of the
compressor. The problem for compressor to perform well will disturb the flow of the
production in industry, thus will make the cost increase. To avoid this situation, the
compressor and its components need to be service for every period that has been set.
Since blade is the one of the main parts to generate the compressor this project will deal
with analysis for the blade of axial compressor. Hope that this study will help to reduce
failure of the blade which is one of the components of the axial compressor. The blade
will be designed base on the actual dimension by using the Solidwork software, and then
it will be exported in the MSC Nastran Patran software. The blade had been simulated in
different of mesh or global length. The best result which has the lowest percentages of
error was selected to undergo for further analysis. After undergo the simulation analysis
with MSC Nastran Patran, the maximum stress was found to be 66MPa while the
maximum displacement is 2.91×10−4 m . The approximation theoretical value for
maximum stress which is 78.66MPa shows the 16% of percentage of error for the
simulation with the Nastran Patran software. Lastly the factor of the safety for the blade
was calculated and the value is 3.65.
v
ABSTRAK
Projek
ini
mempersembahkan
analisis
bilah
pemampat
paksi
dengan
menggunakan Kaedah Unsur Terhingga . Pemampat paksi adalah salah satu peranti
penting yang selalu digunakan dalam industri. Penyelenggaraan untuk pemampat paksi
dan komponen-komponenya adalah perlu untuk memastikan ianya sentiasa berfungsi
dengan baik. Ini hendaklah dilakukan untuk jangka masa tertentu yang telah ditetapkan.
Kadang kala, pemampat akan menghadapi masalah atau gagal berfungsi dengan baik.
Terdapat banyak faktor yang menyebabkan kegagalan pemampat ini. Salah satu faktor
yang menyebabkan kegagalan ini adalah kerosakan pada komponen pemampat. Masalah
kepada pemampat untuk berfungsi dengan baik akan mengganggu aliran pengeluaran
dalam industri, seterusnya akan membuat kos meningkat. Untuk mengelakkan situasi ini,
pemampat dan komponennya perlu diservis untuk setiap jangka masa yang telah
ditetapkan. Memandangkan bilah adalah salah satu bahagian utama untuk menggerakkan
pemampat, projek ini akan berurusan dengan analisis untuk bilah pemampat paksi.
Diharap agar kajian ini akan membantu untuk mengurangkan kegagalan pada bilah
dimana ia adalah salah satu komponen pemampat paksi. Bilah ini telah disimulasikan
dalam berbeza sirat atau panjang global. Keputusan terbaik yang telah mendapat
peratusan terendah ralat telah dipilih untuk menjalani analisis seterusnya. Selepas
menjalani analisis simulasi dengan MSC Nastran Patran, tekanan maksimum yang
diperolehi adalah 66MPa manakala sesaran maksimum adalah
2.91×10−4 m .
Penghampiran nilai teori untuk tekanan maksimum yang mana adalah 78.66 MPa
menunjukkan 16% peratusan ralat untuk simulasi dengan menggunakan perisian Nastran
Patran. Akhir sekali, faktor keselamatan untuk bilah telah dikira dan nilainya adalah
3.65.
vi
TABLE OF CONTENT
CHAPTER
TITLE
PAGE
VERIFICATION
i
DECLARATION
ii
ACKNOWLEDGEMENT
iii
ABSTRACT
iv
ABSTRAK
v
TABLE OF CONTENT
vi
LIST OF TABLE
ix
LIST OF FIGURE
x
LIST OF SYMBOL
xiii
LIST OF APPENDICES
xiv
CHAPTER 1 INTRODUCTION
1
1.1
Background
1
1.2
Objective
2
1.3
Scope
3
1.4
Problem statement
3
CHAPTER 2 LITERATURE REVIEW
4
2.1
Introduction
4
2.2
Investigate blade failure
4
2.3
Performance losses in axial compressor
6
vii
2.4
Analysis using Finite Element
Method (FEM)
CHAPTER 3 FINITE ELEMENT METHOD
8
10
3.1
Finite Element Method Theory
11
3.2
MSC Nastran
14
3.2.1
MSC Nastran benefits
16
3.2.2
MSC Nastran applications
16
3.3
MSC Patran
17
3.3.1
18
Using Patran with MSC and
Third-party solvers
3.4
Results
19
CHAPTER 4 METHODOLOGY
20
4.1
Overview
20
4.2
Flowchart
20
4.3
Model Design using Solidwork
22
4.3.1
23
4.4
4.5
Step in Drawing using Solidwork
Analysis Model in MSC Nastran/Patran
39
4.4.1
Import the model
39
4.4.2
Elements
40
4.4.3
Load and Boundary Conditions
41
4.4.4
Material and Properties
43
4.4.5
Simulation
45
4.4.6
Result
47
4.4.7
Different Mesh
48
Theoretical Calculation
49
viii
CHAPTER 5 RESULT AND DISCUSSION
50
5.1
Expected result
50
5.2
Result
51
5.3
Comparison with Theoretical
5.4
5.5
Calculation
58
The Effect of Mesh
63
5.4.1
65
The Comparison of Mesh
Analysis of the Blade
67
CHAPTER 6 CONCLUSION
70
6.1
Overall Conclusion
70
6.2
Recommendations
71
REFERENCES
72
APPENDIX A
74
APPENDIX B
75
APPENDIX C
76
APPENDIX D
77
APPENDIX E
78
APPENDIX F
79
APPENDIX G
80
ix
LIST OF TABLE
NO
TITLE
PAGE
3.1
Type of element
12
5.1
Properties of AISI 316 Stainless Steel
51
5.2
The Numbers of Nodes and Elements
63
5.3
Comparison Between Mesh
65
x
LIST OF FIGURE
NO.
TITLE
PAGE
3.1
Sample Finite Element Model
11
3.2
Flow of MSC Nastran Patran software
18
3.3
Example of analysis results
19
4.1
Flowchart of the process
22
4.2
Figure of the blade design in Solidwork
23
4.3
The sketch of the blade
24
4.4
Sketch 2 in plane 1
25
4.5
Loft the sketch
26
4.6
The sketch in the first plane
27
4.7
Extrude of the sketch
28
4.8
The sketch and extrude of the part
29
4.9
The sketch and extrude
30
4.10
The sketch and cut extrude
31
4.11
The sketch and cut extrude
32
4.12
The circular pattern
33
4.13
The new plane on part
34
4.14
The sketch on plane 4
35
4.15
The sketch on plane 1
36
4.16
The loft of the sketch
37
xi
NO.
TITLE
PAGE
4.17
The sketch on top plane
38
4.18
The cut extrude of the part
38
4.19
The complete model
39
4.20
The import model
40
4.21
Mesh on the solid model
41
4.22
The fix at the model
42
4.23
The pressure applied
43
4.24
Input properties of the material
44
4.25
The input properties
45
4.26
The analyzed model in Nastran
46
4.27
Access result
47
4.28
Result of the simulation
48
4.29
The input value of global edge length
49
5.1
The area that will have a maximum stress
51
5.2
Simulation 1
52
5.3
Simulation 1
53
5.4
Simulation 2
54
5.5
Simulation 2
55
5.6
Simulation 3
56
5.7
Simulation 3
57
5.8
Graph of Number of Nodes and Elements vs Global
64
Edge Length
5.9
Graph of Maximum Stress vs Number of Elements
66
xii
NO.
TITLE
PAGE
5.10
The critical area
67
5.11
The maximum displacement
68
xiii
LIST OF SYMBOLS
M
-
mass
b
-
width
k
-
stiffness
d
-
distance
F
-
force
Y
-
distance from the neutral axis
I
-
moment inersia
m
-
maximum stress
{u}e
-
the displacement vector
{f}e
-
forces acting on the element.
[k ]
-
stiffness matrix
qtot
-
theoretical total head
qdf
-
loss from disc friction
qth
-
head available
η imp -
efficiency of impeller
η stage -
stage efficiency
qosf
-
frictional forces encountered in the stator
qoa
-
the overall actual adiabatic head
xiv
LIST OF APPENDICES
Appendix
Title
Page
A
GANTT CHART FOR PSM I & II
74
B
Axial Flow Compressor
75
C
Full Blade Drawing
76
D
Full command for the drawing of the blade
77
E
Drawing of the blade
78
F
Assembly Blade Drawing
79
G
Dimension of the blade
80
1
CHAPTER 1
INTRODUCTION
1.1
Background
The axial-flow compressor often use in turbine gas especially over 5MW
units. An axial-flow compressor is one in which the flow enters the compressor in an
axial direction (parallel with the axis of rotation), and exits from the gas turbine also
in an axial direction.The axial-flow compressor compresses its working fluid by first
accelerating the fluid and then diffusing it to obtain a pressure increase. The fluid is
accelerated by a row of rotating airfoils (blades) called the rotor, and then diffused in
a row of stationary blades (the stator). All angles that describe the blade and its
orientation are measured with respect to the shaft (z axis) of the compressor.
2
Blades in axial compressor were designed by arranging thickness distribution
around a camber line. Recent research in the axial flow compressor blade, based on
understanding the flow behaviors in the blades, where stacking lines of the airfoils
are curvilinear, has generated favorable results in terms of loss reduction and thereby
efficiency. The blade also can have some defect or fail to operate successful after a
few year operations. The damage could happen due to many factors. High
temperature and vibration may cause the power loss and damage to the blade in the
axial compressor. This project will investigate and analysis the failure using the
Nasran Patran software. The model of the blade will be designed according to the
real dimension using the Solidwork. The complete model from Solidwork will be
eksported to Nasran Patran software to analysis and calculate the stress on the blade.
1.2
Objectives
This project carried out the study and analyze problem those related to the
failure of blade in axial compressor. The other objectives that contain in this project
are:
1. To model the blade of the axial compressor based on the actual
dimensions by using Solidwork software.
2. To simulate the blade and investigate the failure of axial compressor
blade using MSC Nasran/Patran software.
3
1.3
Scopes
The scopes of this study are:
1. Modeling the blade in axial compressor based on the actual dimension with
Solidwork software.
2. Simulate the blade with different mesh using Nasran Patran and comparison
with theoretical value need to be done.
1.4
Problem Statement
After a long time usage of a blade in axial compressor, it may have some
defect or failed to give a better performance. If this things occur in industry, it will
disturb the flow of production thus will make the cost increase. This thing should not
be happen and must be avoided to ensure that the low cost of the production in order
to make a profit for an industry. So, this study will deal with an analysis using the
MSC Nastran Patran software to simulate the blade.
4
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
The literature review consists of various aspects regarding the investigate
blade failure, performance loses in axial compressor, and analysis using the finite
element method.
2.2
Investigate blade failure
Xiaolei Xu and Zhiwei Yu (2006) have conducted a failure investigation on
the turbine blades used in a locomotive turbochanger, which are made from K418
Ni-base superalloy. Fractography investigation on the troubled blade indicates that
cracks initiated from the surface of the concave side close to the trailing edge and
propagated towards to the leading edge. The multi-origin fatigue fracture is the
dominant failure mechanism of the blade. Metallographic morphology typical of
over-heat damage features, such as re-dissolution of the eutectic + ’ melting of the
local region of the grain boundary appears in the microstructure of the airfoil part of
the failed blades. Appearance of over-heat damage structure in the serviced blades
makes the strength of the blade material decrease intensely to initiate fatigue cracks
and make one of the blades fracture first. Fragments from the blade fractured first
would crash the other blades to make the blades break or bending deformation.
5
From the investigations that have been done, the blades used in a locomotive
turbocharger were damaged to different extent in servicing. The accumulated service
time of the blades is about 6 years. It was reported that a mayor repair had been
conducted on the turbine once. The blade material is specified as K418 superalloy
(C: 0.08–0.16; Al: 5.50–6.40; Si 6 0.50; Nb: 1.80–2.50; Mo: 3.80–4.80; Ti: 0.50–
1.00; Cr: 11.50–13.50; balance: Ni). The observation and analysis of failure of a few
representative failed blades to assess the possible failure reasons.
The method of investigation that uses to determine the chemical composition
of the blade material is spectroscopy chemical analysis method. The microcomposition in various zones of the fracture surfaces was determined by energy
dispersive X-ray spectrometer (EDX). The microstructure of the sectional specimens
near the fracture was observed by scanning electron microscopy (SEM) on a Philips
XL-30 scanning electron microscope. The fracture surfaces were analyzed by visual
and SEM observation to study the failure mechanism.
N. Vardar and A. Ekerim (2006) had done a case study of failure analysis of a
40 MW gas turbine blade made of Udimet 500. The cause of failure is found to be
intergranular cracks which started during exposure to high temperature. The cracks
initiated from the grain boundaries and propagated to the critical length to result in
catastrophic fracture. In many locations M 6C type secondary carbides were found
agglomerated on grain boundaries. Also micro-cavities were found on fracture
surfaces which served as an origin of creeping failure mechanism. The investigation
of the failure was carried out by using several experimental tests, including optical
microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy
(EDS),
X-Ray
diffraction
(XRD)
and
X-Ray
fluorescence
(XRF).
The
microstructural investigation of the blade airfoil revealed the presence of continuous
film of carbides in grain boundaries of the base material as a result of transformation
of carbides of MC type to carbides of M 6C type due to high temperature operation
of the blades.
6
2.3
Performance losses in axial compressor
In axial-flow compressor journal written by Meherwan P. Boyce (2006)
stated that the calculation of the performance of an axial-flow compressor at both
design and off-design conditions requires the knowledge of the various types of
losses encountered in an axial-flow compressor. The accurate calculation and proper
evaluation of the losses within the axial-flow compressor are as important as the
calculation of the blade-loading parameter, since unless the proper parameters are
controlled, the efficiency drops. The evaluation of the various losses is a combination
of experimental results and theory. The losses are divided into two groups: (1) losses
encountered in the rotor, and (2) losses encountered in the stator. The losses usually
are expressed as a loss of heat and enthalpy. A convenient way to express the losses
is in a no dimensional manner with reference to the blade speed. The theoretical total
head available ( qtot ) is equal to the head available from the energy equation
(qth − qtot ) plus the head, which is loss from disc friction.
qtot = qtot + qdf
(1)
The adiabatic head that is actually available at the rotor discharge is equal to
the theoretical head minus the heat losses from the shock in the rotor, the incidence
loss, the blade loadings and profile losses, the clearance between the rotor and the
shroud, and the secondary losses encountered in the flow passage
qia = qth − qin − qsh − qbl − qc − qsf
(2)
7
Therefore, the adiabatic efficiency in the impeller is
qia
η imp =
qtot
(3)
The calculation of the overall stage efficiency must also include the losses
encountered in the stator. Thus, the overall actual adiabatic head attained would be
the actual adiabatic head of the impeller minus the head losses encountered in the
stator from wake caused by the impeller blade, the loss of part of the kinetic head at
the exit of the stator, and the loss of head from the frictional forces encountered in
the stator
qoa = qia − qw − qex − qosf
(4)
Therefore, the adiabatic efficiency in the stage
qoa
η stage =
qtot
(5)
There are many losses that may occur in the axial compressor system. For the
example is disc friction loss. This loss is from skin friction on the discs that house the
blades of the compressors. This loss varies with different types of discs. The other
loss is incidence loss. This loss is caused by the angle of the air and the blade angle
not being coincident. The loss is at a minimum to about an angle of ± 4°, after which
the loss increases rapidly. Blade loading and profile loss. This loss is due to the
negative velocity gradients in the boundary layer, which gives rise to flow
separation. The loss is from skin friction on the blade surfaces and on the annular
walls and this is called a skin friction loss. Clearance loss. This loss is due to the
8
clearance between the blade tips and the casing. Wake loss. This loss is from the
wake produced at the exit of the rotary. Stator profile and skin friction loss. This loss
is from skin friction and the attack angle of the flow entering the stator. For the exit
loss the loss is due to the kinetic energy head leaving the stator.
2.4
Analysis using Finite Element Method (FEM)
The finite element method (FEM) is a numerical technique to find
approximate solutions of partial differential equations (PDE) as well as of integral
equations. This method also called finite element analysis. The solution approach is
based either on eliminating the differential equation completely (steady state
problems), or rendering the PDE into an approximating system of ordinary
differential equations, which are then solved using standard techniques such as
Euler's method, Runge-Kutta, etc.
There are many study cases and analysis had been carried out by using this
method. For the example, Wang Wei, Li Junfeng and Wang Tianshu (2008) had done
a modal analysis of liquid sloshing with different contact line boundary conditions
using finite element method. A finite element method (FEM) for liquid sloshing
modal analysis is established. Surface tension and three kinds of contact line
boundary conditions, namely, free-end, pin-end and wetting boundary conditions, are
taken into account.
Sloshing damping caused by energy dissipation at the wall, in the interior
fluid and at the contact line is calculated. Numerical results are compared with the
analytical values and measurements. For the pin-end and free-end boundary
conditions the differences between numerical value and analytical value are small,
and for the wetting boundary condition,because approximation is used, the
differences are more significant.
9
This finite element also has software to carry out the certain analysis. For
the example is MSC Nastran Patran. M. E. Stavroulaki, G. E. Stavroulakis and B.
Leftheris (1995) had conducted a structural analysis and optimization techniques
within the MSC/NASTRAN software for the analysis of optimal prestress restoration
of buildings. This analysis is done to alleviate admissible stress violations a
minimum prestress reinforcement is sought along with the position of the prestressed
elements. Prestressing is modelled by fictitious thermal loading on the linear (rod)
elements which model the prestressing cables (tendons). A quadratic cost function
for the prestressing cost with a penalty term that counts for stress violations is
assumed for the optimal prestressing problem. Certain aspects of the computer
implementation, including the use of mathematical programming and structural
optimization tools for large-scale structures, are included. The theory is illustrated by
numerical examples concerning the prestress restoration of a masonry wall subjected
to static loading.
IN AXIAL COMPRESSOR
MOHAMMAD ASYRAF B OMAR
This Report Is Submitted In
Partial Fullfillment of Requirements For the
Barchelor Degree of Mechanical Engineering (Structural & Material)
Fakulti Kejuruteraan Mekanikal
Universiti Teknikal Malaysia Melaka
APRIL 2009
ii
DECLARATION
I hereby declare that this project report entitled
INVESTIGATE BLADE FAILURE IN AXIAL COMPRESSOR
is written by me and is my own effort except the ideas and summaries which I have
clarified their sources.
Signature
:…………………………………
Author
:…………………………………
Date
: ………………………………...
i
VERIFICATION
“I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in
terms of scope and quality for the award of degree of Bachelor Mechanical Engineering
(Structure & Material)”
Signature
:…………………………………
Supervisor’s Name
:…………………………………
Date
: ………………………………...
iii
ACKNOWLEGEMENT
Thanks to Allah, for giving me permission to complete this project. In here I
would like to record my graceful thank to all the support, encouragement and
inspirations that I have received during completing this project.
I also would like to express greatest thankfulness and appreciation to my
supervising lecturer, Mr. Nazri b. Md Daud of which we had a good working
relationship, and who had offered me a wonderful help and encouragement. He also
gives me full of support and advice.
Special thanks to Mr. Razmi b. A. Razak who has given me information about
the blade of axial compressor for this project.
All the Lecturers and Technicians of Faculty of Mechanical Engineering, I would
like to acknowledge and express my gratitude for giving me their cooperation and help
in order to complete this project.
Last but not least to my family and all my fellow friends, for their concern,
encouragement and understanding.
iv
ABSTRACT
This project presents the analysis blade of the axial compressor by using the
Finite Element Method (FEM). The axial compressor is one of the important devices
that always use in industry. The maintenance for the compressor and its parts is
necessary in order to ensure that the compressor perform well. This need to be done for
certain period that had been set. Sometimes, the compressor will have a problem or fail
to perform well. There are many factors that cause the failure of this compressor. The
one of the factor that may cause the failure is the damage of the component of the
compressor. The problem for compressor to perform well will disturb the flow of the
production in industry, thus will make the cost increase. To avoid this situation, the
compressor and its components need to be service for every period that has been set.
Since blade is the one of the main parts to generate the compressor this project will deal
with analysis for the blade of axial compressor. Hope that this study will help to reduce
failure of the blade which is one of the components of the axial compressor. The blade
will be designed base on the actual dimension by using the Solidwork software, and then
it will be exported in the MSC Nastran Patran software. The blade had been simulated in
different of mesh or global length. The best result which has the lowest percentages of
error was selected to undergo for further analysis. After undergo the simulation analysis
with MSC Nastran Patran, the maximum stress was found to be 66MPa while the
maximum displacement is 2.91×10−4 m . The approximation theoretical value for
maximum stress which is 78.66MPa shows the 16% of percentage of error for the
simulation with the Nastran Patran software. Lastly the factor of the safety for the blade
was calculated and the value is 3.65.
v
ABSTRAK
Projek
ini
mempersembahkan
analisis
bilah
pemampat
paksi
dengan
menggunakan Kaedah Unsur Terhingga . Pemampat paksi adalah salah satu peranti
penting yang selalu digunakan dalam industri. Penyelenggaraan untuk pemampat paksi
dan komponen-komponenya adalah perlu untuk memastikan ianya sentiasa berfungsi
dengan baik. Ini hendaklah dilakukan untuk jangka masa tertentu yang telah ditetapkan.
Kadang kala, pemampat akan menghadapi masalah atau gagal berfungsi dengan baik.
Terdapat banyak faktor yang menyebabkan kegagalan pemampat ini. Salah satu faktor
yang menyebabkan kegagalan ini adalah kerosakan pada komponen pemampat. Masalah
kepada pemampat untuk berfungsi dengan baik akan mengganggu aliran pengeluaran
dalam industri, seterusnya akan membuat kos meningkat. Untuk mengelakkan situasi ini,
pemampat dan komponennya perlu diservis untuk setiap jangka masa yang telah
ditetapkan. Memandangkan bilah adalah salah satu bahagian utama untuk menggerakkan
pemampat, projek ini akan berurusan dengan analisis untuk bilah pemampat paksi.
Diharap agar kajian ini akan membantu untuk mengurangkan kegagalan pada bilah
dimana ia adalah salah satu komponen pemampat paksi. Bilah ini telah disimulasikan
dalam berbeza sirat atau panjang global. Keputusan terbaik yang telah mendapat
peratusan terendah ralat telah dipilih untuk menjalani analisis seterusnya. Selepas
menjalani analisis simulasi dengan MSC Nastran Patran, tekanan maksimum yang
diperolehi adalah 66MPa manakala sesaran maksimum adalah
2.91×10−4 m .
Penghampiran nilai teori untuk tekanan maksimum yang mana adalah 78.66 MPa
menunjukkan 16% peratusan ralat untuk simulasi dengan menggunakan perisian Nastran
Patran. Akhir sekali, faktor keselamatan untuk bilah telah dikira dan nilainya adalah
3.65.
vi
TABLE OF CONTENT
CHAPTER
TITLE
PAGE
VERIFICATION
i
DECLARATION
ii
ACKNOWLEDGEMENT
iii
ABSTRACT
iv
ABSTRAK
v
TABLE OF CONTENT
vi
LIST OF TABLE
ix
LIST OF FIGURE
x
LIST OF SYMBOL
xiii
LIST OF APPENDICES
xiv
CHAPTER 1 INTRODUCTION
1
1.1
Background
1
1.2
Objective
2
1.3
Scope
3
1.4
Problem statement
3
CHAPTER 2 LITERATURE REVIEW
4
2.1
Introduction
4
2.2
Investigate blade failure
4
2.3
Performance losses in axial compressor
6
vii
2.4
Analysis using Finite Element
Method (FEM)
CHAPTER 3 FINITE ELEMENT METHOD
8
10
3.1
Finite Element Method Theory
11
3.2
MSC Nastran
14
3.2.1
MSC Nastran benefits
16
3.2.2
MSC Nastran applications
16
3.3
MSC Patran
17
3.3.1
18
Using Patran with MSC and
Third-party solvers
3.4
Results
19
CHAPTER 4 METHODOLOGY
20
4.1
Overview
20
4.2
Flowchart
20
4.3
Model Design using Solidwork
22
4.3.1
23
4.4
4.5
Step in Drawing using Solidwork
Analysis Model in MSC Nastran/Patran
39
4.4.1
Import the model
39
4.4.2
Elements
40
4.4.3
Load and Boundary Conditions
41
4.4.4
Material and Properties
43
4.4.5
Simulation
45
4.4.6
Result
47
4.4.7
Different Mesh
48
Theoretical Calculation
49
viii
CHAPTER 5 RESULT AND DISCUSSION
50
5.1
Expected result
50
5.2
Result
51
5.3
Comparison with Theoretical
5.4
5.5
Calculation
58
The Effect of Mesh
63
5.4.1
65
The Comparison of Mesh
Analysis of the Blade
67
CHAPTER 6 CONCLUSION
70
6.1
Overall Conclusion
70
6.2
Recommendations
71
REFERENCES
72
APPENDIX A
74
APPENDIX B
75
APPENDIX C
76
APPENDIX D
77
APPENDIX E
78
APPENDIX F
79
APPENDIX G
80
ix
LIST OF TABLE
NO
TITLE
PAGE
3.1
Type of element
12
5.1
Properties of AISI 316 Stainless Steel
51
5.2
The Numbers of Nodes and Elements
63
5.3
Comparison Between Mesh
65
x
LIST OF FIGURE
NO.
TITLE
PAGE
3.1
Sample Finite Element Model
11
3.2
Flow of MSC Nastran Patran software
18
3.3
Example of analysis results
19
4.1
Flowchart of the process
22
4.2
Figure of the blade design in Solidwork
23
4.3
The sketch of the blade
24
4.4
Sketch 2 in plane 1
25
4.5
Loft the sketch
26
4.6
The sketch in the first plane
27
4.7
Extrude of the sketch
28
4.8
The sketch and extrude of the part
29
4.9
The sketch and extrude
30
4.10
The sketch and cut extrude
31
4.11
The sketch and cut extrude
32
4.12
The circular pattern
33
4.13
The new plane on part
34
4.14
The sketch on plane 4
35
4.15
The sketch on plane 1
36
4.16
The loft of the sketch
37
xi
NO.
TITLE
PAGE
4.17
The sketch on top plane
38
4.18
The cut extrude of the part
38
4.19
The complete model
39
4.20
The import model
40
4.21
Mesh on the solid model
41
4.22
The fix at the model
42
4.23
The pressure applied
43
4.24
Input properties of the material
44
4.25
The input properties
45
4.26
The analyzed model in Nastran
46
4.27
Access result
47
4.28
Result of the simulation
48
4.29
The input value of global edge length
49
5.1
The area that will have a maximum stress
51
5.2
Simulation 1
52
5.3
Simulation 1
53
5.4
Simulation 2
54
5.5
Simulation 2
55
5.6
Simulation 3
56
5.7
Simulation 3
57
5.8
Graph of Number of Nodes and Elements vs Global
64
Edge Length
5.9
Graph of Maximum Stress vs Number of Elements
66
xii
NO.
TITLE
PAGE
5.10
The critical area
67
5.11
The maximum displacement
68
xiii
LIST OF SYMBOLS
M
-
mass
b
-
width
k
-
stiffness
d
-
distance
F
-
force
Y
-
distance from the neutral axis
I
-
moment inersia
m
-
maximum stress
{u}e
-
the displacement vector
{f}e
-
forces acting on the element.
[k ]
-
stiffness matrix
qtot
-
theoretical total head
qdf
-
loss from disc friction
qth
-
head available
η imp -
efficiency of impeller
η stage -
stage efficiency
qosf
-
frictional forces encountered in the stator
qoa
-
the overall actual adiabatic head
xiv
LIST OF APPENDICES
Appendix
Title
Page
A
GANTT CHART FOR PSM I & II
74
B
Axial Flow Compressor
75
C
Full Blade Drawing
76
D
Full command for the drawing of the blade
77
E
Drawing of the blade
78
F
Assembly Blade Drawing
79
G
Dimension of the blade
80
1
CHAPTER 1
INTRODUCTION
1.1
Background
The axial-flow compressor often use in turbine gas especially over 5MW
units. An axial-flow compressor is one in which the flow enters the compressor in an
axial direction (parallel with the axis of rotation), and exits from the gas turbine also
in an axial direction.The axial-flow compressor compresses its working fluid by first
accelerating the fluid and then diffusing it to obtain a pressure increase. The fluid is
accelerated by a row of rotating airfoils (blades) called the rotor, and then diffused in
a row of stationary blades (the stator). All angles that describe the blade and its
orientation are measured with respect to the shaft (z axis) of the compressor.
2
Blades in axial compressor were designed by arranging thickness distribution
around a camber line. Recent research in the axial flow compressor blade, based on
understanding the flow behaviors in the blades, where stacking lines of the airfoils
are curvilinear, has generated favorable results in terms of loss reduction and thereby
efficiency. The blade also can have some defect or fail to operate successful after a
few year operations. The damage could happen due to many factors. High
temperature and vibration may cause the power loss and damage to the blade in the
axial compressor. This project will investigate and analysis the failure using the
Nasran Patran software. The model of the blade will be designed according to the
real dimension using the Solidwork. The complete model from Solidwork will be
eksported to Nasran Patran software to analysis and calculate the stress on the blade.
1.2
Objectives
This project carried out the study and analyze problem those related to the
failure of blade in axial compressor. The other objectives that contain in this project
are:
1. To model the blade of the axial compressor based on the actual
dimensions by using Solidwork software.
2. To simulate the blade and investigate the failure of axial compressor
blade using MSC Nasran/Patran software.
3
1.3
Scopes
The scopes of this study are:
1. Modeling the blade in axial compressor based on the actual dimension with
Solidwork software.
2. Simulate the blade with different mesh using Nasran Patran and comparison
with theoretical value need to be done.
1.4
Problem Statement
After a long time usage of a blade in axial compressor, it may have some
defect or failed to give a better performance. If this things occur in industry, it will
disturb the flow of production thus will make the cost increase. This thing should not
be happen and must be avoided to ensure that the low cost of the production in order
to make a profit for an industry. So, this study will deal with an analysis using the
MSC Nastran Patran software to simulate the blade.
4
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
The literature review consists of various aspects regarding the investigate
blade failure, performance loses in axial compressor, and analysis using the finite
element method.
2.2
Investigate blade failure
Xiaolei Xu and Zhiwei Yu (2006) have conducted a failure investigation on
the turbine blades used in a locomotive turbochanger, which are made from K418
Ni-base superalloy. Fractography investigation on the troubled blade indicates that
cracks initiated from the surface of the concave side close to the trailing edge and
propagated towards to the leading edge. The multi-origin fatigue fracture is the
dominant failure mechanism of the blade. Metallographic morphology typical of
over-heat damage features, such as re-dissolution of the eutectic + ’ melting of the
local region of the grain boundary appears in the microstructure of the airfoil part of
the failed blades. Appearance of over-heat damage structure in the serviced blades
makes the strength of the blade material decrease intensely to initiate fatigue cracks
and make one of the blades fracture first. Fragments from the blade fractured first
would crash the other blades to make the blades break or bending deformation.
5
From the investigations that have been done, the blades used in a locomotive
turbocharger were damaged to different extent in servicing. The accumulated service
time of the blades is about 6 years. It was reported that a mayor repair had been
conducted on the turbine once. The blade material is specified as K418 superalloy
(C: 0.08–0.16; Al: 5.50–6.40; Si 6 0.50; Nb: 1.80–2.50; Mo: 3.80–4.80; Ti: 0.50–
1.00; Cr: 11.50–13.50; balance: Ni). The observation and analysis of failure of a few
representative failed blades to assess the possible failure reasons.
The method of investigation that uses to determine the chemical composition
of the blade material is spectroscopy chemical analysis method. The microcomposition in various zones of the fracture surfaces was determined by energy
dispersive X-ray spectrometer (EDX). The microstructure of the sectional specimens
near the fracture was observed by scanning electron microscopy (SEM) on a Philips
XL-30 scanning electron microscope. The fracture surfaces were analyzed by visual
and SEM observation to study the failure mechanism.
N. Vardar and A. Ekerim (2006) had done a case study of failure analysis of a
40 MW gas turbine blade made of Udimet 500. The cause of failure is found to be
intergranular cracks which started during exposure to high temperature. The cracks
initiated from the grain boundaries and propagated to the critical length to result in
catastrophic fracture. In many locations M 6C type secondary carbides were found
agglomerated on grain boundaries. Also micro-cavities were found on fracture
surfaces which served as an origin of creeping failure mechanism. The investigation
of the failure was carried out by using several experimental tests, including optical
microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy
(EDS),
X-Ray
diffraction
(XRD)
and
X-Ray
fluorescence
(XRF).
The
microstructural investigation of the blade airfoil revealed the presence of continuous
film of carbides in grain boundaries of the base material as a result of transformation
of carbides of MC type to carbides of M 6C type due to high temperature operation
of the blades.
6
2.3
Performance losses in axial compressor
In axial-flow compressor journal written by Meherwan P. Boyce (2006)
stated that the calculation of the performance of an axial-flow compressor at both
design and off-design conditions requires the knowledge of the various types of
losses encountered in an axial-flow compressor. The accurate calculation and proper
evaluation of the losses within the axial-flow compressor are as important as the
calculation of the blade-loading parameter, since unless the proper parameters are
controlled, the efficiency drops. The evaluation of the various losses is a combination
of experimental results and theory. The losses are divided into two groups: (1) losses
encountered in the rotor, and (2) losses encountered in the stator. The losses usually
are expressed as a loss of heat and enthalpy. A convenient way to express the losses
is in a no dimensional manner with reference to the blade speed. The theoretical total
head available ( qtot ) is equal to the head available from the energy equation
(qth − qtot ) plus the head, which is loss from disc friction.
qtot = qtot + qdf
(1)
The adiabatic head that is actually available at the rotor discharge is equal to
the theoretical head minus the heat losses from the shock in the rotor, the incidence
loss, the blade loadings and profile losses, the clearance between the rotor and the
shroud, and the secondary losses encountered in the flow passage
qia = qth − qin − qsh − qbl − qc − qsf
(2)
7
Therefore, the adiabatic efficiency in the impeller is
qia
η imp =
qtot
(3)
The calculation of the overall stage efficiency must also include the losses
encountered in the stator. Thus, the overall actual adiabatic head attained would be
the actual adiabatic head of the impeller minus the head losses encountered in the
stator from wake caused by the impeller blade, the loss of part of the kinetic head at
the exit of the stator, and the loss of head from the frictional forces encountered in
the stator
qoa = qia − qw − qex − qosf
(4)
Therefore, the adiabatic efficiency in the stage
qoa
η stage =
qtot
(5)
There are many losses that may occur in the axial compressor system. For the
example is disc friction loss. This loss is from skin friction on the discs that house the
blades of the compressors. This loss varies with different types of discs. The other
loss is incidence loss. This loss is caused by the angle of the air and the blade angle
not being coincident. The loss is at a minimum to about an angle of ± 4°, after which
the loss increases rapidly. Blade loading and profile loss. This loss is due to the
negative velocity gradients in the boundary layer, which gives rise to flow
separation. The loss is from skin friction on the blade surfaces and on the annular
walls and this is called a skin friction loss. Clearance loss. This loss is due to the
8
clearance between the blade tips and the casing. Wake loss. This loss is from the
wake produced at the exit of the rotary. Stator profile and skin friction loss. This loss
is from skin friction and the attack angle of the flow entering the stator. For the exit
loss the loss is due to the kinetic energy head leaving the stator.
2.4
Analysis using Finite Element Method (FEM)
The finite element method (FEM) is a numerical technique to find
approximate solutions of partial differential equations (PDE) as well as of integral
equations. This method also called finite element analysis. The solution approach is
based either on eliminating the differential equation completely (steady state
problems), or rendering the PDE into an approximating system of ordinary
differential equations, which are then solved using standard techniques such as
Euler's method, Runge-Kutta, etc.
There are many study cases and analysis had been carried out by using this
method. For the example, Wang Wei, Li Junfeng and Wang Tianshu (2008) had done
a modal analysis of liquid sloshing with different contact line boundary conditions
using finite element method. A finite element method (FEM) for liquid sloshing
modal analysis is established. Surface tension and three kinds of contact line
boundary conditions, namely, free-end, pin-end and wetting boundary conditions, are
taken into account.
Sloshing damping caused by energy dissipation at the wall, in the interior
fluid and at the contact line is calculated. Numerical results are compared with the
analytical values and measurements. For the pin-end and free-end boundary
conditions the differences between numerical value and analytical value are small,
and for the wetting boundary condition,because approximation is used, the
differences are more significant.
9
This finite element also has software to carry out the certain analysis. For
the example is MSC Nastran Patran. M. E. Stavroulaki, G. E. Stavroulakis and B.
Leftheris (1995) had conducted a structural analysis and optimization techniques
within the MSC/NASTRAN software for the analysis of optimal prestress restoration
of buildings. This analysis is done to alleviate admissible stress violations a
minimum prestress reinforcement is sought along with the position of the prestressed
elements. Prestressing is modelled by fictitious thermal loading on the linear (rod)
elements which model the prestressing cables (tendons). A quadratic cost function
for the prestressing cost with a penalty term that counts for stress violations is
assumed for the optimal prestressing problem. Certain aspects of the computer
implementation, including the use of mathematical programming and structural
optimization tools for large-scale structures, are included. The theory is illustrated by
numerical examples concerning the prestress restoration of a masonry wall subjected
to static loading.