ii
A STUDY ON VELOCITY PROFILE IN PUMP IMPELLER AND ITS CASING
NOR MERLISA BINTI ALI
A project report submitted in partial fulfillment of the
requirements for the award of the degree of
Master of Mechanical Engineering.
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
DISEMBER 2008
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To my beloved papa and mama
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ACKNOWLEDGEMENTS
Very special thanks to my project advisor, Dr. Jamaluddin Md. Sheriff for
sharing with me his profound insights and give me guidance, ideas and support in doing
this project.
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ABSTRACT
This project is to study velocity profile in pump impeller and its casing using numerical
simulations in commercial software COSMOSFloWorks. The pump has different
number of blades of impeller and a circular casing. The numerical simulations are
carried out with a multiple frame of reference to predict the velocity distribution around
the pump impeller and the casing. The impeller is solved in a rotating frame and the
casing is solved in a stationary frame. This study also shows that the number of blades
in impeller, flowrate and the impeller speed give a great influence in velocity
distribution in pump. The turbulence model used in this study is standard ε−k
Turbulence Model. The velocity distribution is observed by varying the impeller speed
and the flowrate for every number of blades in impeller.
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ABSTRAK
Projek ini adalah untuk mengkaji bentuk halaju di dalam penolak pam dan sarungnya
dengan menggunakan simulasi penomboran dalam perisian komersial
COSMOSFloWorks. Pam ini mempunyai nombor bilah yang berlainan pada
penolaknya dan satu sarung yang berpusing bentuknya. Simulasi penomboran yang
dijalankan menggunakan rujukan bingkai yang pelbagai untuk mengjangka taburan
halaju di sekeliling penolak pam sarungnya. Penolak pam diselesaikan di dalam bingkai
yang berputar manakala sarung pam diselesaikan menggunakan bingkai yang pegun.
Kajian ini juga menunjukkan bahawa bilangan bilah pada penolak pam, kadar aliran dan
kelajuan penolak pam memberi pengaruh yang besar dalam taburan halaju di dalam
pam. Model Golakan (Turbulence Model) yang digunakan di dalam kajian ini ialah
‘standard ε−k Turbulence Model’. Taburan halaju dikaji dengan mengubah halaju
penolak pam and kadar aliran bagi setiap penolak pam yang mempunyai bilah yang
berbeza- beza.
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TABLE OF CONTENTS
CHAPTER TITLE PAGE
Declaration ii
Dedication iii
Acknowledgements iv
Abstract v
Abstrak vi
Table of Contents vii
List of Tables ix
List of Figures x
List of Symbols xii
List of Appendices xiii
I INTRODUCTION
1.1 Background of Project 1
1.2 Problem statement 2
1.3 Objective of Project 2
1.4 Scope of Project 3
1.5 Methodology 3
1.6 Significance of Project 4
1.7 Thesis Outline 4
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II LITERATURE REVIEW
2.1 Introduction 6
2.2 Centrifugal Pump 7
2.2.1 Stationary Components 7
2.2.2 Impeller 8
2.2.2.1 Type of Impeller 9
2.2.3 Working Principle of Centrifugal Pump 10
2.3 Basics Pump Law 10
2.4 Numerical Method 11
2.5 Basic Equation and Turbulence Model Description 14
2.5.1 Basic Equation 14
2.5.2 Turbulence Model 16
2.5.3 The standard ε−k Turbulence Model 17
2.6 Velocity Profile Around Impeller 18
III RESEARCH METHODOLOGY
3.1 Introduction 20
3.2 Research Route 20
3.3 Collecting Information from Literature Review 22
and Reference Books
3.4 Numerical Method 22
3.5 Steps in Numerical Simulations 24
3.6 Flow Solver 25
3.7 Assumptions of the Study 25
3.8 Initial Conditions 25
3.9 Boundary conditions 26
3.9.1 Inlet Conditions 26
3.9.2 Outlet Conditions 27
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3.9.3 Wall Conditions 27
3.10 Analysis Type 27
3.11 Working Fluid Properties 27
IV RESULT AND ANALYSIS
4.1 Numerical Results 29
V CONCLUSION
5.1 Introduction 56
5.2 Recommendations 57
REFERENCES 59
APPENDICES A - C 65
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LIST OF TABLES
TABLE NO. TITLE PAGE
3.1 Properties of water with temperature 28
4.1 Maximum Velocity for Impeller Speed and Flowrate Varies 31
4.2 Velocity contour for impeller speed1500rpm ( 133.0 −= smQ ) 34
4.3 Velocity contour for impeller speed 1500rpm ( 135.0 −= smQ ) 35
4.4 Velocity contour for impeller speed 1500rpm ( 130.1 −= smQ ) 36
4.5 Velocity contour for impeller speed 2000rpm ( 133.0 −= smQ ) 38
4.6 Velocity contour for impeller Speed 2000 rpm )5.0( 13 −= smQ 39
4.7 Velocity contour for impeller speed 2000 rpm )0.1( 13 −= smQ 41
4.8 Velocity contour for impeller speed 2500 rpm ( )133.0 −= smQ 45
4.9 Velocity contour for impeller speed 2500 rpm ( )135.0 −= smQ 48
4.10 Velocity contour for impeller speed 2500 rpm )0.1( 13 −= smQ 51
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LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 (a) Spiral casing (front) of the laboratory centrifugal pump 8
2.1 (b) Spiral casing (back) of the laboratory centrifugal pump 8
2.2 Impeller of the laboratory centrifugal pump 9
2.3 CFD approaches used in turbo machinery
[Reza Aghaei tog et al, 2007] 13
2.4 Static pressure contours (Pa) at nominal flow rate
[Jose Gonzalez et al, 2002] 19
3.1 Research Route 21
3.2 The pump impeller with three blades 23
3.3 The circular casing with the inlet pipe. 23
3.4 The centrifugal pump with a rotating impeller 24
4.1 (a) Maximum velocity versus number of blades (2500rpm) 32
4.1 (b) Maximum velocity versus number of blades (2000rpm) 32
4.1 (c) Maximum velocity versus number of blades (1500rpm) 33
4.2 The velocity contour of front view of the pump
[Speed 2000rpm, flowrate = 0.5 13 −sm ] 40
4.3 The front view of the blade.
[Speed 2000rpm, flowrate = 0.5 13 −sm ] 40
4.4 Velocity Vector in the pump.
[Front view, speed 2000rpm, flowrate = 0.5 13 −sm ] 41
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4.5 Velocity vector at the inlet pipe of the pump.
[Right view, speed 2000rpm, flowrate = 0.5 13 −sm ] 42
4.6 Velocity contour in the inlet pipe of the pump.
[Top view, speed 2000rpm, flowrate = 0.5 13 −sm ] 42
4.6 (a) Velocity vector in pump impeller of 3 blades.
[Front view, speed 2000 rpm, flowrate = 1.0 13 −sm ] 45
4.7 The velocity contour at the surface of the blade.
[Speed 2500rpm, flowrate = 0.3 13 −sm ] 46
4.8 The velocity contour of the 3 blades impeller.
[Front view, speed 2500rpm, flowrate = 0.3 13 −sm ] 46
4.9 Velocity contour of the 4 blades impeller.
[Front view, speed 2500rpm, flowrate = 0.3 13 −sm ] 47
4.10 Velocity contour of the tip of blade for 4 blades impeller.
[Front view, speed 2500rpm, flowrate = 0.3 13 −sm ] 47
4.11 Velocity vector of the pump for 5 blades impeller.
[Front view, speed 2500rpm, flowrate = 0.5 13 −sm ] 49
4.12 Velocity contour of the pump for 5 blades impeller.
[Front view, speed 2500rpm, flowrate = 0.5 13 −sm ] 49
4.13 Velocity contour of the pump for 6 blades impeller.
[Speed 2500rpm, flowrate = 0.5 13 −sm ] 50
4.14 Velocity contour of the tip of blade for 6 blades impeller.
[Speed 2500rpm, flowrate = 0.5 13 −sm ] 50
4.15 Velocity contour of the pump for 3 blades impeller.
[Speed 2500rpm, flowrate = 1.0 13 −sm ] 53
4.16 Velocity contour of the tip of blade for 5 blades impeller.
[Front view, speed 2500rpm, flowrate = 1.0 13 −sm ] 54
4.17 Velocity contour of the tip of blade for 6 blades impeller.
[Front view, speed 2500rpm, flowrate = 1.0 13 −sm ] 54
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LIST OF SYMBOLS
Q - Flowrate
n - Speed
H - Discharge head
P - Pressure
ρ - Density
V - Volume
T - Temperature
t - Time
τ - Shear stress
k - Turbulent kinetic energy
ε - Turbulent dissipation
eµ - Effective viscosity
l - Turbulent length scale
tυ - Turbulent viscosity
tkCCC σσ ,,,, 211 - Constants
K - Bulk Modulus of elasticity
υ - Kinematic viscosity
µ - Dynamic viscosity
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LIST OF APPENDICES
APPENDIX TITLE PAGE
A1 Velocity contour for impeller speed1500rpm ( 133.0 −= smQ ) 66
A2 Velocity contour for impeller speed 1500rpm ( 135.0 −= smQ ) 67
A3 Velocity contour for impeller speed 1500rpm ( 130.1 −= smQ ) 68
A4 Velocity contour for impeller speed 2000rpm ( 133.0 −= smQ ) 69
A5 Velocity contour for impeller Speed 2000 rpm )5.0( 13 −= smQ 70
A6 Velocity contour for impeller speed 2000 rpm )0.1( 13 −= smQ 71
A7 Velocity contour for impeller speed 2500 rpm ( )133.0 −= smQ 72
A8 Velocity contour for impeller speed 2500 rpm ( )135.0 −= smQ 73
A9 Velocity contour for impeller speed 2500 rpm )0.1( 13 −= smQ 74
B1 Pressure contour for impeller speed1500rpm ( 133.0 −= smQ ) 75
B2 Pressure contour for impeller speed 1500rpm ( 135.0 −= smQ ) 76
B3 Pressure contour for impeller speed 1500rpm ( 130.1 −= smQ ) 77
B4 Pressure contour for impeller speed 2000rpm ( 133.0 −= smQ ) 78
B5 Pressure contour for impeller Speed 2000 rpm )5.0( 13 −= smQ 79
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B6 Pressure contour for impeller speed 2000 rpm )0.1( 13 −= smQ 80
B7 Pressure contour for impeller speed 2500 rpm ( )133.0 −= smQ 81
B8 Pressure contour for impeller speed 2500 rpm ( )135.0 −= smQ 82
B9 Velocity contour for impeller speed 2500 rpm )0.1( 13 −= smQ 83
C Maximum Pressure for Impeller Speed and Flowrate Varies 84
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CHAPTER I
INTRODUCTION
1.1 Background of Project
This project is to study the velocity profile in pump impeller and its casing using
numerical methods. The method is using Computer Fluid Dynamics (CFD) by
numerical simulations in Solidworks (COSMOSFloWorks). A selected built-in model
of centrifugal pump is used in the numerical simulations. Centrifugal pump is basically
used to convert mechanical energy into hydraulic energy by centrifugal force on the
liquid used as a device to increase the pressure. Many researches have been done to
optimize the design of centrifugal pump by studying on its velocity profile either at the
pump impeller or in the casing. Some of the researches are based on a purpose to
eliminate the noise from the pump while it is working which produced from the passing
blade. But in this study, it is purposely to determine the velocity profile at the pump
impeller and its casing. Besides that, it is also to gain knowledge about the flow
distribution around the impeller and the casing of centrifugal pump by using the well-
known numerical method, CFD. By running several steps of simulations in the
commercial code COSMOSFloWorks, the flow distribution around the impeller and the
casing can be visualized. Some important parameters such as velocity, pressure and the
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turbulent energy are discussed further in the next chapter. The turbulent model which is
used in this study is the standard ε−K (two equations) turbulence model. The
numerical simulations by using the commercial code COSMOSFloWorks are used in
this study because it provides a faster way of simulation in order to study the flow
analysis especially in rotating components such as centrifugal pump.
1.2 Problem Statement
This study looks ahead to determine the velocity profile at the impeller and its
casing of selected centrifugal pump using numerical simulation. The centrifugal pump
will use variable speed and flow rate and water as its working fluid. The results
obtained will be analyzed to see the difference of velocity profile after applying variable
speed and flow rate to the pump model which has different number of blades.
1.3 Objectives of the Project
The objectives of this project include:
i. To study the velocity profile at the pump impeller and the casing by using
Computational Fluid Dynamics (CFD).
ii. To study the circulating flow around the impeller and the casing.
iii. To observe the velocity distribution at the impeller and the casing for
different impeller speed and flowrate.
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1.4 Scope of Project
The major focus of this project is:
i. Literature review on numerical approach using CFD especially on determination
of the velocity profile in rotating impeller and the casing of centrifugal pump.
ii. This project will be using the selected centrifugal pump model with variable
motor speed and flowrate.
iii. Water will be used its working fluid in the centrifugal pump.
1.5 Methodology
i. Collecting information from journals and books about the related researches
of determination of velocity profile in pump impeller and the casing of
centrifugal pump.
ii. Run the numerical simulation in Solidworks (COSMOS FloWorks) using the
model in the software.
iii. Analyzing the results of the numerical simulations.
iv. Developing conclusions, recommendations and implications of this study.
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1.6 Significance of Project
i. Encouragement for lots more studies and researches on the determination of
flow behavior in pump impeller and the casing by using other CFD software
and flow visualization methods such as PIV.
ii. An idea to other student or new researcher to do research project on flow
behavior (velocity profile) or other parameter such as pressure in pump
impeller and other component in centrifugal pump.
iii. An idea of determination of other flow parameters using other turbulence
model like RNG- ε−K turbulence.
1.7 Thesis Outline
The thesis is organized into five chapters. Chapter I contains of introduction,
objectives, methodologies used, scope and the significance of this study. The idea of
this study is explained in the introduction. Besides that, the problem statement of this
case study is also stated as the reason this project is launched. Chapter II explains about
the three keywords in this study: the centrifugal pump, velocity profile, and CFD. All
the governing equations, the Navier-Stokes equation are also explained in this chapter.
The related researches in other journals and books are reviewed in this second chapter.
Chapter III explains about the methodology of this study which has been used to
complete the project. The procedures of numerical simulation which is carried out by
using the commercial software COSMOSFloWorks are also discussed in this chapter.
The methods are discussed deeper including the initial and boundary conditions used in
this numerical simulation. Chapter IV discusses about the results of the numerical
simulation and the analysis of the result. Some figures of the velocity vectors and the
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velocity contours around the impeller are showed and explained. The last chapter
concludes the study, including with the recommendations for the future use and research
that might be used for others.
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