Title Page
Contents
NOMENCLATURE 10
GREEK SYMBOLS 11
ABSTRACT 12
CHAPTER 1. INTRODUCTION 14
1.1. Background 14
1.1.1. Definition and working principle of centrifugal pumps 14
1.1.2. Centrifugal pumps classification 17
1.1.3. Applications of centrifugal pumps 19
1.2. Applications of CFD in researching centrifugal pump 20
1.2.1. Predict pump's performance at various working conditions 21
1.2.2. Cavitation analysis 23
1.2.3. Parametric study 24
1.2.4. Pump running in turbine mode 26
1.2.5. Interactions between pump's components 27
1.2.6. Non-newtonian fluid handling pumps 28
1.3. Objective and scope 30
CHAPTER 2. THEORY AND NUMERICAL METHOD 32
2.1. Fundamental of centrifugal pump 32
2.1.1. Centrifugal pump's performance curves 32
2.1.2. Centrifugal pump's important terms 33
2.2. Computational Fluid Dynamic 40
2.3. Governing equations 43
2.3.1. Conversation of mass 43
2.3.2. Conversation of momentum 46
2.3.3. Conversation of energy 49
2.4. Turbulence Model 52
CHAPTER 3. COMPUTATIONAL MODELLING 55
3.1. Pump's geometry and specifications 55
3.2. Mesh formation and grid independence 57
3.3. Setup parameters and boundary conditions 59
CHAPTER 4. RESULTS AND DISCUSSIONS 62
4.1. Performance prediction at different operating conditions 62
4.1.1. Pump's characteristic curves 62
4.1.2. Velocity field of internal flow 65
4.1.3. Pressure distribution 72
4.2. Impacts of suction shape on flow development 73
4.2.1. Three types of suction part 73
4.2.2. Flow feature at suction part 75
4.3. Cavitation phenomenon analysis 88
4.3.1. Head drop performance curve at different flow rate 88
4.3.2. Impact of suction pressure on cavitation and loading on the blade 90
CHAPTER 5. CONCLUSIONS 104
REFERENCES 107
Table 3.1. Pump's specifications 57
Table 3.2. Detail of grid size 57
Table 3.3. Boundary conditions and setup parameters for... 60
Table 3.4. Set up parameters for cavitation analyses 61
Table 4.1. Velocity field at different planes at suction domain 78
Table 4.2. Pressure distribution at different planes at suction domain 80
Table 4.3. Streamlines at curved suction part 83
Table 4.4. Streamlines at straight suction part 85
Fig. 1.1. Centrifugal pump 15
Fig. 1.2. Operation principle of centrifugal pump 16
Fig. 1.3. Flow pattern of water inside impeller 16
Fig. 1.4. Pressure contour at impeller and volute at design flow rate 22
Fig. 1.5. Modified shroud and its influence on net head and efficiency 25
Fig. 1.6. 3D geometry of impeller with different outlet blade angle 25
Fig. 2.1. Characteristics of a centrifugal are illustrated by performance curves 32
Fig. 2.2. Classification of pump according to ns[이미지참조] 36
Fig. 2.3. Cavitation damage on impeller's surface 39
Fig. 2.4. Finite control volume fix in space 44
Fig. 2.5. Infinitesimally small, moving fluid element 47
Fig. 2.6. Energy fluxes in an infinitesimally small, moving fluid element 49
Fig. 3.1. Pump' geometry 56
Fig. 3.2. Impeller drawing 56
Fig. 3.3. Impact of grid size on head coefficient 58
Fig. 4.1. Head coefficient curve of modelled pump 63
Fig. 4.2. Efficiency curve of modelled pump 63
Fig. 4.3. Planes' location at suction part 65
Fig. 4.4. Vortex formation in suction domain 67
Fig. 4.5. Velocity vector at mid-span of impeller blade 69
Fig. 4.6. Spiral vortex flow inside the volute for design and off-design condition 70
Fig. 4.7. Pressure distribution inside impeller and volute domain 71
Fig. 4.8. Three shapes of suction geometry 74
Fig. 4.9. Position of planes at suction part 74
Fig. 4.10. Pump head comparison for 3 types of suction shape 86
Fig. 4.11. Efficiency comparison for 3 cases of suction shape 86
Fig. 4.12. Head-NPSH curve at different flow rate 89
Fig. 4.13. NPSH 3% versus Flow rate chart 89
Fig. 4.14. Bubble formation in impeller at high flow rate (1.3Qdesign)[이미지참조] 91
Fig. 4.15. Bubble formation in impeller at design flow rate (Qdesign)[이미지참조] 92
Fig. 4.16. Bubble formation in impeller at high flow rate (1.3Qdesign)[이미지참조] 93
Fig. 4.17. Pressure Coefficient Cp on Impeller blade at 0.5Qdesign[이미지참조] 96
Fig. 4.18. Pressure Coefficient Cp on Impeller blade at Qdesign[이미지참조] 97
Fig. 4.19. Pressure Coefficient Cp on Impeller blade at 1.3Qdesign[이미지참조] 98
Fig. 4.20. Vapour pressure on Impeller blade at 0.5Qdesign[이미지참조] 99
Fig. 4.21. Vapour pressure on Impeller blade at Qdesign [이미지참조] 100
Fig. 4.22. Blade loading chart at 0.5Qdesign[이미지참조] 102
Fig. 4.23. Blade loading chart at Qdesign[이미지참조] 102
Fig. 4.24. Blade loading chart at 1.3Qdesign[이미지참조] 103