Title Page
Contents
NOMENCLATURE 11
GREEK SYMBOLS 12
ABSTRACT 13
CHAPTER 1. INTRODUCTION 15
1.1. Background 15
1.1.1. Definition and working principle of centrifugal pumps 15
1.1.2. Centrifugal pumps classification 18
1.1.3. Applications of centrifugal pumps 20
1.2. Applications of CFD in researching centrifugal pump 21
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 31
CHAPTER 2. THEORY AND NUMERICAL METHOD 33
2.1. Fundamental of centrifugal pump 33
2.1.1. Centrifugal pump's performance cnrves 33
2.1.2. Centrifugal pump's important terms 34
2.2. Computational Fluid Dynamic 41
2.3. Governing equations 43
2.3.1. Conversation of mass 44
2.3.2. Conversation of momentum 47
2.3.3. Conversation of energy 50
2.4. Turbulence Model 53
CHAPTER 3. COMPUTATIONAL MODELLING 56
3.1. Pump's geometry and specifications 56
3.2. Mesh formation and grid independence 58
3.3. Set up parameters and boundary conditions 60
CHAPTER 4. RESULTS AND DISCUSSIONS 63
4.1. Performance prediction at different operating conditions 63
4.1.1. Pump's characteristic curves 63
4.1.2. Velocity field of internal flow 66
4.1.3. Pressure distribution 74
4.2. Impacts of suction shape on flow development 75
4.2.1. Three types of suction part 75
4.2.2. Flow feature at suction part 77
4.3. Cavitation phenomenon analysis 89
4.3.1. Head drop performance curve at different flow rate 89
4.3.2. Impact of suction pressure on cavitation and loading on the blade 91
CHAPTER 5. CONCLUSIONS 105
REFERENCES 108
Table 3.1. Pump's specifications 57
Table 3.2. Detail of grid size 58
Table 3.3. Boundary conditions and setup parameters for... 60
Table 3.4. Set up parameters for cavitation analyses 62
Table 4.1. Velocity field at different planes at suction domain 79
Table 4.2. Pressure distribution at different planes at suction domain 81
Table 4.3. Streamlines at curved suction part 84
Table 4.4. Streamlines at straight suction part 86
Fig. 1.1. Centrifugal pump 16
Fig. 1.2. Operation principle of centrifugal pump 17
Fig. 1.3. Flow pattern of water inside impeller 17
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 26
Fig. 2.1. Characteristics of a centrifugal are illustrated by performance curves 33
Fig. 2.2. Classification of pump according to ns(이미지참조) 37
Fig. 2.3. Cavitation damage on impeller's surface 40
Fig. 2.4. Finite control volume fix in space 45
Fig. 2.5. Infinitesimally small, moving fluid element 48
Fig. 2.6. Energy fluxes in an infinitesimally small, moving fluid element 50
Fig. 3.1. Pump' geometry 57
Fig. 3.2. Impeller drawing 57
Fig. 3.3. Impact of grid size on head coefficient 59
Fig. 4.1. Head coefficient curve of modelled pump 64
Fig. 4.2. Efficiency curve of modelled pump 64
Fig. 4.3. Planes' location at suction part 66
Fig. 4.4. Vortex formation in suction domain 68
Fig. 4.5. Velocity vector at mid-span of impeller blade 70
Fig. 4.6. Spiral vortex flow inside the volute for design and off-design condition 71
Fig. 4.7. Pressure distribution inside impeller and volute domain 73
Fig. 4.8. Three shapes of suction geometry 76
Fig. 4.9. Position of planes at suction part 76
Fig. 4.10. Pump head comparison for 3 types of suction shape 87
Fig. 4.11. Efficiency comparison for 3 cases of suction shape 87
Fig. 4.12. Head-NPSH curve at different flow rate 90
Fig. 4.13. NPSH 3% versus Flow rate chart 90
Fig. 4.14. Bubble formation in impeller at high flow rate 92
Fig. 4.15. Bubble formation in impeller at design flow rate 93
Fig. 4.16. Bubble formation in impeller at high flow rate 94
Fig. 4.17. Pressure Coefficient Cp on Impeller blade at O.5Qdesign(이미지참조) 97
Fig. 4.18. Pressure Coefficient Cp on Impeller blade at Qdesign(이미지참조) 98
Fig. 4.19. Pressure Coefficient Cp on Impeller blade at 1.3Qdesigll(이미지참조) 99
Fig. 4.20. Vapour pressure on Impeller blade at 0.5Qdesign(이미지참조) 100
Fig. 4.21. Vapour pressure on Impeller blade at Qdcsign(이미지참조) 101
Fig. 4.22. Blade loading chart at O.5Qdcsign(이미지참조) 103
Fig. 4.23. Blade loading chart at Qdesign(이미지참조) 103
Fig. 4.24. Blade loading chart at 1.3Qdcsign(이미지참조) 104