Title Page
Abstract
Contents
Nomenclatures 16
Greek Symbols 17
CHAPTER 1. INTRODUCTION 18
1.1. Background of Tidal Energy 18
1.1.1. Definition 18
1.1.2. Tidal technologies 18
1.1.3. Advantages and Disadvantages of Tidal Energy 20
1.1.4. Current Status and Trend of Tidal Energy 22
1.2. Turbines for Tidal Range Technology 26
1.2.1. Bulb Turbine 26
1.2.2. Straflo Turbine 27
1.2.3. Archimedes Crew 28
1.3. Propeller turbine for small-scale applications 29
1.4. Objectives and Scope 33
CHAPTER 2. NUMERICAL METHODOLOGY 35
2.1. Computational Fluid Dynamics 35
2.2. Governing Equations 37
2.2.1. Conservation of Mass 37
2.2.2. Conservation of Momentum 40
2.2.3. Conservation of Energy 42
2.3. Turbulence Model 45
2.4. Fluid-Structure Interaction (FSI) 47
CHAPTER 3. TURBINE DESIGN AND COMPUTATIONAL SIMULATION 50
3.1. Turbine Design 50
3.1.1. Free Vortex Theory 50
3.1.2. Turbine Design Process 53
3.1.3. Turbine's Specifications 56
3.2. Computational Simulations 58
3.2.1. Calculation Domains 58
3.2.2. Meshing Strategy and Grid Independent Study 59
3.2.3. Boundary Conditions and Setup for CFX Simulations 62
3.2.4. FSI Mesh and Setup Conditions 63
3.3. Validation for Numerical Method 66
CHAPTER 4. TURBINE PERFORMANCE EVALUATION 70
4.1. Velocity Pattern 70
4.2. Pressure distribution and Pressure coefficient 78
4.3. Turbine Performance at Various Working Condition 87
CHAPTER 5. TIP CLEARANCE EFFECTS ON TURBINE PERFORMANCE 94
5.1. Tip Clearance and Monitoring Points 94
5.1.1. Tip Clearance and Effects on Turbo-machinery 94
5.1.2. Monitoring Positions 97
5.2. Trajectories of The Tip-Leakage Vortex at Different Tip-clearance Sizes and Various Flow Conditions 99
5.3. Effects of the Tip-leakage vortex on Pressure Fluctuation on Turbine Blade 105
5.4. Effects of Tip-leakage Flow on Turbine Performance 113
CHAPTER 6. FLUID-STRUCTURE INTERACTION ANALYSIS 117
6.1. FSI Analysis and Turbine Blade Material 117
6.1.1. One-way FSI Simulations 117
6.1.2. Material of Turbine Blade 120
6.2. Interaction of Fluid Flow and The Turbine Blade 122
6.2.1. Turbine Natural Frequencies 122
6.2.2. Interaction of Fluid Flow with the Turbine Blade 124
CHAPTER 7. CONCLUSION 131
7.1. Conclusions 131
7.2. Future Work 133
Reference 134
Table 1. Companies involved in tidal energy generation 25
Table 2. Classification of hydro-power plants 29
Table 3. Turbine shape variation with specific speed 54
Table 4. Turbine design parameters 56
Table 5. Chord length and blade angles 57
Table 6. Grid size in relationship with turbine power (P) and efficiency (η) 61
Table 7. CFX boundary conditions 63
Table 8. Setup conditions for FSI analysis 65
Table 9. Head loss in each calculation domain at different speeds 86
Table 10. Maximal pressure fluctuation magnitude at monitoring points 110
Table 11. Dominant frequency at monitoring points for various TCSs 110
Table 11. Physical properties of bronze alloy 121
Table 12. Fabrication properties of bronze alloy 121
Table 13. Summary of the structural analysis for three flow conditions 130
Fig. 1.1. Two-way power generation in tidal range station 19
Fig. 1.2. Tidal stream turbines array 20
Fig. 1.3. Tidal power market-Growth rate, 2020-2025 22
Fig. 1.4. Ocean power generation scenario, 2000-2030 23
Fig. 1.5. Bulb turbine 26
Fig. 1.6. Straflo turbine 27
Fig. 1.7. Archimedes screw 28
Fig. 1.8. Efficiency variation of several types of low-head turbine 30
Fig. 1.9. Application of turbines by head, flow rate, and power output 30
Fig. 2.1. Finite control volume 38
Fig. 2.2. Infinitesimally small, moving fluid element 41
Fig. 2.3. Energy fluxes in a moving fluid element 43
Fig. 3.1. Inlet and exit velocity triangles 52
Fig. 3.2. Turbine design flow chart 53
Fig. 3.3. Geometry of the turbine blade 57
Fig. 3.4. Simulation domains 58
Fig. 3.5. Mesh formation for simulation domains and turbine blades 60
Fig. 3.6. Grid independent analysis 62
Fig. 3.7. Mesh formation for the runner for FSI simulations 64
Fig. 3.8. Five-blade turbine in the experiment 66
Fig. 3.9. Experimental apparatus 67
Fig. 3.10. Five-blade propeller turbine for simulations validation 68
Fig. 3.11. Efficiency comparison for CFD and experiment results 68
Fig. 4.1. Surface streamlines on the turbine blade at 0.88Qd[이미지참조] 71
Fig. 4.2. Surface streamlines on the turbine blade at Qd[이미지참조] 72
Fig. 4.3. Surface streamlines on the turbine blade at 1.2Qd[이미지참조] 73
Fig. 4.4. Velocity contour blade-to-blade view at tip span 74
Fig. 4.5. Velocity vectors at different spans under designed conditions (Qd, ωd)[이미지참조] 76
Fig. 4.6. Velocity distribution at domain cross section under rated speed (ωd)[이미지참조] 77
Fig. 4.7. Pressure distribution at the middle span under designed flow 78
Fig. 4.8. Pressure distribution on the whole domain's cross-section under... 80
Fig. 4.9. Pressure coefficient on three spans at designed flow (Qd)[이미지참조] 83
Fig. 4.10. Pressure coefficient on three spans at designed speed (ωd)[이미지참조] 85
Fig. 4.11. Turbine's head loss at the designed flow rate 86
Fig. 4.12. Relation between efficiency and rotational speed 87
Fig. 4.13. Relation between output power and rotational speed 88
Fig. 4.14. Power number versus rotational speed 90
Fig. 4.15. Relation between efficiency and effective head 90
Fig. 4.16. Turbines' efficiency with respect to the flow rate 92
Fig. 4.17. Geometry of reference turbines 93
Fig. 5.1. Tip clearance in propeller turbine 97
Fig. 5.2. Monitoring points at the blade tip 98
Fig. 5.3. Tip-leakage vortex trajectory at different tip-clearance sizes and flow... 102
Fig. 5.4. Pressure coefficient and velocity vectors distribution at λ=0.5 (Qd) [이미지참조] 103
Fig. 5.5. Swirling intensity on different circumferential sections (δ=0.5%, Qd)[이미지참조] 105
Fig. 5.6. Pressure fluctuation intensity on the blade 107
Fig. 5.7. Frequency diagram for pressure fluctuation at the blade tip 112
Fig. 5.8. Variation of characteristic curves for different TCSs 114
Fig. 5.9. Relationship between power, efficiency, and tip-clearance size under... 115
Fig. 6.1. One-way FSI conducting process 118
Fig. 6.2. Rotation and fixed support assignment 119
Fig. 6.3. Import the pressure loads 120
Fig. 6.4. Natural frequency with maximal deformation 122
Fig. 6.5. Runner deformation at different natural frequencies 123
Fig. 6.6. Total deformation for three cases of flow rate 126
Fig. 6.7. Equivalent stress for three cases of flow rate 127
Fig. 6.8. Equivalent strain for three cases of flow rate 128
Fig. 6.9. Safety factor for three cases of flow rate 129
Fig. 6.10. Maximal deformation and stress in three cases of flow rate 130