Contents
Preface v
1 Introduction 1
1.1 Introduction 1
1.2 The research in China and worldwide 3
1.2.1 Research on wind turbine airfoils 3
1.2.2 Research on aerodynamic shape and performance of wind turbine blades 4
1.2.3 Research on structural design of composite wind turbine blades 5
1.2.4 Research on aeroelastic performance of wind turbine blades 6
2 Aerodynamic characteristics of wind turbine airfoils 9
2.1 Introduction 9
2.2 Basic theory of wind turbine airfoils 9
2.2.1 Geometric parameters of airfoils 9
2.2.2 Reynolds number 10
2.2.3 Mach number 11
2.2.4 Boundary layer 12
2.2.5 Potential flow solving method for an arbitrary airfoil 15
2.3 Aerodynamic characteristic of airfoils 18
2.3.1 Pressure coefficient of the airfoil 18
2.3.2 Lift coefficient 19
2.3.3 Drag coefficient 20
2.3.4 Pitching moment coefficient 21
2.4 Stall on airfoils 22
2.5 Roughness properties of airfoils 23
2.6 Influence of geometric parameters on aerodynamic characteristics 25
2.6.1 Influence of the leading edge radius of an airfoil 25
2.6.2 Influence of the maximum relative thickness and its position 25
2.6.3 Influence of the maximum camber and its position 26
2.7 Influence of Reynolds number on aerodynamic characteristics 26
2.8 Method of predicting aerodynamic performance of airfoils 26
2.8.1 Introduction to XFOIL and RFOIL 27
2.8.2 Airfoil aerodynamic performance calculation cases 27
2.9 Chapter conclusions 30
3 Integrated expressions of wind turbine airfoils 31
3.1 Introduction 31
3.2 Transformation theory of airfoils 31
3.2.1 Conformal transformation 31
3.2.2 Joukowsky transformation of airfoils 33
3.2.3 Theodorsen method 34
3.3 Integrated expression of airfoil profiles 36
3.3.1 The trigonometric series representation of airfoil shape function 37
3.3.2 The Taylor series representation of airfoil shape function 37
3.4 Airfoil profile analysis using integrated expressions 39
3.4.1 Type I airfoil profile 39
3.4.2 Type II airfoil profile 40
3.4.3 Type III airfoil profile 40
3.5 Versatility properties for integrated expression of airfoils 41
3.5.1 First-order fitting 42
3.5.2 Second-order fitting 45
3.5.3 Third-order fitting 45
3.6 Control equation of shape function 47
3.6.1 Characteristics of airfoil sharp trailing edge 47
3.6.2 Horizontal offset characteristics 47
3.6.3 Vertical offset characteristics 48
3.6.4 Design space 48
3.7 Convergence analysis of integrated expression of airfoils 49
3.7.1 Convergence characteristic of airfoil shape 50
3.7.2 Convergence characteristic of airfoil aerodynamic performance 54
3.8 Chapter conclusions 56
4 Theory of parametric optimization for wind turbine airfoils 57
4.1 Introduction 57
4.2 Design requirements of wind turbine airfoils 58
4.2.1 Structural and geometric compatibility 59
4.2.2 Insensitivity of the maximum lift coefficient to leading edge roughness 59
4.2.3 Design lift coefficient 59
4.2.4 The maximum lift coefficient and deep stall characteristics 60
4.2.5 Low noise 60
4.3 Single object optimization of wind turbine airfoils 60
4.3.1 Objective function 60
4.3.2 Design variables 61
4.3.3 Design constraints 61
4.3.4 Optimization method with MATLAB 62
4.3.5 Optimized results 62
4.3.6 Roughness sensitivity of the optimized airfoils 64
4.3.7 Comparative analysis of the performance of optimized airfoils 69
4.4 Multiobjective optimization of the wind turbine airfoils 72
4.4.1 Design variables 72
4.4.2 Objective function 74
4.4.3 Design constraints 76
4.4.4 Multiobjective genetic algorithm 77
4.4.5 WT series wind turbine airfoils of high performance 78
4.4.6 WTH series wind turbine airfoils with high lift-to-drag ratio 87
4.4.7 WTI series wind turbine airfoils with low roughness sensitivities 89
4.5 Design of airfoils with medium relative thickness 91
4.5.1 Geometric characteristics analysis of medium thickness airfoils 91
4.5.2 Aerodynamic characteristics of airfoils with medium thickness 93
4.5.3 The design of a new airfoil with medium thickness 94
4.5.4 The effects of turbulence, Reynolds number and blade rotation 97
4.6 Design of airfoils based on noise 100
4.6.1 Acoustic theory for wind turbines 100
4.6.2 The measurement of noise 101
4.6.3 The acoustics model of the airfoil 103
4.6.4 Comparison of noise calculations 113
4.6.5 Influence of geometric parameters of airfoils on noise 115
4.6.6 Design of wind turbine airfoils with high efficiency and low noise 118
4.7 Airfoil design based on a 2D power coefficient 123
4.7.1 The optimization model 125
4.7.2 The optimization flow chart 127
4.7.3 CQU-DTU-B airfoil series 128
4.7.4 Influence of airfoil trailing edge on the performance of the airfoil 138
4.8 Improved design of airfoils using smooth curvature technique 140
4.8.1 Smooth continuity of