Highlights
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This paper evaluates VAWT performance;
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How Reynolds number influences rotor performance has been studied;
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How Reynolds number is linked to rotor aspect ratio has been investigated;
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A new design procedure governing the rotor’s aspect ratio has been presented;
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The new design procedure maximizes wind turbine efficiency.
Introduction
Designing an H-Rotor
The importance of aspect ratio
Application for a case study
Reference | 1st attempt | 2nd attempt | |
---|---|---|---|
Power (kW) | – | 1 | 1 |
Airfoil | – | NACA 0018 | NACA 0018 |
Wind speed (m/s) | – | 10 | 10 |
Air density (kg/m3) | – | 1.2 | 1.2 |
Kinematic air viscosity (m2/s) | – | 1.46 × 10−5 | 1.46 × 10−5 |
Rotor aspect ratio (h/R) | – | 2 | 2 |
Number of blades (N
b
) | – | 2 | 2 |
First attempt Reynolds | – | 5 × 106 | 2.8 × 105 |
c
pmax
; σ
cpmax
; λ
cpmax
| Fig. 3 | 0.51; 0.3; 3.0 (Fig. 3a) | 0.464; 0.4; 2.96 (Fig. 3c) |
Rotor radius (m) | Eq. 3 | 0.904 | 0.947 |
Airfoil Chord (m) | Eq. 4 | 0.136 | 0.189 |
Rotational speed (rpm) | Eq. 6 | 317 | 299 |
Second attempt Reynolds | Eq. 7 | 2.8 × 105 | 3.8 × 105 |
Next step | – | Go to the 2° attempt | END |
Reference | 1st attempt | 2nd attempt | |
---|---|---|---|
Power (kW) | – | 1 | 1 |
Airfoil | – | NACA 0018 | NACA 0018 |
Wind speed (m/s) | – | 10 | 10 |
Air density (kg/m3) | – | 1.2 | 1.2 |
Kinematic air viscosity (m2/s) | – | 1.46 × 10−5 | 1.46 × 10−5 |
Rotor aspect ratio (h/R) | – | 0.4 | 0.4 |
Number of blades (N
b
) | – | 2 | 2 |
First attempt Reynolds | – | 5 × 106 | 6.2 × 105 |
c
pmax
; σ
cpmax
; λ
cpmax
| Fig. 3 | 0.51; 0.3; 3.0 (Fig. 3a) | 0.475; 0.3; 3.01 (Fig. 3c) |
Rotor radius (m) | Eq. 3 | 2.021 | 2.094 |
Airfoil Chord (m) | Eq. 4 | 0.303 | 0.314 |
Rotational speed (rpm) | Eq. 6 | 142 | 137 |
Second attempt Reynolds | Eq. 7 | 6.2 × 105 | 6.5 × 105 |
Next step | – | Go to the 2° attempt | END |