Influences of Geometrical Parameters of Upstream Deflector on Performance of a H-Type Vertical Axis Marine Current Turbine
Abstract
:1. Introduction
2. Numerical Methodology
2.1. Hydrodynamic Parameters of VAMCT
2.2. Geometrical Parameters of the Turbine and CFD Simulation Strategy
2.3. Mesh Independency Study
2.4. Model Validation
3. Results and Discussions
3.1. Spatial Arrangement of Upstream Deflector Relative to the Turbine Rotor
3.2. Effect of the Distance between Deflector and Turbine Rotor
3.3. Effect of the Deflector Length
3.4. Effect of Installation Angle of the Deflector
4. Conclusions
- When the deflector is too close to the rotor, the low-speed flow behind the deflector has a negative effect on the hydrodynamic performance of the turbine and the averaged power coefficient obviously decreases. When the deflector is away from the turbine, the influence of the accelerating fluid on the blade is weakened, so there exists a proper distance between the deflector and the rotor, which greatly improves the averaged power coefficient of the VAMCT.
- With the increase in the deflector length, more accelerated fluid is guided to the turbine. At the same time, the low-speed fluid region behind the deflector is also extended, and it would deteriorate the energy extraction efficiency of the turbine. Therefore, it is crucial to choose a deflector with an appropriate length to improve the averaged power coefficient of the VAMCT.
- The installation angle of the deflector has a significant impact on the hydrodynamic performance of the turbine. Although the deflector with β = 67.5° and 112.5° can improve the performance of the vertical axis marine current turbine, the effect of the low-speed region behind the deflector causes the fluctuation amplitude of the moment coefficient to increase, which is not conducive to the safe and stable operation of the turbine.
- In this paper, a proper combination of deflector parameters, namely, l/d = 1.00, w/d = 0.56, and β = 45°, was identified. Compared with the turbine without a deflector, a maximum increase of 13.37% is achieved at the optimal tip speed ratio λ = 2.4. In future works, further optimization of the geometry parameters of the deflector would be performed by using orthogonal array design, and the shape of the deflector will also be considered.
Author Contributions
Funding
Conflicts of Interest
Nomenclature
θ | Azimuth angle |
c | Hydrofoil chord length |
Cp | Averaged power coefficient |
λ | Tip speed ratio |
l | Distance between deflector and rotor |
β | Deflector installation angle |
w | Length of the deflector |
U∞ | Freestream velocity far upstream |
D | Diameter of the turbine |
Cm | Moment coefficient |
Cp | Power coefficient |
Re | Reynolds number |
M | Moment of the turbine |
P | Power of the turbine |
T | Rotating period |
ρ | Density of the fluid |
ω | Angular velocity |
A | Turbine swept area |
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Parameter | Value |
---|---|
Rotor diameter | 1030 mm |
Number of blades | 3 |
Blade profile | NAC0021 |
chord | 85.8 mm |
Re | 300,000 |
Tip Speed Ratio λ | Total Cell Number | Averaged Power Coefficient Cp | Difference (%) |
---|---|---|---|
2.6 | 164,000 | 0.41808 | - |
315,000 | 0.43186 | 3.30 | |
582,000 | 0.4368 | 1.14 | |
3.2 | 164,000 | 0.34112 | - |
315,000 | 0.34208 | 0.28 | |
582,000 | 0.34336 | 0.66 |
Parameter | Value |
---|---|
Deflector thickness t (mm) | 10 |
Ratio of distance between deflector and turbine rotor to turbine diameter l/d | 0.69, 1.00, 1.29 |
Ratio of deflector length to turbine diameter w/d | 0.29, 0.56, 0.85 |
Deflector installation angle β (°) | 45.0°, 67.5°, 112.5°, 135.0° |
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Zhou, D.; Sun, X. Influences of Geometrical Parameters of Upstream Deflector on Performance of a H-Type Vertical Axis Marine Current Turbine. Energies 2021, 14, 4087. https://doi.org/10.3390/en14144087
Zhou D, Sun X. Influences of Geometrical Parameters of Upstream Deflector on Performance of a H-Type Vertical Axis Marine Current Turbine. Energies. 2021; 14(14):4087. https://doi.org/10.3390/en14144087
Chicago/Turabian StyleZhou, Donghai, and Xiaojing Sun. 2021. "Influences of Geometrical Parameters of Upstream Deflector on Performance of a H-Type Vertical Axis Marine Current Turbine" Energies 14, no. 14: 4087. https://doi.org/10.3390/en14144087