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| Numerical simulation of new variable-pitch strategy for H-type wind turbine |
| QIAN Siyue, ZHAO Zhenzhou*, TIAN Chen, WANG Ruixin, ZENG Guanyu, ZHENG Yuan |
| School of Energy & Electrical Engineering, Hohai University, Nanjing, Jiangsu 210098, China |
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Abstract When the blades of an H-type wind turbine rotate in a range of 0°-180° azimuth angles, the torque coefficient of the turbine is negative due to zero angle of attack, but also the torque coefficient keeps negative or small value in the vicinity of these two azimuth angles. Therefore, the overall performance of wind turbine must suffer from a more significantly degraded effect. In the paper, a new variable-pitch strategy was proposed and a pitch angle curve was designed at the tip speed ratio of 4.5 to improve the performance at small angle of attack. Additionally, the aerodynamics performance of the turbine with the new variable-pitch curve was simulated by using the sliding mesh technique and the RNG k-ε turbulence model based on Fluent software, and compared with the performance of the turbine with fixed-pitch blades. The results show that the torque coefficient of the wind turbine with new variable-pitch blades increases obviously, and its increment can be as high as 14%. In the range of 30°-80° azimuth angles, the torque coefficient is improved greatly. The coefficient also exhibits a significant improvement when the azimuth angle is a range of 180°-360°(excluding 270°). The flow field in the turbine with new variable-pitch shows a noticeable change in comparison with the turbine with fixed-pitch. Specially, the difference in velocity magnitude is larger and the low-velocity area becomes bigger in the new turbine. According to the vorticity contours, it is observed that the probability of one blade being in the wake of the other blade has been curtailed effectively by the proposed variable-pitch curve. As a result, the impact of wake on the overall performance of the turbine is relieved.
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Received: 21 August 2017
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