Improvement in the performance of Darrieus vertical axis wind turbine using J-type airfoil shape

This study aims to improve the performance of the vertical axis wind turbine using a J-type airfoil shape. In this study we used an optimal airfoil shape called Opt-VF that was obtained in previous research using an optimization method of the Kriging surrogate model approach. We aimed to improve the performance of the optimal airfoil utilizing the J-type airfoil shape, by the realization of good balance to utilize lift and drag forces. 2D computational fluid dynamics (CFD) simulations and experimental performance measurements were performed to confirm the efficiency of the J-type airfoil designs. We designed/evaluated various types of the Jtype airfoils to find the most efficient condition for the optimal airfoil. We also performed flow visualizations to observe the difference between the original and J-type airfoils in detail. Some J-type airfoils achieved better performance than the original optimal airfoil, by generating higher pressure in the inner side of the J-type airfoil and obtaining higher velocity wind flow around the leading edge at certain rotational angles. Finally, experimental evaluations were conducted to compare with the CFD results. Same trends could be confirmed between the CFD and experimental results. In the experimental evaluations, maximum values of power coefficient were increased about 7% and 4% at the cases of two-blades and three-blades, respectively, compared to the original Opt-VF airfoil. These results demonstrated the effectiveness introducing the J-type airfoil shape in the optimal airfoil.