Effects of internal rotor parameters on the performance of curved blade-straight blade vertical axis wind turbine

The Phi-shaped Darrieus wind turbines offer promising applications owing to their omnidirectionality and structural advantages. However, their poor performance at low tip-speed ratios remains a challenge. To address this issue, this study proposes a hybrid rotor consisting of a Phi-shaped and straight-bladed Darrieus rotor. The computational fluid dynamics simulation is employed to investigate the effects of diameter ratio, height ratio, chord length ratio, and inner rotor blade pitch angle on the aerodynamic performance of the hybrid rotor. The findings reveal that the power coefficient reaches a maximum of 0.02531 and the lateral force coefficient is minimized at 0.10588 when the diameter ratio is 0.6. With the height ratio of 0.5, the power coefficient peaks, increasing by 77% compared to the single Phi-shaped rotor. The power coefficient is highly sensitive to the chord length ratio, increasing by 114% compared to the single Phi-shaped rotor when chord length ratio is 1.4. The lateral force coefficient increased significantly when the chord length ratio exceeded 1. In addition, changes in the pitch angle have minimal effects on the thrust and lateral force coefficients, which are beneficial for operational stability. This study provides a theoretical basis for the design of efficient and stable double Darrieus vertical-axis wind turbines, which have promising applications in distributed power generation.