Optimization of the power performance for three hybrid Darrieus-Savonius rotors based on the Taguchi method

Abstract The hybrid vertical-axis wind turbine is a unique design that overcomes the efficiency limitations of Savonius rotors and the start-up challenges of Darrieus rotors. This study uses the Taguchi optimization method to enhance the performance of a cluster of three hybrid Darrieus-Savonius vertical-axis wind turbines. The optimized parameters include distances between adjacent turbine centers, configuration angles, rotational directions, and the pitch angle. The study is the first to investigate the effect of varying the pitch angle of Darrieus airfoil blades on hybrid design performance. The optimal configuration of the three hybrid VAWTs and the isolated rotor is analyzed through flow velocity, pressure, and turbulence kinetic energy contours. The results show that the pitch angles have the greatest effect on the rated power coefficient among other studied influencing parameters. The optimal cluster configuration’s performance improvement is due to the favorable velocity gradient around the blades. Compared to the isolated rotor, the power coefficient enhancement for the optimal case is 46.545% at the rated tip speed ratio of 3.08. The hybrid rotor in the cluster can achieve almost the same power as the isolated rotor up to a tip speed ratio of 4.1 instead of 2.86 for the isolated rotor. However, the decrease in overall efficiency for some cluster configurations is due to wake flow intensity and trapping between the rotors, which causes a stagnation zone.