Numerical and experimental investigations of a vertical wind turbine augmented by combining guide-vanes and a blade-pitch mechanism

Vertical axis wind turbines present many advantages compared with horizontal axis ones despite their low performance. Thus, mechanisms, which aim to improve VAWT performance, are still in continuous development and investigation. The present paper aims to contribute to this improvement by proposing a mechanism for an H-Darrieus wind turbine and aims to gain insights about this improvement by performing numerical and experimental investigations. The proposed solution is a combined scheme of two existing mechanisms, namely a variable blade-pitch mechanism and the omni-directional-guide-vanes (ODGV). Therefore, an experimental test bench with a wind tunnel was built to measure the different combinations performance. Computational fluid dynamics (CFD) simulations were used to provide local properties and flow patterns that give more insight about the flow behaviour. Among the results, we found that the proposed combined-mechanism increases the maximum power at the optimal tip speed ratio compared to the blade-pitch mechanism alone. Furthermore, this combined-mechanism with non-uniform distribution of ODGV provides better performance and increases the maximum extracted power about 35.16% as the experiments show. On the other hand, CFD simulations show that the maximum power coefficient is obtained with two configurations, the non-uniform configuration and the uniform configuration with 4 guide-vanes at 20° of tilt angle. It is found that the power production of an H-Darrieus VAWT with a variable blade pitch can be improved using a non-uniform ODGV, which can improve considerably the power extraction in the downstream turbine half.