A Study on Diffuser Augmentation of a Tidal Turbine

As tidal energy is progressively earning attention worldwide, there is a lot of existing research about the tidal current potency and the tidal turbine design. Especially on turbine design, existing studies deduced that a diffuser augmentation is a superior choice to increase the turbine performance. However, the research in finding the best diffuser angle whose efficiency is maximum, yet minim cavity risk is still limited. Therefore, this study proposes an innovative, optimized design method on diffuser augmentation of a tidal turbine by comparing four diffuser angles in three inflow velocity circumstances. In particular, three airfoil blades design with a rotor diameter of 0.3 m was developed. The combination of computational fluid dynamic and multiobjective optimization using a general algorithm coupled with the artificial neural network was applied by considering the turbine’s power coefficient and cavitation inception as a trade-off objective. The numerical results display that the different inflow velocity affects the turbine performance insignificantly. The optimization analysis and comparison among four diffuser angles in three variations of inflow velocity show that the tidal turbine’s optimal design with diffuser augmentation could be applied to all tidal current speed.