Tidal kinetic energy is characterized by its bidirectional flow nature, which raises unique challenges for efficient power conversion. Conventional tidal current energy systems commonly employ horizontal-axis open-propeller turbines, often requiring additional mechanisms to accommodate changes in flow direction. This study presents the development of a theoretical analysis model aimed at improving the performance of a bidirectional ducted tidal turbine. A systematic design methodology for a bidirectional turbine rotor is proposed, emphasizing simplicity, mechanical reliability, and obedience to fundamental turbomachinery principles. The theoretical framework incorporates actuator disk theory to establish a performance reference, resulting in a maximum power coefficient of 0.385 based on the maximum duct area. This value is proposed as the ducted Betz limit for ducted tidal turbines. A model-scale experimental validation of the bidirectional duct–turbine system was conducted at a blockage ratio of 0.105. The experimental results yielded a maximum power coefficient of 0.093, which, although significantly lower than the theoretical limit, confirms the applicability of the proposed ducted Betz limit as a meaningful performance benchmark. The rotor design approach is based on Euler’s turbomachinery equation, ensuring consistency with angular momentum conservation principles. The integration of a duct allows for a reduction in turbine diameter for a given power output, potentially enhancing structural durability and reducing system costs. Overall, the proposed analytical framework and design methodology provide a structured basis for evaluating and optimizing the performance of bidirectional ducted tidal turbines.
KINOUE et al. (Sun,) studied this question.