Multi-objective optimization of hydraulic performance of an ultra-low head axial-flow turbine with improved blade camber line configuration

Against the backdrop of the progressive and comprehensive development of large-scale hydroelectric facilities, there remains a considerable number of untapped low-head river segments in rural, remote, and hilly areas. Low-head hydropower technology, renowned for its versatility and minimal environmental impact, is the optimal power generation solution for such areas. This technology's high potential and efficiency underscore its crucial role in developing small, low-head hydropower systems. This paper introduces a camber line configuration method that utilizes two segments of second-order Bézier curves based on a fish-friendly ultra-low head axial flow turbine model developed using standard modular hydropower technology. The method accurately describes and controls the maximum camber position of the airfoil during the optimization process, allowing for a decoupling of the blade camber line placement angle and the maximum camber in the airfoil design. Based on the enhanced bone-line design method, optimization is conducted with the specific goal of improving the hydraulic efficiency and output power of the hydraulic turbine. As a result, a remarkable efficiency improvement of 2.79 % and a substantial output power enhancement of 5.93 % were successfully attained, respectively. The analysis indicates that the enhanced bone-line design enables a closer alignment of the fluid flow within the turbine with the desired ideal flow pattern. Consequently, it effectively diminishes internal entropy production losses, improves the pressure distribution on the blades, and ultimately achieves a significant enhancement in turbine performance. These research findings provide valuable insights and references for the bone-line configuration in optimizing the hydraulic design of ultra-low head hydraulic turbines.