Design and performance evaluation of bionics-based combined blade for horizontal axis tidal current hydroturbine

Horizontal axis tidal current hydroturbines are widely used to extract tidal current energy. The blade is an important component of the hydroturbine, and its performance primarily depends on the airfoil pattern of the blade. Based on previous studies and elements of bionic technology, this study proposes a design method using bionic technology in the blade design to obtain a composite blade with NACA and shark airfoils and good hydrodynamic performance. An airfoil with a high lift-drag-ratio or a high torque coefficient is selected from multiple airfoil designs, and the optimal combination airfoil blade model is generated according to the blade element momentum theory and Wilson blade theory. The pressure and velocity fields of different combinations of the airfoil blades are investigated using numerical simulation and underwater experiments. The results demonstrate that the combined blade offers optimal performance when the pitch angle is 60°. Its torque coefficient and turbine speed are higher than those of conventional blades, and its energy coefficient is increased by approximately 14.5%.