Optimal design of low-speed current energy turbine based on turbine blades with different pitch angles

Darrieus water turbines face challenges in starting at low flow velocities. Helical torsional blades along the turbine axis can improve starting capability but may sometimes lead to excessive power reduction. In this paper, model tests and numerical calculations of a straight Darrieus turbine were conducted to analyze the power characteristics. Experimental results agree well with the numerical results. Turbines with linearly changing pitch angle along the height have been compared. Numerical simulations were performed to investigate the flow field of the torsional turbine with different torsion angles, and the influence of torsion angles on the instantaneous power characteristics was analyzed. The turbine with 20° pitch angle difference at blade ends showed improvement in average, maximum and minimum torque. Turbines with changing pitch angle along the blade height can facilitate the further application of vertical axis lift-type turbines in deep-sea and other environments, further maximizing the utilization of tidal current energy.