Combination of propulsive thrust and rotational power for ships from a cyclic pitch Darrieus rotor sail

Abstract

This study aims to analyse the ability of a Darrieus rotor to produce a combination of direct thrust for ship propulsion and rotational power for shipboard electricity generation. A multiple-streamtube model was used to simulate turbine performance using a cyclic-pitching motion of the blades. The rotor produced a useful forward component of thrust under slow-sailing conditions for wind directions coming from all but one octant, while producing useful rotational power at the same time. Directly against the wind, the Darrieus rotor sail produced negative propulsive power in terms of direct thrust, but produced useful rotational power. At other sailing angles the Darrieus rotor sail was found to be less effective in providing direct thrust to the ship than equivalent wing sails. Sailing at an angle of 45° against the wind, the Darrieus rotor sail produced 46% of the power a wing sail using the same symmetrical NACA0012 aerofoil would produce. When sailing directly with the wind, at a 180° wind angle, the Darrieus rotor sail produced 40% of the thrust of its equivalent wing sail. A ship sailing with this technology was simulated to be able to sail at about 26% of its current maximum speed on a Baltic route.