A performance study on the energy recovering turbine behind a marine propeller

This study presents the performance estimation of a turbine, as a new concept of energy saving device (ESD), utilizing the energy in the propeller slip stream. The turbine is designed to recover the rotational energy into torque to drive a generator inside the rudder. First, the problem of performance estimation is formulated by a numerical variational method so that the turbine generates a prescribed torque with minimum propulsion power of the propeller and without loss of the required thrust of the combined system. Each component is represented by vortex lattice lifting lines and the radial distribution of circulation is determined by the solution of the problem. It is investigated how the performance of the system depends on the design parameters such as power coefficient and rotational speed of the turbine. Finally, a turbine blade is designed for a selected case using the information from the parametric study. A CFD analysis based on RANS simulation is applied to look into the flow around the turbine blade. The results of the performance calculation are also compared with the preliminary predictions.