Efficiency and Optimal Loading of Contra-Rotating Marine Turbines

In this paper, an optimization method is developed for determining the loading on each component, which leads to the maximum efficiency (i.e. maximum output power) of a contra-rotating turbine when subject to uniform inflow. The lifting line model is adopted and both the self-induced velocities and the interaction induced velocities between the front and the back components are included. The optimum ratio of rotational velocities for reducing the torque on support structures and the performance effects of the gap distance between two components are investigated. The optimum distance for two in-line turbines in a turbine farm is also analyzed.