Counter-Rotating Type Tidal Range Power Unit

The counter-rotating type tidal range power unit composed of the axial flow type tandem runners and the peculiar generator with double rotational armatures is proposed to utilize effectively the tidal range. In the unit, the front and the rear runners counter-drive the inner and the outer armatures of the generator, respectively. Besides, the flow runs in the axial direction at the rear runner outlet while the flow has not the swirling component at the front runner inlet, because the angular momentum change through the rear runner must coincides with that through the front runner. Such operations are suitable for bidirectional flows, namely working at the seashore with the rising and the falling tidal ranges, and the unit may be able to take place of the traditional bulb type turbines. To promote more the tidal power generation by this type unit, the runners were modified so as to be suitable for both rising and falling flows. The hydraulic performances are acceptable and take the optimum efficiency at the on-cam operation, while the trailing profiles of the runner blades determine mainly the theoretical output.