An experimental investigation of the performance of a power transmission mechanism for a flapping-foil hydrokinetic turbine

In this work, a hydrokinetic turbine that transmits the flapping power of front and rear foils to the final shaft was proposed and verified by conducting experiments in a circulating water tunnel. In particular, a crank-rocker mechanism was adopted for the transmission, with maximum actual power transmission efficiency of 92.1 % achieved, an outcome close to the maximum theoretical power transmission efficiency of 95.3 %. Although apparent negative-torque zones of the rear hydrofoil were observed due to wake effect from the front foil, maximum power efficiency up to 32.1 % was achieved at a reduced frequency of 0.117. Eventually, better transmission performance will be realized by reducing the negative-torque zones and by designing a crank-rocker mechanism with high theoretical power transmission efficiency.