Hydrodynamic analysis of a drag-type water turbine

The turbine is made up of a power shaft, an eccentric shaft, a drum and several rectangular fat blades. The power shaft is fixed coaxially with the drum-rotating axis. The eccentric shaft is axially parallel to the power shaft with an eccentricity. Existing drag-type water turbines are equipped with fixed blades. During a whole revolution, blades generate positive torque in the advancing half cycle and negative torque in the returning cycle. Because torque generated in the advancing half cycle is larger than that in the returning half cycle, the rotor rotates in the direction of the positive torque. A limitation of a drag-type water turbine's efficiency is the negative torque that acts on the blade in the returning half cycle. Two-dimensional computational fluid dynamic (CFD) simulations were performed to determine the output of the turbine. The simulation results show that blades generate high positive torque in the advancing half cycle, while in the returning half cycle, the blades generate nearly zero torque.