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Numerical Investigation on Suitable Flow Guide for Performance Enhancement of Darrieus-type Hydraulic Turbine by 2-D Simulation

The aim of this investigation is improvement of the performance of Darrieus-type hydraulic turbines operated in an open channel. Since the output power is very small in such a utilization of small hydropower, it is important to get more power for the cost reduction. In our previous experimental investigation, the performance of turbine runner installed near the side wall of the channel was better than that installed at the center of the channel. In order to enhance the output power, a flat guide was installed upstream of the runner on the opposite side of the side wall. In the present study, we parametrically investigate the effects of flow guiding angle and installation position of the guide on the turbine performance. Two-dimensional unsteady CFD simulations are carried out to qualitatively understand the flow mechanism leading to the better performance of turbine. As a result, it is found that the turbine performance can be significantly enhanced by the appropriately placed flow guide. This enhancement is found to be achieved by the improvement of turbine efficiency and the increase of the input power.