Numerical Study on the Performance of a Gravitational Water Vortex Hydro Turbine System with a Cylindrical Basin

Gravitational water vortex power systems are one of the cost-effective systems of extracting low head hydro power. This study investigates numerically a gravitational water vortex power system five-blade turbine rotating in a cylindrical basin for three blade shapes (flat, curved, and vertical twist) and three diameters of the discharge orifice at the basin bottom. The numerical simulations adopted a scaled down model using the Froude number similarity and employed the Volume of Fluid, Moving Reference Frame, and SST k − ω turbulence model. The system performance was examined both qualitatively and quantitatively for five turbine rotation speeds over 40–120 revolution/minute (RPM). It was found that blade shape, orifice diameter, and turbine rotation speed have significant effects on system performance. For a specific blade shape and discharge orifice diameter combination, the generated torque and power increases almost linearly at a large rate when the turbine rotation speed is increased from 40 RPM to 80 RPM and then decreases, also essentially linearly, at a much smaller rate from 80 RPM to 120 RPM. The optimal rotation speed was found to be 80 RPM across the speeds considered for all cases. It was also shown that the system with an intermediate diameter ratio performs better for each blade shape and the system with the curved blades performs better than the other two blade shapes. The results further show that for the cases considered, the most favorable operating condition was achieved by using a combination of a five-bladed curved turbine, a medium discharge orifice diameter (do/D ≈ 0.16) in a cylindrical basin, and a rotational speed of 80 RPM, yielding relatively the highest efficiency of up to 62%, which are very good outcomes for such low head hydropower systems.

Energies

Energies

19

1996-1073

N/A

N/A

35