Experimental comparison of runners with twisted and flat blades of a vertical-axis ultra-low-head hydro turbine for isolated low-scale power generation

Ultra-low heads are untapped ultra-low-head hydropower potentials in the world hydropower scenario, with developments in several hydro turbines. The vertical ultra-low-head hydro turbine (VULHT) is a newly developed turbine for small-scale power generation in open-canal flow, tested with flat blades. This research covers a twisted-blade runner for the VULHT, which was designed and experimentally compared with a previous flat-blade runner on a test rig as a novelty. A design flow of 0.085 m 3 /s and a head of 0.5 m, with outlet flow levels ranging from 0 to 500 mm, were compared. The experiment resulted in 57.27% efficiency at 97.8 RPM with twisted blades, which was 2.37% higher than flat-profile blades, with an uncertainty of ±1.94%. For both, the maximum efficiency was recorded at the outlet control of 450 mm. It concluded the significance of twisted blades and outlet control in VULHT. Future research is recommended for simple cambered and optimally twisted blade profiles for simulation and testing.