Effect of blade profile on the efficiency of a waterfall cross-flow hydro turbine.

The effect of blade profile on the efficiency of a waterfall cross-flow hydro turbine was investigated numerically using the non-uniform, thin, and standard blades. Each efficiency of the blade profile was evaluated by varying the tip-speed ratio (=0.3–0.9) and off-axis distance (=0.26–0.48), which are the influential parameters for characterizing the performance of the cross-flow turbine. Although a minor improvement was observed in the peak efficiency 62–63 % by the blade-profile effect, the off-peak efficiency was highly improved up to 8 % on the non-uniform blade and 11 % on the thin blade. The examination of the local and average torque distribution in reference to the flow fields showed that an increased torque on the non-uniform blade was observed at small blade angles due to the increased waterfall impingement, while that on the thin blade was observed at large blade angles caused by increased rebounding flow. This suggests the different torque enhancement mechanism of the cross-flow turbine on the non-uniform and thin blades in comparison with the standard blade. [ABSTRACT FROM AUTHOR]