Performance characteristics of propeller turbine using an outer ring runner

The authors focus on a small propeller turbine utilizing the extremely low head and relatively much flow rate sites. The proposed propeller turbine by the authors previously had fixed pitch vanes, and the vane was made of a constant thickness metal plate to reduce manufacturing cost and required technology. The turbine was in a step in the casing and had an outer ring on the runner vane periphery. The structure effectively suppressed the tip leakage flow but had no significant effect on turbine efficiency improvement. This is the limit of the constant thickness blade rotor. So, this study focuses on making the runner by additive manufacturing by the 3D printer because it is faster and cheaper than conventional production methods and is expected to improve turbine efficiency and physical strength. This study aims to compare the performance of the new ring runner model designed to further improve the efficiency of the turbine by CFD analysis and experiment. As a result, the turbine efficiency improved, tip leakage flow was suppressed by attached to the outer ring compared with the previous model