Abstract
Small hydropower generation is one of important alternative energy, and potential of small hydropower is great.
Efficiency of small hydro turbines is lower than that of large one. Then, there are demands for small hydro turbines to keep
high performance. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance. In this
research, experimental apparatus of the contra-rotating small hydro turbine with 60 mm casing diameter was manufactured
and performance of it was investigated by an experiment. Efficiency of the contra-rotating small hydro turbine was high in
pico-hydro turbines and high efficiency could be kept in wide flow rate range. Unsteady internal flow conditions, which
were difficult to measure experimentally, were shown by the numerical flow analysis. Further, pressure distributions and
wake interactions with a rotor rotation were clarified. Then, a relation between the performance and unsteady internal flow
condition was considered by the experimental and numerical analysis results.
