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, and these small hydro turbine's common problems are out
of operation by foreign materials. Then, there are demands for small hydro turbines to keep high performance and wide
flow passage. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance and enable
to use low-solidity rotors with wide flow passage, in order to accomplish high performance and stable operation. 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 turbine and high efficiency could be kept in wide flow rate range. Internal flow with foreign vegetable materials,
i.e. leaves and grasses, were investigated using a high speed camera and the causes of troubles related to the foreign materials were considered.
