Internal Flow and Performance with Foreign Vegetable Materials in a Contra-Rotating Small Hydro-Turbine

Abstract

Small hydropower generation is one of important alternative energy, and potential of small hydropower is great. Efficiency of small hydro-turbine is lower than that of large one, and these small hydro-turbine's common problems are out of operation by foreign materials. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance and enable to use low-solidity rotors to achieve stable operation. Experimental apparatus of the contra-rotating small hydro-turbine with 60mm casing diameter was manufactured and some experiments were conducted. In this research, the internal flow with foreign vegetable materials, i.e. leaves and grasses, were investigated by a high speed camera, and the performance experiments when two pieces of cudweeds were attached on the blade of front rotor were conducted. As the results shown, the passing rate of small leaves is 41.2% and all of the middle leaves can't pass through the contra-rotating small hydro-turbine. The highest efficiency also decreased about 13%, reaching to 51.2% at 1.4Qd, because of the foreign vegetable materials.