クロスフロー水車における流体振動に関する研究

（ケーシング形状と圧力変動の関係）

抄録

Many small hydropower stations, which is run-off river type, use a cross-flow turbine because of its excellent partial load characteristics with low manufacturing cost. So far, there have been various studies to improve the turbine performance. The authors have been developing a new shape cross-flow turbine with a cylindrical cavity and a guide wall to enhance the performance and make the turbine small. This study focuses on noise and vibration generated from the turbine. Suppression of noise and vibration is, of course, essential to enlarge operating condition and reliability improvement. This study aims to elucidate the cause of the turbine vibration and evaluate the relationship with the casing shape. Previous research shows a large pressure fluctuation point at the end of the turbine nozzle's outer wall. The authors measured turbine vibration and elucidated the pressure fluctuation in the turbine by CFD analysis. As a result, the vibration can be reduced by suppressing pressure fluctuation by modifying the nozzle outer wall shape. The runner rotation causes the vibration. Moreover, the clearance between the runner and the casing wall significantly affects the vibration characteristics and the turbine performance.