Effect of Blade Number on the Performance of a Cross-flow Turbine with a Guide Wall and Cylindrical Cavity

Abstract

Cross-flow turbine is widely used in run-of river type small hydropower stations because of its excellent partial load characteristics with cheap manufacturing cost. The authors proposed the cross-flow turbine with a guide wall and cylindrical cavity that controls the outflow direction from the runner. The outflow separates locally at the guide wall top in a partial load operation, and vibration and noise generate due to the pressure fluctuation around the nozzle tip. Blade number is one of the critical factors that affect the turbine performance. Especially for the outflow from our developed cross-flow turbine, it seems that blade number has a significant effect on them, So, this study focused on the effect of the blade number on the turbine performance and vibration characteristics. As a result, flow separation from the top edge of the guide wall disappears by increasing blade number. The turbine efficiency does not change because of the decrease in the runner torque with the flow rate. Pressure fluctuation between the tip clearance around the outer casing wall tip becomes small by increasing the blade number.