Flow characteristics around a guide vane in cross-flow turbine

A swing-type guide vane is the most popular in a cross-flow turbine, which controls the water flow rate into the turbine. The flow under the guide vane may turn away from the optimum direction in partial load operation by the flow separation from the guide vane leading edge. Maintaining the ideal velocity triangle at the runner inlet is essential to improve the turbine efficiency and to avoid noise and vibration for partial load operation. It is essential to reveal how the angle and shape of those guide vanes affect the flow behavior at the runner inlet and turbine performance. Therefore, this study focuses on the flow characteristics around the guide vane and at the cross-flow runner inlet. The authors verify the evaluation by CFD simulation and compare turbine performance and internal flow between different operating conditions with two guide vanes, the swing-type, and circular segment type. As a result, it is revealed that the swing-type guide vane affects the flow direction, and especially the flow angle is far from the optimum at partial operation. The circular segment type shows superior performance at partial load than the swing-type guide vane.