Performance Characteristics and Flow Field of Axial Flow Hydraulic Turbine in Shallow Open Channel

Abstract

We have been developing an axial flow hydraulic turbine with a collection device that can be used in open channels with shallow water depths such as agricultural waterways and small rivers. However, the addition of a collection device reduces the portability and increases the cost compared to axial flow hydraulic turbines without a collection device. Therefore, it is important to understand the performance characteristics and flow field of the axial flow hydraulic turbine in open channels while considering the possibility of using only an axial flow hydraulic turbine. This study focuses on an axial flow hydraulic turbine operating near both the free and bottom surfaces in an open channel. We conducted a multiphase flow analysis that considers the free surface, as well as a single-phase flow analysis that does not consider it. This study indicates that the maximum power coefficient obtained from multiphase flow analysis was lower than that obtained from single-phase flow analysis. This is thought to be the result of the water-receiving area and inflow velocity becoming smaller, the input power coefficient becoming lower due to the influences of the free surface, and the bottom surface of the channel and the turbine efficiency becoming lower as the result of a non-uniform velocity distribution.