Numerical simulation of the effect of flow direction angle at inlet boundary condition on flow characteristics and performance of axial flow hydraulic propeller turbine runner

The flow behaviour and performance of designed axial flow hydraulic propeller turbine runner were analyzed using computational fluid dynamics (CFD). Numerical simulations were performed in three dimensional computational domain and steady-state type analysis using commercial software ANSYS CFX. The axisymmetric condition of runner and shroud can be simplified by only solving one blade passage in multiple identical regions. In the present simulations, guiding vane which has the main function to adjust turbine load was not modeled, but several flow direction angles at inlet boundary condition were used to direct the flow that enters the domain so the main function of guiding vane can be obtained. The runner rotates at constant rotational speed of 200 rpm. The numerical simulations were carried out for eleven flow direction angles from 60° to 80° with an increment of 2° from tangential direction, specified at inlet boundary condition to see its effects on flow characteristic, such as velocity, pressure, and turbine performance. At flow direction angles of 60°, 70°, and 80°, the resulting torque were 39.457 N.m, 84.523 N.m, and 129.828 N.m respectively, and the resulting power were 828.606 W, 1774.987 W, and 2726.388 W respectively. As the flow direction angle at inlet boundary condition increases, the torque increases. Greater torque leads to increased power.