Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

Under low flow-rate conditions, a Francis turbine exhibits precession of vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration performance as manifested by torque and power output fluctuations. In order suppress swirl component tube, use anti-swirl fins was investigated previous study. However, generation still occurred near cone this study, unsteady-state Reynolds-averaged Navier–Stokes analyses were conducted scale-adaptive simulation shear stress transport turbulence model. This model used observe effects injection tube on unsteady internal considering both active passive suppression methods. The air affected depending rate air. addition, an level 0.5%Q led reduction maximum characteristics.