Control of Secondary Flow Losses in a Turbine Stage via Stator Endwall Fence at a Low Reynolds Number

Under the demand for refined design and increase in turbine load, reducing secondary flow losses in the endwall region has become a research focus in the field of low-pressure turbines. To explore refined control methods of secondary flow in the endwall region, endwall fences with different geometric parameters are applied to the stator of a low-speed turbine stage at a low Reynolds number. The numerical results indicate that installing an endwall fence device with reasonable parameters on the stator of turbine stage can increase the stage efficiency by 0.21%. The cross migration of the endwall boundary layer within the stator passage is effectively blocked which makes the strength of counter vortex significantly reduced. Moreover, the uniformity of the flow field at the inlet of rotor blade row has been improved. The interaction between the fence vortex and the passage vortex is affected by the design parameters of the endwall fences. However, the endwall fence will introduce additional friction losses and vortices in the endwall region of stator passage. To achieve more efficient control of secondary flow in the endwall region, the XGBoost model and improved chaotic particle swarm optimization have been applied to the optimization design of an endwall fence with nonuniform height in the streamwise. The potential for secondary flow regulation of endwall fences has been more fully developed, and the isentropic efficiency of the turbine stage has been improved by 0.33%. The key design parameters of endwall fences are elucidated using sensitivity analysis methods.