Design of Experiments Applied to Francis Turbine Draft Tube to Minimize Pressure Pulsations and Energy Losses in Off-Design Conditions

This paper proposes an original approach to investigate the influence of geometry Francis turbines draft tube on pressure fluctuations and energy losses in off-design conditions. It is based Design Experiments (DOE) steady/unsteady Computational Fluid Dynamics (CFD) simulations internal flow. The test case a turbine unit specific speed Ns=120 m-kW which required operate continuously conditions, either with 45% (part-load) or 110% (full-load) design flow rate. Nine different geometries featuring set geometrical parameters are first defined by orthogonal array-based DOE approach. For each them, unsteady steady CFD from guide vane outlet performed at part-load full-load respectively. parameter both instability resulting pulsations, as well tube, investigated applying Analysis Means (ANOM) numerical results. whole methodology enables identification minimizing occurring conditions while maintaining requested recovery. Finally, results final compared estimated ANOM, demonstrates that proposed also rough preliminary estimation amplitude.