Improvement in the stability of S-shaped characteristics by using misaligned guide vanes

Based on the experimental data of two reversible pump-turbine scale models (RPTs), this work initially represents a methodology to accurately predict S-shaped characteristics and local phenomena in hydraulic machines. The main part of this study deals with the numerical investigation of a specific arrangement of misaligned guide vanes (MGVs) in one selected RPT. Their operating principle, the underlying mechanisms and their influence on the stability of S-shaped characteristics are examined. The computations are performed under steady and transient operating conditions.