Unsteady computational fluid dynamic analysis of the behavior of guide vane trailing-edge injection and its effects on downstream rotor performance in a francis hydroturbine

A unique guide vane design, which includes trailing-edge jets, is presented for a mixedflow Francis hydroturbine. The water injection causes a change in bulk flow direction at the inlet of the rotor. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation. Unsteady CFD simulations show nearly 1% improvement in overall turbine efficiency with the use of injection. This revolutionary concept also has the ability to reduce the intensity of the rotor-stator interactions (RSI) by compensating for the momentum deficit of the wicket gate wakes. This technology may be equally applied to other turbomachinery devices with problematic rotor-stator flow misalignments.