Proposal of a new hydraulic turbine capable of high efficiency operation over a wide range of flow rate and effective head

Hydraulic turbines should keep a high efficiency in the widest range of operation conditions. However, conventional turbine has been designed to reduce swirl at a runner outlet at its design point to maximize efficiency, and is unsuitable for partial load operation due to the growth of swirl at the outlet. The swirl of the runner outflow causes loss and unstable flow at the downstream draft tube. To prevent those problems, we developed a new type of hydraulic turbine capable of a wide range of operation conditions, specifically flow rate and effective head, with a high efficiency. The designed new turbine is equipped with a parallel diffuser and a volute diffuser downstream of the runner, instead of a draft tube. The outflow swirl is arranged to have forward turning constantly against runner rotation. It is possible to decrease downstream loss, and to mitigate the vortex core behaviour this way.