Flow analysis on an overhauled

twin Francis turbine

to prove and justify the identified performance deficit

In course of the refurbishment of a historic Italian Camelback Francis-turbine built in 1924, a completely new Camelback-unit was supplied in 2022. The only parts of the power plant that remained unchanged were the intake and the draft tube downstream of the twin-manifold which diverts the flow from the two horizontal turbine runners in a vertical direction. In course of the commissioning it quickly turned out that there is a quite massive lack of power generated by the turbine.

With the help of a comprehensive CFD-simulation we analysed the flow in the Twin-type Camelback turbine to find out the reasons for the performance deficit. The findings of the CFD-study fully confirmed the operation experience of the turbine.

While there might also be some room for improvement of the runner design, the main problem of the turbine is the unfavourable design of the twin-manifold and the main draft tube. Finally, we developed suggestions on how to significantly improve turbine performance.