Hydraulic optimisation

of a double-regulated mixed-flow turbine for small hydropower applications

In 2020, we developed a double-regulated mixed-flow turbine for a turbine manufacturer. Compared to conventional Francis turbines, this type of turbine is characterised by a smoother efficiency curve and improved partial load capability. A report on this project was published, among others, in the hydropower journal ZEK Hydro, October 2021 issue, and at the Hydro 2022 conference.

Hydraulic optimisation for higher power output and increased head

Following the positive operating experience, we were commissioned to optimise the original design for a site with a higher head and higher output. These optimisations were carried out using computational fluid dynamics (CFD) to increase efficiency, improve cavitation safety and further optimise the mechanical properties.

Particular improvements were made to minimise the adjustment torque of the guide vanes and runner blades and to reduce the axial thrust to almost zero.

Peak efficiency of 94.5 % achieved

After extensive adjustments to the blade geometry and the meridian section, a peak efficiency of 94.5 % was achieved. In addition, the hill chart shows a similarly high-efficiency level in the medium head range of 37 m to 47 m, which makes the design of future projects considerably easier.

Measurements on the reference turbine designed in 2020 confirmed the values predicted by the simulation. They showed that the efficiencies calculated using CFD simulation are achieved both at the best point and in the low partial load range.

Pioneering technology for efficient power plant solutions

The optimised mixed-flow turbine sets new standards in power generation for sites with medium to high heads. Its high efficiency, improved partial load capability and outstandingly quiet operation offer a future-orientated solution for power plant operators who focus on reliability and extended operating ranges.

Find out more about this innovative project in the technical article in ZEK Hydro Magazine, October 2021 issue, and our paper for Hydro 2022.