Consequence and Active Use of Free Gas in Hydro Power

This is an industrial PhD project at NTNU and FDB with financial support from The Research Council of Norway. More information about the industrial PhD project can be found in this interview with The Research Council of Norway.

The main objectives of the project are to investigate the effect of free gas in hydro power plants and how injection of gas can be used to reduce unwanted effects like pressure pulsations, noise and vibration, which are typically present at part load operation of Francis turbines. The project will include experiments both in laboratories and power plants and two experiments have already been carried out.

SAFL study

The experiment was carried out in the cavitation tunnel at St. Anthony Falls Laboratory (SAFL) at the University of Minnesota, Minneapolis. We were looking at the effect of gas content on cavitation and tunnel dynamics. Shedding frequency from a cavitating hydrofoil was used as the excitation frequency for the system and the pressure response was measured in three different location in the tunnel loop.

Svorka Visual

Four plexiglass windows have been installed for visual access to the draft tube flow on Svorka power plant (25 MW), operated by Statkraft. Such visual access to the draft tube flow on an operating machine is unique, as we normally only have visual access in laboratory tests of the model scale runner. A visual study of blade outlet cavitation will be combined with cavitation intensity measurements in this experiment.


Figure 1: Cavitating hydrofoil in SAFL cavitation tunnel


Runner 01

Figure 2: Installation of plexi glass windows on draft tube


DradtTubeWindows 01

Figure 3: Cavitation at runner outlet