Ida Jansson, from division for Fluid and Experimental Mechanics.

Vibrant Bodies of Swirling Flow

Published: 30 September 2013

A risk assessment of rotor vibrations of hydropower units demands consideration of both the inertia of the rotating shaft and the body of the swirling flow in the turbine. Ida Jansson pinpoints this intertwined nature of the inertia of the rotor of hydropower units in her thesis Vibrant Bodies of Swirling Flow - On the Limits of Mechanical Power Transformation.

Ida Jansson has participated in the research program StandUpforEnergy which is part of the Government's strategic investment in energy. One of the overriding aims is to reduce the costs of large-scale production of renewable and environmentally sustainable electricity delivered to the consumer.

The thesis is based on measurements of rotor vibrations levels during start-up of a research and development Kaplan prototype installed in the old machine hall at the Porjus hydropower plant.

The start-up sequence yields large stresses that increases wear and reduces the life length of the machine. Quantification of these negative effects associated with regulation is crucial with today's high demand of regulating power at the deregulated electricity market. The measured vibrations levels are analysed in terms of both time and frequency, which turns out to reveal both the soruce of disturbances and how they propagate in a hydropower machine. 

In the future outlook of the thesis, Ida Jansson discusses how unsteady motions traditionally viewed as a threat in conventional hydropower could be a means of transforming power in new technical devices that harvest energy in flowing water. 

- I believe that mimicing energy transformation at work in usteady flows in technical design gives us solutions less sensitive to disturbances. We have to accept the conditions at hand. The water is cheeky. We better accept that and go with the flow instead of against it, says Ida Jansson.