Kaplan turbine load instabilities in critical operating regions

Deep-part-load and speed-no-load are known to be a critical operating region of hydraulic turbines where many vibrations are induced. More knowledge is necessary for this operating region as the turbines are expected to be operated more often in this operating range.

Hydraulic turbines are subject to an increasing number of start/stops due to the introduction of wind power and the deregulation of the electricity market. Furthermore, some turbines are expected to provide a spinning reserve. During such operation, a turbine must operate under speed-no-load (SNL) conditions, i.e., the turbine operates at its synchronous speed without power generation. Some turbines may also need
to operate at deep-part-load for a more extended period of time. Preliminary results in the literature suggest that a rotating stall may develop in the vaneless space independent of the number of blades for some
turbines. The exact causes leading to such flow phenomenon are still unclear and the necessary measures to mitigate such a phenomenon are not established.

The aim of this project is therefore to investigate the flow instabilities arising in axial turbines at speed no-load and deep part-load to enable spining reserve. The new knowledge will ensure that the industry has knowledge and methods to maintain safe hydropower facilities with continued long-life spans when operating at speed no load and deep part load.