Determination of added parameters in hydraulic turbines

Swedish hydropower units are mainly equipped with Kaplan and Francis runners. Today, the industry uses added parameters based on rules of thumb set some decades ago to determine the function of these parameters, induced by the presence of water, to determine rotor characteristics for safe operation. However, these parameters must be updated to apply also for refurbished runners that are lighter and more powerful.

The design of Kaplan and Francis runners necessitates the determination of the rotor characteristics such as its natural frequencies for safe operation. Such analysis needs the added proprieties (mass, damping, stiffness) induced by the water on the runner for an accurate determination. These added parameters induced by the presence of water are challenging to determine as they are a function of many parameters such as oscillation frequencies, the amplitude of the oscillations, velocity field, viscosity, turbulence, head, geometry, etc. However, refurbished runners, lighter and more powerful, necessitate a more truthful determination of the added parameters and presently no consensus exists on how to determine such parameters. This project aims to develop a numerical methodology allowing the determination of the added parameters in Francis and Kaplan hydraulic turbines. The methodology will be validated with measurements performed at the Vattenfall laboratory.