Author(s)

M.-A. Motte & A.G.H. Lejeune

Abstract

In order that the Coo-2 storage hydropower station could uphold the electrical network rapidly, the owner plans to modify the turbine starting operation, to leave the wheel running in the air and to open the valve and expel the plug toward the downstream reservoir with the result of two-phase transient and unsteady flow. The study describes the effects of the outflow on the holding of the turbine, the draft tube and pipes. Three approaches have been achieved: by computation, scale tests and site tests. The paper will present the most characteristic results of those studies. For instance, we note there is a relationship between the evolution of the air pocket, after opening of the control valve and : - the degree of valve’s opening - the speed of opening of the control valve. A more advanced study of void fraction and velocities of bubbles, with optical probe, is in progress.

Keywords