ELIMINATING CAVITATION IN SPILLWAY OF THE ILHA SOLTEIRA HYDROELECTRIC POWER PLANT USING ANTI-VORTEX DEVICE

摘要

In the 70's, erosions were observed in the surface of the spans of the spillway of Ilha Solteira Hydroelectric Power Plant by Companhia Energetica de Sao Paulo-CESP. The erosions were caused by cavitation, due to the formation of horseshoe type vortex around the deflector blopks existent in the apron. After several types of repairs were unsuccessfully attempted in the eroded areas spillway aeration device were considered to mitigate the cavitation effects. CESP hired Fundacao Centro Tecnologico de Hidraulica-FCTH, to accomplish spillway aeration studies. FCTH built two bidimensional models in the scales 1:50 and 1:20, representing two spans of the spillway. During these studies, the technical team of FCTH idealized an anti-vortex device, seeking an alternative method to combat the cavitation through the elimination of the horseshoe vortex itself. Both the aeration and anti-vortex alternatives were tested. After 10 years of operation, they both presented satisfactory results, however, erosions by cavitation in the lateral of the anti-vortex device continued to be observed. Due to the implementation easiness and involved costs, CESP opted for the anti-vortex device. This paper shows the results obtained from the model and prototype studies including the solutions found and the procedures to be adopted for the elimination of cavitation erosion of the spillway concrete surface.