Monitoring of the cavitation in the Kaplan turbine

Abstract

The phenomena of cavitation in water machines usually causes mechanical damage to the vital parts of the turbine. Because cavitation is usually frequent and unpredictable, the development of a monitoring method is of great importance. Present methods for cavitation detection in water turbines are based on observation of pressure pulsations, acoustic emission and mechanical vibrations on the turbine casing. Changes of dynamic properties of the above variables enable empirical analysis and are measured for the presence of the cavitation and its consequences. On the vital parts of the turbine, a new method of cavitation detection was implemented. Cavitation, a two-phase phenomenon (gas flow in the liquid phase), can be optically established when using proper illumination of the control volume. A method of computer-aided visualization was used, which offers real time evaluation of the cavitation topological structures in the turbine flow field. A new method of cavitation monitoring was tested on a model Kaplan turbine where, besides the computer-aided visualization, various integral parameters were simultaneously observed. The procedure was tested and performed in different integral operational regimes. Results of the study indicate that visualization method is the most suitable for cavitation monitoring; further effort however should be made in this research sphere.