EXPERIMENTAL INVESTIGATIONS CONCERNING EROSIVE AGGRESSIVENESS OF CAVITATION IN A RADIAL TEST PUMP WITH THE AID OF ADHESIVE COPPER FILMS

The experimental results which will be presented in this paper demonstrate the significant effects of imploding cavitation bubbles striking against the surface of radial impeller blades. Based on former investigations at the laboratory of the first three authors, the method using copper coated blades for investigating cavitation erosive aggressiveness has been improved. In the former investigations, galvanic copper layers were used as sensor to quantify the aggressiveness of cavitating flows. Some problems, especially the insufficient reproducibility of the mechanical properties of the galvanic copper layers, led to the application of adhesive copper films. Such copper films can be fixed on the surface of the impeller blades with the help of adhesive films. Experiments were carried out on a special radial test pump with 2-dimensional impeller blades (Figure 1). The outflow from the impeller is realized as an annular casing. This causes an axially symmetric outflow condition for the impeller. Additionally, acoustic measurements were carried out and images of cavitation behaviour were recorded to find correlations between the erosive aggressiveness, acoustic emission and the visual appearance of cavitating flows. The investigations were part of the research project “CAVISMONITOR – Cavitation Monitoring In Hydraulic Machines With Aid Of A Computer Aided Visualization Method” carried out in international cooperation and financially supported by the EU (European Union).