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Summary:In the frame of a joint research programme between EDF, HydroQuébec and IMHEF, different methods are investigated to predict cavitation erosion on Francis turbines from mode!. They are based on measurement of pitting, pressure fluctuations and acceleration. The measurement techniques have been detailed in Part I and Part 2. The present article describes essentially the theoretical and practical aspects of the methods and discusses the results obtained until now from the mode! and prototype tests. The first analysis shows that the methods proposed are suitable to measure cavitation aggressiveness on mode! and on prototype, and that the level on the mode! is several orders of magnitude smaller than on the prototype. To adjust transposition laws, a more complete set of data is needed.

Different measurement techniques have been used to detect cavitation on a Francis turbine model. The results are compared to those obtained on the prototype and presented in the first of this series of articles. The runner mode! used for that study is build on the basis of a geometrical recovery of one of most eroded blade of the prototype. The results of the different measurements are presented and commented by comparison with prototype measurements. This comparison leads to a proposai of the physics which should be involved in transposition laws for the prediction of prototype erosion from cavitation mode! tests. The consequences of such scaling laws, as well as their application to the prototype and mode! results, are part of the third facet of this work.

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