Stochastic modelling of cavitation erosion in Francis runner

[摘要] Reaction turbines, of which Francis turbines, constitute a large proportion of low and medium head turbines installed in hydropower plants. Managing these machines represents a real challenge in terms of efficiency, competitiveness and demands on the energy market. Turbines runner blades exhibit loss of performance from damage due to several reasons. One common source of damage is erosion due to the cavitation phenomenon. Indeed, at a given operating region, rapid changes of velocity can create bubbles in the water flow due to local low pressures. When cavitation bubbles reach pressure recovery, they collapse and may induce wear or erosion in these regions. Even if this phenomenon has been intensively studied in the past decades, cavitation erosion is not fully understood as it is driven by several parameters such as flow dynamic, turbine design, environment, or material properties. Some of these parameters can be studied in laboratory to compare materials resistance between each other. This article aims to model the cavitation by a stochastic model using erosion experimental data observed in the laboratory. The benefit of such models is to consider both the uncertainties and natural fluctuations of the phenomenon. With the proposed framework, the study will highlight the differences observed in cavitation erosion experiments of two common materials used to manufacture Francis's runners. This study is the first step in a project aiming at the prediction of turbines mass loss due to cavitation erosion on actual operating Francis turbines.

[发布机构] Département de Génie Mécanique, École de Technologie Supérieure, 1100 Rue Notre-Dame Ouest, Montréal; QC; H3C 1K3, Canada^1;Expertise - Perf., Evolution et Caracterisation des Actifs, Recherche et Innovation - Production, Institut de Recherche d'Hydro Québec, 1800 boul. Lionel-Boulet, Varennes; QC; J3X 1S1, Canada^2;Modélisation et Sûreté des Systèmes, Université de Technologie de Troyes, 12 Rue Marie Curie, Troyes; 10300, France^3;Département Performance, Risque Industriel, Surveillance pour la Maintenance et l'Exploitation, EDF RandD, 6 quai Watier, Chatou Cedex; 78401, France^4

[关键词] Cavitation bubble;Cavitation phenomenon;Erosion experiments;Loss of performance;Materials resistance;Natural fluctuations;Operating regions;Pressure recovery