Onboard Measurements of Pressure and Strain Fluctuations in a Model of low Head Francis Turbine. Part 1 : Instrumentation

In this first part of a 2 papers series, we present the experimental procedure for onboard measurement of pressure and strain fluctuation in a model of low head Francis turbine. 28 miniature pressure sensors are fitted in the pressure and suction sides of two consecutive blades. A specific technique for sensors mounting has been developed allowing a direct manufacturing of the pressure sensors in the runner blades. This prevents from any geometry alteration of the hydraulic profile. Furthermore, miniature piezo electric strain gauges, 70 times more sensitive than conventional gauges, are embedded in pressure and suction side of 2 runner blades. Data acquisition is ensured by 32 channels onboard digitiser, having 12 bits resolution, 64 K-samples memory depth and 20 kHz maximum sampling frequency. Both static and dynamic calibration procedures of the pressure transducers are described. Analysis of experimental results and comparison with CFD calculation are presented in the second part (Ref. 7)

Cavitation Erosion Prediction on Francis Turbines Part 2 : Model Tests and Flow Analysis

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 built 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 proposal 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

Onboard Measurements of Pressure and Strain Fluctuations in a Model of low Head Francis Turbine. Part 2 : Measurements and Preliminary Analysis Results

In this second part of a 2 papers series, we present the analysis of “onboard” measurements on the runner of a Low Head Francis model and comparison with the same type of measurements on a similar prototype, as well as a comparison with numerical calculations. The details of the experimental procedures for onboard measurement of pressure and strain fluctuation in the model runner are presented in the first part (Ref. 1). Load fluctuations on the blade of a Francis runner depend largely on the different hydrodynamic phenomena that may be present. For instance, the partial load rope vortex, blade trailing edge Karman vortices and any other cavitating occurrences at off-design operating points. Almost all of these phenomena can lead to fatigue failures, which translates into the interest of better understanding their behavior and interaction with the structures. The present paper shows how onboard measurements can be a valuable source of information on these phenomena and how it brings solutions to the evaluation of the fatigue life of turbine components. The good comparisons between the prototype and model results illustrate that the phenomena can be observed at both scales, although the transposition of dynamic component of pressure or stresses, is not yet feasible. The also very good correlation between measurements and numerical calculations of the flow and of the structural response of the runner to the static loading, enables us to progress to the next step, that is, dynamic analysis and fatigue life prediction with reliable data. Finally, we will show also that such measurements can be very useful in the development of numerical calculation tools used for performance optimization

Transformations sociales en Asie

S’ils diffèrent certes par bien des aspects, les pays asiatiques ont toutefois pour spécificité partagée de connaître une période de profondes transformations : migrations entre villes et campagnes, processus de mobilité entre pays, mais aussi forte activité industrielle et rapidité de leur développement… Etudier les « transformations sociales en Asie » permet alors non seulement de s’interroger sur de telles transformations, mais aussi sur la capacité des théories sociologiques à en rendre compte – et par effet de miroir, sur les propres transfor­ma­tions de nos sociétés… Un premier champ d’interrogations, dans cette livraison de Sciences de la Société, porte sur les pays asiatiques et les transformations sociales qui y sont en cours : l’adoption d’un nouveau modèle de développement économique, et parfois la sortie ou la réinvention d’un modèle politique, supposent des réorganisations internes de grande ampleur, sur les plans identitaires, organisationnels… Un deuxième but de ce numéro sera d’analyser la capacité des paradigmes sociologiques à mettre en lumière ces transformations et à en rendre compte : les approches de la sociologie du travail et des relations industrielles ont-elles ainsi – en Chine, en Malaisie ou au Vietnam – la même portée explicative que dans les pays où elles ont été développées ? Quid alors de l’importation d’analyses occidentales concernant des phénomènes similaires en Asie ?... Les articles ont enfin pour objectif ultime une réflexion sur les dynamiques des Policy transfers entre pays asiatiques – ou entre ces derniers et pays occidentaux. Et si cette question des Policy transfers est surtout connue en Europe par des travaux sur l’influence anglo-saxonne, sur les processus de transition en Europe de l’Est ou sur les échanges Nord-Sud, l’étude des transferts entre monde occidental et Asie – ou entre pays asiatiques eux-mêmes – ouvre ici à un regard renouvelé en la matière