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Analyse des phénomènes liés à la présence de la phase liquide dans les turbines à vapeur et élaboration de modèles méridiens pour en prédire les effets

Abstract : During the expansion in a turbine, the enthalpy of the steam fall. This fall leads the steam to cross the saturation line and brings about its spontaneous condensation and the appearance of fog droplets. The deposition of these droplets on downstream blades lies at the root of the creation of a liquid film. This film is torn off by steam flow and creates coarse water. These big droplets can impact downstream blades. Each of these phenomena induces some losses which are generally grouped in the "wetness losses" estimated thanks to Baumann's rule. The aim of this work is to develop, in a throughflow code, some models which allow to take into account the condensation, deposition and liquid film flow and the losses linked to each of these phenomena. An homogeneous two phases flow model is implemented in the throughflow code. Two transport equations on the mass fraction of liquid and on the droplets number are added to Euler's equations written for gas phase. This model is validated on an experimental test case of expansion in nozzle and feeds the model of deposition. The influences of diffusion, turbophoresis, thermophoresis, gravity and of inertia of droplets on the deposition are studied. It appears to be necessary to take into account diffusion, turbophoresisand deposition due to inertia on the leading edges of blades. A model which allows to evaluate the thickness and the velocity of a liquid film submitted to aerodynamic shear, friction on blades and rotational effects has been developed. This model is validated on experimental results of a liquid film flow on a flat plate in some conditions representatives of those encountered in low pressure steam turbines. Finally a calculation realised on a real geometry of a 8-stages low pressure steam turbine has demonstrated that the methodology developed during this work can be used on an industrial test case. The contributions of the phenomena studied to wetness losses are evaluated.
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Submitted on : Monday, April 29, 2013 - 9:44:07 AM
Last modification on : Friday, September 30, 2022 - 10:56:10 AM
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  • HAL Id : tel-00818336, version 1

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Yoann Fendler. Analyse des phénomènes liés à la présence de la phase liquide dans les turbines à vapeur et élaboration de modèles méridiens pour en prédire les effets. Autre. Ecole Centrale de Lyon, 2012. Français. ⟨NNT : 2012ECDL0053⟩. ⟨tel-00818336⟩

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