Étude expérimentale d'une flamme de prémélange stabilisée dans un écoulement turbulent à point d'arrêt

Abstract : Flames in stagnating turbulence are well identified academic situations of turbulent reacting flows that allow a close coordination of experimental, theoritical and computational aspects of combustion research. In the present work, the local and mean characteristics of a stagnating turbulent premixed flame, obtained by impinging a flow against a solid flat surface, are investigated. The experimental situation is characterized by a weak turbulence as well as a flamelet regime, two features that allow the development of an asymptotic analysis of this reactive flow. The presence of the solid wall results in the existence of a mean rate of strain that influences the structure of the flame and may eventually lead to extinction. Morover, heat transfer through the solid wall may also interact with this rate of strain to facilitate this extinction mechanism. This latter situation corresponding to a non-isenthalpic reactive flow is an ongoing research subject. The present work is intented to measure simultaneously velocity and scalar fields, the scalar characterizing the progress of chemical reaction throughout the flow. To this purpose, the Vestales experimental rig was developped: it consists of a nozzle burner providing a stream of reactive mixture (propane-air), fitted out with a perforated grid, facing a flat solid plate. The premixed turbulent flame is then stabilized in the diverging flow between the exit plane and the solid plate. Laser Doppler Anemometry (L.D.A.) and Particle Image Velocimetry (P.I.V.) system are used for velocity measurements. In order to determine simultaneously velocity and progress variable, P.I.V. recordings are analysed as tomographic recordings. A great deal of attention has been paid to implement processing tools: we have shown that the proposed method based on region and edge segmentation combined with deformable models is well suited to extract a continuous front flame contour and to topological analysis purpose. The study concentrates on two mean strain rates (100 and 120 s−1) and two values of the equivalence ratio of the unburned mixture (0.89 and 0.99). Spectral and spatial analysis of flowfield turbulence statistics is proposed. Reynolds and Favre mean quantities of velocity and progress variable are obtained, including scalar turbulent flux, which allows comparison with results obtained through the theoritical asymptotic analysis as well as numerical simulation.
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Electric power. Université de Poitiers, 2006. French


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Submitted on : Monday, October 26, 2009 - 10:06:52 PM
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Xavier Coron. Étude expérimentale d'une flamme de prémélange stabilisée dans un écoulement turbulent à point d'arrêt. Electric power. Université de Poitiers, 2006. French. <tel-00426605>

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