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Communication Dans Un Congrès Année : 2017

Analysis of the transfer function of large and small premixed laminar conical flames

Résumé

The Flame Transfer Function (FTF) of premixed laminar conical flames submitted to flowrate modulations is a configuration of fundamental and practical interest for improving the design of thermo-acoustically stable low power burners. Many theoretical models were developed for relatively large single flames based on labscale experiments, while most domestic and industrial burners operate with a collection of small injectors. Measurements of the FTF of laminar premixed methane/air conical flames are compared with analytical expressions deduced from kinematic descriptions of flame wrinkling when the burner size is reduced. The flame aspect ratio is kept constant corresponding to a flame tip half-angle α = 14.47° and the radius of the injector is reduced from R = 11 mm to R = 1.5 mm. Three different velocity perturbation models are tested, with and without an additional model accounting for the dynamics of the flame anchoring point. For the largest flames R = 11 mm and 7 mm, the best agreement is found for a FTF model with an incompressible velocity disturbance in the fresh reactants stream. The anchoring point dynamics has only a weak influence on the FTF gain and phase-lag plots of these flames. For the smallest flames (R = 1.5 mm), a FTF model based on a uniform flow perturbation yields the best match with experiments for the phase-lag plot, but none of the three velocity perturbation models reproduce the FTF gain evolution as measured in experiments. Including the contribution of the anchoring point dynamics to the FTF significantly changes the FTF gain predictions, but it does not allow to reproduce the main features observed in the measured gain curves and the phase-lag predictions worsen. It is concluded that an additional modeling effort is needed to adequatedly reproduce the FTF of small premixed laminar conical flames.
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Dates et versions

hal-01883220 , version 1 (27-09-2018)

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Citer

R Gaudron, Marco Gatti, Clément Mirat, Thierry Schuller. Analysis of the transfer function of large and small premixed laminar conical flames. ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition, ASME, Jun 2017, Charlotte, United States. ⟨10.1115/gt2017-64231⟩. ⟨hal-01883220⟩
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