Multi-Scale High Intensity Turbulence Generator Applied to a High Pressure Turbulent Burner

Abstract : We report an experimental study dedicated to the investigation of the turbulent flow generated by a multi-scale grid and its interaction with a premixed flame. The multiscale grid is made from the combination of three perforated plates shifted in space such that their mesh size and blockage ratio both increase in the direction of the mean flow. It is found that this multi-scale grid induces a nearly homogeneous and isotropic (at both large and small scales) in the potential core of an axisymmetric premixed burner. A comparison with a single-scale grid shows that the length scales characterizing the multi-scale grid generated turbulence are smaller than those measured downstream the single-scale grid, while the turbulent kinetic energy produced by the multi-scale grid is much larger. The energy distribution through scales is investigated by means of the second-order structure functions highlighting an increase of energy at each scale, which is even more pronounced at small scales. As emphasized by the third-order structure function, energy transfer through scales is significantly enhanced by the multi-scale forcing and results, in turns, to an exceptional fast decay of the turbulent kinetic energy. Our results are compatible with the self-preservation theory where the Taylor microscale is the characteristic length-scale. The potential of the multi-scale forcing is then assessed in a premixed methane-air flame. The influence of the turbulence onto the structure of the flame is evaluated via the turbulent flame speed. The results obtained for the multi-scale grid deviate from those obtained for single-scale grid suggesting that the flame structure may not undergo the influence of large scales alone, in agreement with recent observations of flame front wrinkling by [13].
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Journal articles
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https://hal.archives-ouvertes.fr/hal-02012590
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Submitted on : Friday, February 8, 2019 - 6:18:08 PM
Last modification on : Wednesday, December 4, 2019 - 10:06:01 PM

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Romain Fragner, Nicolas Mazellier, Fabien Halter, Christian Chauveau, Iskender Gökalp. Multi-Scale High Intensity Turbulence Generator Applied to a High Pressure Turbulent Burner. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2015, 94 (1), pp.263-283. ⟨10.1007/s10494-014-9556-2⟩. ⟨hal-02012590⟩

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