Turbulent Structure of a Jet Diffusion Flame in a Co-flowing Air Stream with Grid Turbulence

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The effects of a flame on a shear generated tubulence and on a grid turbulence have been investigated experimentally. A laminar fuel jet, i.e., H_2-Ar mixture (volumetric ratio 1/2.5), was injected from a burner tube. The jet velocity was 5.0 m/s. The velocity of a co-flowing air stream was 7.0 m/s and the turbulent intensities were 3.9% and 0.54% with and without the grid, respectively. Conclusions obtained are as follows : (1) The decay of mean velocity along the centerline is slowed down by the flame. This is mainly attributed to the suppression of turbulent mixing between the jet and the co-flowing air stream caused by increased viscosity. (2) Though the turbulent intensity of the shear generated turbulence is suppressed significantly at the flame zone, such a significant suppression of the gird turbulence is not observed. (3) The grid turbulence is transported towards the centerline by another mechanism than the turbulent mixing, which is dominant in the shear generated turbulence.
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