Investigation of Interaction between Diffusion Flame and Vortex by Advanced Laser Image Diagnostics

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The flame-vortex interaction has attracted research attentions because it constitutes important elements for analyzing the microscopic turbulent flame structure and extinction. Instantaneous and simultaneous measurements of two-dimensional temperature and OH-LIF profiles by combining Rayleigh scattering with laser induced fluorescence (LIF) were demonstrated in nitrogen-diluted hydrogen (H_2 30 % + N_2 70 %) diffusion flame interacted with a large scale vortex induced by the acoustic excitation at the fuel side. It is investigated to analyze dynamic behavior of the diffusion flame extinction and interruption during the flame-vortex interaction processes. The results observed in this study are described as follows.(1) In the case that a large velocity fluctuation is given to the fuel jet, the temperature and the OH-LIF at the reaction zone become significantly lowered at the convex and circumferential part of the vortex where temperature layer of the vortex exists and the thinning of the OH-LIF and temperature layer and the consequent flame extinction are induced.(2) In the case that a larger velocity fluctuation is given to the fuel jet, the reaction zone is interrupted at the circumferential part or backside of the vortex. By curling up motion of the vortex, the burnt gas is pulled up from the upstream reaction zone and makes high temperature region inside the flame and the burnt gas dissipates locally with time. The dissipated burnt gas reduces the supply of fuel into circumferential reaction zone and interruption of the reaction zone is induced. The edge flames are formed inside the flame and at the circumferential part of the vortex.