Abstract
The influence of the initial condition parameters on a free turbulent swirl diffusion flame and on its equivalent isothermal flow was experimentally studied. A parametric study was conducted on a 40 KW coaxial jet burner with a straight exit. The fuel used was methane. Both aerodynamic and flame structures were systematically and independently varied and data were collected for each characteristic condition. The experimental results were compared with existing data, obtained on burners with a diverging quarl. This showed that, besides the burner exit geometry, both fuel and air loading has a significant effect on the characteristics of the flow and its thermal structure. For the condition studied, an increase in the fuel loading or a decrease in the air loading was detrimental to the formation of a central recirculation zone, even leading to its disappearance. High turbulence levels were associated with the region close to the burner exit for high air and fuel loadings, and with the region where the central recirculation zone was steadily established. The flame temperature was reduced by high swirl, in opposition to what is commonly observed, since high swirl is, in general, associated with strong mixing and efficient combustion, and thus high flame temperature. Incomparison with the isothermal case, both favourable and unfavourable effects induced by the combustion were found on the formation of the central recirculation zone.
Published Version
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