Abstract
Non-premixed tubular flames are formed by the opposed tubular burner. A detailed structural investigation using the spontaneous Raman scattering technique is conducted on flames with constant curvature using 15% H2 diluted by N2 against air at various stretch rates. The measured temperature and major species concentrations agree well with the numerical prediction. Compared with the numerical results of the opposed-jet flat flame, it is shown that the curvature weakens the effects of preferential diffusion for the flames studied where the curvature is concave towards the fuel stream. Near-extinction nonpremixed tubular flames using different fuels are also studied. Hydrogen flames (Le 1) prefer concave curvature, which is opposite to the hydrogen flames, and cellular structures appear throughout the burner’s operational range. These phenomena show that for flames with Le 1. Curvature has minimal effects on tubular non-premixed flames with Lewis number close to unity. The comparison between experimental and calculated extinction conditions supports the above conclusions.
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