Stationary source-free spherical flames ('flame balls') in premixed combustible gases were studied by employing low-gravity (micro-g) environments in a drop tower and an aircraft flying parabolic trajectories to diminish the impact of buoyancy-induced convective flow. Flame balls were found in all mixture families tested when: (1) the Lewis number Le of the deficient reactant was sufficiently low; and (2) the compositions were sufficiently close to the flammability limits. Probably as a consequence of the reduction in buoyant convection, the flammability limits at micro-g were significantly more dilute than those at Earth gravity; for example, 3.35% H2 vs 4.0% H2 in lean H2-air mixtures. By comparison with analytical and computational models, it is inferred that the phenomenon is probably related to diffusive-thermal effects in low-Le mixtures in conjunction with flame-front curvature and radiative heat losses from the combustion products. The chemical reaction mechanism appears to play no qualitative role. In the aircraft experiments, the gravity levels (approximately equal 10(exp -2)g(sub 0)) were found to cause noticeable motion of flame balls due to buoyancy, which in turn influenced the behavior of flame balls. At these g levels, a new type of transient, nearly cylindrical flame structure, termed 'flame strings,' was observed.


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    Titel :

    Stationary premixed flames in spherical and cylindrical geometries


    Beteiligte:
    Ronney, P. D. (Autor:in) / Whaling, K. N. (Autor:in) / Abbud-Madrid, A. (Autor:in) / Gatto, J. L. (Autor:in) / Pisowiscz, V. L. (Autor:in)

    Erschienen in:

    Erscheinungsdatum :

    1994-03-01



    Medientyp :

    Sonstige


    Format :

    Keine Angabe


    Sprache :

    Englisch


    Schlagwörter :


    Stationary premixed flames in spherical and cylindrical geometries

    Ronney, P. D. / Whaling, K. N. / Abbud-Madrid, A. et al. | AIAA | 1994



    Experimental and numerical investigation of premixed cylindrical flames

    Mosbacher, D. / Wehrmeyer, J. / Pitz, R. et al. | AIAA | 2002


    A multidimensional numerical model for turbulent premixed flames with fractal geometries

    Zhu,T.T. / ORourke,P.J. / Matthews,R.D. et al. | Kraftfahrwesen | 1995


    A Multidimensional Numerical Model for Turbulent Premixed Flames with Fractal Geometries

    O'Rourke, Peter J. / Matthews, Ronald D. / Zhu, Ting-Ting | SAE Technical Papers | 1995