Strain effects on the structure of counterflowing turbulent premixed flames
- Centre National de la Recherche Scientifique, Orleans (France). Lab. de Combustion et Systemes Reactifs
Dynamic and scalar structures of turbulent premixed flames stabilized in the opposed jet configuration are investigated. The opposed jet burner facility allows control of many parameters of turbulent premixed combustion, including the bulk and turbulent strain rates. The main mixture streams are enveloped in coflowing air to reduce flame bounding, to render the turbulence structure more isotropic and homogeneous at the stagnation plane, and, therefore, to better match the major modelling assumptions. Detailed investigation of the velocity field confirms the strong variation of the initial turbulence parameters as the flow stagnates, and the similarity between nonreacting and reacting flow fields. It is clearly demonstrated that turbulent premixed flames stabilized in the opposed jet configuration are ideal for turbulent combustion model validation, as modification of the turbulence field by the flame is minimized. Two different extinction regimes of opposed jet turbulent premixed flames are identified. For small and moderate burner separations, the total strain rate causes extinction. For large separation distances, mixing and dilution by the external air are the causes of flame extinction. For the first regime, it is confirmed that bulk and turbulent strain rates should be taken into account simultaneously to establish the robustness of turbulent premixed flames. For the first time, the scalar structure of opposed jet turbulent premixed flames is explored by laser-induced Rayleigh light-scattering technique. All the relevant parameters of instantaneous flame fronts are determined, and estimates of the flame surface density are proposed. It is shown that, for constant mixture composition and constant initial turbulence structure, the flame surface density increases with the bulk strain rate before its extinction value is closely approached. This result is discussed by using various ingredients of flamelet models.
- OSTI ID:
- 93271
- Report Number(s):
- CONF-940711-; TRN: IM9537%%315
- Resource Relation:
- Conference: 25. international symposium on combustion, Irvine, CA (United States), 31 Jul - 5 Aug 1994; Other Information: PBD: 1994; Related Information: Is Part Of Twenty-fifth symposium (international) on combustion; PB: 1838 p.
- Country of Publication:
- United States
- Language:
- English
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