Search

Abstract: Simultaneous planar-laser induced fluorescence (PLIF) and particle image velocimetry (PIV) provide a comprehensive view of the molecular mixing and velocity fields in the stabilization region of turbulent, lifted jet diffusion flames. The Mie scattering medium for PIV is a glycerol–water fog, which evaporates at elevated temperatures and allows inference of the location of the high-temperature interface at the flame base. The jet Reynolds numbers vary from 4400 to 10,700. The mixing and velocity fields upstream of the flame base evolve consistently with nonreacting jet scaling. Conditional statistics of the fuel mole fraction at the instantaneous high-temperature interface show that the flame stabilization point does not generally correspond to the most upstream point on the interface (called here the leading point), because the mixture there is typically too lean to support combustion. Instead, the flame stabilization point lies toward the jet centerline relative to the leading point. Conditional axial velocity statistics indicate that the mean axial velocity at the flame front is , where is the stoichiometric laminar flame speed. The data also permit determination of the scalar dissipation rates, χ, with the results indicating that χ values near the high-temperature interfaces do not typically exceed the quenching value. Thus, the flame stabilization process is more consistent with theories based on partial fuel–air premixing than with those dependent on diffusion flame quenching. We propose a description of flame stabilization that depends on the large-scale organization of the mixing field. [Copyright &y& Elsevier]