Structure of a Partially Premixed Iso-Octane/Air Turbulent V-Flame

The effect of the equivalence ratio gradient on a partially premixed, iso-octane/air, rod-stabilized turbulent V-flame was studied. Using a uniquely designed rectangular exit burner, the equivalence ratio was varied linearly along the exit of the burner while the global equivalence ratio was fixed at stoichiometric. A two-dimensional spectrometer provided line measurements along a wide spectral range (UV to near IR) and was used to identify radiating species to characterize each branch of the partially premixed flame (PPF). Chemiluminescence imaging of OH* and CH* was used to evaluate the general structure of the PPF and assess its potential use as an estimate of time averaged heat release rates. Planar Laser Induced Fluorescence of OH (OH-PLIF) images were collected to investigate the varying topography of the PPF. Variations of wrinkling scales, flame brush, and tribrachial flame structure were observed and discussed for different gradients in equivalence ratio.