Time-Resolved Temperature Measurements in the Developing Region of an Elliptic, Jet-Diffusion Flame at a Reynolds Number of 6000

Abstract Time resolved temperature measurements were performed in the developing region of an elliptic, jet-diffusion flame using fine-wire thermocouples compensated for thermal inertia effects. Measurements of mean and rms temperature profiles, as well as power spectral densities and probability density functions of temperature were obtained along the centerline and radially along the major and minor axes for nondimensional axial stations in the range of 5 = z/Dh = 30. Significant differences in the thermal structure of this elliptical jet flame along the minor and major axes were observed. Higher temperature fluctuations along the minor axis in the fuel-side mixing layer and higher temperature fluctuations along the major axis in the air-side mixing layer were observed. Stronger, buoyancy-driven flow structures in the air-side shear layer caused more radial movement of the reaction zone along the major axis as evidenced by rms temperature profiles with substantially higher values (200 K.) farther out radially for all the axial stations where measurements were made. This greater radial movement of the reaction zone was sufficiently strong to cause a faster destruction of the inner, small-scale structures along the fuel side of the major axis such that less mixing of hot and cold fluid pockets (lower rms temperatures)was observed.