LOW REYNOLDS NUMBER TURBULENT LIFTED FLAMES IN HIGH CO-FLOW

Abstract

ABSTRACT This study presents the results of experiments designed to investigate flame lift-off behavior to nozzle velocity, co-flow velocity, fuel-type, and nozzle size for low Reynolds Number turbulent flows (in and near the hysteresis regime). Local excess jet velocities are computed using jet relations from Tieszen et al. The results show that the local excess jet velocity remains linear with respect to nozzle velocity through most of the hysteresis regime, even though flame lift-off height is not linear. This suggests a non-linear relation not captured by Kalghatgi (1984) for lift-off in the near field and hysteresis regime. Local excess jet velocities at the reattachment point were also computed for flames that are lifted more than three nozzle diameters above the burner. The results show that there is a minimum excess jet velocity for which a flame can stabilize. This minimum velocity is inversely proportional to the laminar burning velocity of the fuel squared. A new relation for lift-off height at the reattachment point for flames in the hysteresis region is derived and compared to experimental data.