FLAME AND FLOW CHARACTERISTICS OF DOUBLE CONCENTRIC JETS

The characteristic flame and flow modes of a double concentric type of combustor possessing a central air jet and an annular propane gas are experimentally studied. Subject to the effects of the gravitational, inertial, and pressure forces, the cold flow is classified into three primary patterns: annular fountain unstable fountain, and recirculatio n bubble flows. Using direct and schlieren photography techniques, the flames in the velocity domain of annulus and central jets are systema tically classified into several characteristic modes. At low central j et velocity, a central flame enclosed in a annular diffusion flame mig ht exist. At high central jet velocity, only the annular flames exist. The existence of the central flame dominates the flame and flow behav iors at low central jet velocity. The interaction between the central jet and the recirculation bubble in the near wake region dominates the flame characteristics at high central jet velocity. The interaction b etween the flame behavior and the how patterns in each characteristic mode is comprehensively discussed. The temperature profiles are probed by a fine-wire thermocouple. The radial temperature profiles for each characteristic flame mode at various levels are presented to show the thermal structures. Copyright (C) 1997 by The Combustion Institute