On the flame structure at the base of a pool fire

A detailed mapping is presented of the temperature, CO, CO 2 and O 2 species concentrations, and monochromatic absorption coefficient at the base region of a kerosene pool fire. Comparative analysis of the isotherm and iso-concentration patterns indicates that the buoyant flame has an intermittent character at its base, contrary to its normally attributed persistent, or anchored, character. The temperature field shows a band of temperature maxima that approximately coincides with the luminous flame boundary. The temperature in this band, however, decreases toward the fire axis and is lower than that expected in a kerosene flame. This, in conjunction with the presence of high oxygen concentration in the fuel side of the temperature maxima band, indicates that the flame fluctuates around a mean position, and that as a consequence the measured temperatures are lower averaged values of the fluctuating temperature field. The CO and CO 2 iso-concentration fields show a region of elevated concentrations at the axis near the liquid surface that is displaced toward the fuel side with respect to the temperature maxima region, rather than coinciding with it. The lines of constant absorption coefficient, which can be associated with lines of constant soot concentration, also show a region of elevated values that approximately coincides in location with that of the CO and CO 2 concentrations. These results indicate the fluctuating character of the flame, and suggest the existence of a gas stagnation, or recirculation, zone at the axis near the liquid surface that permits the accumulation of combustion products in this region. From the observed characteristics of the flame structure it can be concluded that the flame at the pool fire base is better described as a fluctuating, laminar, diffusion flame, which later becomes a turbulent, intermittent one as it evolves upward along the fire plume.