Carbon monoxide and soot emissions from liquid-fueled buoyant turbulent diffusion flames

Abstract

Carbon monoxide concentrations, soot concentrations, and mixture fractions were measured in the fuel-lean (overfire) region of liquid-fueled buoyant turbulent diffusion flames burning in still air. Pool-fire configurations were studied with the liquids burning from horizontal round wicks, considering both sooting (toluene, benzene, n-heptane, and isopropanol) and nonsooting (methanol and ethanol) fuels. Flame heights and characteristic residence times also were measured, both for the turbulent flames and at the normal smoke point (for the sooting fuels). Carbon monoxide and soot generation factors (mass of CO or soot emitted per unit mass of fuel carbon burned) were uniform throughout the overfire region and were relatively independent of flame residence times (which were generally an order of magnitude longer than the normal smoke point residence times of the sooting fuels). Processes of carbon monoxide and soot emission for the nonalcohols are closely related, based on the good correlation between their emission factors: 0.37 kg CO/per kg soot with a standard deviation of 0.09. However, nonsooting methanol and ethanol/air flames still emitted low levels of CO so that there is a component of CO emissions that is not associated with soot.