Experimental study of secondary air diffusion effects on soot concentration along a partially premixed acetylene/air flame

Soot emission is determined by the competition between soot formation and oxidation in a flame. Several factors affect these processes, including the type of fuel, the air-to-fuel ratio, flame temperature, pressure, and flow pattern. In this paper, the influence of external air diffusion on the soot axial concentration and centerline flame temperature in a partially premixed acetylene/air flame was assessed. The flame was generated in a vertical axis burner in which the discharge of the fuel-oxidant mixture was surrounded by a coaxial annular flow of nitrogen, which provided a shield which controlled the contact between the flame and secondary air. When primary air premixing decreased, the average soot concentration of the flames without the N2 shield increased more than the concentration of the flames with the shield. The effect of the shield became more intense, in general, as partial premixing increased.