The rate of combustion of soot in turbulent flames

TLDR: In this article, an equation for the rate of combustion in laminar flames is proposed and experiments were made with a turbulent flame in a horizontal water-cooled furnace with an i.i.d. of 0.47 m.

Abstract: The rate of combustion of soot in turbulent flames can differ significantly from that in laminar flames. This paper reports on a study of the rate of combustion in turbulent flames, beginning with a review of the rate of combustion of soot in laminar flames. It is shown that no boundary layer can exist between the soot particle surface and the gas close to the surface. Nevertheless, the specific surface reaction rate of soot can be shown to be 0.01 that of carbon. An equation for the rate of combustion in laminar flames is proposed. Experiments were made with a turbulent flame in a horizontal water-cooled furnace with an i.d. of 0.47 m. Samples drawn from different parts of the flame indicate no significant difference in the mean soot-particle diameter (200 ). It is shown that the axial decay of the amount of soot in a turbulent flame cannot be predicted simply by application of a laminar rate equation and local time-mean values of temperature, oxygen pressure, and soot concentration. The reason for this seems to be that the time-mean values of the oxygen pressure fail, due to the inhomogeneity caused by turbulence, to represent the oxygen pressure close to the soot-particle surface. On the other hand, it is shown that, when the calculated gradients of the flow rate of soot are based on the minimum time-mean value of the oxygen pressure of a cross section, there is agreement with the observed gradients.