光散乱法によるガス拡散火炎中のすす粒子の測定

Abstract

For determining the soot particle size and concentration in flames, the scattered light intensities at various angles has been calculated as a function of particle diameter and complex index of refraction by the Mie's theory. In a preliminary experiment, a water suspensoid of polystyrene latex particles having a diameter of 91 nm and 176 nm were examined and good agreement between experiment and theory were found.In this paper, profiles of local soot particle size (Ds: nm), number density (Ns: particles/cm3 ) and volume fraction (Ns : cm3/cm3) together with temperature are measured in propane/air laminar diffusion flames. A special burner and laser scattering technique are used for this purpose.At the axial distance, the diameters of soot particles lie within the limits of 60 and 200 nm. The number density and volume fraction of soot particles are obtained in the range from 107 to 1011 particles/cm3 and from 10-8 to 10-5 cm3/cm3 respectively.The largest particles are observed in the neighbourhood of nozzle, and then decreases toward the middle of the flame, however, the soot particle density increases strikingly. Large agglomerates of soot are seen to escape the tip of the flame.At the radial distance, a considerably larger particles of soot are found near the flame front as compared with the central pyrolysis zone. It is suggested that the soot particle formation in the diffusion flame is confined to the high-temperature region on the fuel-rich side of the reaction zone.