Fig. 1. Pictures of diffusion flame of three kinds of fuels

Fig. 2. Schematic of experimental setup

Fig. 3. Two-dimensional distributions of soot volume fraction (left) and PAH-LIF intensity (right). (a) Methane diffusion flame; (b) ethylene diffusion flame; (c) propane diffusion flame

Fig. 4. Normalized intensity profiles of PAH-LIF and volume fraction of soot along the centerline in various flames. (a) Methane flame; (b) ethylene flame; (c) propane flame

Fig. 5. Carbon conversion factor as a function of residence time

Fig. 6. Particle size and particle number concentration of soot in different diffusion flames. (a) Methane flame; (b) ethylene flame; (c) propane flame

Fig. 7. Particle number concentration in various size ranges

Fig. 8. Variations of fv, dp and np in different positions with residence time. (a) Central part of flame;(b) annular part of flame

Fig. 9. Specific surface growth rate of soot in annular part of flames

Fig. 10. Average specific surface growth rate of soot in the central flame and annular flame as well as the entire flame