Abstract#x2014;Laser-light scattering and attenuation techniques are applied simultaneously in a complementary fashion to measure the properties of the soot particles in a laminar diffusion flame. The measurements of local soot particle size and number density in the laminar diffusion flame are made together with the measurements of soot mass concentration, gas species concentration and temperature in the same flame. The results are as follows. (I) The average diameters (D;v) of soot panicles in the flame lie between 50 and 120 nm. The largest particles probably are formed in the fuel-rich region just inside the position of the temperature peak. The number density of soot particles is in the range between 108and 1010particles/cm3and the volume fraction occupied by the particles in the flame is estimated to be 10-7to 3 X 10-6cm3/cm3and is a maximum near the flame axis, The soot density is about 2 g/cm3cm. (2) Most likely soot is produced in the fuel-rich region just inside the flame front where unburnt hydrocarbons such as CH4,C2H4, C2H6.and C2H2cracked from the original fuel of C3H3are observed.
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