The formation and coagulation of soot aerosols generated by the pyrolysis of aromatic hydrocarbons

Abstract

We report a study of the formation and growth of soot aerosols in incident shock flows of benzene, toluene, ethylbenzene and indene, highly diluted with argon at temperatures in the range 1600-2300 K at a total carbon concentration in the shock-heated gases of 2.0 x 1017 atoms/cm3. The extent of conversion of hydrocarbon into soot, i.e. the soot yield, during the shock flow was determined from extinction measurements at two different visible wavelengths, while the rate of growth of the soot particles was obtained from the variation in the intensity of Rayleigh scattering of a 1W argon-ion laser beam by the soot particles. Of particular interest is our finding that the soot yield some 2.5 ms after the onset of shock heating falls rapidly with increasing temperature from near 100% at 1750-1800 K to less than 5 % at 2300 K