Soot particle sizing by LII during shock tube pyrolysis of C6H6

Time-resolved laser-induced incandescence (LII) and cw-laser extinction techniques have been used to size soot particles originating from benzene pyrolysis behind reflected shock waves. The LII-technique is based on fast heating of particles by a short laser pulse and on the subsequent time-resolved observation of the particle cooling, as measured by its thermal emission. Additionally, soot formation was measured by a cw-laser-extinction technique, which provides information about induction periods for soot formation and soot yield. Four groups of experiments with different benzene concentrations diluted in Ar were performed. For the experiments within each group the reaction temperature or the delay time interval between shock-induced heating of the mixture and the LII-laser pulse was varied. The analysis of the Lll-data results in time-resolved growth curves for mean particle radii between 1 nm and 11 nm. Higher C6H6-concentrations lead to bigger particles. From the extinction data, high soot yields were found at longer reaction times. The induction periods measured agree with the range of values reported in previous studies. (C) 2002 by The Combustion Institute.