Soot initiation and particle growth in the pyrolysis of toluene at high inert gas pressures

Abstract

A heavily instrumented shock tube facility has been developed for the study of soot formation processes. Pyrolytic soot formation of dilute fuel systems in Argon between 1500 and 2500 K at 10, 20, and 30 atm total pressure was examined using multiple wavelength diagnostic capability. The fuel systems examined were toluene, toluene with hydrogen, toluene with acetylene, and toluene with methanol. The observed soot yields exhibit a characteristic inversion with temperature, with the sooting peaks shifted to lower temperatures for 10 to 30 atm than previously observed for 0.6 atm. In addition, increasing the initial toluene number density at constant pressure (30 atm) gives large increases in soot production, especially at higher temperatures. Neither hydrogen nor acetylene significantly affected soot yields, but methanol substantially decreased the soot production. The 10 to 30 atm data show evidence of extremely rapid particle growth during the ∼2 ms test times. The data indicate a substantial mass fraction of soot particles in the ≳0.1 μm (radius) size range.