The effect of fuel composition and Reynolds number on soot formation processes in turbulent non-premixed toluene jet flames

The soot formation processes in three different turbulent prevaporized non-premixed toluene jet flames stabilized on a jet-in-hot-coflow (JHC) burner were investigated. The jet Reynolds number and the stoichiometric mixture fraction were varied to manipulate the flow time scales and the chemistry, respectively. Time-resolved laser-induced incandescence, non-linear two-line atomic fluorescence of indium, and OH planar laser induced fluorescence were simultaneously applied to yield spatially resolved and instantaneous fields of soot volume fraction, primary particle size, temperature, and OH. The mean distributions of the detected quantities were used to identify major differences among the flames. The highest soot loading was observed for the low Reynolds number and low stoichiometric mixture fraction flame. However, this flame featured also the lowest temperature and primary particle size. Based on these observations, the simultaneously detected data sets and flamelet computations were applied to elucidate differences in the soot formation pathways in the flames. The analyses revealed that the high soot loading caused greater heat losses in the low Reynolds number and low stoichiometric mixture fraction flame. This had a significant impact on the soot formation pathways and caused a reduction in the particle size.