Abstract:

Particulate emissions from combustion devices endanger population health and have adverse effects on the environment. The formation and growth of soot in n-heptane/air turbulent non-premixed jet flames is investigated by performing a set of three-dimensional Direct Numerical Simulations (DNS) at varying Damkoehler number.

Building upon recent work by our group and collaborators (Bisetti et al. Combust. Flame 2012), the soot growth rate and soot yield are related to the turbulent meandering of soot particles across the flame as well as temperature and composition history. The soot growth process is strongly affected by the intermittent turbulent mixing field as described by Lagrangian statistics.

In agreement with well-known results in laminar sooting flames (e.g. Du et al. Int. Symp Combust. 1988), soot growth rates are found to depend strongly on global mixing time scales. Applying a near-ideal hydrodynamic rescaling at constant Reynolds number, the total soot yield is observed to decrease sharply as the Damkoehler number decreases. Conversely, the total number density of soot particles is found to be largely insensitive to varying mixing time scales.