Soot Formation Modelling of Spray-A Using a Transported PDF Approach

Numerical simulations of soot formation were performed for n-dodecane spray using the transported probability density function (TPDF) method. Liquid n-dodecane was injected with 1500 bar fuel pressure into a constant-volume vessel with an ambient temperature, oxygen volume fraction and density of 900 K, 15% and 22.8 kg/m³, respectively. The interaction by exchange with the mean (IEM) model was employed to close the micro-mixing term. The unsteady Reynolds-averaged Navier-Stokes (RANS) equations coupled with the realizable k-ε turbulence model were used to provide turbulence information to the TPDF solver. A 53-species reduced n-dodecane chemical mechanism was employed to evaluate the reaction rates. Soot formation was modelled with an acetylene-based two-equation model which accounts for simultaneous soot particle inception, surface growth, coagulation and oxidation by O₂ and OH. The modelling results for ignition delay, lift-off length, flame length evolution and distribution of soot volume fraction (f_v) are compared with the corresponding experimental data. Good predictions of the temporal evolution and spatial extent of the soot volume fraction have been observed. The findings suggest that the transported probability density function approach for soot modelling is a promising framework.