Modelling of soot coalescence and aggregation with a two-population balance equation model and a conservative finite volume method

摘要

The objective of the present paper is to develop a population balance approach for modelling soot formationthat distinguishes between coalescence and aggregation and accounts for finite-rate fusing ofprimary particles within aggregates, while providing a numerically accurate description of primary particlesurface growth and oxidation within aggregates. To this end, the recently developed conservativefinite volume sectional method for the solution of the population balance equation (PBE) due to Liu andRigopoulos (2019, Combust. Flame 205, 506-521) is extended to a two-PBE approach that allows for amore accurate modelling of primary particle surface growth and oxidation and furthermore involves atimescale for the fusing of primary particles. The accuracy of the numerical method is first tested bycalculating the self-preserving distributions of aggregates with varying fractal dimension. Subsequently,the one-PBE and two-PBE approaches are coupled with CFD and applied to the simulation of the Santorolaminar non-premixed co-flow sooting flame. The results show that both approaches can provide goodprediction of the soot volume fraction, but the two-PBE approach yields a significant improvement in theprediction of soot morphology. At present, the information available for modelling the gradual fusing ofsoot primary particles is based on experiments on silica and titania nanoparticles, and therefore a comprehensivestudy of the impact of the sintering model parameters is conducted. Finally, conclusions aredrawn regarding the predictive potential of the one-PBE and two-PBE approaches.