Abstract

Soot particle production from combustion-based processes represents a crucial research area, whether hydrocarbons originate from fossil or renewable sources. With growing interest in new fuel alternatives, it is essential to develop numerical tools that accurately model the total mass and morphology of the particles generated, ideally from comparable flames in different configurations. This study compares soot formation in two flames: an inverse diffusion flame (IDF) and a normal diffusion flame (NDF). Both configurations used the same burner and fuel consumption rates for a fair comparison. Experimentally, soot temperature and volume fraction fields were measured via optical techniques. Numerically, soot was modeled with fixed sectional discretization and detailed chemistry, containing up to five-ring PAHs. This provides a basis for contrasting soot production processes in both configurations. The IDF exhibits intense soot inception and PAH condensation with minimal HACA and negligible oxidation, producing less soot and yielding a smoking flame. Soot forms on the fuel side of the reaction front, with distinct particle paths governed by local temperatures. In contrast, the NDF experiences competing soot growth processes, yielding higher soot volume fraction. Despite similar carbon input, the carbon-to-soot conversion efficiency differs. Using Lagrangian particle tracking, the temperature-time histories (thermal age) were used to compare soot properties, showing similar inception processes, with deviations after soot formation. Particle size distribution (PSD) predictions indicate that, under comparable thermal age conditions, both flames produced similar PSDs, highlighting thermal influence driving soot production. This study provides a foundation for further analysis and essential experimental data to enhance soot modeling.