Two separated pulses with two-dimensional two-color laser-induced incandescence for multi-parameter characterization of soot particles in flame

Abstract A thorough understanding of soot particle formation and evolution during combustion is essential for improving energy efficiency and reducing pollutant emissions. In this study, we constructed an integrated diagnostic method combining two separate pulses with traditional two-color laser-induced incandescence (LII) and particle size analysis models, enabling simultaneous acquisition of multiple parameters (including initial temperature T 0 , peak temperature T M , absorption function E m , volume fraction f v , and primary particle size D p ). This system has high spatial and temporal resolution, allowing for detailed characterization of soot dynamics within diffusion flames. The results demonstrate that LII can detect particles in the middle and top regions of the flame, the parameters of which exhibit significant spatial non-uniformities and complex interdependencies. It is found that the particles become more and more mature during the particles evolving upwards due to carbonization, and therefore show increasing absorption. At the same time, the volume fraction and size of particles decrease due to oxidation. In addition, the volume fraction and size of particles are larger at the edges of the flame, which is attributed to the more easily happening nucleation and aggregation processes, and an overall physical picture of the generation and evolution of the soot particles is finally provided based on the distributions of those multiple parameters. This study validates the effectiveness of SP-2D-2C-LII for multi-parameter coupling analysis and spatially resolved diagnosis, offering valuable insights into soot particle evolution mechanisms and supporting the optimization of combustion and emission control strategies.