Impact of Fe-doped H-2/O2 flame equivalence ratio on the fate and temperature history of early particles

The temperature and species concentration history experienced by the gas-borne nanoparticles during their evolution in the flame has a major impact on their size, morphology, composition, and crystallinity. In our recent work (Combust. Flame, 244 (2022) 112251), we have reported optical emission measurements of a Fe(CO)5- doped H2/O2/Ar fuel-lean (? = 0.5) flame, revealing that the temperature of the early-formed nanoparticles exceeds the gas temperature by several hundred degrees, while the particle volume fraction increases sharply, followed by rapid disintegration in the reaction zone. This behavior, modeled by single particle Monte-Carlo simulations indicates involvement of heterogeneous reactive processes at the particle surface, such as particle reduction and oxidation, growth and etching. Within the refined approach of the current study, reactive and non-reactive collisions were treated consistently, assuming rapid thermalization between the impinging molecule and the particle, with subsequent random energy sampling to determine reactivity. In the present work, we test the limits and validity of the heterogeneous flame-particle interaction model by manipulating the oxida-tion-reduction and growth-etching balance by varying the equivalence ratio (0.25

Automated summary

The temperature and species concentration history of gas-borne nanoparticles in a flame have a significant impact on their size, morphology, composition, and crystallinity. In a recent study, optical emission measurements were used to analyze Fe(CO)5-doped nanoparticles in a fuel-lean flame, revealing that the early-formed nanoparticles had higher temperatures than the gas and underwent rapid disintegration. Monte-Carlo simulations indicated the involvement of heterogeneous reactive processes at the particle surface, such as reduction, oxidation, growth, and etching. The limits and validity of the flame-particle interaction model were tested by adjusting the oxidation-reduction and growth-etching balance through varying the equivalence ratio (0.25 < ? < 0.5).