Journal: International Journal of Energy Research, vol. 2026, pp. 5447466, 2026.
Title: Soot formation mechanis,s in ethlyene/N2O inverse diffusion flames: insights from dual-wavelength LII and SEM analysis
Authors: Po-Hung Lin, Yu-Yao Cheng, Yueh-Heng Li*, Yan-Hom Li
Rank: 2.4% (1/41), SCIE, ENUCLEAR SCIENCE &TECHNOLOGY, 2024.
Abstract: Nitrous oxide (N2O), with its self-pressurizing capability, strong oxidizing potential, and exothermic decomposition, is considered a promising green propellant oxidizer. However, when combined with hydrocarbon fuels, the concurrent formation of soot and polycyclic aromatic hydrocarbons (PAHs) remains a major challenge for propulsion efficiency and emission control. This study aims to elucidate the synergistic effects of N2O exothermic decomposition and its enhanced oxidizing potential on the transition from PAHs to soot particles using dual-wavelength laser diagnostics. Primary soot was characterized using Laser-Induced Incandescence (LII) at 1064 nm, while incipient soot and PAHs were probed with 532 nm excitation. Ethylene inverse diffusion flames (IDFs) were investigated under two oxidizer conditions: pure N2O and a decomposition-equivalent mixture (67% N2/33% O2). Results show that N2O decomposition significantly accelerates the precursor maturation process, producing up to tenfold higher LII signals with lifetimes over 130 ns, compared to less than 80 ns for O2/N2 flames. The saturation fluence under N2O was as low as 0.26 J/cm2, lower than 0.48–0.59 J/cm2 for O2/N2. Furthermore, the findings reveal a unique interaction: N2O–derived thermal effects dominate soot growth at moderate oxidizer-to-fuel ratios (R = 2–6), promoting distinct soot morphology characterized by compact agglomerates rather than the typical chain-like structures observed in O2/N2 flames. Conversely, oxygen-enriched effects from N2O enhance oxidative consumption at higher ratios (R ≥ 5), ultimately limiting soot accumulation.
