Effects of hydrogen addition on soot formation and radiative characteristics of oxygen-enriched ethylene laminar inverse diffusion flame

In order to optimize combustion processes, it is necessary to have a detailed understanding of the effects of fuel and oxidizer composition on flame. In this work, 18 ethylene coaxial laminar inverse diffusion flames are constructed to investigate the influence of hydrogen and oxygen concentrations on the soot formation and radiative heat transfer. The results show that, as the hydrogen content increases, the flame peak temperature rises, and the increase in peak temperature weakens at higher oxygen indices (OIs). Hydrogen addition significantly decreases the peak soot volume fraction (SVF) due to the inhibition of PAH condensation, and hydrogen has less effect on peak SVF as the OI increases. For flames without hydrogen addition, two regions of high radiative source terms can be found, which are dominated by gaseous species and soot particles, respectively. With the addition of hydrogen, the radiative source terms in both zones decrease due to lower CO₂ concentration and SVF, and the impact of hydrogen on maximum radiative source term increases at higher OIs. These findings provide guidance on the use of hydrogen-hydrocarbon hybrid fuels in oxygen-enriched IDF systems, balancing synergistic soot suppression while maintaining thermal efficiency.