Synergistic effects of DEE on combustion chemistry in C2H4 inverse diffusion sooting flames: an experimental and numerical study

High-concentration diethyl ether (DEE) was known to inhibit soot precursors. This study showed that low-concentration DEE blending (0%, 6%, 9%, and 12% by vol.) in ethylene (C 2 H 4 ) inverse diffusion sooting flames revealed a different behavior. Combined experimental and numerical analysis, with good agreement between measured and simulated species, revealed that DEE blending produced synergistic promotion on multiple species across all investigated blending ratios. Specifically, methane (CH 4 ), propyne (C 3 H 4 -P), and vinylacetylene (C 4 H 4 ) were enhanced at specific flame heights and wing regions. Ethane (C 2 H 6 ) was promoted throughout the flame, while acetylene (C 2 H 2 ) and diacetylene (C 4 H 2 ) were reduced. Notably, benzene (A1) formation was also promoted, in contrast to high-concentration DEE. Kinetic analysis showed that DEE decomposition released C 2 H 5 radicals and generated CH 3 radicals. The C 2 H 5 radicals converted to C 2 H 4 and then to C 2 H 3 , while the CH 3 radicals were similarly diverted to C 2 H 3 , thereby enhancing the C 4 H 5 ‑2 route and promoting A1 formation. Most PAHs were inhibited under DEE addition. Among the nucleation PAHs, the peak concentration of benzo [ghi] fluoranthene (BGHIF) showed a synergistic enhancement with DEE blending, contrasting with the other two which decreased. Consequently, the net reduction in total nucleation PAH peak concentrations limited the precursor availability for soot formation, leading to a lower peak soot concentration. These results provided essential speciation data from multi-dimensional flames and advanced the understanding of kinetic processes in DEE-blended C 2 H 4 combustion.