Experimental and kinetic study on laminar flame propagation and CN kinetic interactions of dimethyl carbonate/ammonia blends at elevated pressures

Ammonia (NH 3 ) is a promising carbon-free fuel, but its practical application is limited by low reactivity. While oxygenated additives like dimethyl carbonate (DMC) are potential promoters, the kinetic interactions between DMC-derived intermediates and nitrogenous species remain poorly understood. This study investigates the laminar burning velocities (LBVs) and flame instabilities of DMC/NH 3 /air mixtures at 393 K and 1–4 atm, over equivalence ratios of 0.7–1.5 and NH 3 mole fractions of 0–40%. A detailed kinetic model incorporating newly characterized C N kinetic interactions was developed through quantum chemistry calculations and validated against the present data. Results reveal that compared with the traditional alkane/NH 3 system, a nonlinear inhibition effect exists in DMC/NH 3 blends, deviating significantly from the ideal linear mixing rule. This non-additive behavior is influenced by a "NH 2 -to-NH 3 recycling loop" in the preheat zone: the low-barrier reaction DMC+NH 2 = CH 3 OCOOCH 2 +NH 3 ( E 0 ​=8.24 kcal/mol) and CH 2 O+NH 2 = NH 3 +HCO ( E 0 = 2.52 kcal/mol) competitively intercepts 42% of the NH 2 flux at T = 900 K and 31.5% of the NH 2 flux at T = 400 K, recycling it back to stable NH 3 . This pathway depletes the active radical pool available for the high-temperature flame front, and its omission leads to the overprediction of the global LBV. Furthermore, quantitative morphological analysis using spherical mapping reconstruction shows that NH 3 addition enhances the intrinsic tendency toward cellular instability of short-chain oxygenates. While elevated pressure is the major physical driver, the synergistic chemical effect of NH 3 advances the onset of cellularity from R ≈ 25 mm to a critical radius of R ≈ 15 mm, this chemical effect becomes less pronounced as pressure increases. Finally, cross-fuel comparison suggests a fuel-structure-dependent stability correlation: short-chain oxygenates (DMC, DME) are prone to NH 3 -induced destabilization, whereas long-chain analogues (PODE 3 , n-butanol) maintain robust stability. This work provides insights into the development of stable, low-emission combustion strategies for ammonia/oxygenated dual-fuel systems.