Chemical kinetics analysis of ammonia/dimethyl ether combustion under water addition conditions

Ammonia has gained considerable interest as a high -energy -density, zero -carbon fuel with potential as a clean energy source for future applications. Nonetheless, its widespread industrial use is constrained by challenges associated with low flammability and elevated levels of NOx emissions. To address the low flammability issue, this study introduces dimethyl ether (DME), a fuel known for its high laminar flame speed, into pure ammonia combustion systems. Moreover, we implement moderate and low -temperature diffusion combustion by incorporating water vapor into high -temperature air, aiming to minimize NOx emissions. We examined the effects of NH3/DME and water vapor mixing ratios on variables including laminar flame speed, key free radicals, NO emissions, and reaction pathways. Computational simulations were conducted using the PREMIX module within Chemkin Pro based on a modified Meng model, which was initially validated against experimental data. Our results indicate that increasing DME concentrations lead to a notable rise in laminar flame speed and the concentration of O, H, and OH radicals. Concurrently, NO concentrations also increased due to DME's oxygenbearing nature, which enhances the oxidation of N -containing radicals. Conversely, elevating the water vapor content results in reduced laminar flame speed, decreased free radical peaks, and diminished NO emissions. Rate of production analyses reveal that specific reactions, such as HNO + H--NO + H2, HNO + OH--NO + H2O, and NH + O--NO + H, significantly contribute to NO formation by consuming active O, H, and OH radicals.