Towards clean and renewable energy: Construction of the premixed ammonia/dimethoxymethane chemical reaction mechanism and numerical simulation analysis

Ammonia (NH3) is recognized as a potential alternative energy source for promoting carbon neutrality. However, the key challenges of NH3 application in power pulsation systems include a slow combustion rate and high ignition energy, which limit the wide use of NH3 as an energy vector. To expand the application of NH3 as a fuel in power generation systems, it is essential to use more reactive fuels that can initiate combustion or enhance the burning rate. Dimethoxymethane (DMM) is considered a promising carbon-neutral renewable fuel that can improve the combustion characteristics of NH3. In this study, the combustion and emission mechanisms of NH3/DMM blends were numerically investigated using zero-dimensional chemical kinetics models. A new mechanism, comprising 150 components and 1,137 elementary reactions, was developed to accurately predict the ignition delay time (IDT) and NO emissions under engine-like conditions. The rate of production (ROP) of NH3 and the heat release rate, in conjunction with sensitivity analysis, demonstrate that the addition of DMM increases the concentrations of primary radicals (OH, HO2), thereby enhancing the heat release rate and accelerating the consumption rate of NH3, while also reducing the ignition delay time of NH3. The effect of varying DMM proportions on NO formation reveals that an increase in the DMM proportion leads to higher NO production. The refined analysis of NO formation reveals a strong negative correlation between the production rate of non-thermal NO and the total NOx generation rate. Furthermore, at different equivalence ratios, the NO production follows the trend based on radical concentration differences: φ = 0.8 > φ = 1.0 > φ = 1.2. The concentration of radicals under different operational conditions is a critical factor influencing both the premixed NH3/DMM combustion and its emission characteristics.