Detailed kinetic analysis of synthetic fuels containing ammonia

Abstract

The imperative to adopt environmentally sustainable energy sources has propelled the exploration of zero-carbon alternatives, such as hydrogen and ammonia for energy supply. Integrating these species with methane is recognized as a viable short-term solution. However, a complete understanding of their chemical behaviour in a wide range of conditions remains elusive, especially in terms of safety parameters, limiting the applicability of this solution. To this aim, this work presents a detailed analysis of the overall reactivity, expressed either in terms of laminar burning velocity or flammability limits, of hydrogen-ammonia-containing fuels. Additional considerations were obtained by the analysis of the maximum pressure rise and maximum pressure obtained in adiabatic conditions. A spectrum of nitrogen/oxygen mixtures was scrutinized, and the influence of initial temperature within the range of 300–500 K was systematically investigated. The estimation quality of the adopted mechanism was evaluated by comparing numerical predictions with experimental measurements obtained by different systems, when available. A tendency in slightly more conservative results on the safe side was detected for the assessment of flammability limits and minimum oxygen concentration. This trend was attributed to the assumption of perfectly adiabatic conditions posed for the numerical analysis, which does not perfectly match the experimental conditions. Conversely, an excellent agreement between numerical and experimental laminar burning velocity was observed. Therefore, the collected data were used for the quantification of input parameters required by well-established correlations suitable for synthetic fuels.