Atomic insights into the NH3/CH4 combustion in air assisted by an electric field

YS Hong and J Wang and YQ Liu and XZ Jiang, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 135, 257-266 (2025).

DOI: 10.1016/j.ijhydene.2025.05.051

Electric field-assisted combustion is an innovative combustion technology which can significantly enhance fuel combustion performance and may have potential for modulate emissions. In the present work, the reactive force field (ReaxFF) molecular dynamics (MD) method was utilized to explore the impact of external electric fields with different intensities on the combustion behavior of ammonia/methane (NH3/CH4) in air and pollution emissions from the combustion. Meanwhile, a detailed analysis of the reaction mechanism was also conducted. The findings indicate that the external electric field significantly affects the fuel consumption rate and ignition delay time in the combustion of NH3/CH4. A scrutiny of the structural changes of the NH3 molecules reveals that the electric field altered the bond length and angle of the NH3 molecules. A center of charge was proposed to evaluate the charge distribution of the system. The center of charge shifts with the electric field, affecting the dynamics of radicals. From the energy perspective, the electric field enhanced the motion of particles, leading to a significant increase in kinetic energy. Moreover, the reaction pathways and intermediates of NH3/CH4 combustion with an external electric field and in the field-free condition were compared. The presence of an electric field generates new elementary reaction pathways and intermediates. Special attention was placed on the nitrogen and carbon emissions formation. In particular, the low-intensity electric fields mitigate the emissions of both nitrogen oxides and carbon oxides. The reduction in NOx and COx emissions was quantified, indicating an approximate reduction of 8.9 % and 3.4 % in COx emissions at 2 x 101 V/m and 2 x 102 V/m, respectively, along with a 1.5 % decrease in NOx emissions at 2 x 102 V/m. This research reveals the microscale mechanism of electric fields on ammonia combustion, laying a theoretical foundation for controlling pollution with external fields.

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