Detailed kinetic model for combustion of NH₃/H₂ blends

Area of Science:

• Combustion Chemistry
• Chemical Kinetics
• Computational Chemistry

Background:

• Ammonia is a promising zero-carbon fuel, but its combustion presents challenges like low reactivity and NOx formation.
• Accurate kinetic models are essential for optimizing ammonia combustion in engines and burners.
• Existing models show significant discrepancies with experimental data, especially for NOx species.

Purpose of the Study:

• To develop an improved detailed kinetic model for ammonia combustion.
• To minimize reliance on estimated parameters by using updated data and ab initio calculations.
• To validate the new model against a wide range of experimental data.

Main Methods:

• Compiled updated thermochemical and kinetic parameters from literature and ab initio calculations.
• Generated a new detailed kinetic mechanism using the Reaction Mechanism Generator (RMG).
• Applied advanced methods for pressure-dependent reactions and third-body efficiencies.

Main Results:

• The new model shows good agreement with experimental data for laminar burning velocities, ignition delay times, and species profiles.
• It reproduces experimental observations without empirical rate-coefficient adjustments.
• Discrepancies highlight persistent uncertainties in nitrogen oxide chemistry.

Conclusions:

• The developed kinetic model offers improved predictions for ammonia combustion.
• It is expected to extrapolate well to untested conditions due to the absence of parameter tuning.
• Further research is needed to resolve uncertainties in NOx chemistry.