Effect of Ammonia Proportion on the Combustion and Emissions in Ammonia/Diesel Dual-Fuel Engines

<div class="section abstract"><div class="htmlview paragraph">This article develops a numerical simulation framework for ammonia/diesel dual-fuel combustion using CONVERGE software. The modeling approach is explained in detail, including theories of numerical computation, mathematical submodels, modeling methodologies, and boundary condition specifications. Based on the developed model, this work investigates the impact of the ammonia fuel ratio on some key combustion and emission characteristics: heat release dynamics, distribution of the in-cylinder temperature field, formation of intermediate combustion species, and pollutant emissions. It provides comprehensive analysis in terms of in-cylinder pressure, mean temperature, heat release rate profile, cumulative heat release, fluctuations in the compositions of n-heptane and ammonia, distribution of the equivalence ratio, turbulent kinetic energy, concentration of OH radicals, formation of formaldehyde, and emissions of pollutants including CO, NOx, N<sub>2</sub>O, soot, and unburned hydrocarbons (HC) with respect to crank angle. The results showed that the fraction of ammonia fuel is the key to affecting in-cylinder combustion, the development of intermediate and final products, and different pollutant emissions. This work can provide important theoretical guidance and practical suggestions for the development of ammonia/diesel dual-fuel combustion technology, as well as promote effective and green utilization of ammonia in internal combustion engines.</div></div>