Study on chemical kinetics and NO behaviors in pre-chamber jet-induced ignition mode with ammonia

Abstract

Ammonia has been supposed to be an important carbon-neutral fuel for the applications in future engines. Its unique physical and chemical properties have great effect on engine combustion. The pre-chamber jet-induced ignition mode can yield very high turbulent jet ignition energy, which should be favorable for the ammonia combustion. To study the effects of key initial parameters in this combustion mode, the ammonia combustion and NOx formation processes were analyzed deeply in constant volume combustion chamber. A 3D CFD model was developed and validated with the visualization experiments, and the initial pressures (Pin) and temperatures (Tin) were numerically studied. The comparisons of different Pin for constant fuel mass (CFM) and constant equivalence ratio (CER) showed that Pin with CFM affects the combustion phase and burning rate more obviously. A higher Pin reduces the NOx emission slightly for CER but leads to higher NOx obviously for CFM, and a higher Pin for CFM also results in a slightly higher N2O emission due to the lower combustion temperature. The comparisons of different Tin showed that a higher Tin can enhance the combustion process greatly, while it also results in higher NOx due to high activity of OH and HNO for HNO + OH → NO+H2O.