A Kinetic Modeling and Engine Simulation Study on Ozone-Enhanced Ammonia Oxidation

Ammonia has attracted the attention of a growing number of researchers in recent years. However, some properties of ammonia (e.g., low laminar burning velocity, high ignition energy, etc.) inhibit its direct application in engines. Several routes have been proposed to overcome these problems, such as oxygen enrichment, partial fuel cracking strategy and co-combustion with more reactive fuels. Improving the reactivity of ammonia from the oxidizer side is also practical. Ozone is a highly reactive oxidizer which can be easily and rapidly generated through electrical plasma and is an effective promoter applicable for a variety of fuels. The dissociation reaction of ozone increases the concentration of reactive radicals and promotes chain-propagating reactions. Thus, obtaining accurate rate constants of reactions related to ozone is necessary, especially at elevated to high pressure range which is closer to engine-relevant conditions. In present work, rate constants of ozone dissociation reaction were recalculated and extended to cover engine-relevant pressure conditions based on multiconfigurational calculation results in literature. A kinetic model was developed based on calculated results in present work and data taken from literature. This model was further used for numerical simulations of ozone-enhanced ammonia oxidation at pressures of 1-5 MPa and temperatures ranging from 700-1000 K. Kinetic analysis based on Chemkin simulation was performed to investigate and evaluate the effect of ozone addition. Engine simulation was also performed to investigate the feasibility of ozone-enhanced ammonia oxidation in engine applications. Present work investigates a different route of enhanced combustion of ammonia and will contribute to the future application of ammonia in engines.