Study on the Effect of Oxygen Enrichment Ratio on Combustion and Emission in Ammonia–Hydrogen Engine

Ammonia, with its extensive industrial foundation, excellent storage and transportation conditions, and high energy density, is a promising renewable zero‐carbon fuel. However, ammonia's extremely high ignition energy and slow combustion speed are major obstacles to its application. This study proposes a hydrogen and oxygen cocombustion strategy to comprehensively improve the performance of ammonia‐fueled engines. Through numerical simulations, the effects of different oxygen‐enriched conditions on the combustion and emission characteristics of ammonia–hydrogen engines are investigated. The oxygen concentration in the air is gradually increased from 21 to 30% while maintaining an ammonia–hydrogen molar ratio of 85% and 15%, and an excess air coefficient of 1. The results show that as the oxygen concentration increases, the engine's indicated mean effective pressure gradually rises in a linear trend, the combustion stability of the in‐cylinder mixture improves, and the combustion duration shortens. The peak in‐cylinder temperature also increases with higher oxygen concentrations, leading to elevated NOx emissions. The indicated thermal efficiency (ITE) initially increases and then gradually declines with rising oxygen levels, and the maximum ITE is 40.1% when Ω = 26%. This research provides new insights for the practical application of ammonia internal combustion engines.