Effect of intake air conditions on combustion and emission performance of ammonia-diesel dual fuel engine

Abstract

Investigating the intake-premixed ammonia engine reveals that it emits a significant amount of N₂O and unburned NH₃, which contradicts ammonia fuel's ability to reduce engine emissions and satisfy ever-tougher pollution regulations. To address these issues, a study utilizing CONVERGE software was conducted, and the effects of raising the intake air temperature and igniting near the Top Dead Center were examined. This study is based on the ammonia energy fraction (30%–80 %), intake air temperature (420K–480K), and O₂ ratio (80%–100 % of original). As the NH₃ energy fraction increases, the engine's combustion and emission performance significantly declines at an intake air temperature of 420 K. The effect of intake air temperature and O₂ ratio on engine performance at 70 % ammonia energy fraction was then investigated. When the intake air temperature increases from 420K to 480K, the engine's combustion performance is greatly improved, but the NOx emissions increase from 3.17g/kWh to 7.09g/kWh. Lower O₂ ratios are more effective in reducing NOx emissions and have less impact on engine performance at higher intake temperatures. Under the conditions of 70 % ammonia energy fraction, 480K intake air temperature, and 80 % of the original O₂ ratio, the indicated thermal efficiency of this engine can reach 52 %, N₂O and NH₃ emissions can be ignored, and NOx emissions are 2.01g/kWh. At this load, an efficient combustion and low-emission operating scheme is provided for the intake-premixed ammonia engine.