Potential of ammonia spray configuration in ammonia-diesel dual-fuel direct injection compression ignition engine: Toward near zero carbon emissions

Abstract

Asymmetrical spray arrangement is an efficient method of enhancing combustion while mitigating NH₃ and N₂O emissions in ammonia/diesel dual-fuel engines. Ammonia is regarded a potentially effective main fuel for decreasing CO₂ emissions due to its higher hydrogen concentration when compared to diesel fuel. In the present work, a little amount of pilot diesel ignites the direct-injected ammonia, which burns in a diffusion combustion regime. It has been found that the interaction between the diesel and ammonia sprays has a major effect on the combustion regimes and flame growth. Simultaneously, a computational CFD model has been constructed to investigate the interaction between spray and flame structure of ammonia/diesel plumes. Two configurations for ammonia spray have been introduced in order to facilitate efficient mixing and combustion process. The asymmetrical configuration eliminates two plumes oriented toward the walls and injects more ammonia into the center of combustion chamber. By presenting an asymmetrical spray configuration for ammonia, it is possible to reduce the allocation of rich ammonia pockets, bringing ammonia technology one step closer to reliability. Asymmetrical spray configuration leads to mitigate the inhibiting effect of ammonia spray on the diesel ignition while introducing ammonia more efficiently into the combustion chamber. Comparing to symmetrical spray configuration, asymmetrical spray confirmation reduces NH₃ emission by 57.5%, N₂O by 23.4%.