Elucidating the effect of gasoline jet ignition on ammonia combustion characteristics via visualization methods: A fundamental study

Ammonia is one kind of the future fuel. Ignition chamber technology is capable of inducing dependable ignition and efficient fuel combustion. Based on the experimental platform of a constant volume combustion chamber with a gasoline ignition chamber, the influences of the combustion pattern, ambient temperature, gasoline energy percentage, and ammonia equivalence ratio on the combustion process of ammonia was investigated by using shadowgraph method. The results revealed that in comparison to ammonia/gasoline mixture combustion pattern, the pattern of ignition chamber with gasoline jet ignition could enhance the peak pressure of main chamber, and significantly shorten the ignition delay and combustion duration, even the gasoline injection quantity was less than 1/20 of the former pattern. Furthermore, as the initial temperature increased, the peak pressure in the main chamber gradually increased, along with an 18.7 % reduction in ignition delay and a 26.7 % decrease in combustion duration. On the other hand, a higher percentage of gasoline energy negatively impacted the jet velocity and ignition capability. Optimal jet ignition performance was achieved at an energy percentage of 1.0 % of gasoline, with a peak pressure of 4.96 MPa and a combustion duration of 70.4 ms, which was 15.4 % shorter than that of the 2.0 % condition. Besides, the effective ammonia combustion performance could be achieved at 1.0 ammonia equivalence ratio compared to that of 0.6 and 0.8 conditions. These results are expected to provide valuable insights for the advancement of ammonia-fueled engines.