Effect of structural parameters of active pre-chamber on ammonia/hydrogen premixed combustion process: A numerical investigation

The development of zero-carbon fuels is of great significance for reducing carbon emissions. Using an ammonia/hydrogen mixture as fuel, the combustion in engine through an active pre-chamber has a good effect on reducing carbon emissions. Moreover, the utilization of active pre-chamber is able to achieve rapid combustion speed, therefore leading to higher overall thermal efficiency. In order to realize an optimized combustion process, it is essential to investigate effects of the structural parameters of active pre-chamber on combustion process. Therefore, in this paper, an active pre-chamber combustion model was established based on a mass-produced gasoline engine, the mixture of ammonia and hydrogen was used as fuel, 8 different pre-chamber structure schemes were proposed, variations such as the angle and number of nozzle holes and the volume ratio of the pre-chamber to engine clearance volume were considered to investigate their influences. The results indicate that scheme 8, with a 60° nozzle angle, 6 holes, 1.6 mm aperture and 3.6 % volume ratio, is the optimal pre-chamber structure proposed in this study. Under this scheme, numerical calculations show an optimum thermal efficiency of 47.93 %. This study also revealed the interaction mechanism between structural parameters of active pre-chamber and the combustion process of ammonia/hydrogen mixture, which is significantly important for optimizing combustion processes and engine performance, and provides research references for the industrial utilization of ammonia-hydrogen combustion engines in passenger vehicles.