Numerical study on the asymmetrical jets formation from active pre-chamber under super-lean combustion conditions.

This paper aims to investigate the mechanism of the asymmetric jets of the TJI system. We analyzed the effects of fuel injection and air flows in pre-chamber and main chamber, initial flame kernel, and evolution of turbulent hot jets. The evaluation indexes of asymmetric jet were proposed. The results show when adding fuel injection into the homogeneous PC with off-central spark plug, the average relative velocity range and average degree of velocity non-uniformity increased by 50.8% and 32.8%, which increased by 75.1% and 46.7% for the real engine condition with intake airflow and fuel injection. A similar phenomenon was observed for central spark plug settings but with a much stronger impact on the asymmetry of jets velocity as proved by the increment of 138.5% and 93.2% under real engine condition. The asymmetric jets can be divided into the asymmetry of jets size and the asymmetry moment of flame jets. The former of different jets' velocity is attributed to the tumble flow in main chamber. The latter is attributed to the irregular flame propagation caused by the off-central ignition and the uneven mixture distribution in pre-chamber. The optimization strategies to efficiency utilize the flow exchange between PC and MC were proposed. • The formation of asymmetrical jets from turbulent-jet-ignition system was investigated. • Different PC structures with spark plug centrally and off-centrally installed were designed. • Ideal homogeneous conditions via semi-ideal environment to real engine operations were discussed. • The asymmetric jets phenomenon was a spatial-temporal related to jets size and flame jets moment. • Specific strategies and PC design were carried out to improve the PC jet performance. [ABSTRACT FROM AUTHOR]