Influence of pre-chamber structure and injection parameters on engine performance and combustion characteristics in a turbulent jet ignition (TJI) engine

Abstract

Abstract Turbulent jet ignition (TJI) has been proven to effectively improve the burning rate and expand the lean-burn limit of gasoline engines. In this work, based on a single-cylinder engine, injection parameters in the pre-chamber were investigated, combustion characteristics were studied, and pollutant emissions were optimized. Results show that the injection timing in the pre-chamber should be carefully controlled to generate a well-mixed air–fuel mixture and to avoid the diffusion of fuel from the pre-chamber to the main chamber. Therefore, the injection event should be set at the early stage of the compression stroke. Besides, excessive fuel supply in the pre-chamber should be avoided to get optimal engine performance and low pollutant emissions. The lowest indicated specific fuel consumption (ISFC) is achieved when the λ is between 1.5 and 1.6, because lean combustion reduces the heat dissipation but too lean combustion causes more fuel to be burned incompletely. Moreover, to further improve the engine performance and reduce the pollutant emissions, three types of optimized pre-chamber are tested, and results show that with lower pre-chamber volume, better engine performance and lower pollutant emissions are both realized because smaller pre-chamber volume leads to less heat dissipation and less fuel burning around stoichiometric equivalence ratio in the pre-chamber. Furthermore, the pre-chamber with one jet hole is effective to improve the burning rate and to expand the lean-burn limit compared with the 7-hole pre-chamber, and the lean-burn limit of λ is expanded to 2.2 by the optimized pre-chamber, when the minimum NOx of 0.15\xa0g/kWh is achieved.