Simulation Investigation of Turbulent Jet Ignition (TJI) Combustion in a Dedicated Hybrid Engine under Stoichiometric Condition

Turbulent jet ignition (TJI) combustion using pre-chamber ignition can accelerate the combustion speed in the cylinder and has garnered growing interest in recent years. However, it is complicated for the optimization of the pre-chamber structure and combustion system. This study investigated the effects of the pre-chamber structure and the intake ports on the combustion characteristics of a gasoline engine through CFD simulation. Spark ignition (SI) combustion simulation was also conducted for comparison. The results showed that the design of the pre-chamber that causes the jet flame colliding with walls severely worsen the combustion, increasing the knocking intendency, and decrease the thermal efficiency. Compared with SI combustion mode, the TJI combustion mode has the higher heat transfer loss and lower unburned loss. The well-optimized pre-chamber can accelerate the flame propagation with knock suppression. Strong-tumble flow distorts the jet flame propagation, which is not conducive to the development of combustion process. The TJI combustion mode combined with the new designed tumble-swirl intake port can increase the ITE by 0.7 % compared to SI combustion mode under condition of n = 3000 r/min and IMEP ≈ 1.0 MPa.