Investigation on the lean-combustion characteristics of non-uniform orifice pre-chamber spark plug in low engine speed working conditions compared with high energy spark ignition

For a long time, pre-chamber jet ignition has been an effective method to achieve stable lean-combustion of the engine. However, due to the lack of an additional fuel injector, the passive pre-chamber easily leads to unstable combustion and even misfires during the engine’s low-speed working conditions. This study used simulation and optical single-cylinder engine visualization experiments to investigate the ignition and combustion performance of the pre-chamber spark plug (PCSP) ignition system and different orientations of the scavenging jet nozzle in the cylinder. The results indicate that the PCSP at low speed (1200 r/min) can improve the lean-combustion load performance by up to 6.7% compared with traditional high-energy spark ignition but cannot significantly improve the lean combustion limit and stability. In addition, under each λ condition, the scavenging jet nozzle face toward one of the intake valves (IV2) is most advantageous. The effect of lean combustion on reducing NO began to manifest after λ > 1.3 and achieved the best at 1.6. This kind of jet ignition pre-chamber provides a more stable ignition solution than high-energy spark ignition for low speed and medium/low load aspects.