Optical Investigation of Lean Combustion Characteristics of Non-Uniform Distributed Orifice Passive Pre-Chamber on a High Compression Ratio GDI Engine

The passive pre-chamber (PC) is valued for its jet ignition (JI) and is suitable for wide use in the field of gasoline direct injection (GDI) for small passenger cars, which can improve the performance of lean combustion. However, the intake, exhaust, and ignition combustion stability of the engine at low speed is a shortcoming that has not been overcome. Changing the structural design to increase the fluidity of the main chamber (MC) and pre-chamber (PC) may reduce jet ignition performance, affecting engine dynamics. This investigation is based on non-uniformly nozzles distributed passive pre-chamber, which is adjusted according to the working medium exchange between PC and MC. The advantages and disadvantages of the ignition mode of PC and SI in the target engine speed range are compared through optical experiments on a small single-cylinder GDI engine. The results show that with the increase of λ from 1.0 to 1.6, the promotion effect of PCJI on dynamic performance gradually decreases, and it is beneficial for the λ=1.0 condition close to the stoichiometric combustion at low speed. However, not all pre-chambers can improve lean burn performance. In addition to many existing conclusions on structural design, the combustion performance is also closely related to the relative arrangement of PC and MC.