Gasoline Fueled Pre-Chamber Ignition System for a Light-Duty Passenger Car Engine with Extended Lean Limit

In this work, a light-duty research engine based on a passenger car engine is equipped with an in-house developed pre-chamber (PC) ignition system replacing the conventional spark plug. By using such kind of ignition system, the combustion in the main chamber is enhanced by radical seeding through jets travelling from the pre-chamber to the main chamber. These radicals serve as high-energy ignition sites for the mixture in the main combustion chamber leading to enhanced burn rates and combustion speed. In contrast to conventional spark-ignited combustion starting from the spot of the electrode gap, an extended lean misfire limit and a mitigated knocking tendency are achieved. The presence of a gasoline direct injector inside the PC enables the system to operate in both passive and active mode. The injection of a small fuel amount allows separating the air-to-fuel equivalence ratio of the pre-chamber and the main chamber. By this, an overall lean mixture is ignited by providing a stoichiometric mixture near the PC spark plug. In this study, different orifice nozzles of the PC are investigated in active operation and compared to conventional spark plug ignition. It is shown that the lean limit is extended significantly for all PC variants compared to conventional spark plug ignition due to the presence of multiple ignition sites with PC operation. The results show that the combination of an orifice number of six and a flat-screen angle is the most promising orifice configuration in terms of combustion efficiency and emission behavior. Additionally, implementing a swirled orifice channel reduces the sensitivity of particle number (PN) emission on injected fuel mass in the PC significantly. Finally, an engine load and speed sweep reveals that the PC operation is not limited in the engine operation map and shows its promising potential especially for low-temperature combustion.