Overview of Current Developments of Pre-chamber Spark Plugs for Passenger Car Applications

The internal combustion engine (ICE) will remain the key technology in the transport sector over the short and medium term. While alternative technologies such as battery electric vehicles face charging and storage limitations, there is still potential for improvements in fuel economy and reduced emissions from ICEs. A promising technology to further improve the efficiency of the spark ignition engine is the passive pre-chamber spark plug. The main advantages of pre-chamber-initiated combustion are knocking mitigation, increase of the in-cylinder turbulence, and combustion, which is faster and more stable in comparison to the conventional (J-gap) spark plug. Moreover, the higher ignition energy compared to J-gap spark plugs enables the operation of load points with higher intake pressure, similar exhaust recirculation rates, and leaner combustion. These advantages are mainly due to volumetric ignition by hot and reactive jets. The pre-chamber plug has two main disadvantages, which are the cold-start behavior and the low-load performance due to low charge motion and higher wall heat transfer at these load points. Furthermore, the heating of the catalytic converter remains challenging due to late ignition timing. In this paper results of development activities on the optimization of the PCI which is a result of cooperation between Federal-Mogul Ignition GmbH and AVL are shown. In this work the differences between J-GAP and pre-chamber spark plug are investigated on single cylinder research engine (SCRE). The objectives of this study are to reduce the emissions and enable the lambda one operation in the entire operation map of the engine for an existing engine design. In this work, the advantages of the pre-chamber are successfully demonstrated, i.e., first the lambda one operation was maintained in the entire engine operation map. Second, on the high-load side a BMEP of 30 bar could be reached without running in to pre-ignition. Finally, the catalyst heating was investigated. The identified pre-chamber design was able to meet the requirements of minimal SEHF (specific exhaust heat flux). Overall, the benefits of a passive pre-chamber were successfully demonstrated and in the next steps the findings will be transferred to the vehicle test.