Ultra-Lean and High EGR Operation of Dual Mode, Turbulent Jet Ignition (DM-TJI) Engine with Active Pre-chamber Scavenging

Continuous efforts to improve thermal efficiency and reduce exhaust emissions of internal combustion engines have resulted in development of various solutions towards improved lean burn ignition systems in spark ignition engines. The Dual Mode, Turbulent Jet Ignition (DM-TJI) system is one of the leading technologies in that regard which offers higher thermal efficiency and reduced NOx emissions due to its ability to operate with very lean or highly dilute mixtures. Compared to other pre-chamber ignition technologies, the DM-TJI system has the distinct capability to work with a very high level of EGR dilution (up to ~40%). Thus, this system enables the use of a three-way catalyst (TWC). Auxiliary air supply for pre-chamber purge allows this system to work with such high EGR dilution rate. This work presents the results of experimental investigation carried out with a Dual Mode, Turbulent Jet Ignition (DM-TJI) optical engine equipped with a cooled EGR system. The results show that the DM-TJI engine could maintain stable operation (COV_IMEP<2%) with 40% external EGR at stoichiometric (λ ~ 1) operating conditions. The relative timing between the auxiliary air and fuel inside the pre-chamber was found to be critical to maintaining successful operation at 40% EGR diluted condition. Ultra-lean (up to λ ~ 2) operation was also demonstrated at two different compression ratios with good combustion stability. A range of pre-chamber nozzle orifice diameters were tested with both lean and EGR diluted conditions. In general, smaller orifice diameters resulted in shorter overall burn duration due to more favorable distribution in ignition sites.