Closed-Loop Combustion Control by Extremum Seeking with the Passive-Chamber Ignition Concept in SI Engines

The passive pre-chamber ignition concept has shown the potential of increasing the combustion efficiency at high load by allowing more advanced combustion phasing due to its rapid combustion. The optimization of the spark advance and the dilution rate is currently a challenging task that would allow these types of engines to maintain spark ignited (SI) engines pollutants with even higher combustion efficiencies than diesel engines.

This paper is focused on the automatic calibration of a SI engine, when using the passive-chamber ignition concept. The sensitivity of the combustion efficiency to spark advance and dilution rate has been studied and an extremum seeking approach has been designed to optimize the control inputs by rejecting disturbances and maintaining certain limitations of cycle-to-cycle variability and misfires. The final algorithm has been validated in a single-cylinder engine using compressed natural gas (CNG) port fuel injection with a conventional SI configuration and by using a passive-chamber with turbulent jet ignition (TJI) combustion mode.