Numerical Investigation of the Effects of Piston Design and Injection Strategy on Passive Pre-chamber Enrichment 2022-01-1041

The pre-chamber combustion can extend the lean limit of internal combustion engines (ICE) and hence increase their overall efficiency. Compared to active pre-chambers equipped with an auxiliary fuel supply system, passive pre-chambers have lower manufacturing costs and require minimal or no design modifications to the conventional spark plug engines. The major challenge of the passive pre-chamber is to extend the lean limit as much as the active pre-chamber. Computational fluid dynamics (CFD) simulations were conducted on a light-duty single-cylinder engine geometry fitted with a passive pre-chamber and using iso-octane as fuel to investigate and optimize the passive pre-chamber fuel enrichment through the pre-chamber nozzles. The non-reacting flow simulations were performed from the intake valve open (IVO) to spark timing. The main goal of this study is to evaluate the impact of injection timing, location, and piston geometry on the fuel enrichment of the pre-chamber as a means to extend the lean limit of the engine operation. A homogeneous air-fuel mixture is initially considered through the intake ports. Subsequently, a small percentage of the fuel was injected through a gasoline direct injector (GDI) into the main chamber and aerodynamically guided into the passive pre-chamber to enrich it. Several piston designs were simulated for side and central direct injection spray guidance. The simulation analysis shows that it was possible to achieve a significantly richer mixture in the pre-chamber while having a lean mixture in the main chamber using direct injection and a specially designed piston.