Numerical and Experimental Investigation on Passive Prechamber Configurations Able to Operate at Low Engine Speed and Load

Turbulent Jet Ignition (TJI) represents one of the most effective solution to improve engine efficiency and to reduce fuel consumption and pollutants emission. Even if active prechambers allow a precise control of the air-fuel ratio close to the spark plug and the ignition of ultra-lean mixtures in the main chamber, passive prechambers represent a more attractive solution especially for passenger cars thanks to their simpler and cheaper configuration, which is easier to integrate into existing engines. The main challenge of passive prechambers is to find a geometry that allows to use TJI in the whole engine map, especially in the low load/speed region, without the use of a second sparkplug in the main chamber. To this end, this works reports a CFD study coupled with an experimental investigation to overcome this limitation. A baseline prechamber configuration able to operate in the whole engine map was firstly studied using the CFD models and validated against the experimental results of a 2.0 L spark-ignition (SI) engine at different equivalent ratios. After the assessment of the proposed approach, different prechamber configurations were investigated to find a proper geometry able to produce similar results of the baseline configuration but with a different spark-plug installation to allow an easier integration into existing engines.