In this article the development of a combustion system with a fuel-scavenged pre-chamber is described. Such a system is commonly used in large-bore engines operated with extremely lean mixtures. The authors implemented the scavenged pre-chamber into a light duty truck-size engine with a bore of 102 mm. The lean burn strategy is intended to achieve very low nitrogen oxide (NOx) emissions at low load. At full load a stoichiometric mixture strategy is applied to achieve sufficient power density while simultaneously enabling the use of a relatively simple three-way catalytic converter for exhaust gas aftertreatment.
This work outlines the pre-chamber design features and introduces the results of an experimental investigation of the effect of pre-chamber ignition on a single cylinder testing engine. Simulation results from three operation regimes from both 1 dimensional (1-D) and computational fluid dynamics (CFD) models are presented to provide an understanding of the complicated processes during the entire working cycle of the engine. The CFD model was used to describe the scavenging of the pre-chamber. The combustion process in the pre-chamber and in the main combustion chamber is characterized by a simplified approach without detailed reaction kinetics.
Based on experiments, the pre-chamber engine is able to operate at low load with an air excess ratio (λ) above 2 and very low engine-out NOx emissions. The naturally aspirated pre-chamber engine is also able to operate with a stoichiometric mixture and fully open throttle. CFD results describe the quantities that are not accessible for direct measurement, namely the effectiveness of pre-chamber scavenging, mixture distribution before the start of combustion, and flame propagation after the start of combustion.