Numerical study of turbulent jet ignition process at different injection strategies in a single-cylinder engine with active pre-chamber

Abstract

ABSTRACT The application of lean-burn technology in engines that aims to meet the low-carbon combustion promotes the development of turbulent jet ignition (TJI) system. A turbulent jet ignition system has great potential in improving ignition stability and accelerating flame propagation. In this study, a numerical investigation of the turbulent injection ignition process in a single-cylinder engine with an active pre-chamber is conducted. The turbulent jet ignition mechanism and the effects of pre-chamber injection timing, injection quantity, and spark ignition timing on the jet ignition process and combustion characteristics are analyzed comprehensively. Based on the temperature and composition at the nozzle, the jet ignition process in the engine can be divided into three main phases:1) cold jet. 2) flame jet. 3) full combustion. It was found that the fuel vapor in the pre-chamber will decrease due to the less time for fuel evaporation when the injection timing is excessively delayed. Larger injection quantities will increase the inhomogeneities in the pre-chamber, which further play an important role in the ignition efficiency of the TJI system. Delaying the spark ignition timing will significantly influence the thermodynamic condition in the combustion and correspondingly change the overall combustion progress. For pollutants, most of the nitrogen oxide emissions in jet ignition engines mainly come from the pre-chamber, while the soot emission is produced in the cylinder.