Understanding the effect of turbulent flow on the combustion cyclic variation in a spark ignition engine using Large-Eddy simulation

Abstract

At the present, emission regulations have been tightened around the world in an effort to reduce emissions from internal combustion engine (ICE) vehicles. The one of the issues in the development of eco-friendly spark ignition (SI) internal combustion engines is a cycle-to-cycle variation (CCV) of combustion. Therefore, research on the CCV is also being actively carried out. Because the causes that affect the cycle deviation are various and complex, it is difficult to conduct detailed research on the source of the CCV through experimental studies. Therefore, the 3D simulation, especially large-eddy simulation (LES) approach is actively carried out.In the present study, the Lagrangian ignition model developed for LES is introduced. The Lagrangian particles were employed to realize the ignition channel and the secondary electric circuit model was implemented to predict the spark energy and the end of ignition time. And 30 LES cycles were performed to identify the cause of the CCV and validated against the experimental data. The vortex produced by wall flow on the secondary tumble plane was identified as an important factor. A new piston shape was designed to strengthen the vortex formation by wall flow. The result of new piston case showed the reduced combustion CCV than the base case. This research provides the guide how to investigate the sources of the combustion CCV and how to reduce the combustion CCV for the future engine development.