Application of LES for Analysis of Unsteady Effects on Combustion Processes and Misfires in DISI Engine

Abstract

Cycle-to-cycle variations of combustion processes strongly affect the emissions, specific fuel consumption and work output. Internal combustion engines such as Direct Injection Spark-Ignition (DISI) are very sensitive to the cyclic fluctuations of the flow, mixing and combustion processes. Multi-cycle Large Eddy Simulation (LES) analysis has been used in order to characterize unsteady effects of combustion processes and misfires in realistic DISI engine. A qualitative analysis of the intensity of cyclic variations of in-cylinder pressure, temperature and fuel mass fraction is presented. The effect of ignition probability and analysis of misfires are pointed out. Finally, the fuel history effects along with the effect of residual gas on in-cylinder pressure and temperature as well as misfires are discussed.