Analysis of misfire processes in realistic Direct Injection Spark Ignition engine using multi-cycle Large Eddy Simulation

Abstract

Multi-cycle Large Eddy Simulation (LES) based analysis is carried out for understanding misfire characteristics in realistic Direct Injection Spark Ignition (DISI) engine. Such Internal Combustion (IC) engines are very sensitive to cyclic fluctuations within the combustion chamber that are induced and superimposed by the flow, the injection and the mixture formation. In stratified operation they can raise serious operating problems, such as misfiring. The influence of mixture preparation on misfires is investigated along with the effects of variable spray boundary conditions on the complex nature of flow instabilities and spray combustion. The results are evaluated by a number of criteria based on characteristic quantities of mixture preparation and ignition conditions at spark plug locations. In particular, a qualitative analysis of the intensity of cycle-to-cycle variations of in-cylinder pressure is presented at different spark-plug locations. Finally, the ignition probability and analysis of misfires are pointed out. These issues are discussed in terms of mean and standard deviation of temperature, velocity, mass fraction and pressure.