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.
Highlights
Cycle-to-cycle variations of combustion processes strongly affect the emissions, specific fuel consumption as well as work output
Direct Injection Spark-Ignition (DISI) engines are very sensitive to cyclic fluctuations within the combustion chamber which can result in different work output for consecutive engine cycles, high fuel consumption and high emissions
Thereby, all Large Eddy Simulation (LES) calculations presented and discussed in present paper are carried out on a computational grid shown in Figure 2a in the following range of CA: 45° Before Top-Dead Center (BTDC) until 45° After Top-Dead Center (ATDC)
Summary
Cycle-to-cycle variations of combustion processes strongly affect the emissions, specific fuel consumption as well as work output. Direct Injection Spark-Ignition (DISI) engines are very sensitive to cyclic fluctuations within the combustion chamber which can result in different work output for consecutive engine cycles, high fuel consumption and high emissions. Multi-cycle LES based analysis has been used for investigating the effects of both unsteady spray combustion processes and misfires for various configurations of the spark-plug. Previous investigations of authors [3, 7,8,9,10] could show that the mixture quality at the spark-plug in air-guided direct injection gasoline engines is strongly affected by the flow inside the combustion chamber. An attempt to define and characterize misfires along with partial burned cycles in DISI engine was provided in [7], where ignition probability and analysis of misfires were discussed for four different positions of the spark-plug without consideration of residual gases and fuel history effects. The summary is provided in the last section of the manuscript
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