Exhaust Gas Recycle (EGR) is a technique more and more adopted in spark-ignition engines for both the control of NOx emissions and the improvement of fuel consumption in certain engine operating points. In this paper, the influence of EGR on the behaviour of a small displacement turbocharged SI engine has been assessed. In particular, engine operation at full load, high rotational speeds, has been analyzed. The intake stroke, compression and combustion process have been simulated by means of a three dimensional numerical model. A commercial 3D code has been used in order to take into account the charge dilution and to estimate knock risks at full load operation. This model has been validated by comparing the numerical results to the measured data obtained in experimental tests. The influence of flow field details within the cylinder has been studied and EGR effects on charge, exhaust gas and temperature distribution have been evaluated. The knock model has been able to detect the knock occurrence in engine off-design operation allowing to locate the knock risk area in the combustion chamber. The knock onset has been detected by considering both the heat released by the predicted self-ignition process and the rising of pressure waves in the combustion chamber.
3-D Analysis of the Effects of Charge Dilution on the Combustion Process of a SI Engine
GALLONI, Enzo;FONTANA, Gustavo;
2011-01-01
Abstract
Exhaust Gas Recycle (EGR) is a technique more and more adopted in spark-ignition engines for both the control of NOx emissions and the improvement of fuel consumption in certain engine operating points. In this paper, the influence of EGR on the behaviour of a small displacement turbocharged SI engine has been assessed. In particular, engine operation at full load, high rotational speeds, has been analyzed. The intake stroke, compression and combustion process have been simulated by means of a three dimensional numerical model. A commercial 3D code has been used in order to take into account the charge dilution and to estimate knock risks at full load operation. This model has been validated by comparing the numerical results to the measured data obtained in experimental tests. The influence of flow field details within the cylinder has been studied and EGR effects on charge, exhaust gas and temperature distribution have been evaluated. The knock model has been able to detect the knock occurrence in engine off-design operation allowing to locate the knock risk area in the combustion chamber. The knock onset has been detected by considering both the heat released by the predicted self-ignition process and the rising of pressure waves in the combustion chamber.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
