engleski

Exploring the potential of EGR in SI engine using 1-D/0-D simulation model

The requirements for significant reduction of fuel combustion and CO2 emissions from SI engines have pushed the development of SI engines towards smaller turbocharged units with high load operation. Charging of SI engine increases the tendency of engine to knock and therefore requires operating conditions that are not on the lowest fuel consumption setting, but rather at a setting that is at knock free operation. Also, if variable turbine geometry (VGT) is considered, the limit on turbine inlet temperature can push operating conditions towards even lower efficiency. In order to assess the influence of exhaust gas recirculation (EGR) on operating conditions of SI engine at full load, to explore the possibility to use EGR for lowering the engine's tendency to knock and for lowering the exhaust gas temperature, and consequently to enable operating conditions with much more favorable efficiency the cycle simulations of multi cylinder engine were performed. The cycle simulation model is based on a non-charged commercial four cylinder engine which is for the purposes of this paper converted to charged model with VGT. For the calculation of combustion the modified fractal combustion model is used together with the novel approach in modeling of cycle to cycle variations and the prediction of knock. The cycle simulation model is run at three different engine speeds at full load and at several different EGR levels. The analysis of results showed that the potential of fuel consumption improvement depends on engine speed and turbocharger settings and changes in the range of 1.5-11.2% for this engine model. The fuel consumption improvement comes as a consequence of enabling operation at stoichiometric conditions without crossing the limit of knock and of exhaust gas temperature at turbine inlet.

AVL Boost, SI engine, EGR, Knock

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