Electronically Controlled EGR Diesel Exergy Analysis And Control Strategy Optimization

Facing the increasingly emissions regulations and the energy crisis, Efficient Low Emissions is always the development solutions. Low temperature combustion mode has drawn extensive attention for its low NOx and Soot emission by using high level EGR to decrease the combustion temperature. This paper, starting from the second law of thermodynamics, studied the exergy and energy distribution and changing characteristics during various combustion processes and the effect of the combustion parameters including intake pressure and injection timing on engine performance to provide evidence for control strategy.EGR system was installed on the Prototype YC6 A engine and this paper involves numerical simulations and experiment validation. The research finds that the exergy destruction accounts for about 30% of the fuel exergy and the share decreases as EGR increases. The burned fuel fraction remains constant as EGR increases at conventional injection timing, while the value decreases as the EGR increases at the late injection timing. The combination of late injection and very high EGR level is seen to contribute to incomplete combustion. The late injection timing has lower heat transfer exergy and higher gas flow exergy compared with the conventional injection timing. When the injection timing is fixed the gas flow exergy increases as EGR increase while the heat transfer remains constant.During simulation and analysis of air pressure and fuel injection pressure, this paper draws conclusions that the engine power increases and fuel consumption reduces when the intake pressure increases. Meanwhile there is more oxygen in the cylinder helps oxidation of soot. By using high EGR and intake pressure can satisfy low emission and high power. Increase injection pressure is the most effective method to dramatically reduce smoke because of the quality improvement of fuel spray and lower fuel consumption. However the NOx emission increases as the injection pressure increases.Increasing injection pressures help to improve the quality of the fuel spray, improve the quality of combustion and reduce the consumption of fuel. Because the working fluid mixing quality improves, the Soot emissions reduce. To obtain low Soot emission, high injection pressure can be adopted when EGR is used on diesel engine.