A study of emissions and performance improvement for future heavy-duty diesel engines

摘要

This paper describes the two alternatives for performance improvement in heavy-duty diesel engines fitted to the anticipated future emissions regulations. One is the optimization of cooled exhaust gas recirculation (EGR) system including theimprovements in combustion and emissions characteristics for turbocharged and aftercooled (TCA) engines The other is the application of homogeneous charge compression ignition (RCCI) combustion.To optimize EGR strategy, numerical simulations were firstly carried out. The results showed that the system equipped with two EGR pipes combined with a variable geometry turbocharger (VGT) was the most promising to introduce enough EGR gas into intakemanifolds without auxiliary intake and/or exhaust throttling. Furthermore, it was found that the multiple fuel injection was effective for the remarkable reduction of both smoke and carbon monoxide (CO) emissions without deteriorating fuel consumptionunder EGR conditions. The combination of the HCCI combustion with the conventional diesel combustion by the multiple fuel injections was able to expand its low nitrogen oxides (NO{sub}x) operating region compared to the HCCI combustion. In this concept, EGR was effective forthe reduction of NO{sub}x emissions and the suppression of the increase in hydrocarbon (HC) emissions. In addition, the mixture of diesel fuel with the oxygenated fuel, Methyl-t-Butyl Ether (MTBE), improved both the emissions and fuel consumption.