Abstract
The heavy-duty diesel engines have achieved the one of the lowest CO2 emission as current prime mover. However they are strongly expected lower NOx and PM emissions than today. In this study the high boost and high rate EGR combustion has been attempted by a single cylinder engine in order to obtain a good engine performance and clean exhaust emission for next generation of heavy-duty diesel engine. The experiment has been done under the conditions of intake air quantity up to 5 times of naturally aspirated (NA) engine and 200 MPa injection pressure. The adopted pressure booster is external supercharger, which can control intake air pressure and temperature independently and also this experimental facility is possible to make high EGR rate in wide speed and high load range respectively. This experimental engine has been designed for enduring the high maximum cylinder pressure such as 30MPa so as to increase much intake air in cylinder for clean exhaust emissions and good thermal efficiency and other technologies have been adopted, such as the monotherm piston and also every engine part has been changed for high cylinder pressure. As the boost pressure increases, lean diesel combustion realizes and the rate of heat release is resemble to the injection rate and becomes sharper and combustion improves and also the brake thermal efficiency becomes better. As the rate of EGR increases in keeping the high boost pressure, the NOx emission becomes low without the increase of CO, THC and smoke and there is slightly penalty of thermal efficiency. PM does not increase by EGR rate 30% in this experimental condition.
Keywords: Diesel, High boost, Cooled EGR, Common rail, NOx, PM