Combustion Technologies to meet Euro 6 Emissions Standards on a Diesel D-segment Passenger Car

摘要

An experimental investigation has been carried out on a 2.0 liter Common Rail Diesel engine to verify the feasibility of Euro 6 emission standards, in a typical European D Segment vehicle application, through the introduction of cost effective advanced combustion technologies. A significant contribution to engine out NO{sub}x reduction is obtained through further exploitation of the Multiple Injection potentials of the Common Rail System, allowed by a new solenoid injector with Digital Injection Rate Shaping capability (Multijet II CRS). A Low Pressure and Clean EGR, drawn after the DPF and added to a conventional High Pressure EGR, allows to reduce the inlet charge temperature and therefore to increase the EGR mass rate at the same air-to-fuel ratio, avoiding fouling problems with heavy EGR rates. Part of the NO{sub}x emissions in NEDC cycle is due to a slow EGR actuation in transient operation, typical of external EGR systems. This problem can be overcome if the HP EGR system is replaced by the MULTIAIR Variable Valve Actuation technology, with a fast and precise internal EGR control. Further technologies that contribute to an increase of the EGR rate and therefore to engine out NO{sub}x reduction are the enhancement of Premixed Combustion at low load operation, that needs a closed loop combustion control with Cylinder Pressure Sensors, to manage combustion instability associated with high ignition delay, and the charging technologies that allow to increase the air boost at part load, such as the Two Stage Turbo. Through a proper selection and packaging of the described technologies it is possible to achieve the Euro 6 emission standards on a 2.0 litre engine installed on a D Segment vehicle, without penalties of fuel consumption/CO{sub}2 emissions and without increase of Soot emissions and Combustion Noise. An improved DOC is however needed to convert the higher CO/HC engine out emissions with high EGR rates.