Abstract
Abstract
The question is discussed as to how a modern diesel engine equipped with a common-rail injection system can be optimised in order to comply with the future requirements regarding the emission legislation in Europe and the USA. An attempt is made to answer the question of which combustion process should be chosen, and whether exhaust-gas after-treatment is needed.
All previous results show that, in future, particulate filters will generally have to be used and that in case that the NOx reduction through after-treatment is required, it will be necessary to choose the SCR concept. For EU5, a cost-benefit analysis of individual measures is presented for three passenger-car weight-classes. There will also be a short exploration of the future diesel fuels and the permissible mixing proportion of biogenetic and synthetic diesel fuels.
Only a combined optimisation of dosing for air path (composition and motion of the cylinder charge) and fuel path, through optimised engine-emission management using map-controlled injection patterns and closed-loop control circuits for the rail pressure, boost pressure and EGR will enable us to make the diesel engine fit for the future.
With the introduction of common rail technology, the diesel engine has undergone a considerable change from the original economical work-horse to the hightorque, fun-to-drive and accommodating power-unit of today. Due to the excellent torque behaviour, in comparison with gasoline engines, many vehicle users have in the meantime come to favour the diesel engine in preference to a gasoline engine of equal power. At the same time, modern common-rail diesel engines have virtually cast off their traditional acoustic disadvantages without giving up their attractive fuel consumption advantages.
Recently, however, they are again facing strong criticism due to particulate emission, an argument which is being provoked by the discussion on the subject of fine particulate. Therefore, for the introduction of EU5, which is still not fixed, there is discussion about a limit value for the PM, which presupposes the use of a filter. In the meantime, a limit value of 200 mg/km NOx has emerged for the nitrogen oxide reduction.