DAF Euro-4 Heavy Duty Diesel Engine with TNO EGR system and CRT Particulates Filter 2001-01-1947
This paper reports on a study of the TNO venturi EGR system and the Johnson Matthey CRT particulates trap on a DAF 355 kW engine. The results obtained indicate that this EGR-CRT combination is an effective means to achieve EURO-4 emission level, while maintaining good fuel economy.
EGR strategy, injection timing and air-fuel ratio were optimised in such a way that good regeneration conditions were obtained across most of the engine operating map. Also transient EGR control is optimised to combine low NOx emission during the ETC with good driveability and good engine out particulates emission.
The size of the oxidation catalyst in the CRT was investigated. It appeared that the larger oxidation catalyst showed a better regeneration performance during a low temperature duty-cycle. Negative aspects of a larger oxidation catalyst are increased costs and increased NO2 emission (because of the catalyst ability to oxidise more NO into NO2).
In order to secure regeneration under all circumstances it was found necessary to develop an active regeneration control strategy. This strategy will temporarily increase exhaust temperature and NOx-PM ratio when a high back pressure is detected.
The EGR-CRT system is installed in a truck to investigate its performance and durability in practise.