Impact of different configurations of a Diesel oxidation catalyst on the CO and HC tail-pipe emissions of a Euro4 passenger car

Different configurations were used to study the impact of a Diesel oxidation catalyst position on the HC and CO oxidation efficiency of a Euro4 Diesel passenger car. An oxidation catalyst of 0.8 L downstream EGR port is the original configuration. Another two configurations are studied in this work: the same catalytic volume put upstream EGR port and four small close-coupled catalysts of 0.06 L each put in the exhaust manifold very close to the engine exhaust valve. The results show that the configuration upstream EGR port leads to a significant increase on HC conversion efficiency; however, CO tail-pipe emissions remain practically unchanged. The four small close-coupled catalysts put in the exhaust manifold, despite the higher exhaust temperature, show lower oxidation efficiency due to the high space velocity, however, they can be used in the case of little available space for a bigger catalyst. In all configurations studied, there is a significant difference on CO and HC conversion efficiency and thus on tail-pipe emissions in the case of aged oxidation catalysts compared to fresh ones.