Optimization of exhaust pipe injection conditions for diesel oxidation

In a Diesel Oxidation Catalyst (DOC) and Catalyzed Soot Filter (CSF) system, the DOC is used to oxidize additional fuel injected into the cylinder and/or exhaust pipe in order to increase the CSF's inlet temperature during soot regeneration. The catalyst's hydrocarbon (HC) oxidation performance is known to be strongly affected by the HC species present and the catalyst design. However, the engine operating conditions and additive fuel supply parameters also affect the oxidation performance of DOCs, but the effects of these variables have been insufficiently examined. Therefore, in this study, the oxidation performance of a DOC was examined in experiments in which both exhaust gas recirculation (EGR) levels and exhaust pipe injection parameters were varied. The results were then analyzed and optimal conditions were identified using modeFRONTIER. In addition, the HC species supplied by exhaust pipe injection were investigated using gas chromatography-mass spectrometry (GC-MS) and two gas analyzers. The results show that increasing the level of EGR and platinum group metals (PGM) loading, and decreasing the assist air pressure, can increase the uniformity of the DOC outlet gas temperature, while keeping it sufficiently high. In addition, various HC species - including C8-C21 alkanes, benzene-derived methyl and/or ethyl radicals, and acetaldehyde (CH ₃CHO) - were detected in the exhaust pipe injections.