The influence of H2 and CO on diesel engine combustion characteristics, exhaust gas emissions, and after treatment selective catalytic NOx reduction

The requirement to significantly reduce NOx and particulate matter (PM) emissions while maintaining efficient combustion performance is one of the main drivers for internal combustion engine research. Modem diesel and premixed charge compression ignition (PCCI) engines have improved engine fuel economy and significantly reduced NOx and PM emissions achieved by advances in both combustion and exhaust aftertreatment technologies. To date, it has been shown that vehicle emissions can be further improved by several catalytic systems including fuel reformers (i.e. partial oxidation, autothermal, and exhaust gas reforming) and aftertreatment systems, such as the selective catalytic reduction (SCR) of NOx under oxygen-rich conditions. Among the most promising on-board reforming technologies is the exhaust-gas reforming, which allows the fuel/air feed to the engine to be enriched with reformate containing H-2 and CO. This method is a combination of reforming and exhaust-gas recirculation (EGR) and referred to as REGR. This paper reports on experimental results obtained when 1%Pt/Al2O3 low temperature hydrocarbon-SCR catalyst was used to treat exhaust gas from a diesel engine operating with addition of simulated REGR (two different compositions). It has been shown that while REGR can directly improve engine performance and emissions by promoting the PCCI combustion mode, it can also benefit the performance of the SCR catalysts due to the presence of unburnt H-2 in the exhaust gas. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.