Increasing exhaust temperature of an idling light-duty diesel engine through post-injection and intake throttling
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Modern Diesel engines rely heavily on aftertreatment systems for reducing tail pipe emissions. However, for operating conditions such as cold start, extended low load operations and idling aftertreatment systems cannot maintain a high enough temperature of approximately 200° C to maintain catalyst activity. In crowded urban areas actual driving conditions may significantly differ from FTP cycles due to operating under idle conditions for an extended period of time in congested traffic, long drive thru lines, traffic lights and so on. This study aimed to increase the exhaust temperature of a fully warmed-up idling light-duty Diesel engine by utilizing two methods: intake throttling and post-injection. Also, effects of these two techniques on HC and NOx emissions as well as IMEP and COV of IMEP were investigated. With start of injection (SOI) of post-injection being the primary variable, engine operating parameters were idle speed of 850, 1100 and 1200 rpm as well as injection pressure of 500 and 800 bar. The exhaust temperature was measured to be 105° C for an idle speed of 850 rpm and WOT with no post injection. I was able to increase the exhaust temperature by nearly 65° C with the first method. A further increase by 25° C vi with combined use of the two methods was possible and that yielded exhaust temperatures of around 200° C while HC and NO[subscript emissions roughly doubled. For higher engine speeds and for the heaviest throttling case exhaust temperature increased up to 240° C however, the engine-out HC emission penalty associated with this was nearly 300%. For all degrees of intake throttling, maximum exhaust temperature and minimum NO[subscript x]emissions were achieved for a SOI of post-injection at 25-30° CA aTDC and beyond this range the temperature showed a downward trend while HC emissions increased significantly.