This work investigated the effects of exhaust back pressure (EBP) on engine combustion and emissions under conventional and low temperature diesel combustion (LTC) modes on a naturally aspirated single cylinder diesel engine. For conventional diesel combustion, the EBP showed a small but noticeable effect on the combustion and emissions. When the engine was running in LTC mode, higher EBP increased the residual gas fraction (RGF), leading to a higher 'effective' EGR rate and trapped charge temperature. Increased EBP did not significantly influence the initial, 'cool flame' reactions. However, at intermediate loads it retarded the main combustion phasing and increased the combustion duration. This is believed to be a result of the higher 'effective' EGR rate, and led to lower NO_x and smoke emissions. At low load, the higher charge temperature advanced the combustion and reduced the unburned hydrocarbon (uHC) emissions.
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