Effect of 2-Ethylhexyl Nitrate Cetane Improver on NO_x Emissions from Premixed Low-Temperature Diesel Combustion

摘要

Production implementation of premixed low-temperature diesel combustion (LTC) is highly attractive because it can lead to low engine-out paniculate matter (PM) and NO_x emissions. It is important for LTC strategies to yield acceptable emissions while consuming commercially available fuel, whose properties vary substantially and which contains various additives. The chemical reactions of 2-ethylhexyl nitrate (2-EHN), an additive used to increase the cetane number of a diesel fuel, show potential to increase the NO, emissions of a diesel engine. While 2-EHN has been widely shown to not affect the emissions of conventional diesel combustion, few results are available for LTC, which features different combustion characteristics and significantly lower NO_x emissions. This paper demonstrates the effect of using a fuel doped with 2-EHN cetane improver in a direct-injection, diesel-fueled LTC operating mode. Testing was conducted at a light-load condition on a modern single-cylinder engine, fueled with two sets of test fuels at matching cetane numbers (47 and 53), with some test fuels using 2-EHN cetane improver. The addition of 2-EHN to the fuel increases the engine-out NO, for the tested LTC operating condition. Decomposition of the nitrate cetane improver forms NO and NO_2 in significant quantities relative to the low engine-out NO_x emissions from LTC.