Study on the Effects on Diesel LTC Combustion of 2-EHN as Cetane Improver

A single cylinder Diesel engine was used to study LTC combustion. We evaluated the 2-EthylHexyl Nitrate (2-EHN) as cetane number improver (CNI) distributed by VeryOne@ on the combustion of six diesel fuels. Tested fuels are a low Cetane Number (CN) diesel fuel (CN of 43.7) and two biodiesel mixed at 20% with the low Cetane number diesel fuel: Soybean oil Methyl Ester (B100 SME) and Rapeseed oil Methyl Ester (B100 RME). Each fuels doped with the 2-EHN were prepared to meet the minimum European CN, 51. LTC strategies could provide low NOx emission without thermal efficiency deterioration. The study investigated engine operation at loads of 2, 6 and 10 bar IMEP at engine speed of 1250 rpm, 1500 rpm and 2000 rpm and the impact against synthetic EGR up to 30%. The low-temperature decomposition of 2-EHN, resulting in the oxidation of the fuel, makes it possible to achieve a very low cycle-to-cycle variation of the IMEP even at very low load or at a very high rate of EGR. From kinetic mechanism analysis, we had shown that the 2-EHN decomposition appeared rapidly when the in-cylinder temperature is greater than 700K. Since NO₂ and heptyl radicals are created from the 2-EHN decomposition, NOx emission was carefully studied at the exhaust of the engine. The result indicated that the Cetane improver did not increase the NOx emission when the combustion phasing was keeping constant. Moreover, the 2-EHN Cetane improver from VeryOne can extend the dilution rate and especially the EGR rate to reach low NOx emission without a deterioration of the combustion.