Regulated and unregulated emissions from a diesel engine fueled with diesel fuel blended with diethyl adipate

Experiments were carried out on a four-cylinder direct-injection diesel engine operating on Euro V diesel fuel blended with diethyl adipate (DEA). The blended fuels contain 8.1%, 16.4%, 25% and 33.8% by volume fraction of DEA, corresponding to 3%, 6%, 9% and 12% by mass of oxygen in the blends. The engine performance and exhaust gas emissions of the different fuels were investigated at five engine loads at a steady speed of 1800 rev/min. The results indicated an increase of brake specific fuel consumption and brake thermal efficiency when the engine was fueled with the blended fuels. In comparison with diesel fuel, the blended fuels resulted in an increase in hydrocarbon (HC) and carbon monoxide (CO), but a decrease in particulate mass concentrations. The nitrogen oxides (NOx) emission experienced a slight variation among the test fuels. In regard to the unregulated gaseous emissions, formaldehyde and acetaldehyde increased, while 1,3-butadiene, ethene, ethyne, propylene and BTX (benzene, toluene and xylene) in general decreased. A diesel oxidation catalyst (DOC) was found to reduce significantly most of the investigated unregulated pollutants when the exhaust gas temperature was sufficiently high.

► DEA leads to a slight increase in the brake specific fuel consumption and in the brake thermal efficiency.
► DEA generates higher CO and HC emissions, while particulate emissions decrease evidently and NOx emissions experience fluctuation with increasing percentage of DEA in the blends.
► The formaldehyde and acetaldehyde increase, whereas ethene, ethyne, propylene, 1,3-butadiene and BTX in general decrease with an increase of DEA in the blends.
► DOC can effectively reduce most of the unregulated emissions.