ADVANCED LIGHT FRACTION FUEL FORMULATION AS A DROP-IN REPLACEMENT FOR DIESEL IN PRE-DPF EURO II TYPE ENGINES

摘要

The use of light fraction or gasoline-range fuels in compression ignition engines has shown the potential to simultaneously decrease criteria pollutants and global carbon emissions. The current study examines the possibility of blending such fuels into commercial diesel asa drop-in replacement in compression ignition engines as a means of improving particulate emissions on pre-DPF equipped vehicles. Three fuel formulations were created with the first aimed at minimizing the content of polyaromatic hydrocarbons while maximizing the H/C ratio and Lower Heating Value (LHV) in an effort tolower particulate and CO_2 emissions. The second variant targeted a minimum viscosity of 1 cSt as a means to address possible fuel viscosity related durability concerns for the fuel injection system. Finally, the third variant was a 50-50 vol% blend of the first and second fuels. A similar cetane number as that found in market available European diesel fuel was targeted for all three fuels. Once the fuels had been prepared, they were tested in a Euro V Volvo MD11 engine recalibrated to reproduce the same NOx-PM trade-off of its Euro II variant. The engine was recalibrated in order to understand the impact of the new fuel formulations on particulate emissions from legacy engines. Euro II homologated engines are present primarily in emerging economies and a drop-in fuel capable of lowering particulate emissions has the potential to improve air quality in these countries without changing the engine calibration. For this reason, the reference diesel fuel was chosen to be representative of the Indian market. The study showed that running these fuels without changing the engine calibration resulted in a decrease in NO_x and an increase in PM with no significant variation in engine efficiency. This was due to a change in fuel injection timing that appeared to be caused by the different physical properties of the fuels and their related impact on the hydraulic behavior of the unit injector fuel injection system. When the calibration was adjusted to advance injection timing to compensate for the hydraulic behavior, the three fuels showed much lower PM emissions and CO_2 with similar NO_x emissions.