Environmental pollution caused by the exhaust emissions from conventional vehicles, such as photochemical smog, dust, greenhouse gases and so on, has been received great concern from all over the world. Although there are many ways to control vehicle exhaust emissions within the specified range, including electric vehicles (EVs), exhaust after-treatment devices such as diesel particulate filter (DPF), diesel oxidation catalyst (DOC), lean NOx trap (LNT), selective catalytic reduction (SCR), and gasoline particulate filter (GPF), but the EVs cannot currently completely replace conventional vehicles due to battery technology and charging technology limitations; the exhaust after-treatment devices such as DPF also need to consider regeneration, cleaning and other problems. They are not the best way. Therefore, it has a great significance to find a new fuel to replace fossil fuel, which can not only improve the energy crisis, but also improve environmental pollution.
Oxygenated fuels such as biodiesel and bioethanol have attracted a lot of attention from many researchers due to their green, non-toxic, renewable and other advantages. In particular, biodiesel has similar physicochemical properties as diesel, and can be mixed with diesel in any proportion to be used directly or indirectly on diesel engines without any modification. In addition, the high oxygen content and cetane number of biodiesel have great advantages in improving the combustion and emissions of diesel engines; and the high oxygen content and latent heat of bioethanol can play a positive role in improving combustion and emissions.
In this study, the combustion, engine performance and emission characteristics were investigated in a common rail direct injection (CRDI) diesel engine fueled with four blend fuels, including 50% diesel blended with 50% palm biodiesel by volume (B50), B50 blended with 5% ethanol (B50E5), B50 blended with 10% ethanol (B50E10) and B50 blended with 15% ethanol (B50E15). The engine speed, engine load and fuel injection pressure was fixed 750 rpm, 30 Nm and 600 bar, respectively. The engine performance, combustion and emission characteristics have been comprehensively compared and investigated according to various main and pilot injection timings.