High cetane number paraffinic diesel fuels and emission reduction in engine combustion

The objective of this study is to discuss and demonstrate the emission reduction potential of high cetane number paraffinic diesel fuels in engine operation. The idea behind the study is to utilize the physical and chemical renewable fuel properties, that are different from those of the traditional crude oil based fuels. The ultimate goal is then to develop optimum combustion technologies for these new fuels and make a remarkable emission reduction in engine combustion. These new fuels do not suffer from storage and low temperature problems, as the Fatty Acid Methyl Ester (FAME) fuels, often called "biodiesel", often do. The very high cetane number, the absence of Polyaromatic Hydrocarbons (PAH) and the absence of Sulphur allow far more advanced combustion strategies than have been possible with current fossil fuels. Due to these advantageous properties, these new combustion technologies allow us to reduce significantly Nitrogen Oxide (NOx) emission without suffering from traditional trade-off between Particulate Matter (PM) and NOx. The paper will first tell about previous studies in Helsinki University of Technology TKK and emission reduction in a standard heavy duty diesel engine. Then the studies in a corresponding single-cylinder research engine "EVE" will be presented. In the single-cylinder EVE engine advanced cycles like Miller cycle and interrnal exhaust gas recirculation (EGR) have been studied. Also the possible benefits of blending oxygenates with the fuels have been considered. The first part of the paper concentrates on high cetane number paraffinic diesel fuels and their oxygenate blends: previous studies on their properties and effect on engine emissions. The second part describes the ongoing research in Aalto University School of Science and Technology (previously TKK, Helsinki University of Technology). In the studies, potential for emission reduction has been estimated to be 70% or more and promising preliminary results have been reached in the first test runs. This study is part of "ReFuel" -project, which is an IEA collaborative task of IEA Combustion Agreement program and a collaboration framework between IEA Combustion Agreement and IEA AMF (Advance Motor Fuels) Agreement.