Optimization of Diesel Combustion and Emissions with Tailor-Made Fuels from Biomass

In order to thoroughly investigate and improve the path from biofuel production to combustion, the Cluster of Excellence “Tailor-Made Fuels from Biomass” was installed at RWTH Aachen University in 2007. Since then, a variety of fuel candidates have been investigated. In particular, 2-methyl tetrahydrofurane (2-MTHF) has shown excellent performance w.r.t. the particulate (PM) / NOx trade-off [1]. Unfortunately, the long ignition delay results in increased HC-, CO- and noise emissions. To overcome this problem, the addition of di-n-butylether (DNBE, CN ∼ 100) to 2-MTHF was analyzed. By blending these two in different volumetric shares, the effects of the different mixture formation and combustion characteristics, especially on the HC-, CO- and noise emissions, have been carefully analyzed. In addition, the overall emission performance has been compared to EN590 diesel. The results show that an addition of DNBE to 2-MTHF can lead to a reduction of HC- and CO-emissions by 75% and noise emissions up to 4 dB. Simultaneously, none of the benefits gained with 2-MTHF with regard to the PM-emissions are not sacrificed. It could be proven, that by blending two molecules that are derived from biomass, a tailor-made fuel can be designed that allows optimizing the diesel combustion according to the desired criteria. In addition, both fuels were investigated in a High Pressure Chamber (HPC). Based on the results, new characteristic fuel numbers shall be developed in order to describe the combustion behaviour of the new fuels in a proper way, since the established ones are not sufficient to describe the combustion and emission performance of these fuels.