Within the Cluster of Excellence “Tailor-Made Fuels from Biomass” at RWTH Aachen University, the Institute for Combustion Engines carried out an investigation program to explore the potential of future biofuel components in Diesel blends. In this paper, thermodynamic single cylinder engine results of today's and future biofuel components are presented with respect to their engine-out emissions and engine efficiency.
The investigations were divided into two phases: In the first phase, investigations were performed with rapeseed oil methyl ester (B100) and an Ethanol-Gasoline blend (E85). In order to analyze the impact of different fuel blends, mixtures with 10 vol-% of B100 or E85 and 90 vol-% of standardized EN590 Diesel were investigated. Due to the low cetane number of E85, it cannot be used purely in a Diesel engine.
To reduce the amount of energy needed for the biofuel production process, future fuels derived from biomass will have a molecular structure which is likely to be similar to the respective bio-feedstock. Thus, a blend with Ethyl levulinate is compared to today's biofuel components, additionally. Ethyl levulinate can easily be gained from levulinic acid which is produced by acid hydrolysis of cellulose.
Previous investigations identified desirable fuel properties like a reduced cetane number, an increased amount of oxygen content and a low boiling temperature for compression ignition combustion processes. Therefore in the second phase, investigations with 30 vol-% E85 and 70 vol-% Diesel are compared to 1-decanol. Both fuels have the same oxygen content but differ in cetane number and boiling characteristics.
Soot emissions can be significantly reduced up to 40 % while maintaining a constant efficiency even when using only 10 vol-% of the biofuel component. Furthermore, the experimental results indicate an additional potential for higher fractions of the biofuel component in the blend. Overall, the low particulate matter emissions provide justification for the consideration of the tested biofuel components for their use in future diesel engines.