Advanced Fuel Formulation Approach using Blends of Paraffinic and Oxygenated Biofuels: Analysis of Emission Reduction Potential in a High Efficiency Diesel Combustion System

摘要

This work is a continuation of earlier results presented by the authors. In the current investigations the biofuels hydrogenated vegetable oil (HVO) and 1-octanol are investigated as pure components and compared to EN 590 Diesel. In a final step both biofuels are blended together in an appropriate ratio to tailor the fuels properties in order to obtain an optimal fuel for a clean combustion. The results of pure HVO indicate a significant reduction in CO-, HC- and combustion noise emissions at constant NO_X levels. With regard to soot emissions, at higher part loads, the aromatic free, paraffinic composition of HVO showed a significant reduction compared to EN 590 petroleum Diesel fuel. But at lower loads the high cetane number leads to shorter ignition delays and therefore, ignition under richer conditions. These circumstances cause slightly increased soot emissions due to the current engine calibration and could easily be compensated by an optimized engine calibration.1-octanol was identified by the cluster of excellence “Tailor-Made Fuels from Biomass (TMFB)” as a promising alternative biofuel which is virtually showing no soot emission. At low loads the HC- and CO emissions are lower compared to Diesel as well but at higher loads the CO emissions surpass the ones of Diesel fuel. However, due to the relatively low cetane number of 1-octanol, the sound emissions are the highest of the investigated fuels. By blending of HVO and 1-octanol the beneficial features of both fuels could be combined, while their individual drawbacks could be reduced. With the addition of 1-octanol, the higher soot emissions of HVO at low loads without an optimized calibration were reduced by more than 50 %. The soot emissions decreased due to the oxygen content of 1-octanol and the lower cetane number of the blend compared to neat HVO. In addition, much lower HC- and CO emissions were achieved, which are nearly half of petroleum based Diesel fuel. Also, the advantages of HVO in terms of combustion noise emissions are still maintained in the range of 3 dB less than baseline Diesel operation at lower part loads. The blending of a novel biofuel candidate (1-octanol) with an advanced commercially available biofuel (HVO) is a potential key step towards a soot- and NOx-free Diesel combustion.