Partly homogeneous combustion (PHC) can assist the reduction of the engine-out emissions but its influence is limited by using conventional diesel fuel. To verify whether alternatively designed fuels can help to improve the PHC performance, the impact of different fuel properties in combination with engine control levers have been studied.
Based on single cylinder heavy duty direct injection diesel engine (DIDE) test results with different diesel and diesel-like fuels, operating under partly homogeneous combustion conditions, the impact of the combination of the fuel properties were investigated.
The fuel matrix was designed such that the fuel properties varied in sufficiently large ranges, in order to be able to detect the impact of the properties at the selected operating points. A statistical principal component analysis (PCA) has been applied to the fuel matrix to specify the interrelationship between the fuel properties, as well as to derive the most independent fuel properties. The analyses have been performed at some representative points of the engine map, with regard to the impact of the changes in fuel properties on the emission results. Additional to the DoE (Design of Experiment) results from the engine tests, combined DoE modeling was applied for the analysis, which included fuel properties as well as the engine control parameters. With this new approach, an optimization of engine performance could be done for independent fuel properties, in combination with engine control parameters.
Out of this study, the fuel properties with a high impact, as well as the optimum values of such fuel properties could be defined. The study also reveals the optimum combination of the most independent fuel properties under partly homogeneous operation. The combination of the slope, Cetane number, average carbon number and aromatic contents are found as the main impacted fuel properties on the engine NOx emission.