Effects of Fuel Properties on Exhaust Emissions from the Latest Light-Duty DI Diesel Engine 2003-01-1882

The great reduction in future diesel engine emission limits, especially PM and NO_x, forces one to develop means to comply with stringent legislation. Environmentally friendly fuels are regarded as a very effective means to decrease emissions. Although the emission reduction is less than could be achieved by the most modern engine technology or alternative fuels, the immediate net effect of reformulated diesel fuel on emissions is significant, as it takes place over the whole vehicle population.

The experimental results presented in this paper were obtained within a research program investigating the effect of different fuels upon emissions from compression-ignition automotive engines. The research were carried out in the laboratories of the BOSMAL Automotive R & D Centre in co-operation to Institute of Internal Combustion Engines at Poznan University of Technology. The partial results of this research program were presented in SAE Paper 2002-01-2219. This paper presents the final results of this research program.

The effect of diesel fuel properties and composition on regulated emissions was investigated in a DI Common Rail, turbocharged passenger car, equipped with an oxidation catalyst and electronically controlled exhaust gas recirculation, representing the latest technology in production at the start of the research programme. Attention was focused primarily on the fuel properties such as: sulphur content and cetane number. To evaluate the influence of fuel properties on emissions, eight different test fuels were prepared: four fuels with the sulphur content varying from less than 5 ppm up to 2000 ppm and four fuels with the cetane number varying from 45 up to 63. The new vehicle homologation procedure introduced in the Directive 98/69/EC, so-called new European driving cycle (NEDC) was selected as a representative test for this study.

Experimental results indicated that fuel sulphur levels have a significant impact on all regulated emissions, especially on PM. From two parts of the NEDC test the second part - the EUDC test - was more sensitive for the diesel fuel sulphur content.

Testing fuels of different ignition qualities showed that HC and CO emissions of high cetane number fuels were significantly lower than emissions of a low cetane number fuel. We observed also a little decrease in NO_x emissions with an increase in cetane number. The effect of cetane number on particulate emissions was more complex, the highest emission was obtained for medium-cetane number fuel.