Abstract
Keywords:diesel, exhaust emissions, diesel fuel, fuel additives, synthetic oxygenates
The experimental results presented in this paper were obtained within a research program investigating the effect of different synthetic oxygenates on emissions from diesel passenger cars. The objective of this study was to select the most promising oxygenate compounds as blending components in diesel fuel for further advanced testing and practical application. The results of the first part of the program were presented during the 31st FISITA World Automotive Congress in Yokohama in the year 2006 (paper F2006P048). In that part of the program, oxygenates from the glycol ethers chemical family were tested and obtained results were promising. In the second part of the program - described in present paper, oxygenates from another chemical families i.e. maleates and carbonates were tested.
The tests were conducted on a light-duty vehicle equipped with DI - Common Rail turbocharged engine, meeting the Euro IV emissions regulation and representing the latest technology in production at the start of the research program. The New European Driving Cycle (NEDC), with separate measurement of urban and extra-urban phase, was selected as a representative test for this study. The total PM, CO, HC, NOx and CO2 as well as fuel consumption were measured. Four different synthetic oxygenated additives - two maleates and two carbonates - were tested. Each of them was evaluated as a fuel additive at a concen-tration of 5% v/v in the same base diesel fuel. The base diesel fuel was a Euro V diesel fuel.
The studies have proven that oxygenated fuels containing maleates and carbonates significantly reduced the PM emissions in the NEDC cycle. The reduction in the PM emissions was from 14 to 32%, depending on the component - fuels containing carbonates were generally more effective. Such fuels, however, caused the growth of NOx emissions by 4 - 9% in the NEDC test, whereas the fuels containing maleates guaranteed the keeping of NOx emissions on the level obtained for fuelling with neat diesel fuel. The general observation may be that all the oxygenated fuels caused a significant improvement of the PM/NOx trade-off. The negative effect of using oxygenated fuels containing maleates and carbonates was the growth of CO and HC emissions. The glycol ethers tested earlier were more favorable in this respect. However, the glycol ethers were less effective in the reduction of PM emissions. The fuels containing maleates and carbonates were characterized with the same CO2 emissions level as in fuelling with neat diesel fuel.