A Comparison of Emissions from Clean Diesel Fuels

Exhaust emissions from various kinds of clean diesel fuels were evaluated using a commercial DI diesel engine in comparison with the emissions from a commercial diesel fuel containing 0.05% sulfur. The blending of a light paraffinic fuel to a commercial diesel fuel reduces HC, CO, PM and NOx emissions and a light fuel with aromatics or kerosene reduces PM and NOx but not HC and CO. The PM and NOx emissions from the paraffinic fuel are lower than these from the kerosene, and these emissions are decreased with an increase in the blending ratio of both light fuels to a commercial diesel fuel. Reformulated diesel fuels such as a clean city diesel fuel and fuels with few aromatics reduce PM and NOx emissions more than commercial diesel fuel, and the reduction rate is highly dependent on aromatic content. The effects on emissions of blending soybean methyl ester or tripropylene glycol methyl ether to a commercial diesel fuel were evaluated. The results showed that the PM reduction rate increases with an increase in the oxygenate content in the sample, and the PM emission from a mixture of 25% glycol and 75% commercial diesel fuel is almost equal to that from a light paraffinic fuel. The analysis of PM composition showed that a reduction in aromatics reduces the SOF caused by the reduction of the unburned fuel portion in the SOF, but not soot. On the other hand, the glycol reduces both the SOF and soot. The PM reduction rate highly depended on aromatic and oxygen content in the sample, and the NOx on aromatic content, according to statistical analysis using all test samples.