Transient Emissions from No. 2 Diesel and Biodiesel Blends in a DDC Series 60 Engine

In this study the effect of blending biodiesel (methyl soyester) with conventional diesel on emissions has been investigated. A 1991 MC Series 60 engine was employed and emissions of NO_x, CO, THC, and PM were determined using the heavy-duty transient test. The fuels tested were a reference diesel, 20%, 35%, and 65% biodiesel blends in the reference diesel, as Well as 100% biodiesel. These tests show that as the percent biodiesel increased, the NO_x, emission increased, while THC, CO and PM decreased. For 35% biodiesel, the composite NO_x emission increased by nearly 1% while the composite particulate emission decreased by 26% relative to the reference diesel. The NO_x increase of 1% was found to be statistically significant at the 99% level. For 100% biodiesel, the composite NO_x increased by 11% while PM was decreased by 66%. CO was reduced by 47% and total hydrocarbon by 44%. For the 100% methyl soyester, the composite NO_x emission exceeded the 1991-1994 NO_x emission standard of 5 g/bhp-h. The composite PM emission for the 0.25 g/bhp-h engine met the 1994 standard of 0.1 g/bhp-h. Engine efficiency was found to be the same for biodiesel and biodiesel blends as for the reference fuel. Fuel consumption for biodiesel blends can therefore be calculated from diesel fuel economy data. A preliminary emissions model describing the effect of diesel properties and oxygen content (from blending biodiesel) on emissions is presented. This model suggests that relatively easily obtainable reductions in aromatic content or increases in cetane number could lead to NO_x, neutral diesel/biodiesel blends as compared to certification diesel fuel.