The Texas Diesel Fuels Project, Part 2: Comparisons of Fuel Consumption and Emissions for a Fuel/Water Emulsion and Conventional Diesel Fuels

The Texas Department of Transportation began using an emulsified diesel fuel in 2002. They initiated a simultaneous study of the effectiveness of this fuel in comparison to 2D on-road diesel fuel and 2D off-road diesel. The study included comparisons of fuel economy and emissions for the emulsion, Lubrizol PuriNOx®, relative to conventional diesel fuels. Two engines and eight trucks, four single-axle dump trucks, and four tandem-axle dump trucks were tested. The equipment tested included both older mechanically-controlled diesels and newer electronically-controlled diesels. The two engines were tested over two different cycles that were developed specifically for this project. The dump trucks were tested using the route technique over one or the other of two chassis dynamometer cycles that were developed for this project In addition to fuel efficiency, emissions of NOx, PM, CO, and HCs were measured. Additionally, second-by-second results were obtained for NOx and HCs. Speciation of the HC emissions was performed for one of the off-road engines operating over two different cycles. On average, over all engines and cycles, PuriNOx provided a NOx benefit of about 16%, a fuel efficiency penalty of about 17%, and a PM benefit of about 20%. In general, the NOx benefit and the fuel efficiency penalty were less pronounced for the electronically-controlled diesels. One truck engine/cycle combination was found for which the effect on NOx was not statistically significant at the 95% confidence level. Similarly, two engine/cycle combinations were found for which the effect on PM was not statistically significant, and there was a statistically significant increase in PM for one dump truck. PuriNOx produced significant increases in the emissions of roughly half of the Toxic Air Contaminants evaluated: formaldehyde, acetaldehyde, acrolien, and MEK. PuriNOx did not yield decreased emissions of any TACs.

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