Effects of PuriNOx™ Water-Diesel Fuel Emulsions on Emissions and Fuel Economy in a Heavy-Duty Diesel Engine

The engine-out emissions and fuel consumption rates for a modern, heavy-duty diesel engine were compared when fueling with a conventional diesel fuel and three water-blend-fuel emulsions. Four different fuels were studied: (1) a conventional diesel fuel, (2) PuriNOx,™ a water-fuel emulsion using the same conventional diesel fuel, but having 20% water by mass, and (3,4) two other formulations of the PuriNOx™ fuel that contained proprietary chemical additives intended to improve combustion efficiency and emissions characteristics. The emissions data were acquired with three different injection-timing strategies using the AVL 8-Mode steady-state test method in a Caterpillar 3176 engine, which had a calibration that met the 1998 nitrogen oxides (NO_X) emissions standard. The weighted NO_X and particulate matter (PM) emissions for the PuriNOx™ fuel were reduced from those for the conventional diesel fuel by 19% and 16%, respectively, while the brake specific energy consumption was reduced by 0.7%. Insight into the spray formation and combustion characteristics of water emulsions was gained through analysis of heat-release rate data, and through laser-based optical/imaging experiments performed in a companion study, using a second, single cylinder, optically-accessible diesel engine. Based on this insight, several in-cylinder mechanisms are proposed which may be responsible for the observed changes in exhaust emissions and fuel consumption observed with these water-blend-fuels.