Effect of ethanol fuel additive on diesel emissions.

Engine-out emissions from a Volkswagen model TDI engine were measured for three different fuels: neat diesel fuel, a blend of diesel fuel and additives containing 10% ethanol, and a blend of diesel fuel and additives containing 15% ethanol. The test matrix covered five speeds from 1,320 to 3,000 rpm, five torques from 15 Nm to maximum plus the 900-rpm idle condition, and most of the points in the FTP-75 and US-06 vehicle tests. Emissions of particulate matter (PM), nitrogen oxides (NO{sub x}), unburned hydrocarbons (HCs), and carbon monoxide (CO) were measured at each point, as were fuel consumption, exhaust oxygen, and carbon dioxide output. PM emissions were reduced up to 75% when ethanol-diesel blends were used instead of neat diesel fuel. Significant reductions in PM emissions occurred over one-half to two-thirds of the test matrix. NO{sub x} emissions were reduced by up to 84%. Although the regions of reduced NO{sub x} emissions were much smaller than the regions of reduced PM emissions, there was considerable overlap between the two regions where PM emissions were reduced by up to 75% and NO{sub x} emissions were reduced by up to 84%. Such simultaneous reduction of both PM and NO{sub x} emissions would be difficult to achieve by any other means. HC and CO emissions were also reduced in the regions of reduced PM and NO{sub x} emissions that overlapped. Because the ethanol-diesel blends contain less energy on both a per-unit-mass basis and a per-unit-volume basis, there was a reduction in maximum torque of up to 10% and an increase in brake-specific fuel consumption of up to 7% when these blends were used.