A numerical investigation into the anomalous slight NOx increase when burning biodiesel; A new (old) theory

FUEL 13

George Ban-Weiss, georgebw@me.berkeley.edu1, JY. Chen1, BB. Buchholz2, and Robert W. Dibble, rdibble@me.berkeley.edu3. (1) Combustion Analysis Laboratory, University of California, Berkeley, 50B Hesse Hall, Berkeley, CA 94720, (2) Lawrence Livermore National Laboratory, Center for Accelerator Mass Spectrometry, 7000 East Ave, Livermore, CA 94550, (3) Department of Mechanical Engineering, University of California, Berkeley, 6159 Etcheverry Hall, M/C 1740, Berkeley, CA 94720
Biodiesel is a notable alternative to diesel fuel because it comes from natural sources, it is essentially carbon dioxide neutral, and it lowers an engine's emission of most pollutants as compared to No. 2 diesel. However, the use of biodiesel often slightly increases a diesel engine's emission of nitrogen oxides (NOx). In this paper, previously proposed theories for this slight NOx increase are reviewed, including theories based on biodiesel's cetane number, which leads to differing amounts of charge preheating, and theories based on the fuel's bulk modulus, which affects injection timing. This paper proposes a new theory explaining this NOx increase; the increase in double bonds in biodiesel, compared to No. 2 diesel, increases its flame temperature, which in turn increases NOx. Numerical simulations found that NOx was predominantly due to the Zeldovich mechanism.
 

Biofuels for Transportation
8:55 AM-12:05 PM, Sunday, 26 March 2006 Georgia World Congress Center -- C204, Oral

Division of Fuel Chemistry

The 231st ACS National Meeting, Atlanta, GA, March 26-30, 2006