Biofuels are an important part of our country’s plan to develop diverse sources of clean and renewable energy. These alternative fuels can help increase our national fuel security through renewable fuel development, while simultaneously reducing emissions from the transportation sector. Biodiesel is a particularly promising biofuel due to its compatibility with the current fuel infrastructure, which is geared toward compression-ignition engines. Biodiesel is also easily produced from domestic renewable resources such as soy, rape-seed, algae, animal fats and waste oils.

Comprehensive computational fluid dynamics modeling of different fuels depends on the ability to predict nozzle flow, spray, combustion and emission characteristics. Because the physical and chemical properties of biodiesel are significantly different from those of traditional diesel fuel, Argonne researchers are developing new spray and combustion models to optimize the performance of biodiesel in engines.

Drop-In Biofuels of Interest

• Diesel #2 -- This biofuel’s properties are being tested at Argonne.
• Soy Methyl Ester (SME) -- This biofuel is prevalent in North America.
• Rapeseed Methyl Ester (RME) -- This biofuel is prevalent in North America.
• Cuphea Methyl Ester (CuME) -- This biofuel has been explored by the United States Department of Agriculture.
• Hydro-treated Vegetable Oil (HVO) -- This biofuel has been researched by the Helsinki University of Technology, Finland.
• Phytol -- This biofuel is being explored at Argonne as a diesel fuel blending agent.

Some properties of these fuels, such as density and distillation curves, are compared in Figure 1a and Figure 1b. Figure 2a and Figure 2b show fuel vapor distribution inside the injector orifice for drop-in biofuels of interest.

Difference in Properties of Drop-in Biofuels

Diesel and HVO fuels are observed to cavitate (formation of fuel vapor in low-pressure regions) extensively, with fuel vapor reaching the nozzle exit. Cuphea methyl ester also cavitates similar to the above fuels. On the other hand, for SME and RME, cavitation patterns do not reach the nozzle exit. The difference in cavitation characteristics of various drop-in fuels is attributed to differences in physical properties such as viscosity and vapor pressure. There are significant differences between fuels in terms of flow characteristics like mass flow rates, injection velocity, discharge coefficient, turbulence characteristics, and etc. These differences are accounted for at the nozzle orifice exit and form boundary conditions for spray and combustion simulations.

Funding

This work is supported by the U.S. Department of Energy’s Vehicle Technologies Program under Kevin Stork.

Publications

1. S. Som, D.E. Longman, ​“Nozzle flow characteristics of alternate fuels for compression ignition engine applications,” ICES2012-81078, ASME Internal Combustion Engine Division Spring Technical Conference, Torino, Italy, May 2012.
2. A.I. Ramirez, S. Som, L.A. LaRocco, T.P. Rutter, D.E. Longman, ​“Investigating the use of heavy alcohols as a fuel blending agent for compression ignition engine applications,” ICES2012-81169, ASME Internal Combustion Engine Division Spring Technical Conference, Torino, Italy, May 2012.
3. S. Som, D.E. Longman, A.I. Ramirez, S.K. Aggarwal, ​“A comparison of injector flow and spray characteristics of biodiesel with petrodiesel,” Fuel 89: 4014-4024, 2010.
4. S. Som, D.E. Longman, ​“Nozzle flow characterization of alternate fuels for compression ignition engine applications,” 2011 SAE World Congress (Presentation Only), Detroit, April 2011.