U.S. Department of Energy - Energy Efficiency and Renewable Energy
Vehicle Technologies Office
Fuel Effects on Advanced Combustion
More than 90 percent of transportation relies on petroleum-based fuels: gasoline and diesel. While alternative fuels and plug-in electric vehicles offer great promise to reduce America's petroleum consumption, petroleum-based fuels are likely to play a substantial role for years to come. However, the sources of these petroleum-based fuels are changing, with more fuels than ever from unconventional sources. Canada, which is the United States' largest supplier of crude oil, is currently getting 40 percent of its petroleum from oil sands. In addition, new advanced combustion engines are particularly sensitive to variations in fuel composition. The Vehicle Technologies Office supports research into fuels to enable more efficient engines and more effective emissions control systems that improve fuel economy and reduce emissions. Much of this research can also provide insight into how biofuels' unique properties can affect these engines and systems.
VTO's work was essential to enabling the low-emission diesel vehicles that are on the road today. To meet the U.S. Environmental Protection Agency's 2006 and 2007 emissions requirements, diesel vehicles had to adopt new emissions control devices, such as lean NOx catalysts. VTO sponsored a comprehensive review of how the available diesel blends, which had on average 350 parts per million of sulfur with a legal maximum of 500 parts per million, affected advanced emission control technologies. The research showed that even fuel far below the average levels of sulfur – any amount substantially above 15 parts per million – could negatively affect these emission control systems. From this research, it was clear that for vehicles to use these new systems, fuel manufacturers needed to significantly lower the amount of sulfur in diesel fuel. Based on these results, EPA passed standards limiting the amount of sulfur in diesel fuel to 15 parts per million. Now, all new diesel vehicles meet the EPA requirements, substantially reducing pollution and improving air quality.
Currently, VTO is supporting research to increase our understanding of how different fuel chemistries affect combustion, engine optimization, emissions, and emissions control systems, especially in advanced technology vehicles. This research includes:
- Designing a standard set of research gasoline and diesel fuels with consistent chemistry and properties. This set should improve the consistency of research on advanced combustion modes and engines and allow researchers to better compare results.
- Developing detailed chemical kinetic reaction models of these fuels, improving our understanding of their basic components
- Identifying fuel properties that can enable controllable extended lift-off combustion (a specific high-efficiency advanced internal combustion engine technology) that results in lower NOx emissions than current technologies
- Identifying the deactivation mechanisms of emission control devices that are preventing manufacturers from adopting efficient lean-burn engine technology (a specific high-efficiency advanced internal combustion engine technology)