Soot particles emitted from gas turbines, diesel engines, furnaces, and other combustion devices can impact human health adversely and contribute to global warming. Because the rate of soot formation in a combustor depends strongly on the structure of the hydrocarbons in the fuel, there is an opportunity to reduce soot emissions by reformulating fuel composition or by using fuel additives. It also means that soot emissions will be affected by any changes from petroleum-based fuels towards alternative fuels, whether based on biomass, coal or other resources.
The objective of this project is to systematically study the dependence of soot formation rates and mechanisms on fuel structure. Structure/reactivity relationships will be developed using both experimental data and fundamental theoretical tools. The results will allow engineers and policymakers to assess the impacts of fuel structure on soot formation rates quantitatively. Mechanistic understanding will also be used to improve computer models and predict soot emissions from practical combustors like car and truck engines.
Hydrocarbons to be tested will be added to methane and burned with air in a laboratory burner. The resulting changes in concentrations of soot and hydrocarbons involved in soot formation will then be measured. The test compounds will be added in small enough amounts that the flame structure will be left unaffected, so any changes in soot and its precursors can be attributed to the direct chemical effect of the additive. A large range of additives will be tested, encompassing the full variety of hydrocarbons found in conventional and alternative fuels.
PI: Lisa Pfefferle Soot particulates produced in combustion devices such as engines and furnaces harm human health and contribute to global warming; the objective of this project was to obtain fundamental knowledge that can be used to reduce their emissions. Soot formation is a complex process that involves a large number of chemical reactions whose identity depends strongly on the composition of the fuel. During the course of this project we made measurements in laboratory-scale flames fueled with various over 200 individual components of fuels such as gasoline, Diesel, and kerosene. These measurements included concentrations of many of the molecular species important in soot formation. From the results we were able to identify the most significant reaction pathways and how their relative importance varies with fuel composition. This knowledge is being used to formulate computer models that can be used to optimize the design of devices to minimize their production of soot without the construction of expensive prototypes. The species measurements are also being used to validate existing chemical mechanisms for soot formation. In an effort to promote science and technology education we have included a large number of people in this project, including high school students and undergraduates. Most of these were female and several were members of underrepresented groups.
