The typical internal combustion engine wastes about 30 percent of its chemical energy in the form of hot exhaust gases. To improve fuel efficiency, the Vehicle Technologies Office (VTO) supports research on turbochargers and thermoelectric devices that can convert some of this lost energy to usable work or electricity. In addition to wasted energy, combustion also produces a variety of pollutants, including NOx, carbon monoxide (CO), unburned hydrocarbons (HC), and particulate matter (PM).
In today's combustion engines, catalytic reactions or filtration systems in the exhaust pipe control these emissions. Currently, these systems rely on heat to drive the catalytic reactions and regenerate (clean) particulate filters. However, as engines become more efficient, they can derive more work from the exhaust gases and there is less heat available to power the catalytic exhaust after-treatment system. Unless researchers design better low temperature exhaust catalyst materials, increased engine efficiency could actually reduce the effectiveness of emissions control systems.
To both improve efficiency and reduce emissions, VTO supports research to develop materials that improve the performance of turbochargers and thermoelectric devices as well as reduce the fuel economy penalties associated with many emission control technologies. These technologies include diesel particulate filters, catalysts, filter substrates, and exhaust-gas recirculation coolers.
For example, VTO works jointly with Oak Ridge National Laboratory (ORNL) and Honeywell in efforts to develop new materials that allow turbochargers to operate at higher temperatures with better efficiency. These materials should lead to engines with better fuel economy and increased power density. VTO-supported past research on ceramic substrates (surfaces) improved researchers' understanding of these materials and the measurement techniques for these devices, resulting in improved lifecycle modeling that enabled scientists to develop diesel particulate filter regeneration strategies that reduce fuel consumption.