Diesel engines are famously high-performance, reliable and economical. In recent years, they have also improved their image through advanced emissions control systems.
An unfortunate side effect of cleaning up diesel exhaust, however, can be a drop in engine efficiency, which translates into increased fuel consumption. Now, a partnership led by researchers at Michigan Technological University is addressing the problem.
The work is being funded by a three-year, $2.8 million grant from the US Department of Energy’s National Energy Technology Laboratory.
Additional support and in-kind goods, services and expertise for the three-year, $2.8 million project are being provided by Michigan Tech; diesel engine companies John Deere, Navistar and Cummins; the sensor manufacturer Watlow; and Johnson Matthey, a producer of diesel catalysts and pollution-control systems. Scientists at Oak Ridge and Pacific Northwest National Laboratories are also collaborating.
The research focuses on on-board diagnostics to monitor two emissions control systems, the diesel particulate filter, which traps particulate matter, and the selective catalytic reduction system, which controls NOx emissions.
Each has its own set of problems. Particulate filters fill up with particulate matter. “To clear that out, you inject diesel fuel,” says John Johnson, a presidential professor of mechanical engineering-engineering mechanics at Michigan Tech. “It ignites and burns out the particulate. The process can affect engine efficiency in two ways, by using excess fuel to clean the filter and, when the filter is clogged, by causing backpressure on the engine.”
Selective catalytic reduction systems use urea to chemically scrub NOx out of the diesel exhaust. Sometimes, however, the system gets overloaded with urea, which is not only wasteful but can also cause toxic emissions of ammonia gas, Johnson says.
The researchers will develop computer models and practical methods to improve the performance of both systems. One focus of their models will be on-board diagnostics, so the driver can tell quickly and easily when an emissions control system needs attention. “It sounds pretty straightforward, but it can be tricky when you are dealing with complicated emissions controls,” says Gordon Parker, professor of mechanical engineering-engineering mechanics.
Lastly, they will study the emissions control systems in engines fueled with a variety of biodiesel blends. “Biodiesel blends are becoming more common, and many engine manufacturers are certifying their engines for 20 percent biodiesel, just as some gasoline engines are certified for use with ethanol blends,” says Jeffrey Naber, associate professor of mechanical engineering-engineering mechanics. “However, the engine and emission systems can react very differently, even to fuels with a low percentage of biodiesel.”
With proper technology, biodiesel could provide even lower emissions than traditional fuel without increasing fuel consumption.
The benefits of the research are numerous, said Johnson. Manufacturers involved in emissions control will be able to apply it to the development of on-board diagnostics and to assess engine performance. Sensor suppliers can draw upon it to develop new technologies that reduce emissions. The results will also be useful in better understanding and reducing biodiesel emissions.
“Finally, the organizational structure, bringing together engine manufacturers and sensor and catalyst developers into a single, focused research program will foster a system-wide research focus with much broader impact than programs that focus only on the sensor or the catalyst or the engine,” Johnson said.
Johnson is he principal investigator on the project. Co-investigators in the mechanical engineering-engineering mechanics department are Parker, Naber and Professor Song-Lin Yang. Jason Keith, an associate professor of chemical engineering, is also a co-investigator.
For more information, visit http://research.me.mtu.edu/opus/news-view.php?id=50 .