Sensors currently used to monitor the quality of diesel fuel and biodiesel blended fuels during engine operation are unable to adequately detect certain important fuel quality concerns. Alan Hansen, professor of agricultural and biological engineering at the University of Illinois, and his colleagues are working to develop new technologies to improve these commercially-available sensors.
"Our research is contributing to the development of a sensor that, when placed in the fuel line prior to where the fuel enters a diesel engine, can detect if there are any contaminants in or other problems with the fuel," Hansen said. "Also, if biodiesel is used, the sensor would determine the quality and quantity of biodiesel entering the engine."
Biodiesel, a renewable fuel derived from natural oils like soybean oil, is typically blended at 2 to 5 percent with regular diesel fuel.
"In some cases, engine manufacturers will support warranties on engines using higher percentages of biodiesel—up to 20 percent. However, they are reluctant to support engines running too much biodiesel because there is some concern that it would affect the engine in a negative way," Hansen said.
Hansen is investigating the use of electrochemical sensors to detect contaminants and other quality issues that today's sensors are missing. By using electrochemical processes, the sensors are expected to be significantly more sensitive to the chemical composition of diesel fuel.
"Electrochemical sensors can be designed to detect specific chemicals, such as sulfur or sulfur-based compounds," he said. "One could then create a system to warn the operator or shut down the engine when the fuel has high sulfur content."
Sulfur is an important contaminant to monitor in diesel fuel, as it can contribute to the release of harmful exhaust emissions. Sulfur damages the catalysts in filters that are part of the engine's after-treatment system. Such filters are needed to comply with the Environmental Protection Agency's (EPA) strict regulations on emissions levels.
"To stay within the EPA's emissions limits, it is no longer possible to simply optimize the combustion process. We now have to capture some of the emissions after the engine, using filters or other methods," Hansen said.
Hansen also noted that when sulfur is involved in the combustion process, it creates sulfuric acid, which is a very corrosive by-product that can damage the engine.
"We've run tests to evaluate how well current sensors work with a range of different fuels, including biodiesel blends. The tests have shown us the limitations of the sensors," Hansen said. "If we can improve these sensors to successfully detect sulfur and monitor other diesel fuel quality concerns, it will be an important breakthrough."
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