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.
This has prompted Alan Hansen, professor of agricultural and biological engineering at the University of Illinois, and his colleagues 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 such as soybean oil, is typically blended in the US at two to five per cent with regular diesel fuel.
‘In some cases, engine manufacturers will support warranties on engines using higher percentages of biodiesel − up to 20 per cent. 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,’ said Hansen.
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 sulphur or sulphur-based compounds,’ he said. ‘One could then create a system to warn the operator or shut down the engine when the fuel has a high sulphur content.’
Sulphur is an important contaminant to monitor in diesel fuel, as it can contribute to the release of harmful exhaust emissions. Sulphur damages the catalysts in filters that are part of the engine’s after-treatment system. Such filters are needed to comply with the (US) Environmental Protection Agency’s (EPA) regulations on emissions levels.
‘To stay within the EPA’s emissions limits, it is no longer possible to simply optimise 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 sulphur is involved in the combustion process it creates sulphuric acid, 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,’ said Hansen. ‘If we can improve these sensors to successfully detect sulphur and monitor other diesel-fuel quality concerns, it will be an important breakthrough.’