WEST LAFAYETTE, IN --- Researchers from Purdue University and Cummins Inc. said they have developed an advanced "closed-loop control" approach for preventing diesel engines from emitting greater amounts of smog-causing nitrogen oxides when running on biodiesel fuels.
Operating truck engines on a blend of biodiesel and ordinary diesel fuel dramatically reduces the emission of particulate matter, or soot. However, the most modern and efficient diesel engines burning biodiesel emit up to 40 percent more nitrogen oxides at some operating conditions, and fuel economy declines by as much as 20 percent.
Unlike conventional diesel, biodiesel contains oxygen, and the researchers have shown that this presence of oxygen is responsible for the majority of the higher emission of nitrogen oxides, said Gregory Shaver, an assistant professor of mechanical engineering and a member of Purdue's Energy Center in Discovery Park.
Another key factor is a recent innovation called exhaust gas recirculation, which reroutes exhaust back into the engine cylinders to reduce emissions. The researchers said they found that nitrogen oxide emissions rise by a higher percentage in engines equipped with this exhaust-recirculation technology compared with older engines that do not. However, the newer engines still emit less nitrogen oxides than the older engines.