Diesel engine performance and NOX emissions from oxygenated biofuels and blends with diesel fuel

Increased pressure from federal and state agencies to improve air quality has resulted in extensive research into the use of biofuels to reduce diesel engine emissions. Oxygenated biofuels such as biodiesel and ethanol blended with diesel fuel are biodegradable, non-toxic, renewable alternatives to imported petroleum diesel, and their use not only creates new markets for domestic agricultural products, but also greatly reduces particulate emissions. Unfortunately, biodiesel has been shown to increase NOX emissions upwards of 10% compared to petroleum diesel. The objective of this investigation was to evaluate the performance and NOX emissions of selected biofuels and blends with petroleum-based diesel fuel in a turbocharged and intercooled diesel engine using a steady-state nonroad ISO 8-mode test schedule. Test fuels included traditional No. 2 diesel and four biofuels comprising 100% soy methyl ester biodiesel, 2% biodiesel, 10% ethanol-diesel fuel, and 5% ethanol in biodiesel. Exhaust NOX emissions were monitored with a Horiba NOX analyzer Reductions in peak torque varying from less than 0.5% to about 10% were measured with the test fuels and were attributed mainly to reduced energy content. Biodiesel fuel showed a 12% increase in NOX emissions, while 2% biodiesel fuel increased emissions 2.3%. The ethanol-diesel fuel blend reduced NOX emissions by 2.7% and was highly sensitive to load, with increased temperature and NOX emissions at light load. Addition of only 5% ethanol to biodiesel suppressed NOX emissions, with only a 2.6% increase occurring. It was concluded that ethanol could act as an effective NOX emissions reducing additive.