Parametric Investigation of NOx Emissions from Biofuels for Compression-Ignition Engines

Wenqiao Yuan, Michael R. Gratten, Alan Christopher Hansen

Research output: Contribution to conferencePaperpeer-review


The consumption of oxygenated biofuels such as biodiesel and ethanol is growing as a result of increased pressure from federal and state agencies to improve air quality. These fuels provide substantial reductions in 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 identify with the aid of heat release analysis and suitable statistical methods the combustion characteristics that influence NO x emissions from a turbocharged and intercooled diesel engine run on selected biofuels. 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. The engine was instrumented with an in-cylinder pressure transducer, a fuel injector control current probe, and an optical shaft encoder to trigger data recordings. Exhaust NOx emissions were monitored with a Horiba NOx analyzer. Correlation results indicated that start of combustion greatly influenced NOx emissions and varied due to cetane number and start of injection. Start of combustion was highly correlated with other crank angle location-based combustion events such as peak temperature location and peak rate of heat release location. Peak temperature was not highly correlated with NOx emissions suggesting thermal NO formation does not adequately explain NOx emissions from biofuels. NOx formation did not demonstrate dependence on fuel oxygen content. The addition of small percentages of ethanol to biodiesel or retarding injection timing appear to be the most effective methods of reducing NO x emissions when combusting biodiesel.

Original languageEnglish (US)
StatePublished - 2005
Event2005 ASAE Annual International Meeting - Tampa, FL, United States
Duration: Jul 17 2005Jul 20 2005


Other2005 ASAE Annual International Meeting
Country/TerritoryUnited States
CityTampa, FL


  • Biodiesel
  • Biofuels
  • Blend
  • Diesel engine
  • Ethanol
  • Heat release
  • No emissions

ASJC Scopus subject areas

  • General Agricultural and Biological Sciences
  • Bioengineering


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