Effects of Fuel Composition on EGR Dilution Tolerance in Spark Ignited Engines

Fuel-specific differences in exhaust gas recirculation (EGR) dilution tolerance are studied in a modern, direct-injection single-cylinder research engine. A total of 6 model fuel blends are examined at a constant research octane number (RON) of 95 using n-heptane, isooctane, toluene, and ethanol. Laminar flame speeds for these mixtures, which are calculated using two different methods (an energy fraction mixing rule and a detailed kinetic simulation), span a range of about 6 cm/s. A nominal load of 350 kPa IMEPg at 2000 rpm is maintained with constant fueling and varying CA50 from 8-20 CAD aTDCf. EGR is increased until a COV of IMEP of 5% is reached. The results illustrate that flame speed affects EGR dilution tolerance; fuels with increased flame speeds have increased EGR tolerance. Specifically, flame speed correlates most closely to the initial flame kernel growth, measured as the time of ignition to 5% mass fraction burned. The effect of the latent heat of vaporization (HoV) on the flame speed is taken into account for the ethanol-containing fuels. At a 30 vol% blend level, the increased enthalpy of vaporization of ethanol compared to conventional hydrocarbons can decrease the temperature at the time of ignition by a maximum of 15°C, which can account for up to a 3.5 cm/s decrease in flame speed. The ethanol-containing fuels, however, still exhibit a flame speed advantage, and a dilution tolerance advantage over the slower flame-speed fuels. The fuel-specific differences in dilution tolerance are significant at the condition examined, allowing for a 50% relative increase in EGR (4% absolute difference in EGR) at a constant COV of IMEP of 3%.

• Record URL:
  • https://doi.org/10.4271/2016-01-0715
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/19463936
• Supplemental Notes:
  • Abstract reprinted with permission of SAE International.
• Authors:
  • Szybist, James P
  • Splitter, Derek
• Conference:
  • SAE 2016 World Congress and Exhibition
  • Location: Detroit Michigan, United States
  • Date: 2016-4-12 to 2016-4-14
• Publication Date: 2016-4-5

Language

• English

Media Info

• Media Type: Web
• Features: References;
• Pagination: pp 819-831
• Serial:
  • SAE International Journal of Engines
  • Volume: 9
  • Issue Number: 2
  • Publisher: SAE International
  • ISSN: 1946-3936
  • EISSN: 1946-3944
  • Serial URL: https://www.sae.org/publications/collections/content/E-JOURNAL-03/

Subject/Index Terms

• TRT Terms: Ethanol; Exhaust gas recirculation; Fuel composition; Motor vehicles; Spark ignition engines
• Subject Areas: Highways; Vehicles and Equipment;

Filing Info

• Accession Number: 01837291
• Record Type: Publication
• Source Agency: SAE International
• Report/Paper Numbers: 2016-01-0715
• Files: TRIS, SAE
• Created Date: Feb 25 2022 8:58AM