Determination of Octane Index and K in a 2.0L, 4-Cylinder Turbocharged SI Engine Using the Primary Reference Fuel (PRF) Method

Research Octane Number (RON) and Motor Octane Number (MON) have traditionally been used to describe fuel anti-knock quality. The test conditions for MON are harsher than those for RON, causing the RON for a particular fuel to be higher than the MON. Previous researchers have proposed the anti-knock performance of a fuel can be described at other operating conditions using the Octane Index (OI), defined as OI=RON-K (RON-MON), where ‘K’ is a weighing factor between RON and MON, and is a function of engine operating condition. The K-factor indicates that at a particular operating condition, knock tolerance is better described by RON as K approaches a value of 0, and MON as K approaches a value of 1. Previous studies claim that K-factor is dependent only on the engine combustion system and the speed-load point, and that it is independent of fuel chemistry. In most of these studies, K was determined experimentally using linear regression. In this particular study, K was determined using the PRF method for two test fuels; EPA certification tier 2 and tier 3 fuel. K was calculated for these fuels at multiple test points and the results showed that the K was different for the two fuels and thus it did depend on fuel chemistry. For a majority of the test points, the fuel with the lower RON and MON values (tier 3 cert fuel) had a lower K-factor as compared to the tier 2 cert fuel. A parameter was developed to relate engine speed, combustion phasing and cylinder trapped mass to predict K-factor, independent of the fuel. The correlation of K with end gas conditions was also investigated as a part of this project.


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Media Info

  • Media Type: Web
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 3219-3230
  • Serial:

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Filing Info

  • Accession Number: 01739912
  • Record Type: Publication
  • Source Agency: SAE International
  • Report/Paper Numbers: 2020-01-0552
  • Files: TRIS, SAE
  • Created Date: May 26 2020 10:16AM