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Determination of Octane Index and K in a 2.0L, 4-Cylinder Turbocharged SI Engine Using the Primary Reference Fuel (PRF) Method
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 14, 2020 by SAE International in United States
This content contains downloadable datasetsAnnotation ability available
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.
CitationGopujkar, S., Worm, J., Duncan, J., and Hansley, W., "Determination of Octane Index and K in a 2.0L, 4-Cylinder Turbocharged SI Engine Using the Primary Reference Fuel (PRF) Method," SAE Technical Paper 2020-01-0552, 2020, https://doi.org/10.4271/2020-01-0552.
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