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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

Michigan Technological University-Siddharth Gopujkar, Jeremy Worm, Joel Duncan, William Hansley
  • Technical Paper
  • 2020-01-0552
To be published on 2020-04-14 by SAE International in United States
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…
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Water Injection as an Enabler for Increased Efficiency at High-Load in a Direct Injected, Boosted, SI Engine

SAE International Journal of Engines

Michigan Tech APS Labs-Jeremy Worm, Jeffrey Naber, Joel Duncan
Nostrum Energy LLC-Sam Barros, William Atkinson
  • Journal Article
  • 2017-01-0663
Published 2017-03-28 by SAE International in United States
In a Spark-Ignited engine, there will come a point, as load is increased, where the unburned air-fuel mixture undergoes auto-ignition (knock). The onset of knock represents the upper limit of engine output, and limits the extent of engine downsizing / boosting that can be implemented for a given application. Although effective at mitigating knock, requiring high octane fuel is not an option for most markets. Retarding spark timing can extend the high load limit incrementally, but is still bounded by limits for exhaust gas temperature, and spark retard results in a notable loss of efficiency. Likewise, enriching the air-fuel mixture also decreases efficiency, and has profound negative impacts on engine out emissions. In this current work, a Direct-Injected, Boosted, Spark-Ignited engine with Variable Valve Timing was tested under steady state high load operation. Comparisons were made among three fuels; an 87 AKI, a 91 AKI, and a 110 AKI off-road only race fuel. The engine was outfitted with a sequential port water injection apparatus. Under full-load, water injection enabled operation with 87 AKI fuel at…
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