The Research and Motor Octane numbers (RON and MON) are the conventional methods used for rating the knock propensity of gasoline fuels in spark ignition (SI) engines. It has been established in the literature that RON and MON are not representative of fuel reactivity in homogeneous charge compression ignition (HCCI) combustion. Instead, the Lund-Chevron HCCI fuel numbers have been shown to be more suitable for rating fuel reactivity in HCCI combustion. . Three RON 90 binary fuel blends, comprised of isooctane/n-heptane, toluene/n-heptane and ethanol/n-heptane, were formulated and tested under RON, MON and HCCI number test conditions. The RON and MON ratings of the fuels were evaluated at the lambdas of highest knock intensity (near stoichiometry), per ASTM test methods, while the HCCI number tests were performed at an excess air to fuel ratio (lambda) of 3. The testing was carried out on a standard Cooperative Fuel Research (CFR) Engine with increased instrumentation to measure the relevant combustion characteristics, flows, temperatures, and pressures. At equivalent intake mixture temperatures and engine speeds to the RON (≈52 °C and 600 rpm) and MON (≈149 °C and 900 rpm) test conditions, the Lund-Chevron HCCI fuel numbers (HCCI #1 and HCCI #4) were also obtained for the three RON 90 fuel blends. While the three fuel blends had the same RON of 90, it was found that their reactivity varied significantly under lean HCCI #1 conditions, with RON intake temperature and engine speed. Similarly under MON intake temperature and engine speed, there wasn’t a linear correlation between the fuels’ standard MON and HCCI #4 ratings. This presentation will use chemical kinetic simulations to explore the chemical reaction pathways as a potential means to understand why the three fuel blends showed different reactivity in HCCI combustion modes than indicated by their standard RON and MON ratings.

Understanding the autoignition chemistry of gasoline fuel surrogates in stoichiometric and lean combustion environments

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.