Ignition delay times (τign) of a gasoline surrogate (iso-octane/toluene/n-heptane/1-hexene at 55/25/15/5% by liquid volume, developed by McCormick et al. 2017) with high-level biofuel-gasoline surrogate blends (50% and 85% biofuel by liquid volume of each ethanol and methyl acetate) were measured behind reflected shock waves. Post-reflected-shock temperatures ranged from 968 to 1361 K at pressures of about 4, 10 , 25, and 50 atm. Data were collected for real fuel-air mixtures at fuel lean and stoichiometric conditions (φ = 0.5, 1.0) with a focus on the more-practical, fuel-lean conditions. Ignition delay times were measured using an OH* chemiluminescence endwall diagnostic centered around 307 nm. The RON and MON of the surrogate were 90.3 and 84.7, respectively, which places it within the range of standard U.S. gasoline. Ethanol was chosen due to its wide use in flex-fuel vehicles and availability, while also providing an increased octane rating; additionally, methyl acetate for its especially high octane rating to investigate the effect of an extreme case. The gasoline surrogate was compared to real gasoline (RD387) and other gasoline surrogate shock-tube experiments to validate its ability to represent gasoline combustion. Clear decreases in τign with increasing pressure and equivalence ratio were observed, with good agreement seen with the literature. Using linear regression analysis of the wide range of conditions studied, a correlation based on equivalence ratio, temperature, and pressure representing the data was developed. Two modern chemical kinetics models targeting gasoline and its surrogates (Mehl et al. 2011 and Ranzi et al. 2012) are compared to the τign measurements. Each model predicts τign values slower than those observed in the experiment for most conditions with better agreement occurring at higher temperature and equivalence ratio. Significant disagreement between the models in the NTC region shape and location prediction is also observed. These high-pressure, high-biofuel concentration tests provide required chemical kinetic data for optimizing fuel and engine design.

Auto-Ignition Study of a Four-Component Gasoline Surrogate with High-Level Blending with Bio-Derived Fuels

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.