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Title: Compositional effects on the ignition of FACE gasolines [Compositional effects on the ignition of FACE gasoline fuels: experiments, surrogate fuel formulation, and chemical kinetic modeling]

As regulatory measures for improved fuel economy and decreased emissions are pushing gasoline engine combustion technologies towards extreme conditions (i.e., boosted and intercooled intake with exhaust gas recirculation), fuel ignition characteristics become increasingly important for enabling stable operation. Here, this study explores the effects of chemical composition on the fundamental ignition behavior of gasoline fuels. Two well-characterized, high-octane, non-oxygenated FACE (Fuels for Advanced Combustion Engines) gasolines, FACE F and FACE G, having similar antiknock indices but different octane sensitivities and chemical compositions are studied. Ignition experiments were conducted in shock tubes and a rapid compression machine (RCM) at nominal pressures of 20 and 40 atm, equivalence ratios of 0.5 and 1.0, and temperatures ranging from 650 to 1270 K. Results at temperatures above 900 K indicate that ignition delay time is similar for these fuels. However, RCM measurements below 900 K demonstrate a stronger negative temperature coefficient behavior for FACE F gasoline having lower octane sensitivity. In addition, RCM pressure profiles under two-stage ignition conditions illustrate that the magnitude of low-temperature heat release (LTHR) increases with decreasing fuel octane sensitivity. However, intermediate-temperature heat release is shown to increase as fuel octane sensitivity increases. Various surrogate fuel mixtures were formulated tomore » conduct chemical kinetic modeling, and complex multicomponent surrogate mixtures were shown to reproduce experimentally observed trends better than simpler two- and three-component mixtures composed of n-heptane, iso-octane, and toluene. Measurements in a Cooperative Fuels Research (CFR) engine demonstrated that the multicomponent surrogates accurately captured the antiknock quality of the FACE gasolines. Simulations were performed using multicomponent surrogates for FACE F and G to reveal the underlying chemical kinetics linking fuel composition with ignition characteristics. Finally, a key discovery of this work is the kinetic coupling between aromatics and naphthenes, which affects the radical pool population and thereby controls ignition.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [1] ;  [4] ;  [4] ;  [1] ; ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [4] ;  [2] ;  [1]
  1. King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia). Clean Combustion Research Center
  2. Univ. of Connecticut, Storrs, CT (United States). Dept. of Mechanical Engineering
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical, Aerospace, and Nuclear Engineering
Publication Date:
Report Number(s):
Journal ID: ISSN 0010-2180
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Combustion and Flame
Additional Journal Information:
Journal Volume: 169; Journal Issue: C; Journal ID: ISSN 0010-2180
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1324348