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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]

Abstract

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

Authors:
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:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1423827
Alternate Identifier(s):
OSTI ID: 1324348
Report Number(s):
LLNL-JRNL-707150
Journal ID: ISSN 0010-2180
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Combustion and Flame
Additional Journal Information:
Journal Volume: 169; Journal Issue: C; Journal ID: ISSN 0010-2180
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 42 ENGINEERING

Citation Formats

Sarathy, S. Mani, Kukkadapu, Goutham, Mehl, Marco, Javed, Tamour, Ahmed, Ahfaz, Naser, Nimal, Tekawade, Aniket, Kosiba, Graham, AlAbbad, Mohammed, Singh, Eshan, Park, Sungwoo, Rashidi, Mariam Al, Chung, Suk Ho, Roberts, William L., Oehlschlaeger, Matthew A., Sung, Chih-Jen, and Farooq, Aamir. 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]. United States: N. p., 2016. Web. doi:10.1016/j.combustflame.2016.04.010.
Sarathy, S. Mani, Kukkadapu, Goutham, Mehl, Marco, Javed, Tamour, Ahmed, Ahfaz, Naser, Nimal, Tekawade, Aniket, Kosiba, Graham, AlAbbad, Mohammed, Singh, Eshan, Park, Sungwoo, Rashidi, Mariam Al, Chung, Suk Ho, Roberts, William L., Oehlschlaeger, Matthew A., Sung, Chih-Jen, & Farooq, Aamir. 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]. United States. doi:10.1016/j.combustflame.2016.04.010.
Sarathy, S. Mani, Kukkadapu, Goutham, Mehl, Marco, Javed, Tamour, Ahmed, Ahfaz, Naser, Nimal, Tekawade, Aniket, Kosiba, Graham, AlAbbad, Mohammed, Singh, Eshan, Park, Sungwoo, Rashidi, Mariam Al, Chung, Suk Ho, Roberts, William L., Oehlschlaeger, Matthew A., Sung, Chih-Jen, and Farooq, Aamir. Sun . "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]". United States. doi:10.1016/j.combustflame.2016.04.010. https://www.osti.gov/servlets/purl/1423827.
@article{osti_1423827,
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]},
author = {Sarathy, S. Mani and Kukkadapu, Goutham and Mehl, Marco and Javed, Tamour and Ahmed, Ahfaz and Naser, Nimal and Tekawade, Aniket and Kosiba, Graham and AlAbbad, Mohammed and Singh, Eshan and Park, Sungwoo and Rashidi, Mariam Al and Chung, Suk Ho and Roberts, William L. and Oehlschlaeger, Matthew A. and Sung, Chih-Jen and Farooq, Aamir},
abstractNote = {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 to 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.},
doi = {10.1016/j.combustflame.2016.04.010},
journal = {Combustion and Flame},
number = C,
volume = 169,
place = {United States},
year = {Sun May 08 00:00:00 EDT 2016},
month = {Sun May 08 00:00:00 EDT 2016}
}

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  • Experiments in a homogeneous charge compression ignition (HCCI) engine have been conducted with four gasoline surrogate fuel blends. The pure components in the surrogate fuels consisted of n-heptane, isooctane, toluene, ethanol and diisobutylene and fuel sensitivities (RON-MON) in the fuel blends ranged from two to nine. The operating conditions for the engine were p{sub in}=0.1 and 0.2 MPa, T{sub in}=80 and 250 C, {phi}=0.25 in air and engine speed 1200 rpm. A semidetailed chemical kinetic model (142 species and 672 reactions) for gasoline surrogate fuels, validated against ignition data from experiments conducted in shock tubes for gasoline surrogate fuel blendsmore » at 1.0{<=} p{<=}5.0MPa, 700{<=} T{<=}1200 K and {phi}=1.0, was successfully used to qualitatively predict the HCCI experiments using a single zone modeling approach. The fuel blends that had higher fuel sensitivity were more resistant to autoignition for low intake temperature and high intake pressure and less resistant to autoignition for high intake temperature and low intake pressure. A sensitivity analysis shows that at high intake temperature the chemistry of the fuels ethanol, toluene and diisobutylene helps to advance ignition. This is consistent with the trend that fuels with the least Negative Temperature Coefficient (NTC) behavior show the highest octane sensitivity, and become less resistant to autoignition at high intake temperatures. For high intake pressure the sensitivity analysis shows that fuels in the fuel blend with no NTC behavior consume OH radicals and acts as a radical scavenger for the fuels with NTC behavior. This is consistent with the observed trend of an increase in RON and fuel sensitivity. With data from shock tube experiments in the literature and HCCI modeling in this work, a correlation between the reciprocal pressure exponent on the ignition delay to the fuel sensitivity and volume percentage of single-stage ignition fuel in the fuel blend was found. Higher fuel sensitivity and single-stage fuel content generally gives a lower value of the pressure exponent. This helps to explain the results obtained while boosting the intake pressure in the HCCI engine. (author)« less
  • Cited by 38