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Title: Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics

Abstract

A detailed chemical kinetic model for the autoignition of toluene reference fuels (TRF) is presented. The toluene submechanism added to the Lawrence Livermore Primary Reference Fuel (PRF) mechanism was developed using recent shock tube autoignition delay time data under conditions relevant to HCCI combustion. For two-component fuels the model was validated against recent high-pressure shock tube autoignition delay time data for a mixture consisting of 35% n-heptane and 65% toluene by liquid volume. Important features of the autoignition of the mixture proved to be cross-acceleration effects, where hydroperoxy radicals produced during n-heptane oxidation dramatically increased the oxidation rate of toluene compared to the case when toluene alone was oxidized. Rate constants for the reaction of benzyl and hydroperoxyl radicals previously used in the modeling of the oxidation of toluene alone were untenably high for modeling of the mixture. To model both systems it was found necessary to use a lower rate and introduce an additional branching route in the reaction between benzyl radicals and O{sub 2}. Good agreement between experiments and predictions was found when the model was validated against shock tube autoignition delay data for gasoline surrogate fuels consisting of mixtures of 63-69% isooctane, 14-20% toluene, and 17% n-heptanemore » by liquid volume. Cross reactions such as hydrogen abstractions between toluene and alkyl and alkylperoxy radicals and between the PRF were introduced for completion of chemical description. They were only of small importance for modeling autoignition delays from shock tube experiments, even at low temperatures. A single-zone engine model was used to evaluate how well the validated mechanism could capture autoignition behavior of toluene reference fuels in a homogeneous charge compression ignition (HCCI) engine. The model could qualitatively predict the experiments, except in the case with boosted intake pressure, where the initial temperature had to be increased significantly in order to predict the point of autoignition. (author)« less

Authors:
 [1];  [2];  [1]; ;  [3]
  1. Department of Chemical Engineering and Technology, Royal Institute of Technology, SE-100 44 Stockholm (Sweden)
  2. (United Kingdom)
  3. Shell Global Solutions, P.O. Box 1, Chester CH1 3SH (United Kingdom)
Publication Date:
OSTI Identifier:
20880637
Resource Type:
Journal Article
Resource Relation:
Journal Name: Combustion and Flame; Journal Volume: 149; Journal Issue: 1-2; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 33 ADVANCED PROPULSION SYSTEMS; TOLUENE; HEPTANE; PRESSURE RANGE MEGA PA 10-100; PRESSURE RANGE MEGA PA 01-10; MIXTURES; BENZYL RADICALS; COMBUSTION; HYDROGEN; SIMULATION; HYDROPEROXY RADICALS; OXYGEN; INTERNAL COMBUSTION ENGINES; CHEMICAL REACTION KINETICS; ACCELERATION; FORECASTING; COMPRESSION; AUTOIGNITION; HYDROCARBONS; TEMPERATURE RANGE 1000-4000 K; DIESEL ENGINES

Citation Formats

Andrae, J.C.G., Shell Global Solutions, P.O. Box 1, Chester CH1 3SH, Bjoernbom, P., Cracknell, R.F., and Kalghatgi, G.T. Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics. United States: N. p., 2007. Web. doi:10.1016/J.COMBUSTFLAME.2006.12.014.
Andrae, J.C.G., Shell Global Solutions, P.O. Box 1, Chester CH1 3SH, Bjoernbom, P., Cracknell, R.F., & Kalghatgi, G.T. Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics. United States. doi:10.1016/J.COMBUSTFLAME.2006.12.014.
Andrae, J.C.G., Shell Global Solutions, P.O. Box 1, Chester CH1 3SH, Bjoernbom, P., Cracknell, R.F., and Kalghatgi, G.T. Sun . "Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics". United States. doi:10.1016/J.COMBUSTFLAME.2006.12.014.
@article{osti_20880637,
title = {Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics},
author = {Andrae, J.C.G. and Shell Global Solutions, P.O. Box 1, Chester CH1 3SH and Bjoernbom, P. and Cracknell, R.F. and Kalghatgi, G.T.},
abstractNote = {A detailed chemical kinetic model for the autoignition of toluene reference fuels (TRF) is presented. The toluene submechanism added to the Lawrence Livermore Primary Reference Fuel (PRF) mechanism was developed using recent shock tube autoignition delay time data under conditions relevant to HCCI combustion. For two-component fuels the model was validated against recent high-pressure shock tube autoignition delay time data for a mixture consisting of 35% n-heptane and 65% toluene by liquid volume. Important features of the autoignition of the mixture proved to be cross-acceleration effects, where hydroperoxy radicals produced during n-heptane oxidation dramatically increased the oxidation rate of toluene compared to the case when toluene alone was oxidized. Rate constants for the reaction of benzyl and hydroperoxyl radicals previously used in the modeling of the oxidation of toluene alone were untenably high for modeling of the mixture. To model both systems it was found necessary to use a lower rate and introduce an additional branching route in the reaction between benzyl radicals and O{sub 2}. Good agreement between experiments and predictions was found when the model was validated against shock tube autoignition delay data for gasoline surrogate fuels consisting of mixtures of 63-69% isooctane, 14-20% toluene, and 17% n-heptane by liquid volume. Cross reactions such as hydrogen abstractions between toluene and alkyl and alkylperoxy radicals and between the PRF were introduced for completion of chemical description. They were only of small importance for modeling autoignition delays from shock tube experiments, even at low temperatures. A single-zone engine model was used to evaluate how well the validated mechanism could capture autoignition behavior of toluene reference fuels in a homogeneous charge compression ignition (HCCI) engine. The model could qualitatively predict the experiments, except in the case with boosted intake pressure, where the initial temperature had to be increased significantly in order to predict the point of autoignition. (author)},
doi = {10.1016/J.COMBUSTFLAME.2006.12.014},
journal = {Combustion and Flame},
number = 1-2,
volume = 149,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}