Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics
- Department of Chemical Engineering and Technology, Royal Institute of Technology, SE-100 44 Stockholm (Sweden)
- Shell Global Solutions, P.O. Box 1, Chester CH1 3SH (United Kingdom)
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)
- OSTI ID:
- 20880637
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 1-2 Vol. 149; ISSN CBFMAO; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACCELERATION
AUTOIGNITION
BENZYL RADICALS
CHEMICAL REACTION KINETICS
COMBUSTION
COMPRESSION
DIESEL ENGINES
FORECASTING
HEPTANE
HYDROCARBONS
HYDROGEN
HYDROPEROXY RADICALS
INTERNAL COMBUSTION ENGINES
MIXTURES
OXYGEN
PRESSURE RANGE MEGA PA 01-10
PRESSURE RANGE MEGA PA 10-100
SIMULATION
TEMPERATURE RANGE 1000-4000 K
TOLUENE