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Title: A comparison of the autoignition chemistry of n-butane and isobutane in an internal combustion engine

Abstract

Butane is the simplest alkane fuel for which more than a single structural isomer is possible. In the present study, n-butane and isobutane are used in a test engine to examine the importance of molecular structure in determining knock tendency, and the experimental results are interpreted using a detailed chemical kinetic model. A sampling valve was used to extract reacting gases from the combustion chamber of the engine. Samples were withdrawn at different times during the engine cycle, providing concentration histories of a wide variety of reactant, olefin, carbonyl, and other intermediate and product species. The chemical kinetic model predicted the formation of all the intermediate species measured in the experiments. The agreement between the measured and predicted values is mixed and is discussed. Calculations show that RO{sub 2} isomerization reactions are more important contributors to chain branching in the oxidation of n-butane than in isobutane. Chain branching in isobutane oxidation is dependent on H-atom abstraction reactions involving HO{sub 2} and CH{sub 3}O{sub 2} radicals that occur at higher temperatures than RO{sub 2} isomerization reactions. Therefore, an isobutane mixture must be raised to a higher temperature than a n-butane mixture to achieve the same overall rate of reaction. 33 refs.,more » 6 figs., 2 tabs.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
DOE/CE
OSTI Identifier:
6956564
Report Number(s):
UCRL-102784; CONF-900282-3
ON: DE90009474
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Annual Society of Acoustical Engineers congress, Detroit, MI (USA), 26 Feb - 2 Mar 1990
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS; BUTANE; COMPARATIVE EVALUATIONS; INTERNAL COMBUSTION ENGINES; CHEMICAL ANALYSIS; COMBUSTION KINETICS; CONCENTRATION RATIO; EQUILIBRIUM; FUELS; IGNITION; MEASURING METHODS; SAMPLING; STRUCTURAL MODELS; TECHNOLOGY ASSESSMENT; TEMPERATURE EFFECTS; ALKANES; CHEMICAL REACTION KINETICS; ENGINES; HEAT ENGINES; HYDROCARBONS; KINETICS; ORGANIC COMPOUNDS; REACTION KINETICS; 330100* - Internal Combustion Engines; 330800 - Emission Control- Alternative Fuels

Citation Formats

Wilk, R D, Green, R M, Pitz, W J, Westbrook, C K, Addagarla, S, Miller, D L, and Cernansky, N P. A comparison of the autoignition chemistry of n-butane and isobutane in an internal combustion engine. United States: N. p., 1990. Web.
Wilk, R D, Green, R M, Pitz, W J, Westbrook, C K, Addagarla, S, Miller, D L, & Cernansky, N P. A comparison of the autoignition chemistry of n-butane and isobutane in an internal combustion engine. United States.
Wilk, R D, Green, R M, Pitz, W J, Westbrook, C K, Addagarla, S, Miller, D L, and Cernansky, N P. 1990. "A comparison of the autoignition chemistry of n-butane and isobutane in an internal combustion engine". United States. https://www.osti.gov/servlets/purl/6956564.
@article{osti_6956564,
title = {A comparison of the autoignition chemistry of n-butane and isobutane in an internal combustion engine},
author = {Wilk, R D and Green, R M and Pitz, W J and Westbrook, C K and Addagarla, S and Miller, D L and Cernansky, N P},
abstractNote = {Butane is the simplest alkane fuel for which more than a single structural isomer is possible. In the present study, n-butane and isobutane are used in a test engine to examine the importance of molecular structure in determining knock tendency, and the experimental results are interpreted using a detailed chemical kinetic model. A sampling valve was used to extract reacting gases from the combustion chamber of the engine. Samples were withdrawn at different times during the engine cycle, providing concentration histories of a wide variety of reactant, olefin, carbonyl, and other intermediate and product species. The chemical kinetic model predicted the formation of all the intermediate species measured in the experiments. The agreement between the measured and predicted values is mixed and is discussed. Calculations show that RO{sub 2} isomerization reactions are more important contributors to chain branching in the oxidation of n-butane than in isobutane. Chain branching in isobutane oxidation is dependent on H-atom abstraction reactions involving HO{sub 2} and CH{sub 3}O{sub 2} radicals that occur at higher temperatures than RO{sub 2} isomerization reactions. Therefore, an isobutane mixture must be raised to a higher temperature than a n-butane mixture to achieve the same overall rate of reaction. 33 refs., 6 figs., 2 tabs.},
doi = {},
url = {https://www.osti.gov/biblio/6956564}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 1990},
month = {Mon Jan 01 00:00:00 EST 1990}
}

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