A comparison of the autoignition chemistry of n-butane and isobutane in an internal combustion engine
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 Samples were withdrawn at different times during the engine cycle, providing concentration histories of a wide variety of reactant, olefin, carbonyl, and other intermediate and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.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- DOE/CE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6956564
- Report Number(s):
- UCRL-102784; CONF-900282-3; ON: DE90009474
- Resource Relation:
- Conference: Annual Society of Acoustical Engineers congress, Detroit, MI (USA), 26 Feb - 2 Mar 1990
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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