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Title: The effects of pressure, temperature and concentration on the reactivity of alkanes; experiments and modeling in a rapid compression machine

Conference ·
 [1];  [1];  [1];  [2];  [2];  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Leeds Univ. (United Kingdom)
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Experiments in a rapid compression machine have examined the influences of variations in pressure, temperature, and equivalence ratio on the autoignition of n-pentane. Equivalence ratios included values from 0.5 to 2.0, compressed gas initial temperatures were varied between 675K and 980K, and compresed gas initial pressures varied from 8 to 20 bar. Numerical simulations of the same experiments were carried out using a detailed chemical kinetic reaction mechanism. The results are interpreted in terms of a low temperature oxidation mechanism involving addition of molecular oxygen to alkyl and hydroperoxyalkyl radicals. Idealized calculations are reported which identify the major reaction paths at each temperature. Results indicate that in most cases, the reactive gases experience a two-stage autoigni tion. The first stage follows a low temperature alkylperoxy radical isomerization pathway that is effectively quenched when the temperature reaches a level where dissociation reactions of alkylperoxy and hydroperoxyalkylperoxy radicals are more rapid than the reverse addition steps. The second stage is controlled by the onset of dissociation of hydrogen peroxide. Results also show that in some cases, the first stage ignition takes place during the compression stroke in the rapid compression machine, making the interpretation of the experiments somewhat more complex than generally assumed. At the highest compression temperatures achieved, little or no first stage ignition is observed.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE Office of Defense Programs (DP)
DOE Contract Number:
W-7405-Eng-48
OSTI ID:
7798
Report Number(s):
UCRL-JC-129728; KC0301020; ON: DE00007798
Resource Relation:
Journal Volume: 27; Journal Issue: 1; Conference: 27th International Symposium on Combustion, Boulder, CO, September 2-7, 1998
Country of Publication:
United States
Language:
English

References (11)

Fundamental features of hydrocarbon autoignition in a rapid compression machine journal November 1993
Experimental and modeling study of oxidation and autoignition of butane at high pressure journal February 1994
Thermokinetic interactions: Fundamentals of spontaneous ignition and cool flames journal January 1987
Reduced kinetic models and their application to practical combustion systems journal January 1995
Rapid compression studies on spontaneous ignition of isopropyl nitrate Part II: Rapid sampling, intermediate stages and reaction mechanisms journal November 1980
Two-stage ignitions during rapid compression: spontaneous combustion in lean fuel-air mixtures journal June 1984
Novel features of end-gas autoignition revealed by computational fluid dynamics journal November 1992
A Comprehensive Modeling Study of n-Heptane Oxidation journal July 1998
High Pressure Oxidation of Liquid Fuels From Low to High Temperature. 1. n-Heptane and iso-Octane. journal December 1993
Spontaneous ignition delays as a diagnostic of the propensity of alkanes to cause engine knock journal December 1997
Effects of Resonance and Structure on the Thermochemistry of Organic Peroxy Radicals and the Kinetics of Combustion Reactions 1 journal March 1965

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Related Subjects

66 PHYSICS
Alkanes
Activation Energy
Temperature Dependence
Pressure Dependence
Concentration Ratio
Compression