A rapid compression machine investigation of oxidation and auto-ignition of n-Heptane: Measurements and modeling

n-Heptane oxidation and auto-ignition in a rapid compression machine is studied in the low and intermediate temperature regimes at high pressures. Experimental ignition delay times and some phenomenological aspects related to knock in engines are presented, providing additional information at lower temperatures on previously published delays from shock tube experiments. The products of oxidation are identified and time profiles are measured during a two-stage ignition process. Eight C7 heterocycles, heptenes, lower 1-alkenes, aldehydes, and carbon monoxide are the main species. Their origin is discussed in relation to the isomerization and decomposition of heptylperoxy radicals. The high selectivity observed in the formation of lower 1-alkenes is explained by the scission of the β CC bond of the β-hydroperoxyheptyl radicals weakened by the presence of oxygen atoms. Numerical simulation of the experiments with Warnatz's comprehensive chemical mechanism gives satisfactory results for cool flame and total ignition delays, but fails to reproduce the detailed chemistry before auto-ignition.

[1]  V. Viossat,et al.  Autoignition of hydrocarbon/air mixtures in a CFR engine : experimental and modeling study , 1993 .

[2]  J. Warnatz,et al.  Automatic generation of reaction mechanisms for the description of the oxidation of higher hydrocarbons , 1990 .

[3]  D. J. Rose,et al.  Fundamental features of hydrocarbon autoignition in a rapid compression machine , 1993 .

[4]  W. Kordylewski,et al.  Experimental and numerical studies of ditertiary butyl peroxide combustion at high pressures in a rapid compression machine , 1993 .

[5]  A. Cavaliere,et al.  Autoignition of n-heptane and n-tetradecane in engine-like conditions , 1993 .

[6]  K. Sahetchian,et al.  Identification of the hydroperoxide formed by isomerization reactions during the oxidation of n-heptane in a reactor and CFR engine , 1991 .

[7]  H. Ciezki,et al.  Shock-tube investigation of self-ignition of n-heptane - Air mixtures under engine relevant conditions , 1993 .

[8]  J. C. Boettner,et al.  Kinetic study of n‐heptane oxidation , 1992 .

[9]  M. Ribaucour,et al.  Experimental and modeling study of oxidation and autoignition of butane at high pressure , 1994 .

[10]  C. Bamford,et al.  Comprehensive Chemical Kinetics , 1976 .

[11]  E. Ratajczak,et al.  Study of the thermochemistry of the ethyl + molecular oxygen .dblharw. ethylperoxy (C2H5O2) and tert-butyl + molecular oxygen .dblharw. tert-butylperoxy (tert-C4H9O2) reactions and of the trend in the alkylperoxy bond strengths , 1986 .

[12]  Adel F. Sarofim,et al.  Fossil fuel combustion: A source book , 1991 .

[13]  Philippe Dagaut,et al.  High Pressure Oxidation of Liquid Fuels From Low to High Temperature. 1. n-Heptane and iso-Octane. , 1993 .