Experimental and modeling study of 1-hexene oxidation behind reflected shock waves M. Yahyaoui a , N. Djebaı ¨li-Chaumeix a , C.-E. Paillard a, * , S. Touchard b , R. Fournet b , P.A. Glaude b , F. Battin-Leclerc b a Laboratoire de Combustion et Syste `mes Re ´actifs, CNRS-LCSR et Universite ´dÕOrle ´ans, France b De ´partement de Chimie Physique des Re ´actions, CNRS-INPL-DCPR, Nancy, France Abstract The auto-ignition delay times s i of 1-C 6 H 12 /O 2 /Ar mixtures have been measured between 1270 and 1700 K using shock tube technique for 3 equivalence ratios (U = 0.5, 1, and 1.5) at a pressure of about 0.2 MPa. At higher temperatures (>1400 K), the logarithm of s i varies linearly as a function of the temper- ature inverse for a given value of equivalence ratio. The apparent activation energy, E a , is approximately equal to 230 kJ mol 1 . At lower temperature (<1400 K), E a strongly decreases and becomes equal to about 120 kJ mol 1 around 1300 K. A correlation between s i , reactant concentrations, and temperature behind reflected shock waves was proposed for each temperature range. These correlations give an estimation of s i with an accuracy better than 12%. A detailed chemical mechanism of the 1-hexene oxidation has been developed with the ‘‘EXGAS’’ program. The agreement between computed and measured values of s i was correct at high temperatures (>1400 K). The major channels of the chemical species fluxes have been dis- cussed: at low temperatures, 1-hexene is mainly consumed by retro-ene reaction to give propene and, in a smaller ratio, by unimolecular decomposition to give allyl and 1-propyl radicals. At high temperature, uni- molecular decomposition becomes more important than retro-ene reaction. The change in E a below 1400 K is not explained by the model. The auto-ignition delay times of 1-hexene have been compared to those of other unsaturated hydrocarbons. For stoichiometric mixtures diluted by 99 mol% of argon at a pressure of 200 kPa, the shortest delays were obtained for 1-octene while the longest delays were obtained for propene. With iso-butene and ethylene, the delay times are closer to 1-hexene in the low temperature side and to propene in the high temperature one. Ó 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Auto-ignition delay times; Shock waves; High temperature; Oxidation; Modelling 1. Introduction Olefins are a family of hydrocarbons that are present in gasoline up to 20%. Many studies were carried out on the oxidation of alkanes, while rel- atively few were conducted on the oxidation of alkenes. In some conditions, their ability to react in air is superior to that of alkanes as well as to that of aromatic compounds [1]. To reduce the emission of pollutants and to increase the engine efficiency, the composition of fuels could be modified. In particular, fuels could be adapted to the working conditions of homogeneous charge 1540-7489/$ - see front matter Ó 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.proci.2004.08.070 * Corresponding Author. Fax: +33 2 38 69 54 79. E-mail address: paillard@cnrs-orleans.fr (C.-E. Paillard). Proceedings of the Combustion Institute 30 (2005) 1137–1145 www.elsevier.com/locate/proci Proceedings of the Combustion Institute