Autoignition Behavior of the Xylene Isomers DAAD 19 - 03 - 1 - 0070 6 . AUTHOR ( S ) W 911 NF - 07 - 1 - 0522

Preignition and Autoignition Behavior of the Xylene Isomers Robert H. Natelson Nicholas P. Cernansky, Ph.D. and David L. Miller, Ph.D. The relative preignition and autoignition reactivity of the xylene isomers (o-, mand p-xylene, or 1,2-, 1,3-, and 1,4-dimethylbenzene) has been studied. The principal objectives were to determine the relative reactivity among the isomers and the key oxidation branching pathways. Preignition experiments were conducted in a pressurized flow reactor facility at 600-850 K temperatures, 8 atm pressure, and lean equivalence ratios. Online analysis of the data included carbon monoxide and carbon dioxide measurements using a nondispersive infrared analyzer and molecular oxygen measurements using an electrochemical oxygen cell. Offline analysis, for identification and quantification of intermediate species, was performed using gas chromatography with flame ionization detection and coupling to a mass spectrometer. Additional experiments were conducted in a single cylinder research engine. Neat oand m-xylene were oxidized in the PFR under preignition conditions. They showed no reactivity, so mixtures of each isomer with n-dodecane were tested and compared, and intermediate species were identified. This data helped resolve a recent controversy regarding the relative reactivity of the xylene isomers. Additionally, a mixture of p-xylene / n-dodecane was studied. To study the autoignition of the xylenes, the isomers neat, in binary mixtures with n-decane, and in six-component JP-8 surrogates were tested in the single cylinder research engine. The experimental data were analyzed and compared to existing chemical kinetic models, and it was concluded that at lower