High pressure effects on the mutual sensitization of the oxidation of NO and CH4–C2H6 blends

Abstract

The mutual sensitization of the oxidation of NO and a CH₄–C₂H₆ (10 : 1) simulated natural gas (NG) blend was studied under fuel lean conditions (Φ = 0.5) at 50 atm and 1000–1500 K in the UIC high pressure shock tube (HPST). New experimental results were also obtained for the mutual sensitization of methane and the NG blend in the CNRS jet stirred reactor (JSR) at 10 atm. A detailed chemical kinetic model was assembled to describe the observed changes in reactivity in the CH₄ and NG blends, with and without NO, in the HPST and the JSR. The data and the validated model (tested against a variety of targets) show a reduced difference of reactivity between methane and NG blends in the presence of NO at characteristic reaction times for the JSR (250–1000 µs). However the HPST data and subsequent simulations using the validated model have revealed that at higher pressures and in the millisecond time scale regime representative of the HPST experiments (and practical combustion devices) there still persists a significant difference in reactivity between methane and NG blends in the presence of NO. The experimental data, the model development and validations and its predictions and utility as a tool to probe the NO–hydrocarbon sensitization effects under practical combustion conditions is discussed.