An experimental and chemical kinetic modelling study of toluene oxidation with nitrous oxide

The oxidation of toluene in the presence of nitrous oxide (N 2 O) is investigated experimentally using shock tubes, and the results are simulated using an improved chemical kinetic model. The improved model is based on GalwayMech1.0 with updated rate constants for the reactions Ċ 6 H 5 + H ˙ (+M) ↔ C 6 H 6 (+M), N 2 O (+M) ↔ N 2 + Ö (+M), N 2 O + H ˙ ↔ N 2 + O ˙ H, N 2 O + Ö ↔ NO + NO, and N 2 O + Ö ↔ N 2 + O 2 . Additionally, the current model includes HNNO and NHNO intermediate chemistry. The proposed mechanism is validated over a wide range of temperatures and equivalence ratios, with validation targets including experimental data for toluene, H 2 /N 2 O, and newly generated toluene/N 2 O blend data from shock tubes. High-pressure shock tube experiments reveal that the toluene/N 2 O mixture is highly susceptible to pre-ignition at low temperatures. The chemical kinetic analysis indicates that the ignition of the toluene/N 2 O mixtures is highly sensitive to the N 2 O (+M) ↔ N 2 + Ö (+M) reaction. The heat released, along with the Ö atoms generated during the decomposition of N 2 O, causes the rapid depletion of toluene at a substantially faster rate than N 2 O. Similarly, H ˙ atoms, mostly produced from toluene chemistry, e.g., through benzyl radical breakup C 6 H 5 ĊH 2 ↔ Ċ 7 H 6 + H ˙ , help the decomposition of N 2 O molecules via N 2 O + H ˙ ↔ NO + N ¨ H. Moreover, other major nitric oxide (NO) producing reactions are identified, including N 2 O + Ö ↔ NO + NO and N ¨ H + Ö ↔ NO + H ˙ . Due to the rapid depletion of toluene, direct chemical interactions between N 2 O and the aromatic ring have little influence on overall combustion chemistry. However, the enthalpy of formation of toluene and benzyl radical do influence N 2 O decomposition significantly.