The oxidation properties of n-heptane have been investigated by conducting experiments in a laminar flow reactor at pressures of 21 and 100 bar, nearstoichiometric (𝛷 = 0.9) and fuel-lean conditions (𝛷 = 0.1), and temperatures of 450-900 K. At 21 bar and stoichiometric conditions, a negative temperature coefficient (NTC) region was detected around 600 K. At increased pressure or oxygen concentration, the NTC behavior was much less pronounced. The observed concentration profiles for the major species were compared to predictions with selected literature mechanisms. While all models provided a satisfactory agreement for the n-heptane profiles at 21 bar fuel lean conditions and at 100 bar, only the mechanisms from NUI and Polimi captured the NTC behavior at 21 bar and stoichiometric conditions. The model from Zhang et al. provided the best overall agreement and was selected for detailed comparison with species concentrations and used in analysis of reaction paths and reaction sensitivity under the present conditions.

No abstract

To evaluate the use of diesel as a pilot fuel in natural gas combustion in two-stroke maritime engines, research on high-pressure oxidation of methane/n-heptane mixtures is of interest. In this study, laminar flow reactor experiments were conducted at pressures of 21 and 100 bar, temperatures in the range 450–900 K, and under stoichiometric and fuel-lean conditions. For all conditions, the n-heptane conversion starts below 600 K. A pronounced negative temperature coefficient region was observed at 21 bar. The n-heptane was depleted at all conditions before reaching 900 K. Methane oxidation was initiated once n-heptane was consumed. Compared to the oxidation of pure n-heptane and NH3/n-heptane mixtures, the presence of methane promoted n-heptane oxidation in the full temperature range. The model from Zhang et al. provided overall a good agreement with the experimental data. However, the low-temperature conversion of n-heptane at 21 bar and stoichiometric conditions is underpredicted, possibly because some chemical coupling between n-heptane and methane is missing in the model.