Oxidation of Methane/n-Heptane Mixtures in a High-Pressure Flow Reactor

To evaluate the use of diesel as a pilot fuel in natural gas combustion in twostroke 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.