Autoignition Delay Time Measurements of Methane, Ethane, and Propane Pure Fuels and Methane-Based Fuel Blends

Autoignition delay experiments in air have been performed in an atmospheric flow reactor using typical natural gas components, namely, methane, ethane, and propane. Autoignition delay measurements were also made for binary fuel mixtures of methane/ethane and methane/propane, and ternary mixtures of methane/ethane/propane. The effect of $CO2$ addition to the methane-based fuel blends on autoignition delay times was also investigated. Equivalence ratios for the experiments ranged between 0.5 and 1.25, and temperatures ranged from 930 K to 1140 K. Consistent with past studies, increasing equivalence ratio and increasing inlet temperatures over these ranges decreased autoignition delay times. Furthermore, addition of 5–10% ethane or propane decreased autoignition delay time of the binary methane-based fuel by 30–50%. Further addition of either ethane or propane showed less significant reduction of autoignition delays. Addition of 5–10% $CO2$ slightly decreased the autoignition delay times of methane fuel mixtures. Arrhenius correlations were used to derive activation energies for the ignition of the pure fuels and their mixtures. Results show a reduction in activation energies at the higher temperatures studied, which suggests a change in ignition chemistry at very high temperatures. Measurements show relatively good agreement with predictions from a detailed kinetics mechanism, specifically developed to model ignition chemistry of C1-C3 alkanes.