An experimental and kinetic modeling study of the auto-ignition of natural gas blends containing C1C7 alkanes

Ignition delay time measurements for multi-component natural gas mixtures were carried out using a rapid compression machine at conditions relevant to gas turbine operation, at equivalence ratios of 0.52.0 in `air in the temperature range 6501050K, at pressures of 1030bar. Natural gas mixtures comprising C1C7 n-alkanes with methane as the major component (volume fraction: 0.350.98) were considered. A design of experiments was employed to minimize the number of experiments needed to cover the wide range of pressures, temperatures and equivalence ratios. The new experimental data, together with available literature data, were used to develop and assess a comprehensive chemical kinetic model. Replacing 1.875% methane with 1.25% n-hexane and 0.625% n-heptane in a mixture containing C1C5 components leads to a significant increase in a mixtures reactivity. The mixtures containing heavier hydrocarbons also tend to show a strong negative temperature coefficient and two-stage ignition behavior. Sensitivity analyses of the C1C7 blends have been performed to highlight the key reactions controlling their ignition behavior.