Auto ignition study of methane and bio alcohol fuel blends

Methane (CH₄) and bio alcohols have different ignition properties. These have been extensively studied and the resulting experimental data have been used to validate chemical kinetic models. Methane is the main component of natural gas, which is of interest because of its relative availability and lower emissions compared to other hydrocarbon fuels. Given growing interest in fuel-flexible systems, there can be situations in which the combustion properties of natural gas need to be modified by adding biofuels, such as bio alcohols. This can occur in dual fuel internal combustion engines or gas turbines with dual fuel capabilities. The combustion behavior of such blends can be understood by studying the auto ignition properties in fundamental combustion experiments. Studies of the ignition of such blends are very limited in the literature. In this work, the auto ignition of methane and bio alcohol fuel blends is investigated using a shock tube facility. The chosen bio alcohols are ethanol (C₂H₅OH) and n-propanol (NC₃H₇OH). Experiments are carried out at 3 atm and 10 atm for stoichiometric and lean mixtures of fuel, oxygen, and argon. The ignition delay times of the pure fuels are first established at conditions of constant oxygen concentration and comparable pressures. The ignition delay times of blends with 50% methane are then measured. The pyrolysis kinetics of the blends is further explored by measuring CO formation during pyrolysis of the alcohol and methane-alcohol blends. The resulting experimental data are compared with the predictions of selected chemical kinetic models to establish the ability of these models to predict the disproportionate enhancement of methane ignition by the added alcohol.