Investigation on the Ignition Properties of 1-Propanol and 1-Butanol under Fuel-Lean Conditions

To mitigate the global warming and to develop sustainable transportation, investigations on combustion properties of carbon neutral fuels i.e., electro-fuels and bio-fuels such as propanol and butanol are essential. In the past, there were very limited researches concerning the fuel-lean combustion of those fuels, which is however a promising method for reducing the NO_x emissions. Moreover, the literature chemical kinetic mechanisms have not been widely validated against the fuel-lean combustion data. Ignition delay time (IDT) is one key parameter and is widely used for validation of chemical kinetic mechanisms. The measurements of IDTs of diluted 1-propanol (nC₃H₇OH, CH₃CH₂CH₂OH) and 1-butanol (nC₄H₉OH, CH₃CH₂CH₂CH₂OH) mixtures (with 90% bath gas (Ar+N₂)) were therefore conducted in a rapid compression machine (RCM), at temperatures between 800 and 1000 K, pressures of 20 and 40 bar, under lean combustion conditions with equivalence ratios (ф) of 0.25, 0.5 and 0.9. The IDTs of 1-propanol are notably longer than those of 1-butanol at the same conditions. The obtained experimental data were further compared with simulated results applying literature chemical kinetic mechanisms. Moreover, the influences of temperature, pressure, and equivalence ratio on IDTs were characterized by sensitivity analyses. The reactions of fuel molecules with HO₂ and OH radicals are dominant for the autoignition of both 1-propanol and 1-butanol.