Shock tube measurements of ignition delay times for the butanol isomers

Ignition delay times of the four isomers of butanol were measured behind reflected shock waves over a range of experimental conditions: 1050–1600 K, 1.5–43 atm, and equivalence ratios of 1.0 and 0.5 in mixtures containing 4% O2 diluted in argon. Additional data were also collected at 1.0–1.5 atm in order to replicate conditions used by previous researchers. Good agreement is seen with past work for 1-butanol ignition delay times, though our measured data for the other isomers were shorter than those found in some previous studies, especially at high temperatures. At most conditions, the ignition delay time increases for each isomer in the following order: 1-butanol, 2-butanol and i-butanol nearly equal, and t-butanol. In addition, t-butanol has a higher activation energy than the other three isomers. In a separate series of high-pressure experiments, ignition delay times of 1-butanol in stoichiometric air were measured at temperatures as low as 800 K. At temperatures below 1000 K, pre-ignition pressure rises as well as significant rollover of ignition delay times were observed. Modeling of all collected data using several different chemical kinetic mechanisms shows partial agreement with the experimental data depending on the mechanism, isomer, and conditions. Only the mechanism developed by Vranckx et al. [1] partially explains the rollover and pre-ignition observed in stoichiometric experiments in air.