Multi-species measurements in 1-butanol pyrolysis behind reflected shock waves

Abstract

The kinetics of 1-butanol pyrolysis were investigated by measuring multi-species time histories using shock tube/laser absorption methods. Species time histories of OH, H2O, C2H4, CO, and CH4 were measured behind reflected shock waves using UV and IR laser absorption during the high-temperature decomposition of 1% 1-butanol/argon mixtures. Initial reflected shock temperatures and pressures for these experiments covered 1250–1650K and 1.3–1.9atm. Measured OH and H2O time histories are in good agreement with previous experimental studies; measured C2H4, CO, and CH4 time histories are the first reported for this fuel in shock tube experiments.Production pathways and sensitivities for the measured species are analyzed using the recent Sarathy et al. (2012) [37] detailed mechanism. Simulations using this mechanism underpredict H2O, OH, and C2H4 mole fractions, overpredict CH4 mole fractions, and significantly underpredict CO mole fractions at early times. As discussed in past papers and confirmed in this study, the branching ratios of H abstraction rates from 1-butanol, which are not precisely known, can significantly affect H2O time history simulations. These simulations show that H2O is produced primarily through H-atom abstraction from 1-butanol by OH, and therefore H2O time histories are extremely sensitive to 1-butanol decomposition channels that contribute to the OH radical pool. Simulations also show that more C2H4 would be produced by faster decomposition of 1-butanol through several channels that also affect H2O production. Finally, simulations show that CO time histories are strongly sensitive to 1-butanol decomposition into nC3H7 and CH2OH, especially at early times. Evidence is presented that indicates this decomposition pathway is too slow in the simulations by a factor of three to five at conditions of the current study.