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Multispecies laser measurements of n-butanol pyrolysis behind reflected shock waves



Time histories of OH, H2O, and 306.8 nm absorbance were measured behind reflected shock waves in mixtures of 1% n-butanol in Ar. Reflected shock conditions covered temperatures (T5) from 1274 to 1439 K and pressures (P5) near 1.5 atm. OH was measured using laser absorption of the R1(5) line of the A–X (0, 0) transition at 306.7 nm. Each experiment was repeated with the laser tuned off the narrow OH absorption feature to subtract broadband interference from CH2O and CH3CHO. Knowledge of the absorption coefficients of CH2O and CH3CHO at this nonresonant wavelength was then used to compare ultraviolet (UV) absorbance to model predictions. H2O was measured using DFB diode laser absorption of a well-characterized absorption feature near 2.5 μm. These measured time histories, which should prove highly useful in reaction mechanism development, were then compared to simulations based on the comprehensive n-butanol oxidation mechanism by Curran et al. (Combust Flame, 2010, 157, 363–373). Using that mechanism, it was determined that the n-butanol decomposition pathways through C4H8OH(γ) should be strongly favored over C4H8OH(α) and that the C4H8OH(δ) pathway should also be increased by 25%. The specific rate adjustments inferred in this work were found to be highly mechanism dependent, though the overall reaction path analyses were very similar for all the mechanisms studied. In addition to Curran et al. (2010), two other mechanisms were examined, revealing the importance of four specific sets of reactions in n-butanol pyrolysis. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 303–311, 2012