Speciation measurements in shock tubes for validation of complex chemical kinetics mechanisms: Application to 2-Methyl-2-Butene oxidation

Shock-tube species time histories can be used to generate multiple validation targets to develop and validate detailed chemical kinetics mechanisms. In this study, new shock-tube species time-history data are provided to further validate the detailed mechanisms for 2-methyl-2-butene (2M2B). Experiments were conducted in mixtures of 2M2B/O-2 diluted in 99.5% inert gas at three equivalence ratios of phi = 0.5, 1.0, and 2.0 over a temperature range of 1396 to 1752 K near atmospheric pressure. Time histories of CO and H2O were measured using laser absorption diagnostics near 4.6 and 1.4 mu m, respectively. Chemiluminescence from OH* was also collected near 307 nm to allow ignition delay time determination. Detailed procedures and considerations for the data processing of the laser absorption experiments are provided. The results from the OH* profiles showed two distinct peaks: one near time-zero and the other later in the experiment corresponding to the main ignition. The predictions from three 2M2B kinetics mechanisms were compared with the experimental results. A quantitative comparison is also presented using the multiple characteristic times extracted from the species time history profiles to quantify the performance of the mechanisms. A reaction pathway analysis was performed on the decomposition of 2M2B, revealing clear discrepancies in the major reaction pathways of these mechanisms. A sensitivity analysis was also performed, leading to similar conclusions regarding the differences among the mechanisms. The sensitivity analysis also showed that the OH* peak near time-zero is mainly due to the rapid 2M2B fuel decomposition reactions, indicating that these reactions can be independently validated using the OH* peak near time-zero as a target. This paper provides not only the first detailed species time-history measurements for 2M2B in a shock tube, but it also documents the proper collection and interpretation of such data, which is useful for future studies. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.