The oxidation of 1,3-butadiene/n-butanol flames was studied in a combined experimental and modeling work. The goal is to provide a detailed combustion chemistry model that allows for identification of the important pathways for butadiene and butanol oxidation as well as the formation of soot precursors and aromatics. Therefore, the chemical composition has been investigated for three low-pressure (20-30 Torr) premixed flames, with different shares of butanol ranging between 25% and 75% compared to butadiene in 50% argon. Mole fraction profiles of reactants, products, and intermediates including C3Hx and C4Hx radicals as well as mono-aromatics such as benzyl radicals, were measured quantitatively as a function of height above burner surface employing flame-sampled molecular-beam mass spectrometry (MBMS) utilizing photoionization with tunable vacuum-ultraviolet synchrotron radiation. The comparison of measured species profiles with modeling results provides a comprehensive view of the reaction model's quality and predictive capability with respect to the combustion chemistry of 1,3-butadiene and n-butanol under the current low-pressure, high-temperature conditions. In general, a good agreement was found between experimental and modeled results. Reaction flux and sensitivity analysis were used to get more insights into the combustion of the fuels.
This paper presents a detailed investigation of 2-methylbutanol combustion chemistry in low-pressure premixed flames. This chemistry is of particular interest to study because this compound is potentially a lignocellulosic-based, next-generation biofuel. The detailed chemical structure of a stoichiometric low-pressure (25 Torr) flame was determined using flame-sampling molecular-beam mass spectrometry. A total of 55 species were identified and subsequently quantitative mole fraction profiles as function of distance from the burner surface were determined. In an independent effort, a detailed flame chemistry model for 2-methylbutanol was assembled based on recent knowledge gained from combustion chemistry studies for butanol isomers ([Sarathy et al. Combust. Flame 159 (6) (2012) 2028-2055]) and iso-pentanol (3-methylbutanol) [Sarathy et al. Combust. Flame 160 (12) (2013) 2712-2728]. Experimentally determined and modeled mole fraction profiles were compared to demonstrate the model's capabilities. Examples of individual mole fraction profiles are discussed together with the most significant fuel consumption pathways to highlight the combustion chemistry of 2-methylbutanol. Discrepancies between experimental and modeling results are used to suggest areas where improvement of the kinetic model would be needed.
In this study, two flames of iso-pentanol were stabilized on a 60-mm flat flame burner at a low pressure of 15 Torr and analyzed by a flame-sampling molecular-beam setup coupled to a mass spectrometer (MBMS). Singlephoton ionization by synchrotron-generated vacuum-UV radiation with high energy resolution (E/ΔE ∼0.04 eV) and/or electron ionization was combined with a custom-built reflectron time-of-flight spectrometer providing high mass resolution (m/Δm = 3000). Mole fraction profiles for more than 40 flame species and the temperature profile were determined experimentally. The flame temperatures were measured using OH laser induced fluorescence and used as input parameters for the model calculations. The experimental dataset was used to guide the development of a combustion chemistry model for the high-temperature oxidation chemistry of iso-pentanol. The chemical kinetic model is herein validated for the first time against detailed speciation profiles of combustion intermediates and product species including C5 branched aldehydes, enols, and alkenes. In a separated study, the model was validated against a number of different datasets including low and high temperature ignition delay in rapid compression machines and shock tubes, jet stirred reactor speciation data, premixed laminar flame speed, and opposed-flow diffusion flame strained extinction.