Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

We have designed an opposed-flow flame system to investigate the chemical composition of non-premixed flames using in situ flame-sampling molecular-beam mass spectrometry with synchrotron-generated tunable vacuum-ultraviolet light as an ionization source. This paper provides details of the experimental apparatus, sampling method, and data-reduction procedures. To test the system, we have investigated the chemical composition of three low-pressure (30-50 Torr), non-premixed, opposed-flow acetylene( Ar)/O2(Ar) flames. We measured quantitative mole-fraction profiles as a function of the distance from the fuel outlet for the major species and several intermediates, including the methyl and propargyl radicals. We determined the temperature profiles of these flames by normalizing a sampling-instrument function to thermocouple measurements near the fuel outlet. A comparison of the experimental temperature and major species profiles with modeling results indicates that flame perturbations caused by the sampling probe are minimal. The observed agreement between experimental and modeled results, apparent for most combustion species, is similar to corresponding studies of premixed flames. © 2012 The Combustion Institute.

The H-assisted isomerization of fulvene to benzene is characterized in detail using quantum chemistry, transition state theory, classical trajectory, and master equation calculations. This multistep isomerization involves 10 transition states, nine of which are found to contribute non-negligibly to the overall kinetics. Calculated temperature- and pressure-dependent rate coefficients are presented for H + fulvene → products, with care taken to quantify uncertainties in the theoretical predictions arising from various aspects of the calculation. The rate coefficients agree with past theoretical work within these estimated uncertainties. This fast isomerization proceeds via a cyclopropylcarbinyl intermediate-a substituted cyclopropyl group adjacent to a radical carbon-that provides a facile route for the carbon bonding rearrangement. Analogous H-assisted isomerization pathways involving cyclopropylcarbinyl intermediates are characterized using quantum chemistry calculations for four second-ring isomers of naphthalene: fulvalene, azulene, 1-methyleneindene, and 2-methyleneindene. These processes, and those for larger polycyclic aromatic hydrocarbons (PAHs), may be characterized in a general way as occurring in five steps: H additions, H shifts, cyclopropylcarbinyl intermediate formation, cyclopropylcarbinyl intermediate ring opening, and H-atom regeneration. Trends in the energetics of each of these steps with respect to PAH size and composition are discussed. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

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.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.