Wing Tsang

Chemical Kinetic Data Base for Combustion Chemistry. Part I. Methane and Related Compounds

This document contains evaluated data on the kinetics and thermodynamic properties of species that are of importance in methane pyrolysis and combustion. Specifically, the substances considered include H, H2, O, O2, OH, HO2, H2O2, H2O, CH4, C2H6, HCHO, CO2, CO, HCO, CH3, C2H5, C2H4, C2H3, C2H2, C2H, CH3CO, CH3O2, CH3O, singlet CH2, and triplet CH2. All possible reactions are considered. In arriving at recommended values, first preference is given to experimental measurements. Where data do not exist, a best possible estimate is given. In making extrapolations, extensive use is made RRKM calculations for the pressure dependence of unimolecular processes and the BEBO method for hydrogen transfer reactions. In the total absence of data, recourse is made to the principle of detailed balancing, thermokinetic estimates, or comparisons with analogous reactions. The temperature range covered is 300–2500 K and the density range 1×1016–1×1021 molecules/cm3. This data base forms a subset of the chemical kinetic data...

Evaluated kinetic data for combustion modeling: supplement II

This compilation updates and expands a previous evaluation of kinetic data on elementary, homogeneous, gas phase reactions of neutral species involved in combustion systems [J. Phys. Chem. Ref. Data 21, 411 (1992)]. The work has been carried out under the auspices of the European Community Energy Research and Development Program. Data sheets are presented for some 78 reactions and two tables in which preferred rate parameters are presented for reactions of ethyl, i‐propyl, t‐butyl, and allyl radicals are given. Each data sheet sets our relevant thermodynamic data, experimental kinetic data, references, and recommended rate parameters with their error limits. A table summarizing the recommended rate data is also given. The new reactions fall into two categories: first, to expand the previous compilation relating largely to the combustion in air of methane, ethane and aromatic compounds; and second, provide data for some of the key radicals involved in the combustion of higher alkanes.

Chemical Kinetic Data Base for Combustion Chemistry. Part 3: Propane

This publication contains evaluated and estimated data on the kinetics of reactions involving propane, isopropyl radical, n‐propyl radical, and various small inorganic and organic species which are of importance for proper small inorganic and organic species which are of importance for proper understanding of propane pyrolysis and combustion. It is meant to be used in conjunction with the kinetic data given in earlier publications which are of direct pertinence to the understanding of methane pyrolysis and combustion, but which also contain a large volume of data that are applicable to the propane system. The temperature range covered is 300–2500 K and the density range 1×1016 to 1×1021 molecules cm−3.

Chemical Kinetic Data Base for Propellant Combustion I. Reactions Involving NO, NO2, HNO, HNO2, HCN and N2O

This publication contains evaluated chemical kinetic data on a number of single step elementary reactions involving small polyatomic molecules which are of importance in propellant combustion. The work involves the collection and evaluation of mechanistic and rate information and the use of various methods for the extrapolation and estimation of rate data where information does not exist. The conditions covered range from 500–2500 K and 1017–1022 particles/cm3. The results of the first years effort lead to coverage of all pertinent reactions of the following species; H, H2, H2O, O, OH, OCHO, CHO, CO, NO, NO2, HNO, HNO2, HCN, and N2O.

Chemical Kinetic Data Base for Combustion Chemistry. Part 2. Methanol

This publication contains evaluated and estimated data on the kinetics of reactions involving methanol and hydroxymethyl radicals and various small inorganic and organic species which are of importance for the proper understanding of methanol combustion and pyrolysis. It is meant to be used in conjunction with the kinetic data given in an earlier publication pertaining to methane pyrolysis and combustion, but which also contains a large volume of data that are applicable to the methanol system. The temperature range covered is 300–2500 K and the density range 1×1016 to 1×1021 molecules cm−3.

Thermochemical and chemical kinetic data for fluorinated hydrocarbons

A comprehensive, detailed chemical kinetic mechanism was developed and is presented for C1 and C2 fluorinated hydrocarbon destruction and flame suppression. Existing fluorinated hydrocarbon thermochemistry and kinetics were compiled from the literature and evaluated. For species where no or incomplete thermochemistry was available, these data were calculated through application of ab initio molecular orbital theory. Group additivity values were determined consistent with experimental and ab initio data. For reactions where no or limited kinetics were available, these data were estimated by analogy to hydrocarbon reactions, by using empirical relationships from other fluorinated hydrocarbon reactions, by ab initio transition state calculations, and by application of RRKM and QRRK methods. The chemistry was modeled considering different transport conditions (plug flow, premixed flame, opposed flow diffusion flame) and using different fuels (methane, ethylene), equivalence ratios, agents (fluoromethanes, fluoroethanes) and agent concentrations. This report provides a compilation and analysis of the thermochemical and chemical kinetic data used in this work.

Chemical Kinetic Data Base for Propellant Combustion. II. Reactions Involving CN, NCO, and HNCO

This paper contains evaluated chemical kinetic data on single step elementary reactions involving small polyatomic molecules which are of importance in propellant combustion. The work consists of the collection and evaluation of mechanistic and rate information and the use of various methods for the extrapolation and estimation of rate data where information does not exist. The conditions covered range from 500‐2500 K and 1017‐1022 particles cm−3. The results of the second year’s effort add to the existing data base reactions involving CN, NCO, and HNCO with each other and the following species: H, H2, H2O, O, OH, HCHO, CHO, CO, NO, NO2, HNO, HNO2, HCN, and N2O.

Heats of Formation of Organic Free Radicals by Kinetic Methods

It has long been recognized that the key intermediates for the majority of the reactions of organic molecules in the gas phase, and frequently in the liquid phase as well, are free radicals. An important prerequisite for the description of the behavior of such systems is their thermodynamic properties. At first glance it may be surprising that thermodynamic properties should have any applicability to transient species that are present in trace quantities and disappear in short times. Indeed, if the kinetic properties of such systems are known, then thermodynamic properties are not really necessary and can in fact be derived from the kinetics. In reality, however, kinetic properties may be unavailable or difficult to measure. Thermodynamic properties serve as limits for kinetics and more generally as a basis for the estimation and evaluation of kinetic information [1]. More directly, through the equilibrium constant, rate constants for the reverse direction can be directly calculated from that in the forward direction. There are other physical situations where local thermodynamic equilibrium turns out to be a satisfactory approximation and kinetic information is not important.

Aromatic and polycyclic aromatic hydrocarbon formation in a premixed propane flame

Experimental and detailed chemical kinetic modeling has been performed to investigate aromatic and polycyclic aromatic hydrocarbon (PAH) formation pathways in a premixed, rich, sooting, propane-oxygen-argon burner stabilized flame. An atmospheric pressure, laminar flat flame operated at an equivalence ratio of 2.6 was used to acquire experimental data for model validation. Gas composition analysis was conducted by an on-line gas chromatograph/mass spectrometer (GC/MS) technique. Measurements were made in the main reaction and post-reaction zones for a number of low molecular weight species, aliphatics, aromatics, and polycyclic aromatic hydrocarbons (PAHs) ranging from two to five-fused aromatic rings Reaction flux and sensitivity analysis were used to help identify the important reaction sequences leading to aromatic and PAH growth and destruction in the propane flame. Benzene formation was shown to be dominated by the propargyl recombination reaction. A secondary benzene formation pathway occurred from ...

Influence of CF3I, CF3Br, and CF3H on the high-temperature combustion of methane☆

Abstract The effects of a number of flame retardants (CF 3 I, CF 3 Br, and CF 3 H) on the high-temperature reactions of methane with air in a plug flow reactor are studied by numerical simulations using the Sandia Chemkin Code. 1 The dependence of (a) the ignition delay and (b) time for substantially complete reaction as a function of temperature and additive concentrations are calculated. In agreement with experiments, the ignition delay can be increased or decreased by the addition of retardants. The reaction time is always increased by additives. The mechanism for these effects has been examined. It is concluded that the ignition delay is controlled by the initial retardant decomposition kinetics, which releases active species into the system. These species can either terminate or initiate chains. The reaction time is largely a function of the concentrations of the active radicals H, OH, and O that are formed during the combustion process. It is shown that their concentrations, particularly those of H atoms, are lowered in the presence of the retardants. We find that the chemical mechanism governing reaction time is very similar to that which controls the flame velocity and a correlation between decreases in flame velocity and H-atom concentration is demonstrated. The calculations suggest that relative reaction time and H-atom concentrations should be effective measures for the estimation of retardant effectiveness.