Hydrocarbon combustion, kinetics

Westbrook, C.K. and Dryer, F.L., Chemical kinetic modeling of hydrocarbon combustion, Prog. Energy Combust. Sci., 1984, 10, 1-57. 

The solution procedure to this equation is the same as described for the temporal isothermal species equations described above. In addition, the associated temperature sensitivity equation can be simply obtained by taking the derivative of Eq. (2.87) with respect to each of the input parameters to the model. The governing equations for similar types of homogeneous reaction systems can be developed for constant volume systems, and stirred and plug flow reactors as described in Chapters 3 and 4 and elsewhere [31-37], The solution to homogeneous systems described by Eq. (2.81) and Eq. (2.87) are often used to study reaction mechanisms in the absence of mass diffusion. These equations (or very similar ones) can approximate the chemical kinetics in flow reactor and shock tube experiments, which are frequently used for developing hydrocarbon combustion reaction mechanisms. 

The new specifications not only limit the concentration of sulfur to 0.05% but also specify that the fuel should have the combustion properties of a 10% or lower aromatics-containing fuel and have a minimum cetane number of 40. Fuels that have more than 10% aromatics are now able to meet these specifications through additives (22). However, as smoke emission standards become more restrictive, the aromatics content of diesel fuels may have to be lowered to a true value of 10% or less. A very thorough review of the consequences of this potential problem has recently been written by Stanislaus and Cooper, which covers in detail aromatic hydrocarbon hydroprocessing kinetics, thermodynamics, catalyst compositions, and mechanisms (109). There is little need to repeat the details of that report... 

There has been a great deal of research on the combustion of small hydrocarbons, including nitrogen-cycle chemistry leading to nitric-oxide formation and abatement [138]. There are a number of methane-air reaction mechanisms that have been developed and validated [274,276,278], the most popular one being GRI-Mech [366]. There is also active research on the kinetics of large hydrocarbon combustion [81,88,171,246,328-330,426]. 

The previous intent has been to use kinetics simply as a tool to describe qualitatively the particular aspect of combustion under study. Numerical values of the kinetic constants were thus assumed for illustrative purposes or approximated from other types of data by making admittedly questionable major assumptions. Approximations include, for example, the extrapolation of low temperature hydrocarbon oxidation rates to high temperature hydrocarbon combustion rates. Other schemes involve application of semiempirical laminar flame speed theories or of flow patterns in the wake of a bluff body immersed in an air stream (43). 

Kinetics of CH Radical Reactions Important to Hydrocarbon Combustion Systems... 

One of the important hydrocarbon combustion reaction intermediates is the CH radical. Although CH chemiluminescence (.42 A — X2ir) has been observed in many hydrocarbon flames, the mechanism of CH formation and its reaction kinetics have been difficult to unravel in situ due to the low steady-state concentrations and the complex nature of combustion reactions. This project was undertaken to investigate a means of CH radical production and to study its reactions with various important species so that an overall picture of the oxidation processes, particularly with regard to the mechanism of NO formation, may be better understood. 

In this work, we have demonstrated that the CH radical can be generated with sufficiently high concentrations by means of the multiphoton dissociation of CHBr at 193 nm for kinetic measurements. The formation and decay of the CH radical was monitored by the laser-induced fluorescence technique using the (A2 b — X2ir) transition at 430 nm. Several rate constants for the reactions relevant to high temperature hydrocarbon combustion have been measured at room temperature. One of the key reactions, CH + N2, has been shown to be pressure-dependent, presumably due to the production of the CHN2 radical at room temperature. 

Petrella, R. V. Studies of the combustion of hydrocarbons by kinetic spectroscopy. II. The explosive combustion of styrene inhibited by halogen compounds, private communication, 1972. 

Production of soot in hydrocarbon combustion is a complicated kinetic process involving transformations of fuel molecules in fuel-rich zones under the influence of heat (called pyrolysis) to produce new fuel molecules that contain more C and less H than the original molecules. The elementary steps involved are so numerous that simplifying approximations are essential for both efficient computation of soot production and development of understanding of the kinetic mechanisms. Progress is being made toward discovery of suitable simplications [49]. It is known that small... 

According to the Semenov theory of chain reactions [2] the rate of oxidation depends strongly (half to first power) on the rate of production of new chain centres. However, the problem that has bedevilled combustion kinetics over many years is the chemical nature of the process. Reactions (1) and (lA) are the primary initiation reactions in hydrocarbon oxidation, to be distinguished from secondary initiation processes such as reaction (13) where radicals are produced from a stable intermediate... 

C.K. Westbrook and F.L. Dryer, Chemical Kinetic Modelling of Hydrocarbon Combustion, Prog. Energy Comb. Sci. 10 (1984) 1. 

The distribution of water and hydrogen as products of the hydrocarbon combustion described by reaction Cl is calculated from the water-gas-shift equilibrium. All reactions are treated as irreversible reactions and the kinetic rates of the reactions (Cl - C3 are taken from (11],... 

Methyl and hydroxyl radicals are formed at an early stage in hydrocarbon combustion processes. The kinetics of the recombination reaction... 

Westbrook, C. K., and F. L. Dryer. 1981. Chemical kinetic modeling of hydrocarbon combustion. Combustion Science Technology 27 31-43. 

Moisan, M., Barbeau, Moreau, S., J., Pelletier, Tabrizian, M., Yahia, L.H. (2001), Int. J. Pharm., vol. 226, p. 1. Molchanov Yu.S., Starik, A.N. (1984), Kinetics of Vibrational Energy Exchange in Hydrocarbon Combustion Products during Gas Expansion in Supersonic Nozzles, Central Institute of Aviation Motors, Preprint 10160,... 

Westbrook, C. K. Dryer, F. L. "Chemical Kinetics Modeling of Hydrocarbon Combustion" Lawrence Livermore National Laboratory Report No. UCRL-88651 February, 1983. 

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