Elementary Chemical Kinetics and Detailed Chemical Kinetic Models

The aim of this article is to present the modern approach to chemical kinetics, in particular as applied to combustion in the broadest sense (from chimney fires to Ariane 6) and to heat treatment. The same approach could be applied to many other fields. Detailed chemical kinetics is now capable of making qualitative predictions for many systems, and quantitative predictions for just a few. This approach does not replace the thermodynamic approach, which gives the temperature, pressure and composition of a system at thermodynamic equilibrium, but complements it in the sense that the thermodynamic approach in no way describes the time needed to reach this equilibrium, if ever, since for many processes the residence time is less than the time needed to reach thermodynamic equilibrium. As a result, the thermodynamic approach is in many cases almost irrelevant, and time must be introduced into the equations to get closer to the reality of the process. This is the domain of chemical kinetics, and requires the writing of detailed kinetic mechanisms. However, like the thermodynamic approach, chemical kinetics requires not only thermodynamic data, but also kinetic data. The detailed kinetic mechanism is then implemented and compared with experimental data (flame structure, detonation velocity, fundamental flame velocities (deflagration), auto-ignition delay, etc.) obtained in so-called ideal laboratory apparatus: shock tubes, flow reactors, perfectly stirred reactors, static reactors, mainly. These data can include species profiles, auto-ignition times and pressure profiles, among others. There is also a wealth of data obtained using industrial equipment that is less conducive to obtaining unambiguous data on experimental conditions (temperature, pressure, flow, etc.). However, all data are of interest, and a model can be expected to reproduce experimental trends if it is not quantitative, which in itself is not without interest.