GRImech version 3.0 is a relatively well-tested reaction mechanism that was developed under the auspices of the Gas Research Institute. This reaction mechanism, consisting of gas-phase chemistry, thermodynamic, and transport data files, is provided as one of the default chemistry sets in Ansys Chemkin in the system data folder. A detailed description of the development and extensive validation of this mechanism is available [9].

The gas-phase kinetics input file contains 5 elements, C, 0, O, N and Ar, 53 chemical species, and 325 reactions. The reaction mechanism describes the combustion of methane and smaller species such as hydrogen, as well as the formation of nitrogen oxide pollutants. Most of the reactions are reversible; only a small number of irreversible reactions are included. Many of the reactions have explicit descriptions of their pressure-dependencies, using the Troe formulation and including enhanced collision efficiencies for particular species.