We test the performance of GRI-Mech extensively as new data becomes known to us and as new optimizations are completed. In general we find that each new version of GRI-Mech performs similarly or slightly better than its predecessor. For some conditions, usually well removed from the ones used in optimizations, we invariably find that there are notable disagreements with some experiments. Examples of such behavior can be found in the validation sections of this document.
The current release
of GRI-Mech is
GRI-Mech 3.0 
It is a compilation of 325 elementary chemical reactions and associated rate coefficient expressions and thermochemical parameters for the 53 species involved in them. It replaces our previous releases of GRI-Mech, both versions 1.2 and 2.11, which are no longer distributed. It differs from the previous release in that kinetics and target data have been updated, improved, and expanded. Propane and C2 oxidation products have been added, and new formaldehyde and NO formation and reburn targets included. For a limited time, the Web page for the previous versions 1.2 and 2.11 may be accessed by investigators concluding their studies with the old mechanism. Later, you will need to contact the authors. Version 3.0 should be used, as it provides superior overall performance and supercedes the previous versions.

The conditions for which GRI-Mech 3.0 was optimized, limited primarily by availability of reliable optimization targets, are roughly 1000 to 2500 K, 10 Torr to 10 atm, and equivalence ratio from 0.1 to 5 for premixed systems. The validation pages show the performance of GRI-Mech 3.0 for an extensive range of combustion conditions. Cautious use of GRI-Mech 3.0 outside the optimization and validation ranges is not unreasonable, essentially because the elementary reactions, which include all steps thought to be important for describing natural gas ignition and flame propagation (including NO formation and reduction) are described by rate parameters that reflect current understanding of elementary reaction rate theory. A few aspects of natural gas combustion chemistry are not described by GRI-Mech 3.0; these include soot formation and the chemistry involved in selective non-catalytic reduction of NO. The latter may be important in natural gas reburning at lower temperatures.

GRI-Mech has been optimized for methane and natural gas as fuel. As such it does include reactions that are involved in the combustion of other hydrocarbon constituents of natural gas (e.g., ethane and propane). However, since the optimization did not include targets relevant to other fuels, GRI-Mech should not be used to model combustion of pure fuels such as methanol, propane, ethylene, and acetylene even though these compounds are on the GRI-Mech species list.

GRI-Mech main menu