These best practices for mechanism reduction are designed for combustion applications.
To accomplish an effective mechanism reduction for engine combustion, you first must know the following:
What is the desired purpose of the reduced mechanism:
Flame speed or ignition time?
Which emissions quantities need to be captured accurately? NOx? CO? UHC? Soot?
The model fuel composition:
Typically, a surrogate for liquid fuels (see the Reaction Workbench tutorial on using the Surrogate Blend Optimizer).
May be the actual or an approximate (surrogate) composition for gaseous fuels.
Engine operating conditions, including:
Estimated ranges of temperatures, pressures, EGR levels, and equivalence ratios in the combustion chamber.
For IC engines, these are the estimated local conditions in the cylinder, prior to ignition (whether the ignition is by compression, spark or knock event); these are not the peak pressures /temperatures achieved by ignition. For flame propagation in spark engines, these are the conditions of the unburned mixture prior to the spark event.