Reaction Workbench has several mechanism reduction techniques available. The majority of mechanism reduction options are accessible through Reaction Workbench within the Guided Mechanism Reduction facility. You can run mechanism reduction seeking either the solution of a nominal run or the solution of a parameter study, whenever available.
The reduction methods available are described below:
DRG, DRGEP, and DRGPFA - DRG/DRGEP/DRGPFA reduction stops when an increase in the species removal threshold leads to error in target parameters beyond tolerance setting. Increasing the threshold removes a larger number of species simultaneously.
Sensitivity Analysis Option in DRG/DRGEP/DRGPFA - This option is used after DRG/ DRGEP/DRGPFA to identify a pool of candidates to be removed from the skeletal mechanism. The method creates a set of candidate species for further reduction and removes each species in the pool and calculates the target error with and without the species. Each species is ranked based on target error.
Isomer Lumping - Lumping uses species SMILES to detect structural isomers among non-cyclic species and groups ("lumps") species into pseudospecies according to similarities, also based on the SMILES. The lumping will run iteratively until the target error is met.
PCA - PCA is a relatively simpler method that employs sensitivity data. This method can be expensive for large mechanisms.
QSSA - The Quasi-steady-state approximation involves solving eigenvalues of the system to determine species and pathways that can be removed. It creates a skeletal form of the mechanism. A list of quasi-steady-state species is identified. Instead of setting up a global reduced mechanism, these QSS species are simply removed from the full mechanism to generate a skeletal mechanism. It is not as robust as DRG or DRGEP and may take significantly more time.
FSSA - A full species sensitivity analysis (FSSA) is provided, to be used as the last resort when the mechanism cannot be reduced further by any other method. The sensitivity analysis is performed in the following steps:
Remove each species individually from the smallest skeletal mechanism generated so far and calculate the induced error on target parameters for this species.
Rank the species using their induced error in ascending order.
Remove candidate species from the skeletal mechanism in the order prescribed in step b and calculate the cumulative induced error on target parameters after each species is removed. Stop the process when the cumulative induced error is beyond the specified tolerance level.
Compare Initial vs. Target Projects - Compare Initial vs. Target Projects performs comparison of the calculated targets from the Initial Ansys Chemkin project and Target Chemkin project. It does not perform any mechanism reduction.
Because the project used to cover the desired range of conditions must be run to calculate the induced error on target parameters, steps a and c in the sensitivity analysis can be extremely time-consuming. Moreover, the number of species removed by the sensitivity analysis is unpredictable, ranging from a few species to 10% to 20% of species in a skeletal mechanism. This method should be used only as the very last step in a mechanism reduction session.