The Reaction Workbench contains a collection of powerful mechanism reduction methodologies. As powerful as they are, however, using a single reduction methodology once can only reduce the mechanism to a limited extent. To generate the smallest skeletal mechanism possible while keeping the target accuracy, different methodologies must be combined in an iterative process to further reduce the size of the mechanism. Multiple reduction steps can be conducted interactively, so you decide which technique to use next after each reduction operation is completed, and each new step automatically builds on the previous results. A mechanism reduction session addresses these issues so that you can record the optimal reduction process on-the-fly and replay the process automatically.

Reaction Workbench provides options to choose the sequence of reduction operations during the iterative process.

Because the PCA requires full sensitivity calculations of the model using the full mechanism, it is not a recommended reduction method. The recommended approach is to first use the Directed Relation Graph method to generate the smallest skeletal mechanism possible from the full mechanism, and then apply the lumping or computational singular perturbation method to generate the reduced mechanism from the skeletal mechanism, if desired. When the solution of a parameter study is used to represent a set of target conditions for mechanism reduction, a higher number of parameter study runs will correspond to a larger number of species retained in the skeletal or reduced mechanism. If a smaller number of species is desired, a smaller number of parameter study runs (that is, a smaller number of target conditions) should be included in the mechanism reduction. Once the skeletal mechanism or the reduced mechanism is generated, the user can obtain a new Ansys Chemkin project using the new mechanism with exactly the same model setup by clicking the Create New Project button. This allows the user to choose a project name and the location of the new working directory during the new project’s setup process.

This automated facility allows you to specify exactly what targets and what degree of accuracy are of interest. The Mechanism Reduction Facility is designed to act on a set of simulations that have been run within an active Ansys Chemkin project. In this way, the reduction can act on the results of a parameter study spanning a range of conditions, as well as on an individual simulation run.

The Reaction Workbench also facilitates the use of a combination of the reduction techniques in sequence. In the Reaction Workbench Tutorial Guide, the tutorial, "Mechanism Reduction for Compression Ignition Conditions" illustrates how the Reaction Workbench can set up a sequence of projects to use multiple reduction techniques.

For a theoretical discussion of the mechanism reduction methods, see Theory for Reaction Workbench Models .