The Chemistry Set Pre-Processing Utility is used to create, modify, select, and validate a chemistry set, which is necessary for setting up an Ansys Forte simulation (see Chemistry). The Pre-Processing panel can be opened or viewed from the Pre-Processing command on the Utility menu. The Pre-Processing panel displays both the Working Dir and the chemistry set defined for the currently selected project. The Working Dir is the directory or folder on your computer’s hard-disk where all generated input and output files will be created when the simulation is run. The chemistry set does not need to be located in the same directory as the Working Directory and each input file contained within the chemistry set can be stored in any location. The default location in Ansys Forte is the System Data directory, which is the data directory of your Ansys Forte installation location.
Note: Ansys Chemkin sample mechanisms and Model Fuel Library mechanisms use the @DATA@ macro to reference the location of the folder containing those mechanisms. The macro typically refers to the data folder under the Ansys installation location: Program Files\ANSYS Inc\V242\reaction\data. When using these mechanisms in Forte, the following message appears, indicating that Forte could not resolve the location referenced by the macro.
The chemistry set contains one or more @DATA@ references. This is meant to resolve to a system data directly, typically the one in which the chemistry set resides. Please specify the location of the data directory in the browser.
Click and a file browser will appear. Provide the correct path to the \reaction\data folder to use the mechanism in Forte.
From the Pre-Processing panel, you can create a new chemistry set, edit an existing chemistry set, or select a different chemistry set. A chemistry set consists of input files that contain species and reaction descriptions, as well as thermodynamic data and, in some cases, gas transport-property data. Pre-processing these files serves to verify the consistency and completeness of the chemistry set. In addition, this step provides information about what chemical species are present in the system, and whether surface chemistry is present.
A chemistry set consists of several input files, each containing a different type of chemical data. The collection of chemical data in a given chemistry set is often called a reaction mechanism. The major components of a chemistry set are:
Gas-phase kinetics file: a file containing a description of the species contained in and the reactions occurring in the gas phase, often named chem.inp;
Surface kinetics file: a file containing a description of the reactons occurring at the gas-surface interface or on the surface, and the species contained in the dispered phase or the bulk liquid phase, often named surf.inp;
Thermodynamics data file: a file containing thermochemical data for the chemical species of interest, often named therm.dat; and
Gas-phase transport data file: a file containing gas-phase transport data, often named tran.dat.
A set of gas-phase and/or surface reactions are generally developed using specific thermochemical data. Thus, the gas-phase kinetics, surface kinetics, and thermodynamic data are most reliable when used together as a set in reacting-flow simulations. Once a chemistry set is defined, it can be saved and referenced easily in future simulations.
The gas-phase kinetics file (chem.inp) is always required in the chemistry set for any gas-phase flow simulation. You can define the thermodynamic data in therm.dat, and define transport data in tran.dat. Alternatively, these data can be included in chem.inp, so that therm.dat and tran.dat are not needed. For more details on the format of chem.inp, refer to Thermodynamic Data in the Chemkin Input Manual.
In two situations, a surface kinetics file, surf.inp, is required:
When the Methods of Moment soot model (see Soot Model) is selected. In this case, the surface kinetics file is required to specify a dispersed particulate bulk phase, and to specify reactions that occur on the particle surface to initiate the formation of soot particles.
When the Eulerian two-phase flow simulation (see Gas-Phase and Eulerian Two-Phase Flow Simulations) is selected. In this case, the surface kinetics file is required to define a bulk phase with keyword
LIQUIDand the species contained within. No reaction specification is needed. The liquid species defined in this file and the gas species defined in the gas-phase kinetics file are used to specify the two-phase working fluid’s concentrations. The specification of thermodynamic data for the liquid species must follow certain format requirements, which are detailed in Thermodynamic Data and Reaction Mechanism Description in the Chemkin Input Manual.
Note: In an Eulerian two-phase flow simulation, if Phase Equilibrium is selected, ensure that at least one of the liquid species defined in the surface kinetics file (surf.inp) has its corresponding vapor species defined in the gas-phase kinetics file (chem.inp).