1.4. Setting Up a Problem with Chemkin

There are six basic steps involved in using Ansys Chemkin to solve a typical chemical process-modeling problem. Depending on the particular Chemkin Reactor Model selected, some of the input discussed here will not be required for a particular problem; these are indicated in parentheses.

  1. Decide on your modeling approach

    For some problems the choice of Reactor Model will be obvious. In other cases, you have a range of options. For example, the reacting-flow region may be modeled as a network of reactor models representing separate zones with different flow characteristics. In other cases, a single, well mixed zone or perfectly stirred reactor may suffice. For network models, there may be recirculation between zones and multiple inlets that need to be defined. Other choices include using a zero-dimensional description of the geometry or using a 1- or 2-dimensional description. For complex systems, we recommend that you employ a hierarchy of approaches, progressing from simpler models (for example, a well mixed or plug-flow reactor) to more complex simulations (for example, networks or 2-D boundary-layer flow) as you learn more about the system and model behavior.

  2. Create a diagram of the reactor or reactor network that represents your modeling approach, including inlets and stream connections where appropriate

  3. Prepare or obtain and then pre-process your Chemistry Set, which consists of:

    Gas-phase Kinetics Input

    (Surface Kinetics Input)

    Species thermodynamic data

    (Gas-phase species transport data)

  4. Set up the reactor and inlet conditions in the appropriate input panels, specifying:

    (Geometry)

    Process Conditions

    (Solution method options)

    (Parameter Study options)

    (Uncertainty Analysis options)

  5. Create the project input files and solve the problem, which can mean:

    • Run one case

    • Run a series of "continuations" or "new runs" within one batch job

    • Run a Parameter Study

    • Perform an Uncertainty Analysis

  6. Analyze the results using one of the following methods:

    • The Ansys Chemkin Visualizer or Post-Processor

    • The Reaction Path Analyzer

    • Export to Excel (on Windows operating systems)

    • Export to other 3rd-party tool via a text file

Step Acquiring Chemical Data is a critical step that must be taken with care to ensure choosing the right reaction mechanism for the application. As mechanisms typically come from various sources, effort sometimes is required to ensure they are in Ansys Chemkin format to allow pre-processing. However, we note that Chemkin input files for chemistry data have long been a standard used by kineticists and other researchers to exchange information about chemically reacting systems. For this reason, there are many sources of data available. More information on how to obtain kinetics data is provided in Acquiring Chemical Data of this manual.