.. _chemkin_hydrogen_oxidation_tutorial:
Hydrogen oxidation in a batch reactor using CHEMKIN mechanism
-------------------------------------------------------------
This tutorial shows how to import thermodynamic information of species
and kinetic mechanism from CHEMKIN into MFiX. A batch reactor in a single
cell is simulated in this tutorial. The mechanism for the oxidiation of hydrogen from
Conaire et al. [1]_ is applied.
Read the project into MFiX
^^^^^^^^^^^^^^^^^^^^^^^^^^
The basic model has been set up in the input file, "hydrogen_oxidation.mfx".
- On the main menu select ``Open project``.
- Open the project by browsing to the tutorial directory ``tutorial/chemkin/hydrogen_oxidation``.
.. note::
The main purpose of this tutorial is to show how to use CHEMKIN mechanism in MFiX.
For more details about the model setup, please refer to other tutorials.
.. _fig_open_project:
.. figure:: /media/chemkin/fig_open_project.png
:width: 8cm
:alt: open project
Generate mesh
^^^^^^^^^^^^^
On the ``Mesher`` pane:
- Click ``Generate`` to generate the mesh
- Clikc ``Accept`` to accept the mesh
.. _fig_create_mesh:
.. figure:: /media/chemkin/fig_create_mesh.png
:width: 8cm
:alt: generate mesh
Import species for fluid phase
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
On the ``Fluid`` pane:
- Click the ``+`` under ``Species``. This will open the Fluid species popup window.
.. figure:: /media/chemkin/fig_add_species.png
:width: 8cm
:alt: add species
- Select ``Load from file (CHEMKIN format)`` in ``Source`` of the popup window
.. figure:: /media/chemkin/fig_import_thermo_file.png
:width: 8cm
:alt: import thermo file
- Click ``Choose file``, choose "thermodynamicInfo.txt" in the popup window, and click ``Open``.
.. figure:: /media/chemkin/fig_select_thermo_file.png
:width: 8cm
:alt: select thermo file
- After importing the file, the species defined in the file will show in the window.
- Select all the species (click on first species "AR" and drag down) and click ``import from database`` to import all species. Click ``Done``.
.. note::
Users have the flexibility to select the required species for their case from the provided list.
If a species is not defined in the CHEMKIN file, users can import it from the built-in
Burcat database or an external Burcat file as well.
.. figure:: /media/chemkin/fig_select_species.png
:width: 8cm
:alt: select species
- For reacting cases, constant specific heat capacity is not allowed. Change it to
"Mixture" in "Properties".
.. figure:: /media/chemkin/fig_setup_cp.png
:width: 8cm
:alt: setup cp
Create Initial and Boundary conditions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
On the ``Initial conditions`` pane, set the following conditions as the initial conditions.
+------------------+--------------------------------------------+
| Property | Initial Value |
+==================+============================================+
| Volume Fraction | 1.0 |
+------------------+--------------------------------------------+
| Temperature | 800 K |
+------------------+--------------------------------------------+
| Pressure | 101325 Ps |
+------------------+--------------------------------------------+
| U-Velocity | 0.0 m/s |
+------------------+--------------------------------------------+
| V-Velocity | 0.0 m/s |
+------------------+--------------------------------------------+
| W-Velocity | 0.0 m/s |
+------------------+--------------------------------------------+
| Composition | H2: 0.1, O2: 0.8, N2: 0.1, OH:0.0 |
+------------------+--------------------------------------------+
On the ``Boundary conditions`` pane, No-Slip and adiabatic walls have been setup.
Import kinetic mechanism
^^^^^^^^^^^^^^^^^^^^^^^^
On the ``Chemistry`` pane, ``Options`` sub-pane:
- Check the ``Enable Arrhenius model for fluid phase reactions`` checkbox
- Change the ``Minimum mass fraction for reactions`` for ``Fluid reactions`` to 0
to consider all species with mass fraction larger than 0 in the reactions
- Check the ``Enable stiff chemistry solver`` checkbox
- Change the ``Absolute tolerance``, ``Relative tolerance`` and ``Minimum reaction rate``
in stiff solver to be 1e-09, 1e-08 and 1e-20.
.. note::
Users can change the minimum mass fraction for reactions and the parameters for stiff solver
based on the accuracy requirement of their cases.
.. figure:: /media/chemkin/fig_arrhenius_setup.png
:width: 8cm
:alt: setup arrhenius rate
On the ``Chemistry`` pane, ``Reactions`` sub-pane:
- Click ``Load reaction definitions from text file`` and select ``Chemkin format``
- Select the mechanism file "chemkin_mechanism.CKI" in the popup window. Click ``Open``.
.. figure:: /media/chemkin/fig_import_mechanism.png
:width: 8cm
:alt: import mechanism
.. figure:: /media/chemkin/fig_select_mechanism.png
:width: 8cm
:alt: select mechanism
- Then all the reactions with all the information will be imported
.. figure:: /media/chemkin/fig_reactions.png
:width: 8cm
:alt: reactions
Setup output, monitor and run parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The output, monitor and run parameters have been setup.
Users can modify them based on their own requirement.
Run the project
^^^^^^^^^^^^^^^
- Save the project by clicking the |save| button
- Run the project by clicking the |play| button
- On the ``Run Solver`` dialog, select the executable from the combo-box
- Click the ``Run`` button to start the simulation
This tutorial simulates the oxidation of H2 in a batch reactor.
Users should expect to see consumption of H2 and O2 and a temperature increase
from the exothermic reaction.
References
----------
.. [1] M. O Conaire, H. J. Curran, J. M. Simmie, W. J. Pitz, C. K. Westbrook. A Comprehensive Modelling Study of Hydrogen Oxidation, Intl. J. Chem. Kinet., 36 (11):603\u2013622 (2004).
.. include:: /icons.rst