4.14.1. Chemical Reactions Setup¶
4.14.1.1. Add Reaction¶
To add a reaction, click on the 
button. Initially the new reaction will
be invalid, and disabled. This is because it is empty, with no species
defined. Add species for reactants and products; make sure the
reaction is balanced, and then the Ok button will be enabled. Click Ok in the
bottom right to finish adding the reaction.
To cancel adding an unfinished reaction, either click the 
button in the
upper left, or the Cancel button in the lower right.
4.14.1.2. Delete Reaction¶
To remove an existing reaction, select the row in the table corresponding to that reaction, and click on the button.
4.14.1.3. Disable/Enable Reaction¶
To disable an existing reaction (without deleting it), uncheck the checkbox in first column of the reaction table.
To re-enable a disabled reaction, re-check the checkbox.
4.14.1.4. Stiff Chemistry Solver¶
This checkbox enables the stiff chemistry solver. This selection is always available.
Chemical reaction input is handled different from keyword pair inputs. All homogeneous gas phase chemical reactions and all heterogeneous gas-tfm solids reactions are specified between @(RXNS) and @(END) in the reaction block. All heterogeneous gas-dem and gas-pic reactions are specified between @(DES_RXNS) and @(END) in the reaction block.
Users use the globally unique species aliases to specify the chemical reaction equation. Each reaction is specified with a unique reaction identify.
4.14.1.5. Reaction Name¶
This is the name of the currently selected reaction in the reaction table. The reaction name is used by the solver to identify the reaction. The name of a reaction must start with a letter, contain alphanumeric characters or underscores, contain no spaces, and is limited to 32 characters.
4.14.1.6. Reactants¶
Lists the reactant species for the currently selected reaction. Use
the and buttons to add and remove species.
4.14.1.7. Products¶
Lists the product species for the currently selected reaction. Use
the and buttons to add and remove species.
4.14.1.8. Coefficients¶
The values in the coefficients column for reactants and products must be set so that the reaction balances stoichiometrically, otherwise the Ok button to save changes is disabled.
The coefficient must be a positive integer or floating point number.
4.14.1.9. Species¶
Use the drop-down menu to select which species to use for the reactant or product. Each species can only be used once.
4.14.1.10. Phase¶
Each species for reactants and products can belong to any of the phases for the model, Fluid or Solid.
4.14.1.11. Specify Heat of Reaction¶
Check this checkbox to optionally specify the user-defined heat of reaction for the currently selected reaction (Joules/kmol).
The “Fraction assigned to (Fluid, Solid 1, …)” is fraction of that heat of the reaction assigned to each phase. Editing the fraction for a phase will automatically adjust the fraction(s) of the other phase(s) to add up to one.
4.14.1.12. Reaction Restrictions¶
For heterogeneous reactions referencing three or more phases, either only one phase has a net mass loss or one phase has a net mass gain. Specifically, two or more phases cannot have a net mass loss while two or more phases have a net mass gain.
The following examples illustrate valid and invalid reactions. For these examples, FC1, FC2, and sSoot, represent solid carbon in solids phases 1, 2 and 3, respectively. All other species belong to the gas.
Example 1: VALID
2*FC1 + O2 –> 2CO
One phase has a net mass loss, one phase has a net mass gain
Example 2: VALID
FC1 + FC2 + O2 –> 2CO
Two phases have a net mass loss, one phase has a net mass gain
Example 3: VALID
2.2*FC1 + O2 –> 2CO + 0.2*sSoot
One phase has a net mass loss, two phases have a net mass gain
Example 4: INVALID
1.1*FC1 + 1.1*FC2 + O2 –> 2CO + 0.2*sSoot
Two phases have a net mass loss, two phases have a net mass gain
The heat of reaction, DH, and how it is distributed between phases, fracDH, must be specified if there are two or more solids phases listed as either reactants or products.
Example 5: DH and fracDH NOT REQUIRED
2.2*FC1 + O2 –> 2CO + 0.2*sSoot
Two solids phases referenced
Solid phase 1, FC1, is a reactant
Solid phase 2, FC2, is a product
Example 6: DH and fracDH REQUIRED
FC1 + FC2 + 2O2 –> 2CO2
Two solids phases referenced as reactants
Example 6: DH and fracDH REQUIRED
sSoot –> FC1 + FC2
Two solids phases referenced as products