7.27. General Chemistry

This section is referenced in the following other sections

Simulation Setup: General Chemistry Reference

7.27.1. General Chemistry

Scope: Aria Material

begin General Chemistry MechanismName

   Activation Energies {=} Value...

   Activation Temperature {=} Value

   Concentration Exponents For SpeciesName {=} Exponents...

   Deactivation Temperature {=} Value Action

   Deactivation Temperature Overshoot {=} Value

   Deactivation Temperature Rate {=} Value Action

   Enthalpy Of Formation For SpeciesName {=} Value

   Heats Of Reaction {=} Value...

   Newton Temperature Solve {=} Value

   Nucleation Time {=} Value

   Number Of Reactions {=} Value

   Phase Transfer Preserved Variable {=} Value

   Post Deactivation Gas Release {=} Value

   Post Deactivation Heat Release {=} Value

   Post Deactivation Release Time {=} Value

   Preexponential Factors {=} Value...

   Species Names {=} Value...

   Species Phases {=} Value...

   Species Variable Name {=} Value

   Steric Coefficients {=} Value...

   Stoichiometric Coefficients For SpeciesName {=} Coefficients...

   Temperature Phases {=} Value...

   Universal Gas Constant {=} Value

   begin Reaction ReactionName
   end

end General Chemistry MechanismName

7.27.1.1. Line Commands

Activation Energies

Syntax: Activation Energies {=} Value…
Summary: Activation energy, E, for each Arrhenius-rate reaction
Description: The units for this quantity may be whatever you like, as long as it results in a dimensionless quantity when combined with the temperature and universal gas constant.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real…	–

Activation Temperature

Syntax: Activation Temperature {=} Value
Summary: Activation temperature
Description: This specifies the activation temperature for general chemistry

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Concentration Exponents For

Syntax: Concentration Exponents For SpeciesName {=} Exponents…
Summary: Concentration exponents, $\mu$ , for each reactant species for each Arrhenius rate reaction
Description: Values of zero imply that the species is not a reactant in the specified reaction

Parameter	Value	Default
SpeciesName	string	–
{=}	{= \| are \| is}	–
Exponents	real…	–

Deactivation Temperature

Syntax: Deactivation Temperature {=} Value Action
Summary: Deactivation temperature
Description: This specifies the deactivation temperature for general chemistry along with the deactivation action (terminate or continue)

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–
Action	string	–

Deactivation Temperature Overshoot

Syntax: Deactivation Temperature Overshoot {=} Value
Summary: Allowable overshoot for deactivation
Description: This specifies the amount the temperature is allowed to overshoot the specified deactivation temperature without failing the timestep

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Deactivation Temperature Rate

Syntax: Deactivation Temperature Rate {=} Value Action
Summary: Deactivation temperature rate
Description: This specifies the deactivation temperature rate for general chemistry along with the deactivation action (terminate or continue)

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–
Action	string	–

Enthalpy Of Formation For

Syntax: Enthalpy Of Formation For SpeciesName {=} Value
Summary: Enthalpy of formation for each species
Description: This specifies the enthalpy of formation at the reference temperature for each species. This should be in a consistent mass or mole-based unit system with the rest of the mechanism.

Parameter	Value	Default
SpeciesName	string	–
{=}	{= \| are \| is}	–
Value	real	–

Heats Of Reaction

Syntax: Heats Of Reaction {=} Value…
Summary: Heat of reaction for each reaction
Description: This specifies the heat of reaction at the reference temperature for each reaction. This should be in a consistent mass or mole-based unit system with the rest of the mechanism. Positive values represent an endothermic reaction and negative values represent an exothermic reaction.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real…	–

Newton Temperature Solve

Syntax: Newton Temperature Solve {=} Value
Summary: Newton Temperature Solve
Description: If set to true, use Newton’s method to solve for the temperature. Otherwise a constant heat capacity is assumed when calculating temperature.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	string	–

Nucleation Time

Syntax: Nucleation Time {=} Value
Summary: Nucleation time to be used in rate calculations
Description: If specified then all reaction rates will be scaled by $\frac{1}{2}\left(1 + tanh\left(\frac{t-t_{nuc}}{t_{nuc}}\right)\right)$ .

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Number Of Reactions

Syntax: Number Of Reactions {=} Value
Summary: Number of reactions in the chemical mechanism

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	integer	–

Phase Transfer Preserved Variable

Syntax: Phase Transfer Preserved Variable {=} Value
Summary: Use isothermal phase transfers
Description: Options are ‘temperature’ or ‘enthalpy’. This allows you to use temperature-preserving transfers of material from one phase to the other, rather than using enthalpy-preserving transfers (the default).

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	string	–

Post Deactivation Gas Release

Syntax: Post Deactivation Gas Release {=} Value
Summary: Gas release after deactivation
Description: Specifies a uniform energy release to be applied after deactivation. The units of this value are moles per volume (e.g. mol/m3)

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Post Deactivation Heat Release

Syntax: Post Deactivation Heat Release {=} Value
Summary: Heat release after deactivation
Description: Specifies a uniform energy release to be applied after deactivation. The units of this value are energy per volume (e.g. J/m3)

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Post Deactivation Release Time

Syntax: Post Deactivation Release Time {=} Value
Summary: Time for heat and gas release after deactivation
Description: Specifies the time to use for the uniform heat and/or gas release terms.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Preexponential Factors

Syntax: Preexponential Factors {=} Value…
Summary: Pre-exponential factor, A, for each Arrhenius-rate reaction
Description: Please note that this is the actual Arrhenius pre-exponential factor, A, and not the logarithm of the value (as was expected in the previous CHEMEQ capability).

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real…	–

Species Names

Syntax: Species Names {=} Value…
Summary: Names of all species participating in chemical mechanism
Description: All of these names must be valid species defined elsewhere in the Material block (or in material phase sub-blocks).

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	string…	–

Species Phases

Syntax: Species Phases {=} Value…
Summary: Name of the material phases for each chemical species
Description: Provide the full name of the material phase for each chemical species, in the same order as the species are listed. If this command is omitted, then all species are assumed to not have a material phase.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	string…	–

Species Variable Name

Syntax: Species Variable Name {=} Value
Summary: Names of the input species variable to be used in rate calculations
Description: If the chemical mechanism is formulated on a molar basis then this field must be in units of molar concentration (e.g. $mol_i/m^3$ ), and if the mechanism is formulated on a mass basis then this field must be in units of mass concentration (e.g. $kg_i/m^3$ ). If the solution variable is neither of these (e.g. mass fraction, mole fraction, etc.), then a material model to compute the required concentrations from the available solution variable must be provided.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	string	–

Steric Coefficients

Syntax: Steric Coefficients {=} Value…
Summary: Steric coefficient exponent for each reaction
Description: The steric coefficient has the form $T^\beta$ , where $\beta$ is the provided value. Zero will be assumed as the default for all reactions if this optional line command is not provided.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real…	–

Stoichiometric Coefficients For

Syntax: Stoichiometric Coefficients For SpeciesName {=} Coefficients…
Summary: Stoichiometric coefficients, $\nu$ , for each reactant species for each reaction
Description: These coefficients must sum to zero for each reaction if using a mass-based formulation.

Parameter	Value	Default
SpeciesName	string	–
{=}	{= \| are \| is}	–
Coefficients	real…	–

Temperature Phases

Syntax: Temperature Phases {=} Value…
Summary: The material phase of the temperature to use for this reaction
Description: In multi-material phase heterogeneous mechanisms, it is required to specify which phase’s temperature to use for each reaction.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	string…	–

Universal Gas Constant

Syntax: Universal Gas Constant {=} Value
Summary: Universal gas constant to be used in rate calculations
Description: This is the standard universal gas constant, for use in the exponential term of the Arrhenius rate expression. The units must be consistent with the provided activation energy. If specifying an activation temperature ( $E/R_u$ ) is preferred, then this can be set to 1 and activation temperatures can be provided for the activation energies.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

7.27.2. Chemistry Solver Parameters For

Scope: Aria Region, Equation System, Explicit Equation System, Root Finder Equation System
Summary: Parameters for the chemistry solver applicable to the previously defined material with chemistry model ModelName. The chemistry solver model produces no independent action since the ModelName must first appear in a SRC term for an ENERGY or SPECIES equation before it be applied.

begin Chemistry Solver Parameters For ModelName

   Absolute Tolerance {=} absTol

   Chemistry Solver Algorithm {=} algorithmType

   Maximum Substeps {=} maxSubSteps

   Minimum Step Size {=} minStepSize

   Ode Solver {=} odeSolver...

   Relative Tolerance {=} relTol

end Chemistry Solver Parameters For ModelName

7.27.2.1. Line Commands

Absolute Tolerance

Syntax: Absolute Tolerance {=} absTol
Summary: Specifies the absolute solution tolerance for the ODE solver

Parameter	Value	Default
{=}	{= \| are \| is}	–
absTol	real	1e-12

Chemistry Solver Algorithm

Syntax: Chemistry Solver Algorithm {=} algorithmType
Summary: This command specifies the coupling algorithm between the chemistry model and transport equations

Parameter	Value	Default
{=}	{= \| are \| is}	–
algorithmType	string	COUPLED

Maximum Substeps

Syntax: Maximum Substeps {=} maxSubSteps
Summary: Specifies the maximum number of chemistry substeps per global time step.

Parameter	Value	Default
{=}	{= \| are \| is}	–
maxSubSteps	integer	100000

Minimum Step Size

Syntax: Minimum Step Size {=} minStepSize
Summary: Specifies the minimum integration step size.

Parameter	Value	Default
{=}	{= \| are \| is}	–
minStepSize	real	1e-30

Ode Solver

Syntax: Ode Solver {=} odeSolver…
Summary: This command selects the ODE solver to use for a segregated solve. For available options, refer to the ‘ODE Solvers’ section of this chapter.

Parameter	Value	Default
{=}	{= \| are \| is}	–
odeSolver	string…	CVODE

Relative Tolerance

Syntax: Relative Tolerance {=} relTol
Summary: Specifies the relative solution tolerance for the ODE solver

Parameter	Value	Default
{=}	{= \| are \| is}	–
relTol	real	1e-6