Chemical Kinetics#

Kinetics Managers #

Kinetics #

class cantera.Kinetics#

Bases: _SolutionBase

Instances of class Kinetics are responsible for evaluating reaction rates of progress, species production rates, and other quantities pertaining to a reaction mechanism.

add_reaction(rxn)#: Add a new reaction to this phase.

creation_rates#: Creation rates for each species. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

creation_rates_ddC#: Calculate derivatives of species creation rates with respect to molar concentration at constant temperature, pressure and mole fractions.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

creation_rates_ddCi#

Calculate derivatives for species creation rates with respect to species concentration at constant temperature, pressure, and concentration of all other species. For sparse output, set ct.use_sparse(True).

The method returns a matrix with n_total_species rows and n_total_species columns.

For a derivative with respect to :math: c_i, all other :math: c_i are held constant.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

Added in version 3.0.

creation_rates_ddP#: Calculate derivatives of species creation rates with respect to pressure at constant temperature, molar concentration and mole fractions.

creation_rates_ddT#: Calculate derivatives of species creation rates with respect to temperature at constant pressure, molar concentration and mole fractions.

creation_rates_ddX#

Calculate derivatives for species creation rates with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

delta_enthalpy#: Change in enthalpy for each reaction [J/kmol].

delta_entropy#: Change in entropy for each reaction [J/kmol/K].

delta_gibbs#: Change in Gibbs free energy for each reaction [J/kmol].

delta_standard_enthalpy#: Change in standard-state enthalpy (independent of composition) for each reaction [J/kmol].

delta_standard_entropy#: Change in standard-state entropy (independent of composition) for each reaction [J/kmol/K].

delta_standard_gibbs#: Change in standard-state Gibbs free energy (independent of composition) for each reaction [J/kmol].

derivative_settings#

Property setting behavior of derivative evaluation.

For BulkKinetics, the following keyword/value pairs are supported:

skip-third-bodies (boolean) … if False (default), third body concentrations are considered for the evaluation of derivatives
skip-falloff (boolean) … if True (default), third-body effects on reaction rates are not considered.
rtol-delta (double) … relative tolerance used to perturb properties when calculating numerical derivatives. The default value is 1e-8.

Derivative settings are updated using a dictionary:

>>> gas.derivative_settings = {"skip-falloff": True}

Passing an empty dictionary will reset all values to their defaults.

destruction_rates#: Destruction rates for each species. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

destruction_rates_ddC#: Calculate derivatives of species destruction rates with respect to molar concentration at constant temperature, pressure and mole fractions.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

destruction_rates_ddCi#

Calculate derivatives for species destruction rates with respect to species concentration at constant temperature, pressure, and concentration of all other species. For sparse output, set ct.use_sparse(True).

The method returns a matrix with n_total_species rows and n_total_species columns. For a derivative with respect to :math: c_i, all other :math: c_i are held constant.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

Added in version 3.0.

destruction_rates_ddP#: Calculate derivatives of species destruction rates with respect to pressure at constant temperature, molar concentration and mole fractions.

destruction_rates_ddT#: Calculate derivatives of species destruction rates with respect to temperature at constant pressure, molar concentration and mole fractions.

destruction_rates_ddX#

Calculate derivatives for species destruction rates with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

equilibrium_constants#: Equilibrium constants in concentration units for all reactions.

forward_rate_constants#

Forward rate constants for all reactions.

The computed values include all temperature-dependent and pressure-dependent contributions. By default, third-body concentrations are only considered if they are part of the reaction rate definition; for a legacy implementation that includes third-body concentrations, see use_legacy_rate_constants.

forward_rate_constants_ddC#: Calculate derivatives for forward rate constants with respect to molar concentration at constant temperature, pressure and mole fractions.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

forward_rate_constants_ddP#: Calculate derivatives for forward rate constants with respect to pressure at constant temperature, molar concentration and mole fractions.

forward_rate_constants_ddT#: Calculate derivatives for forward rate constants with respect to temperature at constant pressure, molar concentration and mole fractions.

forward_rates_of_progress#: Forward rates of progress for the reactions. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

forward_rates_of_progress_ddC#: Calculate derivatives for forward rates-of-progress with respect to molar concentration at constant temperature, pressure and mole fractions.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

forward_rates_of_progress_ddCi#

Calculate derivatives for forward rates-of-progress with respect to species concentrations at constant temperature, pressure and remaining species concentrations. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(c_i\), all other \(c_j\) are held constant.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

Added in version 3.0.

forward_rates_of_progress_ddP#: Calculate derivatives for forward rates-of-progress with respect to pressure at constant temperature, molar concentration and mole fractions.

forward_rates_of_progress_ddT#: Calculate derivatives for forward rates-of-progress with respect to temperature at constant pressure, molar concentration and mole fractions.

forward_rates_of_progress_ddX#

Calculate derivatives for forward rates-of-progress with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

heat_production_rates#

Get the volumetric heat production rates [W/m^3] on a per-reaction basis. The sum over all reactions results in the total volumetric heat release rate. Example: C. K. Law: Combustion Physics (2006), Fig. 7.8.6

>>> gas.heat_production_rates[1]  # heat production rate of the 2nd reaction

heat_release_rate#: Get the total volumetric heat release rate [W/m^3].

kinetics_model#: Return type of kinetics.

kinetics_species_index(species, phase=0)#: The index of species species of phase phase within arrays returned by methods of class Kinetics. If species is a string, the phase argument is unused.

kinetics_species_name(k)#: Name of the species with index k in the arrays returned by methods of class Kinetics.

kinetics_species_names#: A list of all species names, corresponding to the arrays returned by methods of class Kinetics.

modify_reaction(irxn, rxn)#: Modify the Reaction with index irxn to have the same rate parameters as rxn. rxn must have the same reactants and products and use the same rate parameterization (for example, ArrheniusRate, FalloffRate, PlogRate, etc.) as the existing reaction. This method does not modify the third-body efficiencies, reaction orders, or reversibility of the reaction.

multiplier(i_reaction)#: A scaling factor applied to the rate coefficient for reaction i_reaction. Can be used to carry out sensitivity analysis or to selectively disable a particular reaction. See set_multiplier.

n_phases#: Number of phases in the reaction mechanism.

n_reactions#: Number of reactions in the reaction mechanism.

n_total_species#: Total number of species in all phases participating in the kinetics mechanism.

net_production_rates#: Net production rates for each species. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

net_production_rates_ddC#: Calculate derivatives of species net production rates with respect to molar density at constant temperature, pressure and mole fractions.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

net_production_rates_ddCi#

Calculate derivatives for species net production rates with respect to species concentration at constant temperature, pressure, and concentration of all other species. For sparse output, set ct.use_sparse(True).

The method returns a matrix with n_total_species rows and n_total_species columns. For a derivative with respect to :math: c_i, all other :math: c_i are held constant.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

Added in version 3.0.

net_production_rates_ddP#: Calculate derivatives of species net production rates with respect to pressure at constant temperature, molar concentration and mole fractions.

net_production_rates_ddT#: Calculate derivatives of species net production rates with respect to temperature at constant pressure, molar concentration and mole fractions.

net_production_rates_ddX#

Calculate derivatives for species net production rates with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

net_rates_of_progress#: Net rates of progress for the reactions. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

net_rates_of_progress_ddC#: Calculate derivatives for net rates-of-progress with respect to molar concentration at constant temperature, pressure and mole fractions.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

net_rates_of_progress_ddCi#

Calculate derivatives for net rates-of-progress with respect to species concentrations at constant temperature, pressure and remaining species concentrations. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(c_i\), all other \(c_j\) are held constant.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

Added in version 3.0.

net_rates_of_progress_ddP#: Calculate derivatives for net rates-of-progress with respect to pressure at constant temperature, molar concentration and mole fractions.

net_rates_of_progress_ddT#: Calculate derivatives for net rates-of-progress with respect to temperature at constant pressure, molar concentration and mole fractions.

net_rates_of_progress_ddX#

Calculate derivatives for net rates-of-progress with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set ct.use_sparse(True).

Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

product_stoich_coeff(k_spec, i_reaction)#: The stoichiometric coefficient of species k_spec as a product in reaction i_reaction.

product_stoich_coeffs#

The array of product stoichiometric coefficients. Element [k,i] of this array is the product stoichiometric coefficient of species k in reaction i.

For sparse output, set ct.use_sparse(True).

Changed in version 3.0: Method was changed to a property in Cantera 3.0.

product_stoich_coeffs_reversible#

The array of product stoichiometric coefficients of reversible reactions. Element [k,i] of this array is the product stoichiometric coefficient of species k in reaction i.

For sparse output, set ct.use_sparse(True).

reactant_stoich_coeff(k_spec, i_reaction)#: The stoichiometric coefficient of species k_spec as a reactant in reaction i_reaction.

reactant_stoich_coeffs#

The array of reactant stoichiometric coefficients. Element [k,i] of this array is the reactant stoichiometric coefficient of species k in reaction i.

For sparse output, set ct.use_sparse(True).

Changed in version 3.0: Method was changed to a property in Cantera 3.0.

reaction(i_reaction)#: Return a Reaction object representing the reaction with index i_reaction. Changes to this object do not affect the Kinetics or Solution object until the modify_reaction function is called.

reaction_equations(indices=None)#

Returns a list containing the reaction equation for all reactions in the mechanism if indices is unspecified, or the equations for each reaction in the sequence indices. For example:

>>> gas.reaction_equations()
['2 O + M <=> O2 + M', 'O + H + M <=> OH + M', 'O + H2 <=> H + OH', ...]
>>> gas.reaction_equations([2,3])
['O + H + M <=> OH + M', 'O + H2 <=> H + OH']

InterfaceKinetics #

class cantera.InterfaceKinetics#

Bases: Kinetics

A kinetics manager for heterogeneous reaction mechanisms. The reactions are assumed to occur at an interface between bulk phases.

advance_coverages(dt, rtol=1e-07, atol=1e-14, max_step_size=0.0, max_steps=20000, max_error_test_failures=7)#: This method carries out a time-accurate advancement of the surface coverages for a specified amount of time.

advance_coverages_to_steady_state()#: This method advances the surface coverages to steady state.

get_creation_rates(phase)#: Creation rates for each species in phase phase. Use the creation_rates property to get the creation rates for species in all phases.

get_destruction_rates(phase)#: Destruction rates for each species in phase phase. Use the destruction_rates property to get the destruction rates for species in all phases.

get_net_production_rates(phase)#: Net production rates for each species in phase phase. Use the net_production_rates property to get the net production rates for species in all phases.

interface_current(phase)#: The interface current is useful when charge transfer reactions occur at an interface. It is defined here as the net positive charge entering the phase phase (Units: A/m^2 for a surface, A/m for an edge reaction).

phase_index(phase)#: Get the index of the phase phase, where phase may specified using the phase object, the name, or the index itself.

write_yaml(filename, phases=None, units=None, precision=None, skip_user_defined=None)#: See _SolutionBase.write_yaml.

Reactions #

This class contains the definition of a single reaction, independent of a specific Kinetics object. Reaction rate evaluation is handled by ReactionRate objects.

Reaction #

class cantera.Reaction(reactants=None, products=None, rate=None, *, equation=None, init=True, third_body=None)#

Bases: object

A class which stores data about a reaction and its rate parameterization so that it can be added to a Kinetics object.

Parameters:

reactants – Value used to set reactants
products – Value used to set products
rate –
The rate parameterization for the reaction, given as one of the following:
- a ReactionRate object
- a dict containing the parameters needed to construct a ReactionRate object, with keys corresponding to the YAML format
- a dict containing Arrhenius parameters (A, b, and Ea)
equation – The reaction equation, used to set the reactants and products if values for those arguments are not provided.

Examples:

R = ct.Reaction({"O": 1, "H2": 1}, {"H": 1, "OH": 1},
                ct.ArrheniusRate(38.7, 2.7, 26191840.0))
R = ct.Reaction(equation="O + H2 <=> H + OH",
                rate={"A": 38.7, "b": 2.7, "Ea": 26191840.0})
R = ct.Reaction(equation="HO2 <=> OH + O", rate=ChebyshevRate(...))

The static method list_from_file can be used to create a list of Reaction objects from existing definitions in the YAML format. The following will produce a list of the 325 reactions which make up the GRI 3.0 mechanism:

R = ct.Reaction.list_from_file("gri30.yaml", gas)

where gas is a Solution object with the appropriate thermodynamic model, which is the ideal-gas model in this case.

The static method list_from_yaml can be used to create lists of Reaction objects from a YAML list:

rxns = '''
  - equation: O + H2 <=> H + OH
    rate-constant: {A: 3.87e+04, b: 2.7, Ea: 6260.0}
  - equation: O + HO2 <=> OH + O2
    rate-constant: {A: 2.0e+13, b: 0.0, Ea: 0.0}
'''
R = ct.Reaction.list_from_yaml(rxns, gas)

The method from_yaml can be used to create individual Reaction objects from definitions in the YAML format. It is important to verify that either the pre-exponential factor and activation energy are supplied in SI units, or that they have their units specified:

R = ct.Reaction.from_yaml('''{equation: O + H2 <=> H + OH,
        rate-constant: {A: 3.87e+04 cm^3/mol/s, b: 2.7, Ea: 6260 cal/mol}}''',
        gas)

ID#: Get/Set the identification string for the reaction, which can be used in filtering operations.

allow_negative_orders#: Get/Set a flag which is True if negative reaction orders are allowed. Default is False.

allow_nonreactant_orders#: Get/Set a flag which is True if reaction orders can be specified for non-reactant species. Default is False.

clear_user_data()#: Clear all saved input data, so that the data given by input_data or Solution.write_yaml will only include values generated by Cantera based on the current object state.

duplicate#: Get/Set a flag which is True if this reaction is marked as a duplicate or False otherwise.

equation#: A string giving the chemical equation for this reaction. Determined automatically based on reactants and products.

classmethod from_dict(data, kinetics, hyphenize=True)#

Create a Reaction object from a dictionary corresponding to its YAML representation. By default, underscores in keys are replaced by hyphens.

An example for the creation of a Reaction from a dictionary is:

rxn = Reaction.from_dict(
    {"equation": "O + H2 <=> H + OH",
     "rate-constant": {"A": 38.7, "b": 2.7, "Ea": 26191840.0}},
    kinetics=gas)

In the example, gas is a Kinetics (or Solution) object.

Parameters:

data – A dictionary corresponding to the YAML representation.
kinetics – A Kinetics object whose associated phase(s) contain the species involved in the reaction.

classmethod from_yaml(text, kinetics)#

Create a Reaction object from its YAML string representation.

An example for the creation of a Reaction from a YAML string is:

rxn = Reaction.from_yaml('''
    equation: O + H2 <=> H + OH
    rate-constant: {A: 38.7, b: 2.7, Ea: 6260.0 cal/mol}
    ''', kinetics=gas)

In the example, gas is a Kinetics (or Solution) object.

Parameters:

text – The YAML reaction string.
kinetics – A Kinetics object whose associated phase(s) contain the species involved in the reaction.

input_data#: Get input data for this reaction with its current parameter values, along with any user-specified data provided with its input (YAML) definition.

static list_from_file(filename, kinetics, section='reactions')#

Create a list of Reaction objects from all of the reactions defined in a YAML file. Reactions from the section section will be returned.

Directories on Cantera’s input file path will be searched for the specified file.

static list_from_yaml(text, kinetics)#: Create a list of Reaction objects from all the reactions defined in a YAML string.

orders#: Get/Set the reaction order with respect to specific species as a dict with species names as the keys and orders as the values, or as a composition string. By default, mass-action kinetics is assumed, with the reaction order for each reactant species equal to each its stoichiometric coefficient.

product_string#: A string representing the products side of the chemical equation for this reaction. Determined automatically based on products.

products#: Get/Set the products in this reaction as a dict where the keys are species names and the values, are the stoichiometric coefficients, for example {'CH3':1, 'H2O':1}, or as a composition string, for example 'CH3:1, H2O:1'.

Changed in version 3.1: This is a read-only property

rate#: Get/Set the reaction rate evaluator for this reaction.

rate_coeff_units#: Get reaction rate coefficient units

reactant_string#: A string representing the reactants side of the chemical equation for this reaction. Determined automatically based on reactants.

reactants#: Get/Set the reactants in this reaction as a dict where the keys are species names and the values, are the stoichiometric coefficients, for example {'CH4':1, 'OH':1}, or as a composition string, for example 'CH4:1, OH:1'.

Changed in version 3.1: This is a read-only property

reaction_type#: Retrieve the native type name of the reaction.

reversible#: Get/Set a flag which is True if this reaction is reversible or False otherwise.

third_body#: Returns a ThirdBody object if Reaction uses a third body collider, and None otherwise.

Added in version 3.0.

third_body_name#: Returns name of ThirdBody collider if Reaction uses a third body collider, and None otherwise.

Added in version 3.0.

update_user_data(data)#: Add the contents of the provided dict as additional fields when generating YAML phase definition files with Solution.write_yaml or in the data returned by input_data. Existing keys with matching names are overwritten.

Reaction Rates #

ReactionRate #

class cantera.ReactionRate#

Bases: object

Base class for ReactionRate objects.

ReactionRate objects are used to calculate reaction rates and are associated with a Reaction object.

conversion_units#: Get the units for converting the leading term in the reaction rate expression to different unit systems.

classmethod from_dict(data, hyphenize=True)#

Create a ReactionRate object from a dictionary corresponding to its YAML representation. By default, underscores in keys are replaced by hyphens.

An example for the creation of a ReactionRate from a dictionary is:

rate = ReactionRate.from_dict(
    {"rate-constant": {"A": 38.7, "b": 2.7, "Ea": 26191840.0}})

Parameters:: data – A dictionary corresponding to the YAML representation.

classmethod from_yaml(text)#

Create a ReactionRate object from its YAML string representation.

An example for the creation of a ReactionRate from a YAML string is:

rate = ReactionRate.from_yaml(
    "rate-constant: {A: 38.7, b: 2.7, Ea: 6260.0 cal/mol}")

Units for A require a unit system with length in m and quantity in kmol (standard Cantera units).

Parameters:: text – The YAML reaction rate string.

input_data#: Get input data for this reaction rate with its current parameter values.

sub_type#: Get the C++ ReactionRate sub-type

type#: Get the C++ ReactionRate type

ArrheniusRateBase #

class cantera.ArrheniusRateBase(input_data)#

Bases: ReactionRate

Base class collecting commonly used features of Arrhenius-type rate objects. Objects should be instantiated by specialized classes, for example ArrheniusRate, BlowersMaselRate and TwoTempPlasmaRate.

activation_energy#: The activation energy E [J/kmol].

allow_negative_pre_exponential_factor#: Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

pre_exponential_factor#: The pre-exponential factor A in units of m, kmol, and s raised to powers depending on the reaction order.

temperature_exponent#: The temperature exponent b.

ArrheniusRate #

class cantera.ArrheniusRate(A, b, Ea)#

Bases: ArrheniusRateBase

A reaction rate coefficient which depends on temperature only and follows the modified Arrhenius form:

\[k_f = A T^b \exp(-\tfrac{E_a}{RT})\]

where A is the pre_exponential_factor, b is the temperature_exponent, and Ea is the activation_energy.

BlowersMaselRate #

class cantera.BlowersMaselRate(A, b, Ea, w)#

Bases: ArrheniusRateBase

A reaction rate coefficient which depends on temperature and enthalpy change of the reaction follows the Blowers-Masel approximation and modified Arrhenius form described in ArrheniusRate.

bond_energy#: Average bond dissociation energy of the bond being formed and broken in the reaction E [J/kmol].

delta_enthalpy#

Enthalpy change of reaction deltaH [J/kmol]

The enthalpy change of reaction is a function of temperature and thus not an independent property. Accordingly, the setter should be only used for testing purposes, as any value will be overwritten by an update of the thermodynamic state.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

TwoTempPlasmaRate #

class cantera.TwoTempPlasmaRate(A, b, Ea_gas, Ea_electron)#

Bases: ArrheniusRateBase

A reaction rate coefficient which depends on both gas and electron temperature with the form similar to the modified Arrhenius form. Specifically, the temperature exponent (b) is applied to the electron temperature instead. In addition, the exponential term with activation energy for electron is included.

\[k_f = A T_e^b \exp(-\tfrac{E_{a,g}}{RT}) \exp(\tfrac{E_{a,e}(T_e - T)}{R T T_e})\]

where \(A\) is the pre_exponential_factor, \(b\) is the temperature_exponent, \(E_{a,g}\) (Ea_gas) is the activation_energy, and \(E_{a,e}\) (Ea_electron) is the activation_electron_energy.

activation_electron_energy#: The activation electron energy \(E_{a,e}\) [J/kmol].

ElectronCollisionPlasmaRate #

class cantera.ElectronCollisionPlasmaRate(energy_levels=None, cross_sections=None, input_data=None)#

Bases: ReactionRate

A reaction rate coefficient which depends on electron collision cross section and electron energy distribution

cross_sections#: The cross sections [m2]. Each cross section corresponds to a energy level of energy_levels.

energy_levels#: The energy levels [eV]. Each level corresponds to a cross section of cross_sections.

FalloffRate #

class cantera.FalloffRate#

Bases: ReactionRate

Base class for parameterizations used to describe the fall-off in reaction rates due to intermolecular energy transfer.

Note that FalloffRate is a base class for specialized fall-off parameterizations and cannot be instantiated by itself.

allow_negative_pre_exponential_factor#: Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

chemically_activated#: Get whether the object is a chemically-activated reaction rate.

falloff_coeffs#: The array of coefficients used to define this falloff function.

falloff_function(temperature, conc3b)#: Evaluate the falloff function based on temperature and third-body concentration.

high_rate#: Get/Set the Arrhenius rate constant in the high-pressure limit

low_rate#: Get/Set the Arrhenius rate constant in the low-pressure limit

LindemannRate #

class cantera.LindemannRate(low, high, falloff_coeffs)#

Bases: FalloffRate

The Lindemann falloff parameterization.

This class implements the simple falloff function \(F(T,P_r) = 1.0\).

TroeRate #

class cantera.TroeRate(low, high, falloff_coeffs)#

Bases: FalloffRate

The 3- or 4-parameter Troe falloff function.

Parameters:: falloff_coeffs – An array of 3 or 4 parameters: \([a, T^{***}, T^*, T^{**}]\) where the final parameter is optional (with a default value of 0).

SriRate #

class cantera.SriRate(low, high, falloff_coeffs)#

Bases: FalloffRate

The 3- or 5-parameter SRI falloff function.

Parameters:: falloff_coeffs – An array of 3 or 5 parameters: \([a, b, c, d, e]\) where the last two parameters are optional (with default values of 1 and 0, respectively).

TsangRate #

class cantera.TsangRate(low, high, falloff_coeffs)#

Bases: FalloffRate

The Tsang falloff parameterization.

PlogRate #

class cantera.PlogRate(rates)#

Bases: ReactionRate

A pressure-dependent reaction rate parameterized by logarithmically interpolating between Arrhenius rate expressions at various pressures.

rates#: Get/Set the rate coefficients for this reaction, which are given as a list of (pressure, Arrhenius) tuples.

ChebyshevRate #

class cantera.ChebyshevRate(temperature_range, pressure_range, data)#

Bases: ReactionRate

A pressure-dependent reaction rate parameterized by a bivariate Chebyshev polynomial in temperature and pressure.

data#: 2D array of Chebyshev coefficients where rows and columns correspond to temperature and pressure dimensions over which the Chebyshev fit is computed.

n_pressure#: Number of pressures over which the Chebyshev fit is computed (same as number of columns of data property).

n_temperature#: Number of temperatures over which the Chebyshev fit is computed. (same as number of rows of data property).

pressure_range#: Valid pressure range [Pa] for the Chebyshev fit

temperature_range#: Valid temperature range [K] for the Chebyshev fit

CustomRate #

class cantera.CustomRate(k)#

Bases: ReactionRate

A custom rate coefficient which depends on temperature only.

The simplest way to create a CustomRate object is to use a lambda function, for example:

rr = CustomRate(lambda T: 38.7 * T**2.7 * exp(-3150.15/T))

Warning

This class is an experimental part of the Cantera API and may be changed or removed without notice.

set_rate_function(k)#

Set the function describing a custom reaction rate:

rr = CustomRate()
rr.set_rate_function(lambda T: 38.7 * T**2.7 * exp(-3150.15/T))

ExtensibleRate #

class cantera.ExtensibleRate#

Bases: ReactionRate

A base class for a user-defined reaction rate parameterization. Classes derived from this class should be decorated with the extension decorator to specify the name of the rate parameterization and its corresponding data class, and to make these rates constructible through factory functions and input files.

Classes derived from ExtensibleRate should implement the set_parameters, get_parameters, eval, and (optionally) validate methods, which will be called as delegates from the C++ ReactionRate class.

Warning

The delegatable methods defined here are an experimental part of the Cantera API and may change without notice.

Added in version 3.0.

eval(data: ExtensibleRateData) → float#: Responsible for calculating the forward rate constant based on the current state of the phase, stored in an instance of a class derived from ExtensibleRateData.

get_parameters(params: AnyMap) → None#

Responsible for serializing the state of the ExtensibleRate object, using the same format as a YAML reaction entry. This is the inverse of set_parameters.

Serialization methods may request output in unit systems other than Cantera’s native mks+kmol system. To enable conversions to the user-specified unit system, dimensional values should be added to params using the methods AnyMap.set_quantity and AnyMap.set_activation_energy.

set_parameters(params: AnyMap, rate_coeff_units: UnitStack) → None#

Responsible for setting rate parameters based on the input data. For example, for reactions created from YAML, params is the YAML reaction entry converted to an AnyMap. rate_coeff_units specifies the units of the rate coefficient.

Input values contained in params may be in non-default unit systems, specified in the user-provided input file. To convert them to Cantera’s native mks+kmol unit system, use the functions AnyMap.convert, AnyMap.convert_activation_energy, and AnyMap.convert_rate_coeff as needed.

validate(equation: str, soln: Solution) → None#: Responsible for validating that the rate expression is configured with valid parameters. This may depend on properties of the Solution, for example temperature ranges over which the rate expression can be evaluated. Raises an exception if any validation fails.

InterfaceRateBase #

class cantera.InterfaceRateBase#

Bases: ArrheniusRateBase

Base class collecting commonly used features of Arrhenius-type rate objects that include coverage dependencies.

beta#: Return the charge transfer beta parameter

coverage_dependencies#: Get/set a dictionary containing adjustments to the Arrhenius rate expression dependent on surface species coverages. The keys of the dictionary are species names, and the values are dictionaries specifying the three coverage parameters a, m and E which are the modifiers for the pre-exponential factor [m, kmol, s units], the temperature exponent [nondimensional], and the activation energy [J/kmol], respectively.

set_species(species)#: Set association with an ordered list of all species associated with an InterfaceKinetics object.

site_density#

Site density [kmol/m^2]

The site density is not an independent property, as it is set by an associated InterfaceKinetics object. Accordingly, the setter should be only used for testing purposes, as the value will be overwritten by an update of the thermodynamic state.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

uses_electrochemistry#: Return boolean flag indicating whether rate involves a charge transfer.

InterfaceArrheniusRate #

class cantera.InterfaceArrheniusRate(A, b, Ea)#

Bases: InterfaceRateBase

A reaction rate coefficient which depends on temperature and interface coverage

InterfaceBlowersMaselRate #

class cantera.InterfaceBlowersMaselRate(A, b, Ea0, w)#

Bases: InterfaceRateBase

A reaction rate coefficient which depends on temperature and enthalpy change of the reaction follows the Blowers-Masel approximation and modified Arrhenius form described in ArrheniusRate.

bond_energy#: Average bond dissociation energy of the bond being formed and broken in the reaction E [J/kmol].

delta_enthalpy#

Enthalpy change of reaction deltaH [J/kmol]

The enthalpy change of reaction is a function of temperature and thus not an independent property. Accordingly, the setter should be only used for testing purposes, as any value will be overwritten by an update of the thermodynamic state.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

StickRateBase #

class cantera.StickRateBase#

Bases: InterfaceRateBase

Base class collecting commonly used features of Arrhenius-type sticking rate objects that include coverage dependencies.

motz_wise_correction#: Get/Set a boolean indicating whether to use the correction factor developed by Motz & Wise for reactions with high (near-unity) sticking coefficients when converting the sticking coefficient to a rate coefficient.

sticking_order#

The exponent applied to site density (sticking order).

The sticking order is not an independent property and is detected automatically by Cantera. Accordingly, the setter should be only used for testing purposes.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

sticking_species#: The name of the sticking species. Needed only for reactions with multiple non-surface reactant species, where the sticking species is ambiguous.

sticking_weight#

The molecular weight of the sticking species.

The sticking weight is not an independent property and is detected automatically by Cantera. Accordingly, the setter should be only used for testing purposes.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

StickingArrheniusRate #

class cantera.StickingArrheniusRate(A, b, Ea)#

Bases: StickRateBase

A surface sticking rate expression based on the Arrhenius parameterization

StickingBlowersMaselRate #

class cantera.StickingBlowersMaselRate(A, b, Ea0, w)#

Bases: StickRateBase

A surface sticking rate expression based on the Blowers-Masel parameterization

bond_energy#: Average bond dissociation energy of the bond being formed and broken in the reaction E [J/kmol].

delta_enthalpy#

Enthalpy change of reaction deltaH [J/kmol]

The enthalpy change of reaction is a function of temperature and thus not an independent property. Accordingly, the setter should be only used for testing purposes, as any value will be overwritten by an update of the thermodynamic state.

Warning

This property is an experimental part of the Cantera API and may be changed or removed without notice.

Auxiliary Reaction Data #

ExtensibleRateData #

class cantera.ExtensibleRateData#

Bases: object

A base class for data used when evaluating instances of ExtensibleRate. Classes derived from ExtensibleRateData are used to store common data needed to evaluate all reactions of a particular type.

Classes derived from ExtensibleRateData must implement the update method. After the update method has been called, instances of ExtensibleRateData are passed as the argument to ExtensibleRate.eval.

Added in version 3.0.

update(soln)#

This method takes a Solution object and stores any thermodynamic data (for example, temperature and pressure) needed to evaluate all reactions of the corresponding ReactionRate type.

If this state data has changed since the last time update was called and the reaction rates need to be updated, this method should return True. Otherwise, it should return False.

ThirdBody #

class cantera.ThirdBody(collider='M', *, efficiencies=None, default_efficiency=None)#

Bases: object

Class representing third-body collision partners in three-body or falloff reactions.

Parameters:

collider – Name of the third-body collider. If M (default), the default_efficiency is set to 1 and the collider is assumed to participate in a three-body reaction. If the collider includes parentheses, - for example (+M), - a falloff form is assumed, where the collider is not considered for the law of mass action. For species other than M, the third-body collider represents a named species with collision efficiency 1, and the default_efficiency is set to zero.
efficiencies – Non-default third-body efficiencies
default_efficiency – Default third-body efficiency

Added in version 3.0.

default_efficiency#: Get/Set the default third-body efficiency for this reaction, used for species not in efficiencies.

efficiencies#: Get/Set a dict defining non-default third-body efficiencies for this reaction, where the keys are the species names and the values are the efficiencies.

efficiency(species)#: Get the efficiency of the third body named species considering both the default efficiency and species-specific efficiencies.

mass_action#: Retrieve flag indicating whether third-body collider participates in the law of mass action.

name#: Get the name of the third-body collider used in the reaction equation.

Arrhenius #

class cantera.Arrhenius(A, b, E)#

Bases: object

A reaction rate coefficient which depends on temperature only and follows the modified Arrhenius form:

\[k_f = A T^b \exp(-\tfrac{E}{RT})\]

where A is the pre_exponential_factor, b is the temperature_exponent, and E is the activation_energy.

activation_energy#: The activation energy E [J/kmol].

pre_exponential_factor#: The pre-exponential factor A in units of m, kmol, and s raised to powers depending on the reaction order.

temperature_exponent#: The temperature exponent b.

Reaction Path Analysis #

ReactionPathDiagram #

class cantera.ReactionPathDiagram(kin: Kinetics, element: str)#

Bases: object

Create a reaction path diagram for the fluxes of the element element according the the net reaction rates determined by the Kinetics object kin.

add(other)#: Add fluxes from other to this diagram

arrow_width#: Get/Set the arrow width. If < 0, then scale with flux value.

bold_color#: Get/Set the color for bold lines

bold_threshold#: Get/Set the minimum relative flux for bold lines

build(verbose=False)#: Build the reaction path diagram. Called automatically by methods which return representations of the diagram, for example write_dot().

dashed_color#: Get/Set the color for dashed lines

display_only(k)#: Include only species and fluxes that are directly connected to the species with index k. Set to -1 to include all species.

dot_options#: Get/Set options for the ‘dot’ program

flow_type#: Get/Set the way flows are drawn. Either ‘NetFlow’ or ‘OneWayFlow’

font#: Get/Set the name of the font used

get_data()#: Get a (roughly) human-readable representation of the reaction path diagram.

get_dot()#: Return a string containing the reaction path diagram formatted for use by Graphviz’s ‘dot’ program.

label_threshold#: Get/Set the minimum relative flux for labels

log#: Logging messages generated while building the reaction path diagram

normal_color#: Get/Set the color for normal-weight lines

normal_threshold#: Get/Set the maximum relative flux for dashed lines

scale#: Get/Set the scaling factor for the fluxes. Set to -1 to normalize by the maximum net flux.

show_details#: Get/Set whether to show the details of which reactions contribute to the flux.

threshold#: Get/Set the threshold for the minimum flux relative value that will be plotted.

title#: Get/Set the diagram title

write_dot(filename)#: Write the reaction path diagram formatted for use by Graphviz’s ‘dot’ program to the file named filename.