Warning

This documentation is for an old version of Cantera. You can find docs for newer versions here.

# Objects Representing Phases¶

## Composite Phase Objects¶

These classes are composite representations of a substance which has thermodynamic, chemical kinetic, and (optionally) transport properties.

class cantera.Solution(infile='', phaseid='', source=None, thermo=None, species=(), kinetics=None, reactions=(), **kwargs)

Bases: cantera._cantera.ThermoPhase, cantera._cantera.Kinetics, cantera._cantera.Transport

A class for chemically-reacting solutions. Instances can be created to represent any type of solution – a mixture of gases, a liquid solution, or a solid solution, for example.

Class Solution derives from classes ThermoPhase, Kinetics, and Transport. It defines no methods of its own, and is provided so that a single object can be used to compute thermodynamic, kinetic, and transport properties of a solution.

To skip initialization of the Transport object, pass the keyword argument transport_model=None to the Solution constructor.

The most common way to instantiate Solution objects is by using a phase definition, species and reactions defined in an input file:

gas = ct.Solution('gri30.cti')


If an input file defines multiple phases, the phase name (in CTI) or id (in XML) can be used to specify the desired phase:

gas = ct.Solution('diamond.cti', 'gas')
diamond = ct.Solution('diamond.cti', 'diamond')


Solution objects can also be constructed using Species and Reaction objects which can themselves either be imported from input files or defined directly in Python:

spec = ct.Species.listFromFile('gri30.cti')
rxns = ct.Reaction.listFromFile('gri30.cti')
species=spec, reactions=rxns)


where the thermo and kinetics keyword arguments are strings specifying the thermodynamic and kinetics model, respectively, and species and reactions keyword arguments are lists of Species and Reaction objects, respectively.

For non-trivial uses cases of this functionality, see the examples extract_submechanism.py and mechanism_reduction.py.

In addition, Solution objects can be constructed by passing the text of the CTI or XML phase definition in directly, using the source keyword argument:

cti_def = '''
ideal_gas(name='gas', elements='O H Ar',
species='gri30: all',
reactions='gri30: all',
options=['skip_undeclared_elements', 'skip_undeclared_species', 'skip_undeclared_third_bodies'],
initial_state=state(temperature=300, pressure=101325))'''
gas = ct.Solution(source=cti_def)

class cantera.Interface(infile='', phaseid='', phases=(), thermo=None, species=(), kinetics=None, reactions=())

Bases: cantera._cantera.InterfacePhase, cantera._cantera.InterfaceKinetics

Two-dimensional interfaces.

Instances of class Interface represent reacting 2D interfaces between bulk 3D phases. Class Interface defines no methods of its own. All of its methods derive from either InterfacePhase or InterfaceKinetics.

To construct an Interface object, adjacent bulk phases which participate in reactions need to be created and then passed in as a list in the phases argument to the constructor:

gas = ct.Solution('diamond.cti', 'gas')
diamond = ct.Solution('diamond.cti', 'diamond')
diamond_surf = ct.Interface('diamond.cti', 'diamond_100', [gas, diamond])

class cantera.DustyGas(infile, phaseid='')

Bases: cantera._cantera.ThermoPhase, cantera._cantera.Kinetics, cantera._cantera.DustyGasTransport

A composite class which models a gas in a stationary, solid, porous medium.

The only transport properties computed are the multicomponent diffusion coefficients. The model does not compute viscosity or thermal conductivity.

## Pure Fluid Phases¶

The following convenience functions can be used to create PureFluid objects with the indicated equation of state:

cantera.CarbonDioxide()

Create a PureFluid object using the equation of state for carbon dioxide.

cantera.Heptane()

Create a PureFluid object using the equation of state for heptane.

cantera.Hfc134a()

Create a PureFluid object using the equation of state for HFC-134a.

cantera.Hydrogen()

Create a PureFluid object using the equation of state for hydrogen.

cantera.Methane()

Create a PureFluid object using the equation of state for methane.

cantera.Nitrogen()

Create a PureFluid object using the equation of state for nitrogen.

cantera.Oxygen()

Create a PureFluid object using the equation of state for oxygen.

cantera.Water()

Create a PureFluid object using the equation of state for water.

## Representing Quantities of Phases¶

class cantera.Quantity(phase, mass=None, moles=None, constant='UV')

Bases: object

A class representing a specific quantity of a Solution. In addition to the properties which can be computed for class Solution, class Quantity provides several additional capabilities. A Quantity object is created from a Solution with either the mass or number of moles specified:

>>> gas = ct.Solution('gri30.xml')
>>> gas.TPX = 300, 5e5, 'O2:1.0, N2:3.76'
>>> q1 = ct.Quantity(gas, mass=5) # 5 kg of air


The state of a Quantity can be changed in the same way as a Solution:

>>> q1.TP = 500, 101325


>>> q1.volume
7.1105094
>>> q1.enthalpy
1032237.84


The size of a Quantity can be changed by setting the mass or number of moles:

>>> q1.moles = 3
>>> q1.mass
86.552196
>>> q1.volume
123.086


or by multiplication:

>>> q1 *= 2
>>> q1.moles
6.0


Finally, Quantities can be added, providing an easy way of calculating the state resulting from mixing two substances:

>>> q1.mass = 5
>>> q2 = ct.Quantity(gas)
>>> q2.TPX = 300, 101325, 'CH4:1.0'
>>> q2.mass = 1
>>> q3 = q1 + q2 # combine at constant UV
>>> q3.T
432.31234
>>> q3.P
97974.9871
>>> q3.mole_fraction_dict()
{'CH4': 0.26452900448117395,
'N2': 0.5809602821745349,
'O2': 0.1545107133442912}


If a different property pair should be held constant when combining, this can be specified as follows:

>>> q1.constant = q2.constant = 'HP'
>>> q3 = q1 + q2 # combine at constant HP
>>> q3.T
436.03320
>>> q3.P
101325.0

DP

Get/Set density [kg/m^3] and pressure [Pa].

DPX

Get/Set density [kg/m^3], pressure [Pa], and mole fractions.

DPY

Get/Set density [kg/m^3], pressure [Pa], and mass fractions.

G

Get the total Gibbs free energy [J] represented by the Quantity.

H

Get the total enthalpy [J] represented by the Quantity.

HP

Get/Set enthalpy [J/kg or J/kmol] and pressure [Pa].

HPX

Get/Set enthalpy [J/kg or J/kmol], pressure [Pa] and mole fractions.

HPY

Get/Set enthalpy [J/kg or J/kmol], pressure [Pa] and mass fractions.

ID

The ID of the phase. The default is taken from the CTI/XML input file.

P

Pressure [Pa].

P_sat

Saturation pressure [Pa] at the current temperature.

S

Get the total entropy [J/K] represented by the Quantity.

SP

Get/Set entropy [J/kg/K or J/kmol/K] and pressure [Pa].

SPX

Get/Set entropy [J/kg/K or J/kmol/K], pressure [Pa], and mole fractions.

SPY

Get/Set entropy [J/kg/K or J/kmol/K], pressure [Pa], and mass fractions.

SV

Get/Set entropy [J/kg/K or J/kmol/K] and specific volume [m^3/kg or m^3/kmol].

SVX

Get/Set entropy [J/kg/K or J/kmol/K], specific volume [m^3/kg or m^3/kmol], and mole fractions.

SVY

Get/Set entropy [J/kg/K or J/kmol/K], specific volume [m^3/kg or m^3/kmol], and mass fractions.

T

Temperature [K].

TD

Get/Set temperature [K] and density [kg/m^3 or kmol/m^3].

TDX

Get/Set temperature [K], density [kg/m^3 or kmol/m^3], and mole fractions.

TDY

Get/Set temperature [K] and density [kg/m^3 or kmol/m^3], and mass fractions.

TP

Get/Set temperature [K] and pressure [Pa].

TPX

Get/Set temperature [K], pressure [Pa], and mole fractions.

TPY

Get/Set temperature [K], pressure [Pa], and mass fractions.

T_sat

Saturation temperature [K] at the current pressure.

U

Get the total internal energy [J] represented by the Quantity.

UV

Get/Set internal energy [J/kg or J/kmol] and specific volume [m^3/kg or m^3/kmol].

UVX

Get/Set internal energy [J/kg or J/kmol], specific volume [m^3/kg or m^3/kmol], and mole fractions.

UVY

Get/Set internal energy [J/kg or J/kmol], specific volume [m^3/kg or m^3/kmol], and mass fractions.

V

Get the total volume [m^3] represented by the Quantity.

X

Get/Set the species mole fractions. Can be set as an array, as a dictionary, or as a string. Always returns an array:

>>> phase.X = [0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5]
>>> phase.X = {'H2':0.1, 'O2':0.4, 'AR':0.5}
>>> phase.X = 'H2:0.1, O2:0.4, AR:0.5'
>>> phase.X
array([0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5])

Y

Get/Set the species mass fractions. Can be set as an array, as a dictionary, or as a string. Always returns an array:

>>> phase.Y = [0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5]
>>> phase.Y = {'H2':0.1, 'O2':0.4, 'AR':0.5}
>>> phase.Y = 'H2:0.1, O2:0.4, AR:0.5'
>>> phase.Y
array([0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5])

add_reaction

Add a new reaction to this phase.

add_species

Add a new species to this phase. Missing elements will be added automatically.

atomic_weight

Atomic weight [kg/kmol] of element m

atomic_weights

Array of atomic weight [kg/kmol] for each element in the mixture.

basis

Determines whether intensive thermodynamic properties are treated on a mass (per kg) or molar (per kmol) basis. This affects the values returned by the properties h, u, s, g, v, density, cv, and cp, as well as the values used with the state-setting properties such as HPX and UV.

binary_diff_coeffs

Binary diffusion coefficients [m^2/s].

chemical_potentials

Array of species chemical potentials [J/kmol].

concentrations

Get/Set the species concentrations [kmol/m^3].

cp

Heat capacity at constant pressure [J/kg/K or J/kmol/K] depending on basis.

cp_mass

Specific heat capacity at constant pressure [J/kg/K].

cp_mole

Molar heat capacity at constant pressure [J/kmol/K].

creation_rates

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

critical_density

Critical density [kg/m^3 or kmol/m^3] depending on basis.

critical_pressure

Critical pressure [Pa].

critical_temperature

Critical temperature [K].

cv

Heat capacity at constant volume [J/kg/K or J/kmol/K] depending on basis.

cv_mass

Specific heat capacity at constant volume [J/kg/K].

cv_mole

Molar heat capacity at constant volume [J/kmol/K].

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].

density

Density [kg/m^3 or kmol/m^3] depending on basis.

density_mass

(Mass) density [kg/m^3].

density_mole

Molar density [kmol/m^3].

destruction_rates

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

electric_potential

Get/Set the electric potential [V] for this phase.

electrical_conductivity

Electrical conductivity. [S/m].

electrochemical_potentials

Array of species electrochemical potentials [J/kmol].

element_index

The index of element element, which may be specified as a string or an integer. In the latter case, the index is checked for validity and returned. If no such element is present, an exception is thrown.

element_name

Name of the element with index m.

element_names

A list of all the element names.

element_potentials

Get the array of element potentials. The element potentials are only defined for equilibrium states. This method first sets the composition to a state of equilibrium at constant T and P, then computes the element potentials for this equilibrium state.

elemental_mass_fraction

Get the elemental mass fraction $$Z_{\mathrm{mass},m}$$ of element $$m$$ as defined by:

$Z_{\mathrm{mass},m} = \sum_k \frac{a_{m,k} M_m}{M_k} Y_k$

with $$a_{m,k}$$ being the number of atoms of element $$m$$ in species $$k$$, $$M_m$$ the atomic weight of element $$m$$, $$M_k$$ the molecular weight of species $$k$$, and $$Y_k$$ the mass fraction of species $$k$$.

Parameters: m – Base element, may be specified by name or by index.
>>> phase.elemental_mass_fraction('H')
1.0

elemental_mole_fraction

Get the elemental mole fraction $$Z_{\mathrm{mole},m}$$ of element $$m$$ (the number of atoms of element m divided by the total number of atoms) as defined by:

$Z_{\mathrm{mole},m} = \frac{\sum_k a_{m,k} X_k} {\sum_k \sum_j a_{j,k} X_k}$

with $$a_{m,k}$$ being the number of atoms of element $$m$$ in species $$k$$, $$\sum_j$$ being a sum over all elements, and $$X_k$$ being the mole fraction of species $$k$$.

Parameters: m – Base element, may be specified by name or by index.
>>> phase.elemental_mole_fraction('H')
1.0

enthalpy

Get the total enthalpy [J] represented by the Quantity.

enthalpy_mass

Specific enthalpy [J/kg].

enthalpy_mole

Molar enthalpy [J/kmol].

entropy

Get the total entropy [J/K] represented by the Quantity.

entropy_mass

Specific entropy [J/kg].

entropy_mole

Molar entropy [J/kmol/K].

equilibrate(XY=None, *args, **kwargs)

Set the state to equilibrium. By default, the property pair self.constant is held constant. See ThermoPhase.equilibrate.

equilibrium_constants

Equilibrium constants in concentration units for all reactions.

forward_rate_constants

Forward rate constants for all reactions. Units are a combination of kmol, m^3 and s, that depend on the rate expression for the reaction.

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.

g

Gibbs free energy [J/kg or J/kmol] depending on basis.

gibbs

Get the total Gibbs free energy [J] represented by the Quantity.

gibbs_mass

Specific Gibbs free energy [J/kg].

gibbs_mole

Molar Gibbs free energy [J/kmol].

h

Enthalpy [J/kg or J/kmol] depending on basis.

int_energy

Get the total internal energy [J] represented by the Quantity.

int_energy_mass

Specific internal energy [J/kg].

int_energy_mole

Molar internal energy [J/kmol].

is_reversible

True if reaction i_reaction is reversible.

isothermal_compressibility

Isothermal compressibility [1/Pa].

kinetics_species_index

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.

mass_fraction_dict
max_temp

Maximum temperature for which the thermodynamic data for the phase are valid.

mean_molecular_weight

The mean molecular weight (molar mass) [kg/kmol].

min_temp

Minimum temperature for which the thermodynamic data for the phase are valid.

mix_diff_coeffs

Mixture-averaged diffusion coefficients [m^2/s] relating the mass-averaged diffusive fluxes (with respect to the mass averaged velocity) to gradients in the species mole fractions.

mix_diff_coeffs_mass

Mixture-averaged diffusion coefficients [m^2/s] relating the diffusive mass fluxes to gradients in the species mass fractions.

mix_diff_coeffs_mole

Mixture-averaged diffusion coefficients [m^2/s] relating the molar diffusive fluxes to gradients in the species mole fractions.

modify_reaction

Modify the Reaction with index irxn to have the same rate parameters as rxn. rxn must have the same reactants and products and be of the same type (i.e. ElementaryReaction, FalloffReaction, PlogReaction, etc.) as the existing reaction. This method does not modify the third-body efficiencies, reaction orders, or reversibility of the reaction.

modify_species
mole_fraction_dict
molecular_weights

Array of species molecular weights (molar masses) [kg/kmol].

moles

Get/Set the number of moles [kmol] represented by the Quantity.

multi_diff_coeffs

Multicomponent diffusion coefficients [m^2/s].

multiplier

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_atoms

Number of atoms of element element in species species. The element and species may be specified by name or by index.

>>> phase.n_atoms('CH4','H')
4

n_elements

Number of elements.

n_phases

Number of phases in the reaction mechanism.

n_reactions

Number of reactions in the reaction mechanism.

n_selected_species

Number of species selected for output (by slicing of Solution object)

n_species

Number of species.

n_total_species

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

name

The name assigned to this phase. The default is taken from the CTI/XML input file.

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_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.

partial_molar_cp

Array of species partial molar specific heat capacities at constant pressure [J/kmol/K].

partial_molar_enthalpies

Array of species partial molar enthalpies [J/kmol].

partial_molar_entropies

Array of species partial molar entropies [J/kmol/K].

partial_molar_int_energies

Array of species partial molar internal energies [J/kmol].

partial_molar_volumes

Array of species partial molar volumes [m^3/kmol].

phase

Get the underlying Solution object, with the state set to match the wrapping Quantity object.

product_stoich_coeff

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.

products

The products portion of the reaction equation

reactant_stoich_coeff

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.

reactants

The reactants portion of the reaction equation

reaction

Return a Reaction object representing the reaction with index i_reaction.

reaction_equation

The equation for the specified reaction. See also reaction_equations.

reaction_equations

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']


See also reaction_equation.

reaction_phase_index

The index of the phase where the reactions occur.

reaction_type

Type of reaction i_reaction.

reactions

Return a list of all Reaction objects

reference_pressure

Reference state pressure [Pa].

report

Generate a report describing the thermodynamic state of this phase. To print the report to the terminal, simply call the phase object. The following two statements are equivalent:

>>> phase()
>>> print(phase.report())

reverse_rate_constants

Reverse rate constants for all reactions. Units are a combination of kmol, m^3 and s, that depend on the rate expression for the reaction.

reverse_rates_of_progress

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

s

Entropy [J/kg/K or J/kmol/K] depending on basis.

selected_species
set_equivalence_ratio

Set the composition to a mixture of fuel and oxidizer at the specified equivalence ratio phi, holding temperature and pressure constant. Considers the oxidation of C and H to CO2 and H2O. Other elements are assumed not to participate in oxidation (i.e. N ends up as N2):

>>> gas.set_equivalence_ratio(0.5, 'CH4', 'O2:1.0, N2:3.76')
>>> gas.mole_fraction_dict()
{'CH4': 0.049900199, 'N2': 0.750499001, 'O2': 0.199600798}

>>> gas.set_equivalence_ratio(1.2, {'NH3;:0.8, 'CO':0.2}, 'O2:1.0')
>>> gas.mole_fraction_dict()
{'CO': 0.1263157894, 'NH3': 0.505263157, 'O2': 0.36842105}

Parameters: phi – Equivalence ratio fuel – Fuel species name or molar composition as string, array, or dict. oxidizer – Oxidizer species name or molar composition as a string, array, or dict.
set_multiplier

Set the multiplier for for reaction i_reaction to value. If i_reaction is not specified, then the multiplier for all reactions is set to value. See multiplier.

set_unnormalized_mass_fractions

Set the mass fractions without normalizing to force sum(Y) == 1.0. Useful primarily when calculating derivatives with respect to Y[k] by finite difference.

set_unnormalized_mole_fractions

Set the mole fractions without normalizing to force sum(X) == 1.0. Useful primarily when calculating derivatives with respect to X[k] by finite difference.

species

Return the Species object for species k, where k is either the species index or the species name. If k is not specified, a list of all species objects is returned.

species_index

The index of species species, which may be specified as a string or an integer. In the latter case, the index is checked for validity and returned. If no such species is present, an exception is thrown.

species_name

Name of the species with index k.

species_names

A list of all the species names.

standard_cp_R

Array of nondimensional species standard-state specific heat capacities at constant pressure at the current temperature and pressure.

standard_enthalpies_RT

Array of nondimensional species standard-state enthalpies at the current temperature and pressure.

standard_entropies_R

Array of nondimensional species standard-state entropies at the current temperature and pressure.

standard_gibbs_RT

Array of nondimensional species standard-state Gibbs free energies at the current temperature and pressure.

standard_int_energies_RT

Array of nondimensional species standard-state internal energies at the current temperature and pressure.

thermal_conductivity

Thermal conductivity. [W/m/K].

thermal_diff_coeffs

Return a one-dimensional array of the species thermal diffusion coefficients [kg/m/s].

thermal_expansion_coeff

Thermal expansion coefficient [1/K].

transport_model

Get/Set the transport model associated with this transport model.

Setting a new transport model deletes the underlying C++ Transport object and replaces it with a new one implementing the specified model.

u

Internal energy in [J/kg or J/kmol].

v

Specific volume [m^3/kg or m^3/kmol] depending on basis.

viscosity

Viscosity [Pa-s].

volume

Get the total volume [m^3] represented by the Quantity.

volume_mass

Specific volume [m^3/kg].

volume_mole

Molar volume [m^3/kmol].

## Representing Multiple States¶

class cantera.SolutionArray(phase, shape=(0, ), states=None, extra=None)

Bases: object

A class providing a convenient interface for representing many thermodynamic states using the same Solution object and computing properties for that array of states.

SolutionArray can represent both 1D and multi-dimensional arrays of states, with shapes described in the same way as Numpy arrays. All of the states can be set in a single call.

>>> gas = ct.Solution('gri30.cti')
>>> states = ct.SolutionArray(gas, (6, 10))
>>> T = np.linspace(300, 1000, 10) # row vector
>>> P = ct.one_atm * np.linspace(0.1, 5.0, 6)[:,np.newaxis] # column vector
>>> X = 'CH4:1.0, O2:1.0, N2:3.76'
>>> states.TPX = T, P, X


Similar to Numpy arrays, input with fewer non-singleton dimensions than the SolutionArray is ‘broadcast’ to generate input of the appropriate shape. In the above example, the single value for the mole fraction input is applied to each input, while each row has a constant temperature and each column has a constant pressure.

Computed properties are returned as Numpy arrays with the same shape as the array of states, with additional dimensions appended as necessary for non- scalar output (e.g. per-species or per-reaction properties):

>>> h = states.enthalpy_mass
>>> h[i,j] # -> enthalpy at P[i] and T[j]
>>> sk = states.partial_molar_entropies
>>> sk[i,:,k] # -> entropy of species k at P[i] and each temperature
>>> ropnet = states.net_rates_of_progress
>>> ropnet[i,j,n] # -> net reaction rate for reaction n at P[i] and T[j]


In the case of 1D arrays, additional states can be appended one at a time:

>>> states = ct.SolutionArray(gas) # creates an empty SolutionArray
>>> for phi in np.linspace(0.5, 2.0, 20):
...     states.append(T=300, P=ct.one_atm,
...                   X={'CH4': phi, 'O2': 2, 'N2': 2*3.76})
>>> # 'states' now contains 20 elements
>>> states.equilibrate('HP')
>>> states.T # -> adiabatic flame temperature at various equivalence ratios


SolutionArray objects can also be ‘sliced’ like Numpy arrays, which can be used both for accessing and setting properties:

>>> states = ct.SolutionArray(gas, (6, 10))
>>> states[0].TP = 400, None # set the temperature of the first row to 400 K
>>> cp = states[:,1].cp_mass # heat capacity of the second column


If many slices or elements of a property are going to be accessed (i.e. within a loop), it is generally more efficient to compute the property array once and access this directly, rather than repeatedly slicing the SolutionArray object, e.g.:

>>> mu = states.viscosity
>>> for i,j in np.ndindex(mu.shape):
...     # do something with mu[i,j]


Information about a subset of species may also be accessed, using parentheses to specify the species:

>>> states('CH4').Y # -> mass fraction of CH4 in each state
>>> states('H2','O2').partial_molar_cp # -> cp for H2 and O2


Properties and functions which are not dependent on the thermodynamic state act as pass-throughs to the underlying Solution object, and are not converted to arrays:

>>> states.element_names
['O', 'H', 'C', 'N', 'Ar']
>>> s.reaction_equation(10)
'CH4 + O <=> CH3 + OH'


Data represnted by a SolutionArray can be extracted and saved to a CSV file using the write_csv method:

>>> states.write_csv('somefile.csv', cols=('T','P','X','net_rates_of_progress'))

Parameters: phase – The Solution object used to compute the thermodynamic, kinetic, and transport properties shape – A tuple or integer indicating the dimensions of the SolutionArray. If the shape is 1D, the array may be extended using the append method. Otherwise, the shape is fixed. states – The initial array of states. Used internally to provide slicing support.
DP

Get/Set density [kg/m^3] and pressure [Pa].

DPX

Get/Set density [kg/m^3], pressure [Pa], and mole fractions.

DPY

Get/Set density [kg/m^3], pressure [Pa], and mass fractions.

HP

Get/Set enthalpy [J/kg or J/kmol] and pressure [Pa].

HPX

Get/Set enthalpy [J/kg or J/kmol], pressure [Pa] and mole fractions.

HPY

Get/Set enthalpy [J/kg or J/kmol], pressure [Pa] and mass fractions.

ID

The ID of the phase. The default is taken from the CTI/XML input file.

P

Pressure [Pa].

PV

Get/Set the pressure [Pa] and specific volume [m^3/kg] of a PureFluid.

PX

Get/Set the pressure [Pa] and vapor fraction of a two-phase state.

P_sat

Saturation pressure [Pa] at the current temperature.

SH

Get/Set the specific entropy [J/kg/K] and the specific enthalpy [J/kg] of a PureFluid.

SP

Get/Set entropy [J/kg/K or J/kmol/K] and pressure [Pa].

SPX

Get/Set entropy [J/kg/K or J/kmol/K], pressure [Pa], and mole fractions.

SPY

Get/Set entropy [J/kg/K or J/kmol/K], pressure [Pa], and mass fractions.

ST

Get/Set the entropy [J/kg/K] and temperature [K] of a PureFluid.

SV

Get/Set entropy [J/kg/K or J/kmol/K] and specific volume [m^3/kg or m^3/kmol].

SVX

Get/Set entropy [J/kg/K or J/kmol/K], specific volume [m^3/kg or m^3/kmol], and mole fractions.

SVY

Get/Set entropy [J/kg/K or J/kmol/K], specific volume [m^3/kg or m^3/kmol], and mass fractions.

T

Temperature [K].

TD

Get/Set temperature [K] and density [kg/m^3 or kmol/m^3].

TDX

Get/Set temperature [K], density [kg/m^3 or kmol/m^3], and mole fractions.

TDY

Get/Set temperature [K] and density [kg/m^3 or kmol/m^3], and mass fractions.

TH

Get/Set the temperature [K] and the specific enthalpy [J/kg] of a PureFluid.

TP

Get/Set temperature [K] and pressure [Pa].

TPX

Get/Set temperature [K], pressure [Pa], and mole fractions.

TPY

Get/Set temperature [K], pressure [Pa], and mass fractions.

TV

Get/Set the temperature [K] and specific volume [m^3/kg] of a PureFluid.

TX

Get/Set the temperature [K] and vapor fraction of a two-phase state.

T_sat

Saturation temperature [K] at the current pressure.

UP

Get/Set the specific internal energy [J/kg] and the pressure [Pa] of a PureFluid.

UV

Get/Set internal energy [J/kg or J/kmol] and specific volume [m^3/kg or m^3/kmol].

UVX

Get/Set internal energy [J/kg or J/kmol], specific volume [m^3/kg or m^3/kmol], and mole fractions.

UVY

Get/Set internal energy [J/kg or J/kmol], specific volume [m^3/kg or m^3/kmol], and mass fractions.

VH

Get/Set the specfic volume [m^3/kg] and the specific enthalpy [J/kg] of a PureFluid.

X

Get/Set the species mole fractions. Can be set as an array, as a dictionary, or as a string. Always returns an array:

>>> phase.X = [0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5]
>>> phase.X = {'H2':0.1, 'O2':0.4, 'AR':0.5}
>>> phase.X = 'H2:0.1, O2:0.4, AR:0.5'
>>> phase.X
array([0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5])

Y

Get/Set the species mass fractions. Can be set as an array, as a dictionary, or as a string. Always returns an array:

>>> phase.Y = [0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5]
>>> phase.Y = {'H2':0.1, 'O2':0.4, 'AR':0.5}
>>> phase.Y = 'H2:0.1, O2:0.4, AR:0.5'
>>> phase.Y
array([0.1, 0, 0, 0.4, 0, 0, 0, 0, 0.5])

append(state=None, **kwargs)

Append an element to the array with the specified state. Elements can only be appended in cases where the array of states is one-dimensional.

The state may be specified in one of three ways:

• as the array of [temperature, density, mass fractions] which is returned by Solution.state:

mystates.append(gas.state)

• as a tuple of three elements that corresponds to any of the full-state setters of Solution, e.g. TPY or HPX:

mystates.append(TPX=(300, 101325, 'O2:1.0, N2:3.76'))

• as separate keywords for each of the elements corresponding to one of the full-state setters:

mystates.append(T=300, P=101325, X={'O2':1.0, 'N2':3.76})

atomic_weight

Atomic weight [kg/kmol] of element m

atomic_weights

Array of atomic weight [kg/kmol] for each element in the mixture.

basis

Determines whether intensive thermodynamic properties are treated on a mass (per kg) or molar (per kmol) basis. This affects the values returned by the properties h, u, s, g, v, density, cv, and cp, as well as the values used with the state-setting properties such as HPX and UV.

binary_diff_coeffs

Binary diffusion coefficients [m^2/s].

chemical_potentials

Array of species chemical potentials [J/kmol].

collect_data(cols=('extra', 'T', 'density', 'Y'), threshold=0, species='Y')

Returns the data specified by cols in a single 2D Numpy array, along with a list of column labels.

Parameters: cols – A list of any properties of the solution that are scalars or which have a value for each species or reaction. If species names are specified, then either the mass or mole fraction of that species will be taken, depending on the value of species. cols may also include any arrays which were specified as ‘extra’ variables when defining the SolutionArray object. The special value ‘extra’ can be used to include all ‘extra’ variables. threshold – Relative tolerance for including a particular column. The tolerance is applied by comparing the maximum absolute value for a particular column to the maximum absolute value in all columns for the same variable (e.g. mass fraction). species – Specifies whether to use mass (‘Y’) or mole (‘X’) fractions for individual species specified in ‘cols’
concentrations

Get/Set the species concentrations [kmol/m^3].

coverages

Get/Set the fraction of sites covered by each species.

cp

Heat capacity at constant pressure [J/kg/K or J/kmol/K] depending on basis.

cp_mass

Specific heat capacity at constant pressure [J/kg/K].

cp_mole

Molar heat capacity at constant pressure [J/kmol/K].

creation_rates

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

critical_density

Critical density [kg/m^3 or kmol/m^3] depending on basis.

critical_pressure

Critical pressure [Pa].

critical_temperature

Critical temperature [K].

cv

Heat capacity at constant volume [J/kg/K or J/kmol/K] depending on basis.

cv_mass

Specific heat capacity at constant volume [J/kg/K].

cv_mole

Molar heat capacity at constant volume [J/kmol/K].

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].

density

Density [kg/m^3 or kmol/m^3] depending on basis.

density_mass

(Mass) density [kg/m^3].

density_mole

Molar density [kmol/m^3].

destruction_rates

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

electric_potential

Get/Set the electric potential [V] for this phase.

electrical_conductivity

Electrical conductivity. [S/m].

electrochemical_potentials

Array of species electrochemical potentials [J/kmol].

element_index

The index of element element, which may be specified as a string or an integer. In the latter case, the index is checked for validity and returned. If no such element is present, an exception is thrown.

element_name

Name of the element with index m.

element_names

A list of all the element names.

elemental_mass_fraction(*args, **kwargs)
elemental_mole_fraction(*args, **kwargs)
enthalpy_mass

Specific enthalpy [J/kg].

enthalpy_mole

Molar enthalpy [J/kmol].

entropy_mass

Specific entropy [J/kg].

entropy_mole

Molar entropy [J/kmol/K].

equilibrate(*args, **kwargs)
equilibrium_constants

Equilibrium constants in concentration units for all reactions.

forward_rate_constants

Forward rate constants for all reactions. Units are a combination of kmol, m^3 and s, that depend on the rate expression for the reaction.

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.

g

Gibbs free energy [J/kg or J/kmol] depending on basis.

gibbs_mass

Specific Gibbs free energy [J/kg].

gibbs_mole

Molar Gibbs free energy [J/kmol].

h

Enthalpy [J/kg or J/kmol] depending on basis.

int_energy_mass

Specific internal energy [J/kg].

int_energy_mole

Molar internal energy [J/kmol].

is_reversible

True if reaction i_reaction is reversible.

isothermal_compressibility

Isothermal compressibility [1/Pa].

kinetics_species_index

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.

max_temp

Maximum temperature for which the thermodynamic data for the phase are valid.

mean_molecular_weight

The mean molecular weight (molar mass) [kg/kmol].

min_temp

Minimum temperature for which the thermodynamic data for the phase are valid.

mix_diff_coeffs

Mixture-averaged diffusion coefficients [m^2/s] relating the mass-averaged diffusive fluxes (with respect to the mass averaged velocity) to gradients in the species mole fractions.

mix_diff_coeffs_mass

Mixture-averaged diffusion coefficients [m^2/s] relating the diffusive mass fluxes to gradients in the species mass fractions.

mix_diff_coeffs_mole

Mixture-averaged diffusion coefficients [m^2/s] relating the molar diffusive fluxes to gradients in the species mole fractions.

modify_reaction

Modify the Reaction with index irxn to have the same rate parameters as rxn. rxn must have the same reactants and products and be of the same type (i.e. ElementaryReaction, FalloffReaction, PlogReaction, etc.) as the existing reaction. This method does not modify the third-body efficiencies, reaction orders, or reversibility of the reaction.

molecular_weights

Array of species molecular weights (molar masses) [kg/kmol].

multi_diff_coeffs

Multicomponent diffusion coefficients [m^2/s].

multiplier

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_atoms

Number of atoms of element element in species species. The element and species may be specified by name or by index.

>>> phase.n_atoms('CH4','H')
4

n_elements

Number of elements.

n_phases

Number of phases in the reaction mechanism.

n_reactions

Number of reactions in the reaction mechanism.

n_species

Number of species.

n_total_species

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

name

The name assigned to this phase. The default is taken from the CTI/XML input file.

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_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.

partial_molar_cp

Array of species partial molar specific heat capacities at constant pressure [J/kmol/K].

partial_molar_enthalpies

Array of species partial molar enthalpies [J/kmol].

partial_molar_entropies

Array of species partial molar entropies [J/kmol/K].

partial_molar_int_energies

Array of species partial molar internal energies [J/kmol].

partial_molar_volumes

Array of species partial molar volumes [m^3/kmol].

product_stoich_coeff

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.

products

The products portion of the reaction equation

reactant_stoich_coeff

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.

reactants

The reactants portion of the reaction equation

reaction

Return a Reaction object representing the reaction with index i_reaction.

reaction_equation

The equation for the specified reaction. See also reaction_equations.

reaction_equations

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']


See also reaction_equation.

reaction_phase_index

The index of the phase where the reactions occur.

reaction_type

Type of reaction i_reaction.

reactions

Return a list of all Reaction objects

reference_pressure

Reference state pressure [Pa].

reverse_rate_constants

Reverse rate constants for all reactions. Units are a combination of kmol, m^3 and s, that depend on the rate expression for the reaction.

reverse_rates_of_progress

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

s

Entropy [J/kg/K or J/kmol/K] depending on basis.

set_multiplier

Set the multiplier for for reaction i_reaction to value. If i_reaction is not specified, then the multiplier for all reactions is set to value. See multiplier.

site_density

Get/Set the site density. [kmol/m^2] for surface phases; [kmol/m] for edge phases.

species

Return the Species object for species k, where k is either the species index or the species name. If k is not specified, a list of all species objects is returned.

species_index

The index of species species, which may be specified as a string or an integer. In the latter case, the index is checked for validity and returned. If no such species is present, an exception is thrown.

species_name

Name of the species with index k.

species_names

A list of all the species names.

standard_cp_R

Array of nondimensional species standard-state specific heat capacities at constant pressure at the current temperature and pressure.

standard_enthalpies_RT

Array of nondimensional species standard-state enthalpies at the current temperature and pressure.

standard_entropies_R

Array of nondimensional species standard-state entropies at the current temperature and pressure.

standard_gibbs_RT

Array of nondimensional species standard-state Gibbs free energies at the current temperature and pressure.

standard_int_energies_RT

Array of nondimensional species standard-state internal energies at the current temperature and pressure.

thermal_conductivity

Thermal conductivity. [W/m/K].

thermal_diff_coeffs

Return a one-dimensional array of the species thermal diffusion coefficients [kg/m/s].

thermal_expansion_coeff

Thermal expansion coefficient [1/K].

transport_model

Get/Set the transport model associated with this transport model.

Setting a new transport model deletes the underlying C++ Transport object and replaces it with a new one implementing the specified model.

u

Internal energy in [J/kg or J/kmol].

v

Specific volume [m^3/kg or m^3/kmol] depending on basis.

viscosity

Viscosity [Pa-s].

volume_mass

Specific volume [m^3/kg].

volume_mole

Molar volume [m^3/kmol].

write_csv(filename, cols=('extra', 'T', 'density', 'Y'), *args, **kwargs)

Write a CSV file named filename containing the data specified by cols. The first row of the CSV file will contain column labels.

Additional arguments are passed on to collect_data. This method works only with 1D SolutionArray objects.

## Utility Functions¶

cantera.add_directory(directory)

Add a directory to search for Cantera data files.

cantera.get_data_directories()

Get a list of the directories Cantera searches for data files.