Thermodynamic Properties¶

Phases
Mixture
Species
Species Thermodynamic Properties
Element

Phases ¶

These classes are used to describe the thermodynamic state of a system.

ThermoPhase ¶

class cantera.ThermoPhase(infile='', phaseid='')¶

Bases: cantera._cantera._SolutionBase

ThermoPhase(*args, **kwargs)

A phase with an equation of state.

Class ThermoPhase may be used to represent the intensive thermodynamic state of a phase of matter, which might be a gas, liquid, or solid.

Class ThermoPhase is not usually instantiated directly. It is used as a base class for classes Solution and Interface.

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 identifier of the object. The default value corresponds to the CTI/XML/YAML input file phase entry.

Deprecated since version 2.5: To be deprecated with version 2.5, and removed thereafter. Usage merged with name.

P¶: Pressure [Pa].

P_sat¶: Saturation pressure [Pa] at the current temperature.

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.

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.

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])

activities¶: Array of nondimensional activities. Returns either molar or molal activities depending on the convention of the thermodynamic model.

activity_coefficients¶: Array of nondimensional, molar activity coefficients.

add_species(self, Species species)¶: Add a new species to this phase. Missing elements will be added automatically.

add_species_alias(self, name, alias)¶: Add the alternate species name alias for an original species name.

atomic_weight(self, m)¶: 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.

case_sensitive_species_names¶: Enforce case-sensitivity for look up of species names

charges¶: Array of species charges [elem. charge].

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].

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].

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].

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

electrochemical_potentials¶: Array of species electrochemical potentials [J/kmol].

element_index(self, element) → int ¶: 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(self, m)¶: Name of the element with index m.

element_names¶: A list of all the element names.

elemental_mass_fraction(self, m)¶

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 \(k\):

>>> phase.elemental_mass_fraction('H')
1.0

Parameters: m – Base element, may be specified by name or by index.

elemental_mole_fraction(self, m)¶

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 \(k\):

>>> phase.elemental_mole_fraction('H')
1.0

Parameters: m – Base element, may be specified by name or by index.

enthalpy_mass¶: Specific enthalpy [J/kg].

enthalpy_mole¶: Molar enthalpy [J/kmol].

entropy_mass¶: Specific entropy [J/kg/K].

entropy_mole¶: Molar entropy [J/kmol/K].

equilibrate(self, XY, solver=u'auto', double rtol=1e-9, int max_steps=1000, int max_iter=100, int estimate_equil=0, int log_level=0, **kwargs)¶

Set to a state of chemical equilibrium holding property pair XY constant.

Parameters

XY –
A two-letter string, which must be one of the set:
```
['TP','TV','HP','SP','SV','UV']
```
solver –
Specifies the equilibrium solver to use. May be one of the following:
- 'element_potential' - a fast solver using the element potential method
- 'gibbs' - a slower but more robust Gibbs minimization solver
- 'vcs' - the VCS non-ideal equilibrium solver
- 'auto' - The element potential solver will be tried first, then if it fails the Gibbs solver will be tried.
rtol – The relative error tolerance.
max_steps – The maximum number of steps in composition to take to find a converged solution.
max_iter – For the Gibbs minimization solver, this specifies the number of outer iterations on T or P when some property pair other than TP is specified.
estimate_equil – Integer indicating whether the solver should estimate its own initial condition. If 0, the initial mole fraction vector in the ThermoPhase object is used as the initial condition. If 1, the initial mole fraction vector is used if the element abundances are satisfied. If -1, the initial mole fraction vector is thrown out, and an estimate is formulated.
log_level – Set to a value greater than 0 to write diagnostic output.

equivalence_ratio(self, fuel=None, oxidizer=None, basis='mole')¶

Get the equivalence ratio of the current mixture, which is a conserved quantity. Considers the oxidation of C to CO2, H to H2O and S to SO2. Other elements are assumed not to participate in oxidation (that is, N ends up as N2). If fuel and oxidizer are not specified, the equivalence ratio is computed from the available oxygen and the required oxygen for complete oxidation. The basis determines the composition of fuel and oxidizer: basis='mole' (default) means mole fractions, basis='mass' means mass fractions:

>>> gas.set_equivalence_ratio(0.5, 'CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
>>> gas.equivalence_ratio('CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
0.5

Parameters

fuel – Fuel species name or mole/mass fractions as string, array, or dict.
oxidizer – Oxidizer species name or mole/mass fractions as a string, array, or dict.
basis – Determines if fuel and oxidizer are given in mole fractions (basis='mole') or mass fractions (basis='mass')

find_isomers(self, comp)¶: Find species/isomers matching a composition specified by comp.

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

get_equivalence_ratio(self, oxidizers=[], ignore=[])¶

Get the composition of a fuel/oxidizer mixture. This gives the equivalence ratio of an unburned mixture. This is not a quantity that is conserved after oxidation. Considers the oxidation of C to CO2, H to H2O and S to SO2. Other elements are assumed not to participate in oxidation (that is, N ends up as N2).

Parameters

oxidizers – List of oxidizer species names as strings. Default: with oxidizers=[], every species that contains O but does not contain H, C, or S is considered to be an oxidizer.

ignore –

List of species names as strings to ignore.

>>> gas.set_equivalence_ratio(0.5, 'CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
>>> gas.get_equivalence_ratio()
0.5
>>> gas.get_equivalence_ratio(['O2'])  # Only consider O2 as the oxidizer instead of O2 and NO
0.488095238095
>>> gas.X = 'CH4:1, O2:2, NO:0.1'
>>> gas.get_equivalence_ratio(ignore=['NO'])
1.0

Deprecated since version 2.5: To be deprecated with version 2.5, and removed thereafter. Replaced by function equivalence_ratio.

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.

has_phase_transition¶: Returns true if the phase represents a substance with phase transitions

int_energy_mass¶: Specific internal energy [J/kg].

int_energy_mole¶: Molar internal energy [J/kmol].

is_compressible¶: Returns true if the density of the phase is an independent variable defining the thermodynamic state of a substance

is_pure¶: Returns true if the phase represents a pure (fixed composition) substance

isothermal_compressibility¶: Isothermal compressibility [1/Pa].

mass_fraction_dict(self, double threshold=0.0)¶

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.

mixture_fraction(self, fuel, oxidizer, basis='mole', element='Bilger')¶

Get the mixture fraction of the current mixture (kg fuel / (kg oxidizer + kg fuel)) This is a quantity that is conserved after oxidation. Considers the oxidation of C to CO2, H to H2O and S to SO2. Other elements are assumed not to participate in oxidation (that is, N ends up as N2). The basis determines the composition of fuel and oxidizer: basis="mole" (default) means mole fractions, basis="mass" means mass fractions. The mixture fraction can be computed from a single element (for example, carbon with element="C") or from all elements, which is the Bilger mixture fraction (element="Bilger"). The Bilger mixture fraction is computed by default:

>>> gas.set_mixture_fraction(0.5, 'CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
>>> gas.mixture_fraction('CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
0.5

Parameters

fuel – Fuel species name or mole/mass fractions as string, array, or dict.
oxidizer – Oxidizer species name or mole/mass fractions as a string, array, or dict.
basis – Determines if fuel and oxidizer are given in mole fractions (basis='mole') or mass fractions (basis='mass')
element – Computes the mixture fraction from the specified elemental mass fraction (given by element name or element index) or as the Bilger mixture fraction (default)

modify_species(self, k, Species species)¶

mole_fraction_dict(self, double threshold=0.0)¶

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

n_atoms(self, species, element)¶

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

n_species¶: Number of species.

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_of_matter¶: Get the thermodynamic phase (gas, liquid, etc.) at the current conditions.

reference_pressure¶: Reference state pressure [Pa].

report(self, show_thermo=True, float threshold=1e-14)¶

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())

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

set_equivalence_ratio(self, phi, fuel, oxidizer, basis='mole')¶

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 to CO2, H to H2O and S to SO2. Other elements are assumed not to participate in oxidation (that is, N ends up as N2). The basis determines the fuel and oxidizer compositions: basis='mole' means mole fractions (default), basis='mass' means mass fractions:

>>> gas.set_equivalence_ratio(0.5, 'CH4', 'O2:1.0, N2:3.76', basis='mole')
>>> gas.mass_fraction_dict()
{'CH4': 0.02837633052851681, 'N2': 0.7452356312613029, 'O2': 0.22638803821018036}
>>> gas.set_equivalence_ratio(1.2, {'NH3':0.8, 'CO':0.2}, 'O2:1.0', basis='mole')
>>> gas.mass_fraction_dict()
{'CO': 0.14784006249290754, 'NH3': 0.35956645545401045, 'O2': 0.49259348205308207}

Parameters

phi – Equivalence ratio
fuel – Fuel species name or mole/mass fractions as string, array, or dict.
oxidizer – Oxidizer species name or mole/mass fractions as a string, array, or dict.
basis – Determines if fuel and oxidizer are given in mole fractions (basis='mole') or mass fractions (basis='mass')

set_mixture_fraction(self, mixture_fraction, fuel, oxidizer, basis='mole', mixFrac=None)¶

Set the composition to a mixture of fuel and oxidizer at the specified mixture fraction mixture_fraction (kg fuel / kg mixture), holding temperature and pressure constant. Considers the oxidation of C to CO2, H to H2O and S to SO2. Other elements are assumed not to participate in oxidation (that is, N ends up as N2). The basis determines the composition of fuel and oxidizer: basis='mole' (default) means mole fractions, basis='mass' means mass fractions:

>>> gas.set_mixture_fraction(0.5, 'CH4', 'O2:1.0, N2:3.76')
>>> gas.mass_fraction_dict()
{'CH4': 0.5, 'N2': 0.38350014242997776, 'O2': 0.11649985757002226}
>>> gas.set_mixture_fraction(0.5, {'NH3':0.8, 'CO':0.2}, 'O2:1.0')
>>> gas.mass_fraction_dict()
{'CO': 0.145682068778996, 'NH3': 0.354317931221004, 'O2': 0.5}

Parameters

mixture_fraction – Mixture fraction (kg fuel / kg mixture)
fuel – Fuel species name or mole/mass fractions as string, array, or dict.
oxidizer – Oxidizer species name or mole/mass fractions as a string, array, or dict.
basis – determines if fuel and oxidizer are given in mole fractions (basis='mole') or mass fractions (basis='mass')

set_unnormalized_mass_fractions(self, Y)¶: 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(self, X)¶: 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(self, k=None)¶: 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. Changes to this object do not affect the ThermoPhase or Solution object until the modify_species function is called.

species_index(self, species) → int ¶: 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(self, k)¶: 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.

state¶: Get/Set the full thermodynamic state as a single array, arranged as [temperature, density, mass fractions] for most phases. Useful mainly in cases where it is desired to store many states in a multidimensional array.

state_size¶: Return size of vector defining internal state of the phase.

stoich_air_fuel_ratio(self, fuel, oxidizer, basis='mole')¶

Get the stoichiometric air to fuel ratio (kg oxidizer / kg fuel). Considers the oxidation of C to CO2, H to H2O and S to SO2. Other elements are assumed not to participate in oxidation (that is, N ends up as N2). The basis determines the composition of fuel and oxidizer: basis='mole' (default) means mole fractions, basis='mass' means mass fractions:

>>> gas.set_mixture_fraction(0.5, 'CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
>>> gas.stoich_air_fuel_ratio('CH3:0.5, CH3OH:.5, N2:0.125', 'O2:0.21, N2:0.79, NO:0.01')
8.148040722239438

Parameters

fuel – Fuel species name or mole/mass fractions as string, array, or dict.
oxidizer – Oxidizer species name or mole/mass fractions as a string, array, or dict.
basis – Determines if fuel and oxidizer are given in mole fractions (basis='mole') or mass fractions (basis='mass')

thermal_expansion_coeff¶: Thermal expansion coefficient [1/K].

thermo_model¶: Return thermodynamic model describing phase.

u¶: Internal energy in [J/kg or J/kmol].

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

volume_mass¶: Specific volume [m^3/kg].

volume_mole¶: Molar volume [m^3/kmol].

InterfacePhase ¶

class cantera.InterfacePhase(infile='', phaseid='')¶

Bases: cantera._cantera.ThermoPhase

A class representing a surface or edge phase

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

set_unnormalized_coverages(self, cov)¶: Set the surface coverages without normalizing to force sum(cov) == 1.0. Useful primarily when calculating derivatives with respect to cov[k] by finite difference.

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

PureFluid ¶

class cantera.PureFluid(infile='', phaseid='')¶

Bases: cantera._cantera.ThermoPhase

A pure substance that can be a gas, a liquid, a mixed gas-liquid fluid, or a fluid beyond its critical point.

DPQ¶: Get the density [kg/m^3], pressure [Pa], and vapor fraction.

DPX¶: Get the density [kg/m^3], pressure [Pa], and vapor fraction.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to DPQ.

HPQ¶: Get the enthalpy [J/kg or J/kmol], pressure [Pa] and vapor fraction.

HPX¶: Get the enthalpy [J/kg or J/kmol], pressure [Pa] and vapor fraction.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to HPQ.

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

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.

Deprecated since version 2.5: To be deprecated with version 2.5, and removed thereafter. Renamed to PQ.

Q¶: Get/Set vapor fraction (quality). Can be set only when in the two-phase region.

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

SPQ¶: Get the entropy [J/kg/K or J/kmol/K], pressure [Pa], and vapor fraction.

SPX¶: Get the entropy [J/kg/K or J/kmol/K], pressure [Pa], and vapor fraction.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to SPQ.

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

SVQ¶: Get the entropy [J/kg/K or J/kmol/K], specific volume [m^3/kg or m^3/kmol], and vapor fraction.

SVX¶: Get the entropy [J/kg/K or J/kmol/K], specific volume [m^3/kg or m^3/kmol], and vapor fraction.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to SVQ.

TDQ¶: Get the temperature [K], density [kg/m^3 or kmol/m^3], and vapor fraction.

TDX¶: Get the temperature [K], density [kg/m^3 or kmol/m^3], and vapor fraction.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to TDQ.

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

TPQ¶

Get/Set the temperature [K], pressure [Pa], and vapor fraction of a PureFluid.

An Exception is raised if the thermodynamic state is not consistent.

TPX¶

Get/Set the temperature [K], pressure [Pa], and vapor fraction of a PureFluid.

An Exception is raised if the thermodynamic state is not consistent.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to TPQ.

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

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.

Deprecated since version 2.5: To be deprecated with version 2.5, and removed thereafter. Renamed to TQ.

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

UVQ¶: Get the internal energy [J/kg or J/kmol], specific volume [m^3/kg or m^3/kmol], and vapor fraction.

UVX¶: Get the internal energy [J/kg or J/kmol], specific volume [m^3/kg or m^3/kmol], and vapor fraction.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to UVQ.

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

X¶: Get/Set vapor fraction (quality). Can be set only when in the two-phase region.

Deprecated since version 2.5: Behavior changes after version 2.5, when X will refer to mole fraction. Renamed to Q.

Mixture ¶

class cantera.Mixture¶

Bases: object

Class Mixture represents mixtures of one or more phases of matter. To construct a mixture, supply a list of phases to the constructor, each paired with the number of moles for that phase:

>>> gas = cantera.Solution('gas.cti')
>>> gas.species_names
['H2', 'H', 'O2', 'O', 'OH']
>>> graphite = cantera.Solution('graphite.cti')
>>> graphite.species_names
['C(g)']
>>> mix = cantera.Mixture([(gas, 1.0), (graphite, 0.1)])
>>> mix.species_names
['H2', 'H', 'O2', 'O', 'OH', 'C(g)']

Note that the objects representing each phase compute only the intensive state of the phase – they do not store any information on the amount of this phase. Mixture objects, on the other hand, represent the full extensive state.

Mixture objects are ‘lightweight’ in the sense that they do not store parameters needed to compute thermodynamic or kinetic properties of the phases. These are contained in the (‘heavyweight’) phase objects. Multiple mixture objects may be constructed using the same set of phase objects. Each one stores its own state information locally, and synchronizes the phases objects whenever it requires phase properties.

P¶: Get or set the Pressure [Pa] of all phases in the mixture. When set, the temperature of the mixture is held fixed.

T¶: Get or set the Temperature [K] of all phases in the mixture. When set, the pressure of the mixture is held fixed.

charge¶: The total charge in Coulombs, summed over all phases.

chemical_potentials¶: The chemical potentials of all species [J/kmol].

element_index(self, element) → int ¶

Index of element with name ‘element’.

>>> mix.element_index('H')
2

element_moles(self, e)¶: Total number of moles of element e, summed over all species. The element may be referenced either by index number or by name.

equilibrate(self, XY, solver='auto', rtol=1e-9, max_steps=1000, max_iter=100, estimate_equil=0, log_level=0)¶

Set to a state of chemical equilibrium holding property pair XY constant. This method uses a version of the VCS algorithm to find the composition that minimizes the total Gibbs free energy of the mixture, subject to element conservation constraints. For a description of the theory, see Smith and Missen, “Chemical Reaction Equilibrium.”

Parameters

XY –
A two-letter string, which must be one of the set:
```
['TP', 'HP', 'SP']
```
solver – Set to either ‘auto’, ‘vcs’, or ‘gibbs’ to choose implementation of the solver to use. ‘vcs’ uses the solver implemented in the C++ class ‘VCSnonideal’, ‘gibbs’ uses the one implemented in class ‘MultiPhaseEquil’. ‘auto’ will try the ‘vcs’ solver first and then the ‘gibbs’ solver if that fails.
rtol – Error tolerance. Iteration will continue until (Delta mu)/RT is less than this value for each reaction. Note that this default is very conservative, and good equilibrium solutions may be obtained with larger error tolerances.
max_steps – Maximum number of steps to take while solving the equilibrium problem for specified T and P.
max_iter – Maximum number of temperature and/or pressure iterations. This is only relevant if a property pair other than (T,P) is specified.
estimate_equil – Flag indicating whether the solver should estimate its own initial condition. If 0, the initial mole fraction vector in the phase objects are used as the initial condition. If 1, the initial mole fraction vector is used if the element abundances are satisfied. if -1, the initial mole fraction vector is thrown out, and an estimate is formulated.
log_level – Determines the amount of output displayed during the solution process. 0 indicates no output, while larger numbers produce successively more verbose information.

max_temp¶: The maximum temperature for which all species in multi-species solutions have valid thermo data. Stoichiometric phases are not considered in determining max_temp.

min_temp¶: The minimum temperature for which all species in multi-species solutions have valid thermo data. Stoichiometric phases are not considered in determining min_temp.

n_atoms(self, k, m)¶

Number of atoms of element m in the species with global index k. The element may be referenced either by name or by index.

>>> n = mix.n_atoms(3, 'H')
4.0

n_elements¶: Total number of elements present in the mixture.

n_phases¶: Number of phases

n_species¶: Number of species.

phase(self, n)¶

phase_charge(self, p)¶: The charge of phase p in Coulombs.

phase_index(self, p)¶: Index of the phase named p.

phase_moles(self, p=None)¶: Moles in phase p, if p is specified, otherwise the number of moles in all phases.

phase_names¶: Names of all phases in the order added.

report(self, threshold=1e-14)¶

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

>>> mix()
>>> print(mix.report())

set_phase_moles(self, p, moles)¶: Set the number of moles of phase p to moles

species_index(self, phase, species)¶

Parameters

phase – Phase object, index or name
species – Species name or index

Returns the global index of species species in phase phase.

species_moles¶

Get or set the number of moles of each species. May be set either as a string or as an array. If an array is used, it must be dimensioned at least as large as the total number of species in the mixture. Note that the species may belong to any phase, and unspecified species are set to zero.

>>> mix.species_moles = 'C(s):1.0, CH4:2.0, O2:0.2'

species_name(self, k)¶: Name of the species with index k. Note that index numbers are assigned in order as phases are added.

species_names¶

Species ¶

class cantera.Species(name=None, composition=None, charge=None, size=None, init=True, *args, **kwargs)¶

Bases: object

A class which stores data about a single chemical species that may be needed to add it to a Solution or Interface object (and to the underlying ThermoPhase and Transport objects).

Parameters

name – A string giving the name of the species, e.g. 'CH4'
composition – The elemental composition of the species, given either as a dict or a composition string, e.g. {'C':1, 'H':4} or 'C:1, H:4'.
charge – The electrical charge, in units of the elementary charge. Default 0.0.
size – The effective size [m] of the species. Default 1.0.
init – Used internally when wrapping Species objects returned from C++

Example: creating an ideal gas phase with a single species:

ch4 = ct.Species('CH4', 'C:1, H:4')
ch4.thermo = ct.ConstantCp(300, 1000, 101325,
                           (300, -7.453347e7, 1.865912e5, 3.576053e4))
tran = ct.GasTransportData()
tran.set_customary_units('nonlinear', 3.75, 141.40, 0.0, 2.60, 13.00)
ch4.transport = tran
gas = ct.Solution(thermo='IdealGas', species=[ch4])

The static methods fromYaml, fromCti, fromXml, listFromFile, listFromYaml, listFromCti, and listFromXml can be used to create Species objects from existing definitions in the CTI or XML formats. Either of the following will produce a list of 53 Species objects containing the species defined in the GRI 3.0 mechanism:

S = ct.Species.listFromFile('gri30.yaml')

import pathlib
S = ct.Species.listFromYaml(
    pathlib.Path('path/to/gri30.yaml').read_text(),
    section='species')

charge¶: The electrical charge on the species, in units of the elementary charge.

composition¶: A dict containing the elemental composition of the species. Keys are element names; values are the corresponding atomicities.

static fromCti(text)¶: Create a Species object from its CTI string representation.

Deprecated since version 2.5: The CTI input format is deprecated and will be removed in Cantera 3.0.

static fromXml(text)¶: Create a Species object from its XML string representation.

Deprecated since version 2.5: The XML input format is deprecated and will be removed in Cantera 3.0.

static fromYaml(text)¶: Create a Species object from its YAML string representation.

static listFromCti(text)¶: Create a list of Species objects from all the species defined in a CTI string.

Deprecated since version 2.5: The CTI input format is deprecated and will be removed in Cantera 3.0.

static listFromFile(filename, section='species')¶

Create a list of Species objects from all of the species defined in a YAML, CTI or XML file. For YAML files, return species from the section section.

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

In the case of an XML file, the <species> nodes are assumed to be children of the <speciesData> node in a document with a <ctml> root node, as in the XML files produced by conversion from CTI files.

Deprecated since version 2.5: The CTI and XML input formats are deprecated and will be removed in Cantera 3.0.

static listFromXml(text)¶: Create a list of Species objects from all the species defined in an XML string. The <species> nodes are assumed to be children of the <speciesData> node in a document with a <ctml> root node, as in the XML files produced by conversion from CTI files.

Deprecated since version 2.5: The XML input format is deprecated and will be removed in Cantera 3.0.

static listFromYaml(text, section=None)¶: Create a list of Species objects from all the species defined in a YAML string. If text is a YAML mapping, the section name of the list to be read must be specified. If text is a YAML list, no section name should be supplied.

name¶: The name of the species.

size¶: The effective size [m] of the species.

thermo¶: Get/Set the species reference-state thermodynamic data, as an instance of class SpeciesThermo.

transport¶: Get/Set the species transport parameters, as an instance of class GasTransportData.

Species Thermodynamic Properties ¶

These classes are used to describe the reference-state thermodynamic properties of a pure species.

SpeciesThermo ¶

class cantera.SpeciesThermo(T_low, T_high, P_ref, coeffs)¶

Bases: object

Base class for representing the reference-state thermodynamic properties of a pure species. These properties are a function of temperature. Derived classes implement a parameterization of this temperature dependence. This is a wrapper for the C++ class SpeciesThermoInterpType.

Parameters

T_low – The minimum temperature [K] at which the parameterization is valid
T_high – The maximum temperature [K] at which the parameterization is valid
P_ref – The reference pressure [Pa] for the parameterization
coeffs – An array of coefficients for the parameterization. The length of this array and the meaning of each element depends on the specific parameterization.

coeffs¶: Array of coefficients for the parameterization. The length of this array and the meaning of each element depends on the specific parameterization.

cp(self, T)¶: Molar heat capacity at constant pressure [J/kmol/K] at temperature T.

h(self, T)¶: Molar enthalpy [J/kmol] at temperature T

max_temp¶: Maximum temperature [K] at which the parameterization is valid.

min_temp¶: Minimum temperature [K] at which the parameterization is valid.

n_coeffs¶: Number of parameters for the parameterization.

reference_pressure¶: Reference pressure [Pa] for the parameterization.

s(self, T)¶: Molar entropy [J/kmol/K] at temperature T

ConstantCp ¶

class cantera.ConstantCp(T_low, T_high, P_ref, coeffs)¶

Bases: cantera._cantera.SpeciesThermo

Thermodynamic properties for a species that has a constant specific heat capacity. This is a wrapper for the C++ class ConstCpPoly.

Parameters

coeffs –

An array of 4 elements:

coeffs[0] = \(T_0\) [K]

coeffs[1] = \(H^o(T_0, p_{ref})\) [J/kmol]

coeffs[2] = \(S^o(T_0, p_{ref})\) [J/kmol-K]

coeffs[3] = \(c_p^o(T_0, p_{ref})\) [J/kmol-K]

NasaPoly2 ¶

class cantera.NasaPoly2(T_low, T_high, P_ref, coeffs)¶

Bases: cantera._cantera.SpeciesThermo

Thermodynamic properties for a species which is parameterized using the 7-coefficient NASA polynomial form in two temperature ranges. This is a wrapper for the C++ class NasaPoly2.

Parameters

coeffs –

An array of 15 elements, in the following order:

coeffs[0]: The mid-point temperature [K] between the two parameterizations

coeffs[1:8]: The 7 coefficients of the high-temperature parameterization

coeffs[8:15]: The 7 coefficients of the low-temperature parameterization

This is the coefficient order used in the standard fixed-format NASA input files.

ShomatePoly2 ¶

class cantera.ShomatePoly2(T_low, T_high, P_ref, coeffs)¶

Bases: cantera._cantera.SpeciesThermo

Thermodynamic properties for a species which is parameterized using the Shomate equation in two temperature ranges. This is a wrapper for the C++ class ShomatePoly2.

Parameters

coeffs –

An array of 15 elements, in the following order:

coeffs[0]: The mid-point temperature [K] between the two parameterizations

coeffs[1:8]: The 7 coefficients of the low-temperature parameterization

coeffs[8:15]: The 7 coefficients of the high-temperature parameterization

These coefficients should be provided in their customary units (i.e. such that \(c_p^o\) is in J/gmol-K and \(H^o\) is in kJ/gmol, as in the NIST Chemistry WebBook).

Element ¶

class cantera.Element(self, arg)¶

Bases: object

An element or a named isotope defined in Cantera.

Class Element gets data for the elements and isotopes defined in Elements.cpp. This class can be used in two ways. The first way is to get information about all of the elements stored in Cantera. The three attributes num_elements_defined, element_symbols, and element_names can be accessed by:

>>> ct.Element.num_elements_defined
>>> ct.Element.element_symbols
>>> ct.Element.element_names

Otherwise, if the class Element is called with an argument, it stores the data about that particular element. For example:

>>> ar_sym = ct.Element('Ar')
>>> ar_name = ct.Element('argon')
>>> ar_num = ct.Element(18)

would all create instances with the information for argon. The available argument options to create an instance of the Element class with the element information are the name, symbol, and atomic_number. Once an instance of the class is made, the name, atomic_number, symbol, and atomic weight can be accessed as attributes of the instance of the Element class.

>>> ar_sym.name
'argon'
>>> ar_sym.weight
39.948
>>> ar_sym.atomic_number
18
>>> ar_sym.symbol
'Ar'

The elements available are listed below, in the element_symbols and element_names attribute documentation.

num_elements_defined = 118¶

element_symbols = ['H', 'He', 'Li', 'Be', 'B', 'C', 'N', 'O', 'F', 'Ne', 'Na', 'Mg', 'Al', 'Si', 'P', 'S', 'Cl', 'Ar', 'K', 'Ca', 'Sc', 'Ti', 'V', 'Cr', 'Mn', 'Fe', 'Co', 'Ni', 'Cu', 'Zn', 'Ga', 'Ge', 'As', 'Se', 'Br', 'Kr', 'Rb', 'Sr', 'Y', 'Zr', 'Nb', 'Mo', 'Tc', 'Ru', 'Rh', 'Pd', 'Ag', 'Cd', 'In', 'Sn', 'Sb', 'Te', 'I', 'Xe', 'Cs', 'Ba', 'La', 'Ce', 'Pr', 'Nd', 'Pm', 'Sm', 'Eu', 'Gd', 'Tb', 'Dy', 'Ho', 'Er', 'Tm', 'Yb', 'Lu', 'Hf', 'Ta', 'W', 'Re', 'Os', 'Ir', 'Pt', 'Au', 'Hg', 'Tl', 'Pb', 'Bi', 'Po', 'At', 'Rn', 'Fr', 'Ra', 'Ac', 'Th', 'Pa', 'U', 'Np', 'Pu', 'Am', 'Cm', 'Bk', 'Cf', 'Es', 'Fm', 'Md', 'No', 'Lr', 'Rf', 'Db', 'Sg', 'Bh', 'Hs', 'Mt', 'Ds', 'Rg', 'Cn', 'Nh', 'Gl', 'Mc', 'Lv', 'Ts', 'Og']¶

element_names = ['hydrogen', 'helium', 'lithium', 'beryllium', 'boron', 'carbon', 'nitrogen', 'oxygen', 'fluorine', 'neon', 'sodium', 'magnesium', 'aluminum', 'silicon', 'phosphorus', 'sulfur', 'chlorine', 'argon', 'potassium', 'calcium', 'scandium', 'titanium', 'vanadium', 'chromium', 'manganese', 'iron', 'cobalt', 'nickel', 'copper', 'zinc', 'gallium', 'germanium', 'arsenic', 'selenium', 'bromine', 'krypton', 'rubidium', 'strontium', 'yttrium', 'zirconium', 'nobelium', 'molybdenum', 'technetium', 'ruthenium', 'rhodium', 'palladium', 'silver', 'cadmium', 'indium', 'tin', 'antimony', 'tellurium', 'iodine', 'xenon', 'cesium', 'barium', 'lanthanum', 'cerium', 'praseodymium', 'neodymium', 'promethium', 'samarium', 'europium', 'gadolinium', 'terbium', 'dysprosium', 'holmium', 'erbium', 'thulium', 'ytterbium', 'lutetium', 'hafnium', 'tantalum', 'tungsten', 'rhenium', 'osmium', 'iridium', 'platinum', 'gold', 'mercury', 'thallium', 'lead', 'bismuth', 'polonium', 'astatine', 'radon', 'francium', 'radium', 'actinium', 'thorium', 'protactinium', 'uranium', 'neptunium', 'plutonium', 'americium', 'curium', 'berkelium', 'californium', 'einsteinium', 'fermium', 'mendelevium', 'nobelium', 'lawrencium', 'rutherfordium', 'dubnium', 'seaborgium', 'bohrium', 'hassium', 'meitnerium', 'darmstadtium', 'roentgenium', 'copernicium', 'nihonium', 'flerovium', 'moscovium', 'livermorium', 'tennessine', 'oganesson']¶

property atomic_number¶: The atomic number of the element or isotope.

property name¶: The name of the element or isotope.

property symbol¶: The symbol of the element or isotope.

property weight¶: The atomic weight of the element or isotope.

Thermodynamic Properties¶

Phases ¶

ThermoPhase ¶

InterfacePhase ¶

PureFluid ¶

Mixture ¶

Species ¶

Species Thermodynamic Properties ¶

SpeciesThermo ¶

ConstantCp ¶

NasaPoly2 ¶

ShomatePoly2 ¶

Element ¶

Table of Contents

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