Set up a PyChemkin project#

This example shows how to set up a PyChemkin project and start to use PyChemkin features. You begin by importing the PyChemkin package, which is named ansys.chemkin.core, and optionally the PyChemkin logger package, which is named ansys.chemkin.core.logger.

Next, you use the Chemistry() method to instantiate and preprocess a chemistry set. This requires specifying the file names (with full file paths) of the mechanism file, thermodynamic data file, and optional transport data file.

Once the chemistry set instance is instantiated, you use the preprocess() method to preprocess the mechanism data. You can then start to use PyChemkin features to build your simulation.

Note

Running PyChemkin requires Ansys 2025 R2 or later.

Import PyChemkin packages#

Import the ansys.chemkin.core package to start using PyChemkin in the project. Importing the ansys.chemkin.core.logger package is optional.

from pathlib import Path

import ansys.chemkin.core  # import PyChemkin
from ansys.chemkin.core.logger import logger

Set up the file paths of the mechanism and data files#

The ansys_dir variable on your local computer specifies the location of your Ansys installation.

Use os.path methods to construct the file names with the full paths.

Assign the files to the corresponding chemistry set arguments:

mech_file: Mechanism input file
therm_file: Thermodynamic data file
tran_file: Transport data file (optional)

# create GRI 3.0 mechanism from the data directory
mechanism_dir = Path(ansys.chemkin.core.ansys_dir) / "reaction" / "data"
# set up mechanism file names
mech_file = str(mechanism_dir / "grimech30_chem.inp")
therm_file = str(mechanism_dir / "grimech30_thermo.dat")
tran_file = str(mechanism_dir / "grimech30_transport.dat")

Instantiate the chemistry set#

Use the Chemistry() method to instantiate a chemistry set named GasMech.

GasMech = ansys.chemkin.core.Chemistry(
    chem=mech_file, therm=therm_file, tran=tran_file, label="GRI 3.0"
)

Preprocess the chemistry set#

Preprocess the GRI 3.0 chemistry set.

status = GasMech.preprocess()

Check the preprocessing status#

if status != 0:
    # failed
    print(f"Preprocessing: Error encountered. Code = {status:d}.")
    print(f"See the summary file {GasMech.summaryfile} for details.")
    logger.error("Preprocessing failed.")
    exit()

Start to use PyChemkin features#

Start to use PyChemkin features to build your simulation. For example, using the Mixture() method, create an air mixture based on the GasMech chemistry set.

# create 'air' mixture based on 'GasMech' chemistry set
air = ansys.chemkin.core.Mixture(GasMech)
# set 'air' condition
# mixture pressure in [dynes/cm2]
air.pressure = 1.0 * ansys.chemkin.core.P_ATM
# mixture temperature in [K]
air.temperature = 300.0
# mixture composition in mole fractions
air.x = [("O2", 0.21), ("N2", 0.79)]

Print the properties of the air mixture for verification#

Note

The default units of temperature and pressure are [K] and [dynes/cm²], respectively.
The constant P_ATM is a conversion multiplier for pressure.
Transport property methods such as mixture_viscosity() require transport data. You must include the transport data file when creating the chemistry set.

# print pressure and temperature of the `air` mixture
print(f"Pressure    = {air.pressure / ansys.chemkin.core.P_ATM} [atm]")
print(f"Temperature = {air.temperature} [K]")
# print the 'air' composition in mass fractions
air.list_composition(mode="mass")
# get 'air' mixture density [g/cm3]
print(f"Mixture density   = {air.rho} [g/cm3]")
# get 'air' mixture viscosity [g/cm-sec] or [poise]
print(f"Mixture viscosity = {air.mixture_viscosity() * 100.0} [cP]")

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