Converting Data from NASA ThermoBuild

Thermodynamic data for a range of species can be obtained from the NASA ThermoBuild tool. This thermodynamic data is described using the 9-coefficient NASA polynomial parameterization, which is implemented by Cantera.

To generate an input file containing thermodynamic data, use the ThermoBuild web interface to select the elements you want to include, and click process. Then, select the species you want to include in your mechanism and click continue. Select the content on the resulting page starting with the line that says thermo, and ending with the line that says END REACTANTS and save it to a file.

Next, we need to make a few modifications to this file so it contains all of the information needed to be processed by Cantera’s CK file parser. For this example, let’s suppose you have selected just the species CO and CO2 from ThermoBuild.

• Modify the first line of the file so that it reads thermo nasa9. This is done to distinguish this input format from the one used for the 7-coefficient NASA polynomials.

• Replace the last two lines (END PRODUCTS and END REACTANTS) with a single line that reads END.

Creating species definitions only

If you only want to generate a species database that can be referenced from other Cantera input files, the above modifications are sufficient. The last step is simply to convert the input file to the Cantera YAML format using ck2yaml. If you named the file mythermo.txt, then the command to convert it would be:

ck2yaml --thermo=mythermo.txt

This will generate the file mythermo.yaml. You can then reference the species definitions from this file in phase definitions in other Cantera input files, for example:

phases:
- name: gas
  thermo: ideal-gas
  species:
  - {mythermo.yaml/species: all}

Creating a complete phase definition

To create a complete phase definition, you also need to add two sections to the top of the ThermoBuild input file. First, a section declaring all of the elements:

elements
C O
end

And second, a section declaring all of the species:

species
CO CO2
end

The resulting input file should look like the following:

elements
C O
end

species
CO CO2
end

thermo nasa9
   200.000  1000.000  6000.000 20000.000   9/09/04
CO                Gurvich,1979 pt1 p25 pt2 p29.
 3 tpis79 C   1.00O   1.00    0.00    0.00    0.00 0   28.0101000    -110535.196
    200.000   1000.0007 -2.0 -1.0  0.0  1.0  2.0  3.0  4.0  0.0         8671.104
 1.489045326D+04-2.922285939D+02 5.724527170D+00-8.176235030D-03 1.456903469D-05
-1.087746302D-08 3.027941827D-12                -1.303131878D+04-7.859241350D+00
   1000.000   6000.0007 -2.0 -1.0  0.0  1.0  2.0  3.0  4.0  0.0         8671.104
 4.619197250D+05-1.944704863D+03 5.916714180D+00-5.664282830D-04 1.398814540D-07
-1.787680361D-11 9.620935570D-16                -2.466261084D+03-1.387413108D+01
   6000.000  20000.0007 -2.0 -1.0  0.0  1.0  2.0  3.0  4.0  0.0         8671.104
 8.868662960D+08-7.500377840D+05 2.495474979D+02-3.956351100D-02 3.297772080D-06
-1.318409933D-10 1.998937948D-15                 5.701421130D+06-2.060704786D+03
CO2               Gurvich,1991 pt1 p27 pt2 p24.
 3 g 9/99 C   1.00O   2.00    0.00    0.00    0.00 0   44.0095000    -393510.000
    200.000   1000.0007 -2.0 -1.0  0.0  1.0  2.0  3.0  4.0  0.0         9365.469
 4.943650540D+04-6.264116010D+02 5.301725240D+00 2.503813816D-03-2.127308728D-07
-7.689988780D-10 2.849677801D-13                -4.528198460D+04-7.048279440D+00
   1000.000   6000.0007 -2.0 -1.0  0.0  1.0  2.0  3.0  4.0  0.0         9365.469
 1.176962419D+05-1.788791477D+03 8.291523190D+00-9.223156780D-05 4.863676880D-09
-1.891053312D-12 6.330036590D-16                -3.908350590D+04-2.652669281D+01
   6000.000  20000.0007 -2.0 -1.0  0.0  1.0  2.0  3.0  4.0  0.0         9365.469
-1.544423287D+09 1.016847056D+06-2.561405230D+02 3.369401080D-02-2.181184337D-06
 6.991420840D-11-8.842351500D-16                -8.043214510D+06 2.254177493D+03
END

This file (saved for example as myphase.txt) can then be converted to the Cantera YAML format using the ck2yaml utility from a shell:

ck2yaml --input=myphase.txt

This will generate a an input file named myphase.yaml with a phase named gas that can be directly imported in Cantera.