Adding user-defined heat of formation/heat release to a given species/element

[Partth]

Hi All,

I am trying to perform validation on some one-step mechanism. The idea is to define a gaseous species for air (whose properties are given in the NASA7 mod polynomial data, see: https://shepherd.caltech.edu/EDL/PublicResources/sdt/SDToolbox/cti/NASA7/nasa7mod.dat) but with a user-defined heat release (in this case, it would be the heat of formation/R or the last value in the air entry: 1.50965000E+01). By changing this, different heating can be applied to the 1-step mech.

I have added my user species gas_A to represent this "air" as a separate species with the  curve fit for the thermo properties. I have modified the nasa_gas.dat here and added the following modification:

 ...

units: {length: cm, time: s, quantity: mol, activation-energy: cal/mol}
elements:
- symbol: GA
  atomic-weight: 24.50
species:
- name: gas_A
  composition: {GA: 1}
  thermo:
    model: NASA7
    temperature-ranges: [200.0, 1000.0, 6000.0]
    data:
    - [3.56839620,-6.78729429e-04, 1.55371476e-06,-3.29937060e-12, -4.66395387e-13,
      -1.06234659e+03, 3.71582965E+00]
    - [3.08792717, 1.24597184e-03, -4.23718945e-07, 6.74774789e-11, -3.97076972E-15,
      -9.95262755e+02, 5.95960930]

Here, the species gas_A comprises the reactant for the reactant-to-product 1-step system and assumes the curve-fit properties of air. The product gas_B would be set up identically.

1. Did I define the new elements and species correctly and in the correct location?
   
2.  Given gas_A, and gas_B are identical, the difference would be the chemical heat release which I am looking to specify. From what I understand, Cantera evaluates the heat release directly so how can I facilitate this?

Thanks,

-Partth

[Partth]

For reference see the paper link (https://doi.org/10.1063/5.0122240) for a different mixture (ethylene-oxygen mixture, Table 1); I would like to reproduce the kinetics of something similar to Oran's 1-step modeling shown herein in Cantera using the idealGas reactor. I use the Python version for reference. The chemical heat release is what I am trying to make a user-defined parameter:

The paper is too long to attach here.

-Partth

[Ray Speth]

Hi Partth,

I think you’re on the right track with modifying the NASA polynomials. If you look the definition of the equations, The coefficients that you want to adjust are the “a5” coefficients for both the low and high temperature polynomials of the “products” species. These are the second to last values in each row of the data section of the YAML input. All of Cantera’s calculations of heat release, explicit or implicit, proceed from these thermodynamic properties.

Your definition of the custom element looks right to me.

Regards,
Ray

​

[Partth]

I see, thanks for confirming these details. I think I also found a different way to accomplish something similar in a different way so I will try to compare these means as they should be identical. For the NASA9 parametrization, the coefficients to modify would be "a7", correct? In any case, I think I have a way to move forward.

Thanks for your help.

-Partth