Which Heat Release in Cantera?

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pierrealexa...@gmail.com

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Sep 9, 2021, 6:55:14 AM9/9/21

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Dear all,

I am currently comparing the Heat Release obtained by a 3D DNS code and 1D equivalent free-flames with Cantera. When taking a careful look at the equations we find that there is a difference between the so-called Heat Release per unit volume for the equation written with total energy (classically what is done with DNS) and the equation is written in terms of gas temperature (what is done with Cantera). This is well explained in the book of Thierry Poinsot and Denis Veynante (Theoretical and Numerical Combustion), where one finds:

Capture d’écran 2021-09-09 à 12.50.32.png

In the documentation of Cantera, we find same the definition for \dot{\omega}_T though by looking at the code and the following page : https://cantera.org/tutorials/python-tutorial.html I find no difference by computing the HR with the h_k and the \Delta h_f,k^0. Also in the code the HR for FreeFlames seems computed with the reference formation enthalpies, not comprising the sensible enthalpy. Is this normal? Am I missing something?

Sincerely,

- PAM

Ray Speth

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Sep 16, 2021, 9:15:28 PM9/16/21

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Hi,

The heat release in Cantera’s 1D flames corresponds to what you call $\dot{\omega}_T^\prime$ . Cantera’s nomenclature regarding “reference states” and “standard states” is a bit confusing. but if you’ve looked at StFlow.cpp, you’ll see that it uses the method enthalpy_RT_ref which gives the enthalpies at the current temperature and at the reference pressure. But since for an ideal gas there is no pressure dependence for the enthalpy, this is the enthalpy $h_k$ at the current temperature and pressure. There is no function in Cantera that calculates the standard enthalpies of formation, besides simply setting the mixture to that state.