Get/Set Equivalence Ratio/Mixture Fraction Functions for C++

[g3bk47]

Abstract

I implemented the set_equivalence_ratio functionality from python in the C++ interface. In addition to the original python function, the new functions support the composition of fuel and oxidizer being passed as mole and mass fractions. Also, the get_equivalence_ratio function in the current implementation seems to be wrong. A fixed version is provided together with functions to determine the mixture fraction. A fork with some proof of concept code can be found here:
g3bk47/cantera@d00b40f
The implementation itself is quite trivial, but there are some open questions about the naming schemes, calling C++ from python and other minor points.

Motivation

Describe the need for the work being done:

• What problem is it trying to solve?
  Bring the functionality from python to C++, add the mixture fraction concept and fix the get_equivalence_ratio function
• Who is affected by the change?
  No breaking changes, only additions

Description

For a detailed description, see the threads in the user group:
https://groups.google.com/forum/embed/#!topic/cantera-users/owoAebI6rr8
https://groups.google.com/forum/embed/#!topic/cantera-users/gs-wHjo18Do

References

g3bk47/cantera@d00b40f
https://groups.google.com/forum/embed/#!topic/cantera-users/owoAebI6rr8
https://groups.google.com/forum/embed/#!topic/cantera-users/gs-wHjo18Do

[ischoegl]

@g3bk47 ... looking at your fork, the work is mostly done. The remaining things are to link everything back into the cython interface, and to convert your proof_of_work.py to unit tests. For the former, you need to add your new C++ methods to _cantera.pxd so you can use them from thermo.pyx. Once the cython calls work, the latter is straightforward. One relatively short and recent example for how a cython function is moved to C++ is in Cantera/cantera@7a87819.

As the next Cantera release (2.5) is relatively close, it may make sense to create a pull request. I can give some pointers, although I’m not among those who make decisions about adoption.

[g3bk47]

@ischoegl Thanks for offering your help. I will prepare a pull request until Tuesday so that it can hopefully be included in the 2.5 release.

[g3bk47]

Changes have been merged (Cantera/cantera#851)