I am not entirely sure if this is better suited to Chemistry.SE or Matter modelling, but hey, you guys are nicer.
I am fascinated by just how complicated combustion processes are.
I was watching an old SpaceX video on how they model the combustion processes in their Raptor engines. (Here is a really relevant video with timestamp, which I recommend people watch in full.)
They give the example of hydrogen burning with oxygen, which requires 23 separate chemical equations to model, and that is with the reduced mechanism.
(Incidentally, I would like to know what column 'b' refers to in the table above.)
The situation with methane combustion is even worse. 53 species and 325 reactions are involved.
If one were to attempt to model simplified versions of these processes, how would they go about it?
Is there an a-priori way of telling which individual reactions contribute little to the overall combustion, just by the identity of the species involved and the other entries in the table? Intuitively, one expects the interactions of two different rare high-energy intermediates to not contribute greatly to the overall combustion, but what if it does?
While highly nonlinear, I don't believe these equations are chaotic, at least in a situation with perfect mixing. Even so, I suspect changes in the proportion of trace intermediates could very easily have large effects on subsequent reactions.
Does it come down to running the full simulation, then successively removing reactions until the accuracy drops below an acceptable threshold? Or are there tricks one can use to simplify these equations?