Geometric combustion laws

Dear researcher,
Hello, may I ask if it is possible to simplify the chemical reaction process in chemical reactions? I have practiced the chemical reaction cases provided in the tutorial.
I currently want to write a chemical reaction that allows particle combustion to follow geometric combustion laws. How should I write a UDF?

Can you provide a little more detail about what you are trying to do? What are “geometric combustion laws”? (Searching for this term leads back to this posting!)