I get a message error: "there is no oxygen in the reagents" when I ask it to calculate, whereas my combustion model does have an inlet port and a perfect air intake port exiting the compressor.

Answer: For THERMOPTIM to be able to calculate a combustion, the oxidant or the fuel must contain oxygen. The substance "perfect air" is a very special pure gas, which was included only to enable users to perform calculations on perfect gases. It does not contain any oxygen. You have to chose the protected compound gas "air" or "atmospheric air", or create a moist air compound gas if you want to take into account the humidity of the air. Another common error when modeling combustion is to chose a vapor instead of the corresponding ideal gas as a fuel, for example the vapor "methane" instead of the pure ideal gas "CH4-methane". THERMOPTIM calculates the combustion by decoding the chemical formula of the different components of the ideal gases representing the oxidant and the fuel.