Hey guys (and girls?) I'm new here, just registered, because I have a problem that my textbooks or google can't help me with: I am making "Brayton cycle diagrams" for a study in jet engine efficiency. It's basically a Temperature - Entropy diagram for those of you who are unfamiliar with it. I know how to calculate the temperature increase with a pressure increase (basic isentropic relationships), and the entropy increase with fuel addition (delta S = q * LN( delta T)). The problem I'm having is calculating lines of constant pressure in this diagram. Every source talks about them, but no source tells me how to calculate them. I know they are supposed to be increasing curves (the temperature difference for a pressure ratio is higher at higher entropy). Does anyone have a clue to calculate these isobars? Any help is greatly appreciated!