Gas turbine fuel/air ratio & cooling, help please! Hello Dear Colleagues, I am doing a gas turbine project and I wonder why we use cooling air instead of decreasing the fuel/air ratio after getting the following results from my gas turbine thermodynamic model. I have a mechanism in my model which adjust the fuel/air ratio for different pressure ratios and ambient conditions to reach the desired TIT (turbine inlet temp.) of 1755 K. For selected pressure ratio of 20, I get the following results from the combustion of methane : Using %80 of the compressor air for cooling and the rest for combustion, I can only reach a maximum TIT of 1360 K at the equivalence ratio 1.019 for stoichiometric combustion of methane. In this case the fuel/air ratio is 0.0584. Using %50 of the compressor air for cooling and the rest for combustion, I can reach my desired TIT of 1755 K at the equivalence ratio 0.835. In this case the fuel/air ratio is 0.0488, a high value for gas turbines which usually have a fuel/air ratio around 0.02. When I don't use ant cooling air, I can reach my desired TIT at the equivalence ratio 0.458 and fuel/air ratio of 0.0267. From these results I come to a conclusion that there is no need for cooling air. If there is a need for that I please ask how I can define the minimum value needed. I can provide any information needed. Please give me a hand, I am really stuck on this. Thank you in advance. Kayhan.