State-of-the-art gas turbine engines usually work under extremely high temperatures. This is directly related to efficiency of the gas turbines – in order to receive the maximum thermodynamics value, it is necessary to increase the gas temperature after the combustion chamber. Engine temperature can be higher than blades’ metal temp up to 500-600 K. Blades, nozzles, and the GT details are manufactured with special heat-resistant steels and in some cases, they require a special coating. That allows them to resist turning into liquid metal under these working temperatures like the T-1000 did in the “Terminator 2: Judgment Day” movie even under high temperatures :).
However, metal has the property of “creep” – this is the tendency of hard metal to move slowly or permanently deform under stress. This occurs as a result of prolonged exposure to high stresses above the yield point, especially when exposed to high temperatures. Obviously, the solution to this problem is a cooling system for heat-stressed parts, which has allowed the gas temperature to increase by 600 K compared with uncooled machines. Since the gas turbines usually work with air, the simplest way to cool the system is by using this. Typically, the air exhausts to different parts of the compressors and is supplied to the cooling paths and blades which influence the thermodynamics efficiency of the gas turbine engine. Thus, it is crucial to ensure enough cooling to remove the heat on the one hand and on the other hand – to receive the lowest amount of air which requires cooling. Read More