Gas turbine engines are one of the most efficient means of producing energy. Gas turbine power, efficiency, and economics generally increase when the temperature of gas flowing through the turbine increases. A limiting factor of most gas turbine engines is the turbine inlet temperature, however, because the blade metal temperature generally must be kept below 1400° F. to avoid hot corrosion problems.
Advances in air cooling and blade metallurgy have permitted the inlet temperatures of gas turbines to increase considerably. Specifically, by providing a means to remove heat from the blades, the turbine can be operated with a combustion gas temperature higher than the metallurgical limit of the blade material. Air cooling technology bleeds cooling air from the compressor and directs the cooling air to the stator, rotor, and other parts of the rotor and casing.
Current cooling technology relies on stator passages to convey cooling air from the outer surfaces of the casing to the engine centerline regions. Heat pickup in these configurations is significant, resulting in a pronounced reduction in both cycle efficiency and power output.
Thus, there exists a need to reduce the heat pickup in the stator passages such that the cooling air maintains a low temperature, desirably close to its inlet temperature. Such improvements will minimize the amount of cooling air required at the lowest temperature to maximize cycle efficiency and power output.