An analysis has been made to permit a comparative evaluation of the turbine rotor cooling-air requirements with convection-cooled, blades for the following four combustor-outlet radial gas-temperature profiles along the blade span: (l) a uniform profile, (2) a profile representable by a complete cycle of the cosine wave using the cooler gas layers 'near the turbine casing and stator inner ring and a hot gas core, (3) a profile representable by one-half cycle of the cosine wave using the cooler gas layers near the stator inner ring and the hotter gas layers near the tur¬bine casing, and (4) an optimum profile resulting in the absolute minimum cooling-air requirements. In each case, the cooling-air-flow requirements are compared with profile (l), which has been used in turbine-cooling analyses. This uniform profile can be obtained only at the expense of combustor pressure drop or length or both. Profiles (2) and (3) are ob¬tainable from present combustor designs that have good performance. These profiles have the advantage of either eliminating or decreasing the turbine casing and stator-ring cooling problems at elevated temperatures, profile (2) being better in this respect.
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