The reheat-gas-turbine maximum-reheat turbine-inlet temperature (RHTIT) is presently limited to about 2200°F (1204°C) due to an arbitrary exhaust temperature ceiling set at 1300°F (704°C). Last-stage power-turbine blading, support struts, casings and exhaust-hood construction and materials has imposed this restraint. This paper outlines a way to steam-cool these large parts. It presents an analysis of the combined cycle where the efficiency improvement is 2.4 percent and the output gain is 9.9 percent with a 200°F (111°C) higher RHTIT and a corresponding extended exhaust temperature and where the overall combined cycle efficiency approaches 60 percent (LHV).

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