Gas turbine combined cycle system

Gas turbine combined cycle system is improved to enhance gas turbine efficiency and combined efficiency by effecting steam-cooling of combustor tail tube and turbine blades. In the combined cycle system comprising; gas turbine (8) having generator (1), compressor (2), combustor (3), blade cooling air cooler (4), fan (5) and turbine (6); steam turbine (29) having high pressure turbine (21), intermediate pressure turbine (22) and low pressure turbine (23); and waste heat recovery boiler (9), saturated water of intermediate pressure economizer (12) is partially led into fuel heater (30) for heating fuel and the water cooled thereby is supplied to feed water heater (10). Steam of intermediate pressure superheater (16) is led into the combustor tail tube for cooling thereof and the steam is then supplied to inlet of the intermediate pressure turbine (22). Steam of outlet of the high pressure turbine (21) is led into the turbine (6) for cooling blades thereof and the steam used for cooling stationary blades is supplied to the inlet of the intermediate pressure turbine (22) and the steam used for cooling moving blades is supplied to reheater (20). Thus, the efficiency is enhanced.