OUTLET TUBE COUPLING OF NOZZLE FOR CLOSED CIRCUIT VAPOR COOLING GAS TURBINE AND METHOD FOR MANUFACTURING THE SAME

PROBLEM TO BE SOLVED: To provide an outlet tube coupling provided on an outer band of a nozzle segment for a gas turbine using a closed circuit cooling system and a method for manufacturing the same. SOLUTION: A nozzle segment 10 of a gas turbine includes an inner band portion 12, an outer band portion 14, and stationary blades 16 elongated between the band portions 12, 14. Each of the inner and outer band portions 12, 14 is divided into a first plenum 24 and a second plenum 26 separated by an impingement plate 22. Cooling vapor is supplied to a first cavity to flow through an aperture 30 and to cool a wall of an outer nozzle. The vapor flows into the first cavity of the inner band portion passing through a front edge cavity of the stationary blade, and flows through the aperture of the impingement plate 22 to cool a wall of an inner nozzle. The used cooling vapor flows through a plurality of stationary blades, and is discharged outward through the outlet tube 38 of the outer band. The outlet tube 38 is directly fixed at its inside end to a wall of the stationary blade of the nozzle surrounding an outlet cavity, and is fixed at the position between the ends of the outlet tube 38 to the edge of the impingement plate 22 and the edge of the aperture 30. Therefore, access to each coupling from the outside becomes possible during the forming of the coupling and the following inspection step.