Steam cooled gas turbine

摘要

A steam-cooling gas turbine in which cooling steam is fed from a center portion of a rotating shaft and recovered through passages disposed at the outer side of the center portion with steam leaking through a seal portion from a feeding steam being effectively recovered. Feed steam (30) serving as coolant is supplied to a cavity (27) from a inner cylinder (10) and hence fed to moving blades (11, 12) through recesses (40) formed in a coupling portion (26) interposed between a final-stage disk (24) and a turbine shaft (1), steam feeding pipes (15) and steam feeding passages (11a, 12a). After cooling of the moving blades, steam (31) is recovered through steam recovering passages (11b, 12b), steam recovering pipes (16), radial steam-recovering passages (17), axial steam-recovering passages (18) and outlet openings (5a). In a portion of the turbine shaft (1) located adjacent to the coupling portion (26), temperature becomes higher when compared with the other portion. Thus, the coupling portion (26) is forced to hermetically close under thermal stress, whereby leakage of the feed steam (30) is prevented. Steam leaking through a seal portion constituted by stationary and rotatable seal fin assemblies (4a, 4b) can be effectively recovered. The inner cylinder (10) can move in the axial direction through cooperation of piston rings (43) and a centering piece (6) adapted for absorbing thermal stress induced in the inner cylinder (10). Upstream tip end portions of steam feeding pipes (15) and steam recovering pipes (16) are secured onto a side surface of the first-stage disk (21) through sleeves removably fitted thereto.