Gas Turbine

Abstract

A gas turbine is provided that can suppress an increase in the supplied amount of cooling air in clearance adjustment through casing cooling. The gas turbine 101 includes a turbine casing 19 enclosing a turbine shaft 105 , the turbine casing 19 including a cooling air header 21 and a cooling passage 24 ; and an exhaust diffuser 113 connected to the exhaust side of the casing 19 , the exhaust diffuser 113 including an exhaust diffuser cooling passage 26 . A plate 22 formed with a plurality of impingement cooling holes 28 is installed inside the cooling air header, and a route is formed which allows cooling air introduced from the impingement cooling holes to flow from the casing cooling passage to the diffuser cooling passage.

What is claimed is: 
     
         1 . A gas turbine comprising:
 a casing enclosing a turbine shaft, the casing including a cooling air header and a casing cooling passage; and   an exhaust diffuser connected to an exhaust side of the casing, the exhaust diffuser including an exhaust diffuser cooling passage;   wherein a plate formed with a plurality of impingement cooling holes is installed inside the cooling air header, and a route is formed which allows cooling air introduced from the impingement cooling holes to flow from the casing cooling passage to the diffuser cooling passage.   
     
     
         2 . The gas turbine according to  claim 1 ,
 wherein the plate is disposed to impingement-cool a casing located at a position corresponding to a front-stage side of turbine stages composed of a plurality of stages.   
     
     
         3 . The gas turbine according to  claim 1 ,
 wherein the casing has a cover isolating the cooling air header from outside space.   
     
     
         4 . The gas turbine according to  claim 3 ,
 wherein the plate is attached inside the cover and the cover is configured to be attachable to and detachable from the casing integrally with the plate.   
     
     
         5 . The gas turbine according to  claim 1   wherein the casing includes an upper-half casing and a lower-half casing separated from each other, the upper-half casing and the lower-half casing being joined to each other via respective flanges thereof,   a plurality of the plates are installed along a circumferential direction of the casing,   a plurality of systems are provided which each supply cooling air to each of spaces defined by the plates, and   a flow rate control device for regulating a flow rate of cooling air is mounted in the system connected to a space defined by a plate located on the flange side among the plurality of plates.   
     
     
         6 . The gas turbine according to  claim 1   wherein the casing includes an upper-half casing and a lower-half casing separated from each other, the upper-half casing and the lower-half casing being joined to each other via respective flanges thereof,   a plurality of the plates are installed along a circumferential direction of the casing,   a plurality of systems are provided which each supply cooling air to each of spaces defined by the plates,   an orifice is attached to each of the systems, and   respective diameters of the orifices are set based on, at circumferential positions of the gas turbine, a clearance value between a rotating body and a stationary body in a stationary state of the gas turbine, and a relationship between the size of a diameter of the orifice and an amount of deformation of the casing.