Turbine inner shell heating and cooling flow circuit

The method is used to operate a turbine with a rotor with axially spaced buckets forming parts of turbine stages. There are outer and inner containment shells about the rotor. The method involves forming partially circumferentially extending first portions (46,58) of a passage in the sections of the inner shell at each axial location of the buckets of the respective stages. A passageway (56) is provided in the inner shell connecting the first passage portions to one another. A thermal medium is flowed through a first passage portion (46) of one section, through the first passageway (56) and through a first passage portion of another section. Circumferentially extending second portions (60,48) of the passage are formed in the sections of the inner shell at each axial location of the buckets of the respective stages. A second passageway (68) is provided in the inner shell connecting the second passage portions to one another. Finally the method controls the thermal ra dial expansion and contraction of the inner shell and the clearance between tips of the buckets and shrouds of each stage. A method of operating a gas turbine having inner and outer shells (36,34) is described , with the inner shell being radially movable relative to rotor bucket tip passage in the inner shell for flowing a thermal medium. A pair of passage portions (46,48,58,60) are formed in each of the aft and forward inner shell sections with axially communicating passageways (56,68) between the passage portions (46,48,58,60). A thermal medium, preferably from an off-turbine site, is provided for flow through the second-stage aft inner shell section, along axial passageways (56) along the mid-line of the inner shell to a first passage portion (58) of the forward inner shell section. Cross-over paths (62,64) flow the thermal medium from the first passage portions (58) to second circumferentially extending passage portions (60) of the forward inner shell section, in turn, in communication with axial passageways (68), extending from the forward section to the aft section. A second pair of passage portions (48) flow the thermal medium to an outlet (54) in the aft section. By controlling the temperature of the thermal medium for flow through the aft and forward sections of the inner shell, the clearance between the shrouds and the tips of the buckets for at least the first and second stages of the turbine is controllably adjusted.