Structure for gas turbine casing

A structure for a gas turbine casing, capable of preventing gas from leaking when the structure is subjected to pressure. A structure for a gas turbine casing, divided by a horizontal plane at flange sections into two halves comprising an upper-half casing (10) and a lower-half casing (11). The structure is provided with bolts (12) which are disposed in the inner surfaces of the upper-half casing (10) and the lower-half casing (11) so as to bridge therebetween, upper nuts (13) which are disposed in the inner surface of the upper-half casing (10) and attached to the bolts (12), and lower nuts (14) which are disposed in the inner surface of the lower-half casing (11) and attached to the bolts (12).

TECHNICAL FIELD

This invention relates to a gas turbine casing structure.

BACKGROUND ART

A gas turbine casing of a gas turbine accommodating interiorly components, such as a rotor and a nozzle diaphragm, is composed of a structure, which is divided into two halves by a horizontal plane and fastened by bolts in flange structures, in order to facilitate the installation and inspection of these components, and to prevent gas leakage during operation (see, for example, Patent Document 1 to be described below).

FIG. 4is a schematic view showing a conventional gas turbine casing structure. InFIG. 4, its cross section in the axial direction of a bolt is illustrated.

As shown inFIG. 4, the gas turbine casing structure is divided into two halves, namely, an upper-half casing100and a lower-half casing101. The upper-half casing100and the lower-half casing101are composed of shell sections100a,101aand flange sections100b,101b, respectively. The bonding between the upper-half casing100and the lower-half casing101is performed by fastening each bolt102, each upper nut103and each lower nut104together.

That is, each flange of the gas turbine casing is divided into equal halves, i.e., the flange section100bof the upper-half casing100and the flange section101bof the lower-half casing101. The flange sections100b,101bare provided with many bolt holes100c,101c. The bolt102is disposed in each of the bolt holes100c,101c, and fastened with the upper nut103and the lower nut104.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In recent years, gas turbines have become so great in capacity and output that their upsizing and high pressure run have been performed. In accordance with these trends, there have been gas leakage during operation, and increases in the pressure acting on the gas turbine casing during operation. With the conventional gas turbine casing structure shown inFIG. 4, moment has increased during application of a pressure as indicated by arrows P inFIG. 4. As indicated by short dashed lines inFIG. 4, therefore, the amounts of opening between the flange section100bof the upper-half casing100and the flange section101bof the lower-half casing101have increased. As a result, there has been a possibility for a gas to leak through the bolt holes100c,101c, as shown by arrows G inFIG. 4.

FIG. 5is a schematic view showing the conventional gas turbine casing structure with the flange sections heightened. InFIG. 5, a cross section of the structure in the axial direction of the bolt is illustrated.

As shown inFIG. 5, the flange section100bof the upper-half casing100and the flange section101bof the lower-half casing101are increased in height, and the upper-half casing100and the lower-half casing101are fastened together by the bolts102, the upper nuts103and the lower nuts104at the middle of the wall thickness of the shell sections100a,101a, in order to prevent gas leakage. This procedure is more advantageous, because it can diminish the moment during application of pressure as indicated by the arrows P inFIG. 5.

When the heights of the flange section100bof the upper-half casing100and the flange section101bof the lower-half casing101are increased, however, the heat capacity of the flange sections100b,101bgrows. During a process in which the temperature at start rises, the difference in temperature between the flange sections100b,101band the shell sections100a,101aincreases. Consequently, thermal stress occurs at the boundaries between the flange sections100b,101band the shell sections101a,102aindicated by arrows S inFIG. 5. In this case, decline in strength due to fatigue is feared.

It is an object of the present invention, therefore, to provide a gas turbine casing structure which can prevent gas leakage when pressure is exerted on the structure.

Means for Solving the Problems

A gas turbine casing structure according to a first aspect of the present invention for solving the above-mentioned problems is a gas turbine casing structure divided by a horizontal plane at flange sections into two halves composed of an upper-half casing and a lower-half casing, the gas turbine casing structure including

bolts which are disposed in inner surfaces of the upper-half casing and the lower-half casing so as to bridge therebetween,

upper nuts which are disposed in the inner surface of the upper-half casing and attached to the bolts, and

lower nuts which are disposed in the inner surface of the lower-half casing and attached to the bolts.

A gas turbine casing structure according to a second aspect of the present invention for solving the above-mentioned problems is a gas turbine casing structure divided by a horizontal plane at flange sections into two halves composed of an upper-half casing and a lower-half casing, the gas turbine casing structure including:

separate members each disposed between a groove formed in each of the flange sections of the upper-half casing and a groove formed in each of the flange sections of the lower-half casing, the separate members being capable of acting differently from the upper-half casing and the lower-half casing, and

sealing members installed in concave portions formed in an upper surface of the separate member, a lower surface of the separate member, an upper side surface of the separate member beside an inner surface of the upper-half casing, and a lower side surface of the separate member beside an inner surface of the lower-half casing.

A gas turbine casing structure according to a third aspect of the present invention for solving the above-mentioned problems is the gas turbine casing structure according to the second aspect of the present invention, wherein

the sealing members are disposed at positions at which the sealing members contact the upper-half casing and the lower-half casing and can seal them when pressure is exerted on the gas turbine casing structure.

Effects of the Invention

According to the present invention, there can be provided a gas turbine casing structure which can prevent gas leakage during application of pressure.

MODE FOR CARRYING OUT THE INVENTION

The gas turbine casing structure according to the present invention will be described below by reference to drawings.

Hereinbelow, a first embodiment of the gas turbine casing structure according to the present invention will be described.

FIGS. 1(a) and1(b) are schematic views showing cross sections of a gas turbine casing structure according to the present embodiment.FIG. 1(a) is a schematic view showing a cross section in the axial direction of a bolt.FIG. 1(b) is a schematic view showing a cross section taken along the arrowed line A-A inFIG. 1(a).

As shown inFIG. 1(a), the gas turbine casing structure according to the present embodiment is divided into two halves, i.e., an upper-half casing10and a lower-half casing11, by a horizontal plane at flange sections. The upper-half casing10and the lower-half casing11are composed of shell sections10a,11aand flange sections10b,11b.

In the gas turbine casing structure according to the present embodiment, bolt installation grooves10c,11cfor installing bolts12are formed to span the inner surface of the flange section10bof the upper-half casing10and the inner surface of the flange section11bof the lower-half casing11.

Above each of the bolt installation grooves10cin the inner surface of the flange section10bof the upper-half casing10, a concave portion10dis formed for installing an upper nut13. Above each of the bolt installation grooves11cin the inner surface of the flange section11bof the lower-half casing11, a concave portion11dis formed for installing a lower nut14.

As shown inFIGS. 1(a) and1(b), a lower wall surface of the concave portion10dfor installing the upper nut13of the upper-half casing10constitutes a bearing surface10efor the upper nut13, while an upper wall surface of the concave portion11dfor installing the lower nut14of the lower-half casing11constitutes a bearing surface11efor the lower nut14.

The bolt12and the upper nut13are fastened together in the inner surface of the upper-half casing10, and the bolt12and the lower nut14are fastened together in the inner surface of the lower-half casing11, whereby the upper-half casing10and the lower-half casing11are fastened together.

In the gas turbine casing structure according to the present embodiment, deficient parts are produced by forming the concave portion10dof the upper-half casing10and the concave portion11dof the lower-half casing11. In order to ensure the strength of the deficient parts, minimum required reinforcement is carried out in the height direction and the thickness direction of the flange section10bof the upper-half casing10and the flange section11bof the lower-half casing11.

With the gas turbine casing structure according to the present embodiment, therefore, the moment during exertion of pressure can be minimized, in comparison with the placement of the bolt on the external side of the flange section as in the conventional gas turbine casing structure, by disposing the bolt12in the inner surfaces of the upper-half casing10and the lower-half casing11. By this procedure, the amount of opening of the flange section10bof the upper-half casing10relative to the flange section11bof the lower-half casing11can be diminished.

By so disposing the bolt12in the inner surfaces of the upper-half casing10and the lower-half casing11, moreover, gas leakage through the bolt holes100c,101ccan be eliminated, because it is not that the bolt holes100c,101c(seeFIG. 4) penetrate the flanges10b,11bas in the conventional gas turbine casing structure.

By thus disposing the bolt12in the inner surfaces of the upper-half casing10and the lower-half casing11, moreover, gas can be sealed in reliably, because contact pressure acting between the outside of the flange section10bof the upper-half casing10and the outside of the flange section11bof the lower-half casing11can be raised by the moment.

Hereinbelow, a second embodiment of the gas turbine casing structure according to the present invention will be described.

FIG. 2is a schematic view showing a cross section of the gas turbine casing structure according to the present embodiment.FIG. 2is the schematic view showing the cross section in the axial direction of a bolt.

As shown inFIG. 2, the gas turbine casing structure according to the present embodiment is composed of an upper-half casing20and a lower-half casing21. The upper-half casing20and the lower-half casing21are composed of shell sections20a,21aand flange sections20b,21b.

Bolt holes20care formed in the flange section20bof the upper-half casing20, and bolt holes21care formed in the flange section21bof the lower-half casing21. Binding between the upper-half casing20and the lower-half casing21is performed by fastening together bolts22installed in the bolt holes20c,21c, upper nuts23and lower nuts24.

In the gas turbine casing structure according to the present embodiment, grooves20dare formed within the flange sections20bof the upper-half casing20, grooves21dare formed within the flange sections21bof the lower-half casing21, and separate members25which can act independently of the flange sections20b,21bare inserted into the grooves.

In each separate member25, a concave portion25ais formed in its upper surface, a concave portion25bis formed in its lower surface, a concave portion25cis formed in its upper side surface beside the inner surface of the upper-half casing20, and a concave portion25dis formed in its lower side surface beside the inner surface of the lower-half casing21. Sealing members26are installed in the concave portions25a,25b,25c,25dof the separate member25. In the present embodiment, metallic E-seals are used as the sealing members26.

FIG. 3is a schematic view showing the cross section of the gas turbine casing structure according to the present embodiment when pressure is exerted on the gas turbine casing structure.FIG. 3is also a schematic view showing the cross section in the axial direction of the bolt. InFIG. 3, it is to be noted that the gas turbine casing structure is expressed exaggeratedly, in comparison with its actual state, for understanding.

In the gas turbine casing structure according to the present embodiment, as shown inFIG. 3, the separate member25inserted between the groove20dand the groove21dmakes a motion different from those of the flange sections20b,21bwhen pressure is exerted as indicated by arrows P inFIG. 3. As a result, the sealing members26contact the upper-half casing20and the lower-half casing21, making sealing possible. That is, the sealing members26are arranged in advance at positions where they contact the upper-half casing20and the lower-half casing21during application of pressure, making sealing possible.

With the gas turbine casing structure according to the present embodiment, therefore, gas can be sealed in reliably by installing the sealing members26in the concave portions of the separate member25inserted between the groove20dand the groove21d.

With the gas turbine casing structure according to the present invention, as described above, there can be provided a gas turbine casing structure which can prevent gas leakage during application of pressure.

INDUSTRIAL APPLICABILITY

The present invention can be utilized, for example, for the gas turbine casing structure of a gas turbine.

EXPLANATIONS OF LETTERS OR NUMERALS