Gas turbine spindle bolt seal device

Abstract: In gas turbine constructed such that steam is used for cooling of gas turbine high temperature portion to be then recovered, steam is prevented from leaking in spindle bolt portion of turbine disc. Seal hole 4 is formed in turbine disc 8 portion through which spindle bolt 1 passes. In the seal hole 4, seal piece 3 having smaller coefficient of linear expansion than the spindle bolt 1 and seal piece cover 5 for covering the seal piece 3 are disposed. The seal piece cover 5 is bored with pressure hole 6 through which high pressure side steam pressure is introduced into inner side of the seal piece cover 5 so that the seal piece 3 of inner side is urged on sheet surface 7 of the seal hole 4.

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to a spindle bolt seal device of a gas turbine which is constructed such that. steam is used for cooling of a gas turbine high temperature portion and is then recovered. Description of the Prior Art: In a tendency to make a gas turbine to a high temperature operation, such a gas turbine as having a recovery type steam cooled system in which steam is used for cooling of a gas turbine high temperature portion and, after used for the cooling, is recovered is being developed. In the recovery type steam cooled system, the steam which has been used for the cooling and recovered is made effective use of for performing another work, hence to prevent the steam from leaking uselessly before it is recovered leads to enhancement of the cycle efficiency. Moreover, if the steam for cooling mixes into a gas path of the gas turbine, there is a fear of lowering of performance of the gas turbine itself. On the other hand, first to fourth stage discs and end rotors of the gas turbine are fastened to be connected to each other by a spindle bolt and an outlined structure thereof is shown in Fig. 4. In Fig. 4, numeral 01 designates a first stage disc, which carries a first stage moving blade 04, numeral 02 designates a second stage disc, which carries a second stage moving blade 05 and numeral 03 designates a third stage disc, which carries a third stage moving blade 06. Numeral 1 designates a spindle bolt, which passes through the discs 01 to 03 to fasten to connect them. Cooling steam flows into the respective moving blades from each of the discs, as shown by arrows, and is collected to be recovered into cavities formed between the discs. In the prior art gas turbine, as shown in Fig. 3, there is provided none of seal structure for the spindle bolt 1 but there is rather formed a clearance 9 between a disc 8 and the spindle bolt 1 in a bolthole 2 so as to be appropriate for cooling of the spindle bolt 1. However, in the gas turbine which employs the recovery type steam cooled system, spaces between each of the discs 8 are filled with.steam, hence there is a problem that the steam leaks toward upstream side through the clearance 9 between the disc 8 and the spindle bolt 1 to mix into the gas path. SUMMARY OF THE INVENTION: In view of the problem in a prior art gas turbine having a recovery type steam cooled system, it is an object of the present invention to provide a gas turbine spindle bolt seal device which is able to reduce a steam leakage from a turbine disc spindle bolt portion. In order to attain said object, in a gas turbine spindle bolt seal device of the present invention, a seal hole is formed in a turbine disc portion through which a spindle bolt passes and in said seal hole, there are disposed a seal piece fitted around said spindle bolt and a seal piece cover for covering said seal piece. Said seal piece is made of a material having a smaller coefficient of linear expansion than said spindle bolt. Further, there is bored in said seal piece cover a pressure hole through which a high pressure side steam pressure is introduced into an inner side of said seal piece cover so as to urge said seal piece in said seal piece cover on a sheet surface of said seal hole. According to the gas turbine spindle bolt seal device of the present invention constructed as above, the seal piece disposed in the seal hole is urged on the sheet surface of the seal hole by the steam pressure, thereby the steam is prevented from leaking along the sheet surface. Also, the seal piece is made of a material having a smaller coefficient of linear expansion than the spindle bolt, thereby the clearance between the seal piece and the spindle bolt becomes smaller in operation and the steam is prevented from leaking along the spindle bolt. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a cross sectional view showing construction of a gas turbine spindle bolt seal device of an embodiment according to the present invention. Fig. 2 is a perspective view showing construction of a seal piece, split into two, used in the embodiment. Fig. 3 is a cross sectional view showing construction of a prior art gas turbine spindle bolt. Fig. 4 is an explanatory view showing construction example of a gas turbine having a recovery type steam cooled system. DESCRIPTION OF THE PREFERRED EMBODIMENTS Herebelow, description will be made on a spindle bolt seal device of the present invention concretely based on embodiments shown in Figs. 1 and 2. Fig. 1 is an enlarged view of a portion which corresponds to portion A of Fig. 4 and in this Fig. 1, numeral 4 designates a seal hole, which is formed in a disc 8 around a spindle bolt 1. A seal piece 3, split into two, as shown in Fig. 2 is fitted around the' spindle bolt 1 in the seal hole 4. The seal piece 3 is made of a material which has a smaller coefficient of linear expansion than the spindle bolt 1. The seal piece 3 has in each of its two split surfaces a seal face formed by a stepped portion as shown in Fig. 2 so that steam is prevented from leaking through a split portion thereof. A cylindrical seal piece cover 5 is fitted around the seal piece 3 and a pressure hole 6 of an appropriate size and number is bored in the seal piece cover 5 along an axial direction of the spindle bolt 1 so that steam pressure P 1 acts on the seal piece 3 therethrough. There is a differential pressure of P 1 > P 2 between pressures P 1 on the right of the seal hole 4 in Fig. 1 and P 2 on the left thereof and the seal piece 3 is urged on a sheet surface 7 of the seal hole 4 by that differential pressure. Also, because of the differential pressure (P 1 - P 2 ) between the right and left sides of the seal hole 4, there occur a leakage L 1 along the sheet surface 7 and a leakage L 2 along the spindle bolt 1. Thus, the design is made such that the leakage L 1 is prevented by the seal piece 3 being urged on the sheet surface 7 by the differential pressure (P 1 - P 2 ) and the leakage L 2 is prevented by a clearance between the seal piece 3 and the spindle bolt 1 being made as small as possible in operation by the material of the seal piece 3 being selected from that having a smaller coefficient of linear expansion than the spindle bolt 1. By use of the construction mentioned above, contact area of the sheet surface 7 can be made smaller, thereby surface pressure between the seal piece 3 and the sheet surface 7 is made higher. Further, a duplicate seal structure of the sheet surface 7 is formed by the seal piece cover 5 and the seal piece 3. That is, the seal piece 3 on the inner side is made of the material having a smaller coefficient of linear expansion than the spindle bolt 1 so as to make the clearance between the seal piece 3 and the spindle bolt 1 smaller in operation and is urged on the sheet surface 7 by the differential pressure (P 1 - P 2 ), thereby the seal piece 3 effects its sealing function. Also, the seal piece cover 5 on the outer side of the seal piece 3 is urged on the sheet surface 7 by the differential pressure (P 1 - P 2 ), thereby the seal piece cover 5 effect its sealing function. That is, the seal piece cover 5 together with the seal piece 3 provides the mentioned duplicate seal structure of the sheet surface 7 so that'the sealing effect is strengthened. With the sealing functions mentioned above, steam leakage in a rotor system can be reduced and performance enhancement of a recovery type steam cooled plant becomes possible.

Claims: A spindle bolt seal device of a gas turbine which is constructed such that discs (8) are fastened to be connected to each other by a spindle bolt (1) and steam is used for cooling of a high temperature portion to be then recovered, characterized in that a seal hole (4) is formed in a turbine disc (8) portion through which said spindle bolt (1) passes, a seal piece (3) is fitted around said spindle bolt (1) in said seal hole (4), said seal piece (3) being made of a material having a smaller coefficient of linear expansion than said spindle bolt (1), and a seal piece cover (5) is disposed so as to cover said seal piece (3) in said seal hole (4) and there is bored in said seal piece cover (5) a pressure hole (6) through which a high pressure side steam pressure (P1) is introduced into an inner side of said seal piece cover (5) so as to urge said seal piece (3) in said seal piece cover (5) on a sheet surface (7) of said seal hole (4). A spindle bolt seal device as claimed in claim 1, characterized in that said seal piece (3) is split into two parts and a stepped portion is formed in the split surfaces of said parts facing each other.

Inventors: NAKAMURA TAKESHI, SAKATA KAORU, NAKAMURA, TAKESHI, SAKATA, KAORU, Nakamura, Takeshi, Mitsubishi Heavy Industries Ltd, Sakata, Kaoru, Mitsubishi Heavy Industries Ltd.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 1998
Main classification: F16J15
IPC codes: F01D5, F02C7, F16J15, F01D11