JP2012163053A - Gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas turbine capable of further improving efficiency by suppressing a rise in the temperature of internal air in a stationary blade outer cavity.SOLUTION: In order to solve the problem, the gas turbine includes stationary blades held directly or indirectly via other stationary members on a casing, and the cavity communicating in a circumferential direction between the inner circumferential face of the casing and the outer circumferential faces of the stationary blades and shut off by the stationary blades and the other stationary members from a gas path in which fuel gas flows. In the gas turbine, a heat shield with a plurality of metal plates piled in a radial direction and air layers formed between the metal plates is installed near surfaces of the stationary blade outer circumferential faces in the cavity.

Description

  The present invention relates to a gas turbine, and more particularly to a gas turbine suitable for one having a sealing structure that prevents combustion gas from flowing into a space between a rotor and a stationary member.

  FIG. 2 shows a configuration example of a general power generation gas turbine system. As shown in the figure, the gas turbine system 1 is combusted by adding fuel to the working fluid compressed by the compressor 2 in the combustor 3 and driving the turbine 4 by the high-temperature and high-pressure combustion gas 6 generated in the combustor 3. For example, the generator 5 converts it into energy such as electric power.

  It is desirable that the electric energy obtained for the consumed fuel is as much as possible. As is well known, the gas turbine system 1 is expected to improve performance by increasing the temperature and pressure of the combustion gas 6 at the inlet of the turbine 4. Has been.

  FIG. 3 shows a partial schematic configuration of the turbine 4 described above. As shown in the drawing, a moving blade 8 is attached to a turbine wheel 9 which is a rotating body, and a small radial gap between the radial tip of the moving blade 8 and the stationary shroud 11, so-called A blade tip gap 18 is formed.

  The blade tip clearance 18 is caused by the difference between the thermal expansion of the turbine wheel 9 and the blade 8 due to thermal expansion and centrifugal force and the thermal deformation of the stationary member (the casing 10, the stationary shroud 11, the stationary blade 12, etc.). The size changes depending on the operating state of the gas turbine system 1. When the size of the rotor blade tip gap 18 is too large, air passing therethrough increases the tip leakage loss of the rotor blade 8. 18 is preferably as small as possible.

  On the other hand, if the blade tip clearance 18 is too small and the tip of the blade 8 comes into contact with a stationary member, it will cause destruction. Therefore, in general, an initial motion that does not fall below the design minimum gap value to avoid contact. A blade tip clearance 18 is determined.

  One of the factors that greatly affects the thermal deformation of the stationary member is the thermal expansion of the casing 10 holding the high temperature members of the stationary shroud 11 and the stationary blade 12. The casing 10 has heat conduction inside the casing 10 itself, contact heat conduction from a holding portion (for example, an engaging portion between the stationary shroud 11 and the stationary blade 12) in contact with the high temperature member, and between the high temperature member and the casing 10. The heat transfer with the sealing air 17 existing in the stationary blade outer cavity 20, the heat radiation from the stationary blade 12, the heat radiation from the outer circumferential surface of the casing 10 to the outer circumferential direction, the heat transmission, etc. The temperature distribution changes depending on the position in the axial direction and the circumferential direction, and undesirable deformation such as excessive thermal deformation and non-uniform deformation may occur.

  In view of this, Patent Documents 1 and 2 disclose techniques for restricting heat input to the casing 10 and heat radiation from the casing 10 during gas turbine operation to make the thermal deformation more uniform.

  Patent Document 1 discloses a technique for improving heat insulation of a casing by providing a thermal protection sheet between a stationary ring of a turbine and a sealing ring held by the casing, paying attention to heat insulation from the casing's thermal radiation. Has been.

  Patent Document 2 discloses a technique for preventing heat input due to heat radiation from the nozzle by installing a heat shield on the inner peripheral surface of the casing in the space between the casing and the stationary blade.

JP 2009-103129 A US Pat. No. 5,2018,846

  In order to increase the efficiency of the gas turbine, in addition to reducing the rotor blade tip gap 18, the combustion gas 6 flows into the space between the rotor and the stationary member (hereinafter referred to as the wheel space 22). Therefore, it is important to reduce the flow rate of the seal air 17.

  Various seal structures are employed on the inner peripheral side of the gas path through which the fuel gas 6 passes in response to the phenomenon of leaking into the wheel space 22. Furthermore, by introducing the concept of allowable temperature in consideration of the life of the turbine wheel 9 and supplying the seal air 17 to the wheel space 22, the temperature of the leakage air becomes lower than the allowable temperature of the wheel space 22. The long-term reliability (long life) of the space 22 is ensured.

  Since the sealing air 17 generally uses a part of the compressor bleed air 7 (see FIG. 2), a large amount of consumption of the sealing air 17 leads to a decrease in efficiency of the gas turbine.

  Therefore, in order to increase the efficiency of the gas turbine, it is important to prevent the combustion gas 6 from leaking with less sealing air 17, so that the temperature of the sealing air 17 should be supplied to the relevant part in the lowest possible state. desirable. For this purpose, it is necessary to suppress heat input in the supply path of the seal air 17.

  On the other hand, the stationary vane outer cavity 20 formed by the inner circumferential surface of the casing 10 and the outer circumferential surface of the stationary blade 12 and, in some cases, the side surfaces of other stationary members, is one of the supply paths of the seal air 17. However, in particular, when the stationary blade 12 is an uncooled member having no cooling structure, the metal temperature of the stationary blade 12 is increased depending on the temperature of the gas, so that the heat input to the seal air 17 is large. It is a part that is considered to be. In the conventional technology, heat input from the high temperature member to the internal air of the stationary blade outer cavity 20 is not considered.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a gas turbine capable of further increasing efficiency by suppressing the temperature rise of internal air in the vane outer cavity.

  In order to achieve the above object, a gas turbine according to the present invention has a stationary blade directly held by a casing or indirectly through another stationary member, and has an inner circumferential surface and a stationary blade outer circumferential surface of the casing. In a gas turbine having a cavity that communicates in a circumferential direction and is blocked from a gas path through which fuel gas passes by the stationary blade and other stationary members, in the vicinity of the surface of the outer surface of the stationary blade of the cavity In addition, a plurality of metal plates are stacked in the radial direction, and a heat shield is provided to form an air layer between the metal plates.

  According to the present invention, it is possible to suppress the temperature rise of the internal air inside the stationary blade outer cavity, so that the rotor blade tip gap can be reduced, and the temperature rise of the seal air can be suppressed to reduce the seal air flow rate. This makes it possible to further increase the efficiency of the gas turbine.

It is a fragmentary sectional view showing one example of a gas turbine of the present invention. It is a figure showing a schematic structure of a general gas turbine system. It is a fragmentary sectional view which shows the example of the conventional gas turbine. It is a perspective view which shows the heat shielding shield employ | adopted as the gas turbine of this invention. It is a perspective view which shows the state which looked at the heat shield shown in FIG. 4 from the downward direction. It is a figure which shows the example of installation of the heat shield shield employ | adopted as the gas turbine of this invention. It is a figure which shows the other example of installation of the heat-shielding shield employ | adopted as the gas turbine of this invention. It is a perspective view which shows the other example of the heat-shielding shield employ | adopted as the gas turbine of this invention. It is a perspective view which shows the state which looked at the heat shield shown in FIG. 8 from the downward direction.

  Hereinafter, the gas turbine of the present invention will be described based on the illustrated embodiments. Incidentally, the same reference numerals are used for the same reference numerals as in the prior art, and the detailed description thereof is omitted.

  FIG. 1 shows an embodiment of a gas turbine according to the present invention. As shown in the figure, in this embodiment, a heat shield 30 is installed in the vicinity of the outer peripheral surface of the stationary blade 12 in the outer cavity 20 of the stationary blade. Other configurations are substantially the same as those of the conventional example shown in FIG.

  Details of the heat shield 30 installed near the outer peripheral surface of the stationary blade 12 in the above-described stationary blade outer cavity 20 will be described with reference to FIG.

  As shown in FIG. 4, the heat shield 30 of the present embodiment is bent so that curved surfaces are formed at both ends of the thin metal plate 33, and further, the metal plates 33 are overlapped in the radial direction, and the space between the metal plates 33 is increased. The air layer 34 is formed in the space.

  According to the configuration of this embodiment, since the heat shield 30 is installed in the vicinity of the outer peripheral surface of the stationary blade 12 in the stationary blade outer cavity 20, the sealing air 17 is generated inside the stationary blade outer cavity 20. It is possible to avoid direct contact with the stationary blade 12 heated to a high temperature by the combustion gas 6 when moving.

  Moreover, since the air layer 34 is formed in the space between the radial directions of the metal plate 33, the heat shield 30 can suppress heat transfer in the radial direction due to heat transfer of air. Furthermore, also from the viewpoint of heat radiation, since a plurality of radiation surfaces (the front surface and the back surface of the metal plate 33) are formed in the radial direction, the temperature difference between the radiation surfaces can be reduced, and the casing 10 The amount of heat radiation to can be reduced.

  Therefore, the temperature rise of the casing 10 can be suppressed, and as a result, heat input due to heat transfer from the casing 10 to the seal air 17 can be suppressed. Desirably, one surface of the metal plate 33 is polished and bent so that the polished surface becomes the outer surface of the heat shield 30. Since the outer surface of the heat shield 30 is polished, the heat transfer coefficient and emissivity of the surface are lowered, and thus heat transfer due to convection and radiation can be further suppressed.

  Further, the heat shield 30 is formed with a seal air passage hole 31 communicating in the radial direction. The sealing air passage hole 31 supplies the sealing air 17 to the stationary blade hollow portion 15, and one or more sealing air passage holes 31 are formed on the outer peripheral side of the stationary blade hollow portion 15.

  FIG. 5 shows an inner peripheral surface when the heat shield 30 shown in FIG. 4 is viewed from below.

  As shown in the figure, on the inner peripheral surface side of the heat shield shield 30, a seal air passage hole whose periphery is surrounded so that a protrusion 32 surrounds the periphery of an arbitrary place, for example, two seal air passage holes 31. 31 or at the end of the inner peripheral surface.

  A space having a height approximately equal to the height of the protrusion 32 can be formed between the protrusion 32 and the stationary blade 12 on the surface of the stationary blade 12. That is, the height of the protrusion 32 of the heat shield 30 is substantially equal to the radial distance of the space between the heat shield 30 and the outer peripheral surface of the stationary blade 12. Further, the protrusion 32 serves to positively stop the flow of the sealing air 17 in the space. The protrusion 32 forms an air layer 34 with a slow air flow in a space formed between the heat shield 30 and the stationary blade 12, thereby reducing the heat transfer coefficient of air on the surface of the stationary blade 12. Thus, the amount of heat input by heat transfer to the internal air of the stationary vane outer cavity 20 can be further reduced.

  The arrangement of the protrusions 32 described above preferably separates the sealing air 17 flowing into the stationary blade hollow portion 15 from the sealing air 17 positioned between the heat shield 30 and the stationary blade 17 as shown in FIG. In addition, it is preferable to arrange the protrusion 32 around the sealing air passage hole 31. The protrusion 32 can be easily formed by pressing the metal plate 33. In addition, a member other than the metal plate 33 may be attached as the protrusion 32, and in that case, a low heat conductive material such as ceramic may be used.

  Next, how to install the above-described heat shield 30 will be described. FIG. 6 is an example of an installation example of the heat shield 30.

  As shown in the figure, in this example, the heat shield 30 is fixed to the stationary blade 12 or the stationary shroud 11 by a plurality of pins 40. The pin 40 has a structure that allows thermal deformation of the heat shield 30, that is, a structure that does not completely fix the heat shield 30, but moves somewhat when it is thermally deformed. Moreover, the pin 40 does not need to be plural and may be fixed by one.

  FIG. 7 shows another example of how to install the heat shield 30. In the example shown in FIG. 7, the heat shield 30 is fixed to the stationary blade 12 with a welded portion 41.

  Depending on the structure of the heat shield 30 described above and the installation method, it is possible to suppress the temperature rise of the casing 10 to reduce the rotor blade tip gap 18 and to suppress the temperature rise of the seal air 17. It is possible to further increase the efficiency of the gas turbine by reducing the flow rate of 17.

  Next, another example of the heat shield will be described with reference to FIG. As shown in the figure, the heat shield 35 of this example has a structure in which an outer peripheral side metal plate 36 and an inner peripheral side metal plate 37 are stacked in the radial direction, and a spacer 38 is provided between them.

  FIG. 9 shows an inner peripheral surface of the heat shield 35 shown in FIG. 8 as viewed from below.

  As shown in the drawing, on the inner peripheral surface side of the heat shield shield 35, a seal air passage hole whose periphery is surrounded so that a protrusion 32 surrounds the periphery of two seal air passage holes 31, for example. 31 or at the end of the inner peripheral surface.

  With this structure, the air layer 34 is formed in the radial space between the outer peripheral side metal plate 36 and the inner peripheral side metal plate 37, so that the effect is almost the same as that of the heat shield 35 of the embodiment shown in FIG. 4. It is possible to obtain.

  The spacer 38 can be easily formed by pressing the outer peripheral side metal plate 36 or the inner peripheral side metal plate 37. Further, a member other than the outer peripheral side metal plate 36 and the inner peripheral side metal plate 37 may be attached as the spacer 38, and in that case, a low heat conductive material such as ceramic may be used.

  According to the present embodiment described above, it is possible to suppress an increase in the temperature of the internal air of the stationary blade outer cavity 20 that becomes the seal air 17 supplied to the wheel space 22 by the following three effects.

  First, by disposing the heat shields 30 and 35 on the inner peripheral side (the stationary blade 12 side) of the stationary blade outer cavity 22, the internal air of the stationary blade outer cavity 22 moves to the supply destination. Sometimes, it is possible to prevent direct contact with the high temperature stationary blade 12 and heat input by heat transfer.

  Next, the heat shielding shields 30 and 35 have a structure in which a plurality of thin metal plates 33, an outer peripheral side metal plate 36, and an inner peripheral side metal plate 37 are stacked in the radial direction. Since the air layer 34 is formed in the space between the inner peripheral side metal plates 37 of the plate 36, the heat insulation efficiency of the heat shields 30 and 35 themselves can be increased.

  Next, with the protrusion 32 arbitrarily provided on the inner peripheral surface side of the heat shields 30 and 35, the air flow is positively stopped in the space formed between the heat shields 30 and 35 and the stationary blade 12. The heat transfer rate of air on the surface of the stationary blade 12 can be reduced, and the amount of heat input by heat transfer to the internal air of the stationary blade outer cavity 20 can be further reduced.

  Finally, since heat radiation from the high-temperature stationary blade 12 to the casing 10 is largely suppressed by the heat shield shields 30 and 35, the temperature of the inner peripheral surface of the casing 10 can also be reduced, and from the inner peripheral surface of the casing 10 Heat input to the internal air of the stationary vane outer cavity 20 can also be suppressed.

  By these effects, it becomes possible to reduce the temperature of the casing 10 by reducing the temperature rise of the casing 10 and to reduce the flow rate of the seal air 17 by suppressing the temperature rise of the seal air 17. It is possible to achieve higher efficiency.

  DESCRIPTION OF SYMBOLS 1 ... Gas turbine system, 2 ... Compressor, 3 ... Combustor, 4 ... Turbine, 5 ... Generator, 6 ... Combustion gas, 7 ... Compressor extraction air, 8 ... Rotor blade, 9 ... Turbine wheel, 10 ... Casing 11 ... Static shroud, 12 ... Static blade, 13 ... Diaphragm, 15 ... Static blade hollow portion, 16 ... Static blade inner peripheral hole, 17 ... Sealed air, 20 ... Static blade outer cavity, 21 ... Diaphragm cavity, 22 ... Foil Space, 23 ... Diaphragm seal air supply hole, 30, 35 ... Heat shield, 31 ... Seal air passage hole, 32 ... Projection, 33 ... Metal plate, 34 ... Air layer, 36 ... Outer metal plate, 37 ... Inner circumference Side metal plate, 38 ... spacer, 40 ... pin, 41 ... weld.

Claims (12)

A stationary blade held directly on the casing or indirectly through another stationary member, communicated in a circumferential direction between an inner peripheral surface of the casing and an outer peripheral surface of the stationary blade, and the stationary blade In a gas turbine having a cavity that is interrupted by a gas path through which fuel gas passes by blades and other stationary members,
A gas turbine characterized in that a plurality of metal plates are stacked in the radial direction near the surface of the outer peripheral surface of the stationary blade of the cavity, and a heat shield is formed to form an air layer between the metal plates. The gas turbine according to claim 1, wherein
The heat shield shield is a gas turbine characterized in that a thin metal plate is bent to be double, and an internal space is used as the air layer. The gas turbine according to claim 2, wherein
A gas turbine comprising a plurality of protrusions extending in an arbitrary direction on an inner peripheral surface of the metal plate. The gas turbine according to claim 3, wherein
The gas turbine according to claim 1, wherein a height of the protrusion is substantially equal to a radial distance of a space between the heat shield shield and the outer peripheral surface of the stationary blade. The gas turbine according to claim 3 or 4,
The projection is formed by pressing the metal plate. The gas turbine according to any one of claims 3 to 5,
The gas turbine is characterized in that the material of the protrusion is a low thermal conductor. The gas turbine according to any one of claims 1 to 6,
The gas turbine according to claim 1, wherein the heat shield has a hole for supplying seal air passing through the cavity to the inside of the stationary blade. The gas turbine according to claim 7, wherein
The gas turbine according to claim 1, wherein the protrusion is disposed so as to surround a hole for supplying seal air passing through the cavity to the inside of the stationary blade. The gas turbine according to claim 1, wherein
2. The gas turbine according to claim 1, wherein the heat shield has a structure in which two metal plates are stacked with a certain distance in the radial direction, and an air layer is formed therebetween. The gas turbine according to claim 9, wherein
The gas turbine according to claim 1, wherein the heat shield has a structure in which at least one of an outer peripheral side metal plate and an inner peripheral side metal plate is pressed in a radial direction. The gas turbine according to claim 9 or 10,
In the gas turbine, the heat shield includes a spacer disposed between an outer peripheral side metal plate and an inner peripheral side metal plate, and a space that is separated in the radial direction of the spacer is used as the air layer. The gas turbine according to any one of claims 1 to 11,
The gas turbine according to claim 1, wherein the heat shield is a metal plate having an outer surface finished.

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