JP2004052598A - Strut structure of gas turbine exhausting section - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a strut structure of a gas turbine exhausting section causing no crack with a low cycle fatigue owing to a thermal stress. <P>SOLUTION: The strut structure of the gas turbine exhausting section is provided with a cylindrical cabin wall 23; a cylindrical outside diffuser 25 installed inside the cabin wall; a cylindrical inside diffuser 27 installed inside the outside diffuser 25; a strut having an outer end secured to the cabin wall 23; and an inner end penetrating the outside diffuser 25 secured to the circumference of the inside diffuser 27, and a strut cover 35 for covering the strut, and securing the outer end and the cabin wall 23, the circumference of the middle part and the outside diffuser 25, and the inner end and the inside diffuser 27, respectively. An expanding means (slide structure 35a) freely expandable in the axial direction is provided in the strut cover between the cabin wall 23 and the outside diffuser 25. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a strut structure for a gas turbine exhaust.
[0002]
[Prior art]
In a gas turbine, air sucked from an intake chamber is compressed by rotation of a rotor in a compressor, and is brought into a high temperature and high pressure state and guided to a combustor. The air guided to the combustor is mixed with the supplied fuel and burned, resulting in high-temperature and high-pressure combustion gas. The combustion gas expands in the turbine section, and its energy is converted into the torque of the turbine. A part of the rotational force is used as power for the compressor, and the other part is used as output of the gas turbine. The combustion gas that has been converted into rotational force in the turbine section passes through the exhaust section and is discharged to the exhaust duct.
[0003]
As shown in FIG. 3, the exhaust portion 1 includes an outer casing wall 3 formed in a cylindrical shape, a cylindrical outer diffuser 5 provided inside the casing wall 3, and an inner diffuser 5 inside the outer diffuser 5. A cylindrical inner diffuser 7 provided. The vehicle cabin wall 3 is supported by a base plate (not shown), and a bearing for a rotor (not shown) is provided on the inner peripheral side of the cylindrical inner diffuser 7. Accordingly, the casing wall 3, the outer diffuser 5, and the inner diffuser 7 each having a cylindrical shape are arranged concentrically so that an annular outer peripheral cavity is provided between the casing wall 3 and the outer diffuser 5. 9, and an annular combustion gas passage 11 is formed between the outer diffuser 5 and the inner diffuser 7.
[0004]
Incidentally, the inner diffuser 7 is supported by the vehicle cabin wall 3 via struts (not shown). That is, the strut supports the inner diffuser 7 by fixing the outer end to the vehicle interior wall 3 and fixing the inner end that penetrates the outer diffuser 5 to the outer periphery of the inner diffuser 7. In the illustrated example, a tangential type strut support is shown, and the inner ends of the six struts are connected to the outer peripheral surface of the inner diffuser 7 in a tangential direction.
[0005]
The struts are exposed to the hot combustion gases since they support the inner diffuser 7 across the combustion gas passages 11. For this reason, the strut is provided with a gap 13 shown in FIG. 4 between the strut and the outer surface, and is covered with a strut cover 15, and a part of the compressed air from the compressor is introduced into the gap 13 as cooling air to thereby reduce the temperature. The rise is prevented and the occurrence of thermal expansion is suppressed. As shown in FIG. 5, the strut cover 15 is fixed to the outer end and the cabin wall 3, the outer periphery of the central portion and the outer diffuser 5, and the inner end and the inner diffuser 7 by welding portions 17. That is, the strut cover 15 covers the struts and forms a flow path for cooling air, and also plays a role as a support member for the outer diffuser 5. In some cases, the strut cover 15 has a flare shape in which the outer end (root), which is a connection portion with the cabin wall 3, has a significantly bulged outer shape, unlike the illustrated example.
[0006]
[Problems to be solved by the invention]
However, while the temperature of the exhaust gas flowing through the combustion gas passage is 600 ° C. or higher, the temperature of the strut cover is lower than that of the vehicle interior wall located on the opposite side of the outer peripheral cavity from the combustion gas passage. It becomes uneven. Further, the temperature distribution differs between when the gas turbine is started and when it is stopped. That is, the temperatures of the outer diffuser and the inner diffuser are high at the time of starting and lower than that at the time of stopping. On the other hand, the temperature of the cabin wall is low at the time of starting and higher than that at the time of stopping. Accordingly, the strut cover generates a thermal stress in association with the strut cover, and particularly, the expansion and contraction of the strut in the axial direction increases. However, since the strut cover is fixed by welding to the outer end and the cabin wall, the outer periphery of the central portion and the outer diffuser, and the inner end and the inner diffuser, particularly when a tension occurs, the structurally weak portion ( strut cover the base of the flared portion, etc.) stress is concentrated on the low-cycle (10 ⁴ times due to thermal stress) fatigue occurs. This low cycle fatigue also causes cracks. For this reason, repairs occur at each periodic inspection, which requires repair time and repair costs, and also causes a reduction in responsiveness (availability).
The present invention has been made in view of the above circumstances, and provides a strut structure of a gas turbine exhaust part in which cracks due to low cycle fatigue due to thermal stress do not occur, thereby reducing repair time and repair cost, and preventing reduction in availability. The purpose is to plan.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the strut structure of the gas turbine exhaust part according to claim 1 of the present invention includes: a cylindrical casing wall; a cylindrical outer diffuser provided inside the casing wall; A cylindrical inner diffuser provided inside the diffuser, a strut having an outer end fixed to the cabin wall and an inner end penetrating the outer diffuser fixed to the outer periphery of the inner diffuser, and a strut covering the outer strut, the outer end and the vehicle. In a strut structure of a gas turbine exhaust unit including a chamber wall, a strut cover to which each of an outer periphery and an outer diffuser of a central portion and an inner end and an inner diffuser are fixed, a strut cover between a cabin wall and an outer diffuser is provided. , Characterized in that an expansion / contraction means is provided which can expand and contract in the axial direction.
[0008]
In the strut structure of the exhaust part of the gas turbine, the strut cover between the cabin wall and the outer diffuser is provided with a telescopic means capable of expanding and contracting in the axial direction. Even if it expands and contracts, the expansion and contraction is absorbed by the expansion and contraction means. As a result, the strut cover is no longer stretched, and cracks due to low cycle fatigue caused by thermal stress do not occur.
[0009]
The strut structure of the gas turbine exhaust part according to claim 2 is the strut structure of the gas turbine exhaust part according to claim 1, wherein the expansion and contraction means slides the inner end of the outer cover and the outer end of the inner cover in the axial direction. It is a slide structure part freely fitted.
[0010]
In the strut structure of the exhaust portion of the gas turbine, when the strut cover expands and contracts in the axial direction, the fitting portion between the outer cover and the inner cover slides, and the increase / decrease length is absorbed. Accordingly, the strut cover is prevented from being stretched with a simple structure without using a separate member, and low cycle fatigue caused by thermal stress is suppressed.
[0011]
According to a third aspect of the present invention, in the strut structure of the gas turbine exhaust unit according to the first aspect, the expansion / contraction means is interposed between an inner end of the outer cover and an outer end of the inner cover. It is a flexible structure member that can be stretched and contracted in the axial direction.
[0012]
In the strut structure of the exhaust portion of the gas turbine, when the strut cover expands and contracts in the axial direction, the flexible structure member expands and contracts, and the length of the increase and decrease is absorbed. This eliminates the struts of the strut cover while securing the airtightness between the outer cover and the inner cover, and suppresses low cycle fatigue caused by thermal stress.
[0013]
The strut structure of the gas turbine exhaust part according to claim 4 is the strut structure of the gas turbine exhaust part according to claim 1, wherein the spring member that supports the vehicle interior wall and the outer diffuser so as to be relatively displaceable, It is characterized in that it is provided over the cabin wall and the outer diffuser.
[0014]
In the strut structure of the exhaust portion of the gas turbine, the spring member is provided between the vehicle interior wall and the outer diffuser, and the rigidity enough to support the outer diffuser and the inner diffuser while securing the displacement absorbing action by the expansion and contraction means. Is provided to the strut cover at the portion where the elastic means is interposed.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a strut structure of a gas turbine exhaust unit according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is an enlarged sectional view of a main part showing a strut structure of a gas turbine exhaust part according to the present invention.
[0016]
The exhaust part 21 includes an outer casing wall 23 formed in a cylindrical shape, a cylindrical outer diffuser 25 provided inside the casing wall 23, and a cylindrical inner diffuser provided inside the outer diffuser 25. And a diffuser 27. The vehicle cabin wall 23 is supported by a base plate (not shown), and a rotor bearing (not shown) is provided on the inner peripheral side of the cylindrical inner diffuser 27. Therefore, the casing wall 23, the outer diffuser 25, and the inner diffuser 27, each of which has a cylindrical shape, are arranged concentrically so that an annular outer peripheral cavity is provided between the casing wall 23 and the outer diffuser 25. 29, and an annular combustion gas passage 31 is formed between the outer diffuser 25 and the inner diffuser 27.
[0017]
The inner diffuser 27 is supported by the cabin wall 23 via struts (not shown). That is, the strut supports the inner diffuser 27 by fixing the outer end to the vehicle cabin wall 23 and fixing the inner end passing through the outer diffuser 25 to the outer periphery of the inner diffuser 27.
[0018]
The strut is provided with a gap 33 between the strut and the outer surface, and is covered with a strut cover 35, and a part of the compressed air from the compressor is introduced as cooling air into the gap 33 to prevent a rise in temperature and to prevent thermal expansion. The occurrence of is suppressed. In the strut cover 35, the outer end and the cabin wall 23, the outer periphery of the central portion and the outer diffuser 25, and the inner end and the inner diffuser 27 are fixed by welding portions 36, respectively. That is, the strut cover 35 covers the strut and forms a flow path of the cooling air, and further serves as a support member for the outer diffuser 25.
[0019]
The strut cover 35 has an expansion / contraction means between the vehicle interior wall 23 and the outer diffuser 25, the expansion / contraction means being able to expand and contract in the axial direction. The strut cover 35 has an outer end fixed to the interior wall 23 and an inner end opened between the interior wall 23 and the outer diffuser 25, and an inner end fixed to the inner diffuser 27. And an inner cover 39 having an outer end fixed to the outer diffuser 25 and an outer end slidably fitted to an inner end of the outer cover 37. In the present embodiment, the expansion / contraction means is a slide structure portion 35a in which the inner end of the outer cover 37 and the outer end of the inner cover 39 are slidably fitted in the axial direction. In the present embodiment, an example is shown in which the inner peripheral side of the inner cover 39 is extrapolated to the outer peripheral side of the outer cover 37, but a reverse fitting structure may be adopted.
[0020]
In the vicinity of the strut cover 35, a spring member (leaf spring) 40 for supporting the vehicle interior wall 23 and the outer diffuser 25 so as to be relatively displaceable is provided between the vehicle interior wall 23 and the outer diffuser 25. . The leaf spring 40 is formed in a rectangular shape, with one end fixed to the vehicle cabin wall 23 and the other end fixed to the outer diffuser 25 with the bent portion as the center. In the present embodiment, a pair of leaf springs 40 are provided on the left and right sides of the strut cover 35. Thereby, uniform support rigidity can be provided on the left and right sides of the expansion / contraction means. In addition, since FIG. 1 is a front view in which the flow direction is viewed from the upstream side of the gas flow, the plate spring 40 has a plate surface extending in a direction parallel to the gas flow. That is, they are mounted in a direction that does not increase the exhaust resistance.
[0021]
According to the strut structure of the exhaust portion of the gas turbine configured as described above, the strut cover 35 between the cabin wall 23 and the outer diffuser 25 is provided with the slide structure portion 35a that is expandable and contractible in the axial direction. Even if the strut cover 35 expands and contracts due to a temperature distribution and its fluctuation, the expansion and contraction is absorbed by the slide structure 35a. Thereby, the strut cover 35 is no longer stretched, and cracks due to low cycle fatigue caused by thermal stress do not occur.
[0022]
Further, when the strut cover 35 expands and contracts in the axial direction, the fitting portion 35a between the outer cover 37 and the inner cover 39 slides, and the increase or decrease length is absorbed. Accordingly, the strut cover 35 is prevented from being stretched with a simple structure without using a separate member, and low cycle fatigue caused by thermal stress is suppressed.
[0023]
Further, in the strut structure of the exhaust portion of the gas turbine, since the leaf spring 40 is disposed between the cabin wall 23 and the outer cover 37, the outer diffuser 25, Rigidity enough to support the inner diffuser 27 can be given to the slide structure 35 a of the strut cover 35.
[0024]
Next, another embodiment according to the present invention will be described.
FIG. 2 is a main part enlarged sectional view showing another embodiment. The same members as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted.
In the strut structure of the gas turbine exhaust unit according to the present embodiment, the expansion and contraction means is an axially expandable and contractible flexible structure member 45 interposed between the inner end of the outer cover 41 and the outer end of the inner cover 43. . The flexible structure member 45 may be, for example, a bellows tube that is freely expandable and contractable in the axial direction and that connects the inner end of the outer cover 41 and the outer end of the inner cover 43 so as to approach and separate from each other.
[0025]
In the strut structure of the gas turbine exhaust part, when the strut cover 47 expands and contracts in the axial direction, the flexible structure member 45 expands and contracts, and the increase or decrease length is absorbed. Thereby, while ensuring the airtightness between the outer cover 41 and the inner cover 43, the struts of the strut cover 47 can be eliminated, and low-cycle fatigue caused by thermal stress can be suppressed.
[0026]
【The invention's effect】
As described in detail above, according to the strut structure of the exhaust part of the gas turbine according to the first aspect of the present invention, the strut cover between the cabin wall and the outer diffuser is provided with the telescopic means that is telescopic in the axial direction. Is provided, even if the strut cover expands and contracts due to non-uniform temperature distribution and its fluctuation, the expansion and contraction can be absorbed by the expansion and contraction means. As a result, the strut cover is no longer stretched, and cracks due to low cycle fatigue caused by thermal stress do not occur. As a result, the repair time and the repair cost can be reduced, and a decrease in availability can be prevented.
[0027]
According to the strut structure of the exhaust portion of the gas turbine according to the second aspect, since the expansion / contraction means is a slide structure in which the inner end of the outer cover and the outer end of the inner cover are slidably fitted in the axial direction, the strut is provided. When the cover expands and contracts in the axial direction, the fitting portion between the outer cover and the inner cover slides, and the increased or decreased length can be absorbed. Thus, the strut cover can be prevented from being stretched with a simple structure without using a separate member, and low cycle fatigue caused by thermal stress can be suppressed.
[0028]
According to the strut structure of the exhaust portion of the gas turbine according to the third aspect, since the expansion and contraction means is an axially expandable and contractible flexible structure member interposed between the inner end of the outer cover and the outer end of the inner cover. When the strut cover expands and contracts in the axial direction, the flexible structure member expands and contracts, and the length of increase and decrease can be absorbed. Thereby, while ensuring the airtightness between the outer cover and the inner cover, the struts of the strut cover can be eliminated, and low cycle fatigue caused by thermal stress can be suppressed.
[0029]
According to the strut structure of the exhaust portion of the gas turbine according to the fourth aspect, since the spring member for supporting the casing wall and the outer diffuser so as to be relatively displaceable is provided over the casing wall and the outer diffuser, the expansion and contraction means is provided. Stiffness enough to support the outer diffuser and the inner diffuser can be imparted to the portion of the strut cover where the expansion / contraction means is interposed, while ensuring the displacement absorbing action of the strut cover.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of a main part showing a strut structure of a gas turbine exhaust part according to the present invention.
FIG. 2 is an enlarged sectional view of a main part showing another embodiment.
FIG. 3 is a cross-sectional view of a conventional exhaust unit in a direction orthogonal to an axis.
FIG. 4 is an enlarged sectional view of a main part of a conventional exhaust unit.
FIG. 5 is an enlarged perspective view of a main part of a conventional exhaust unit.
[Explanation of symbols]
21; exhaust unit 23; cabin wall 25; outer diffuser 27; inner diffuser 35; strut cover 35a;
37; outer cover 39; inner cover 40; leaf spring (spring member)
41; outer cover 43; inner cover 45; flexible structure member (expansion / contraction means)
47; strut cover

Claims (4)

A cylindrical casing wall, a cylindrical outer diffuser provided inside the casing wall, a cylindrical inner diffuser provided inside the outer diffuser, and an outer diffuser having an outer end fixed to the casing wall. A strut whose inner end penetrating is fixed to the outer periphery of the inner diffuser, and a strut cover that covers the strut, the outer end and the cabin wall, the outer periphery of the central portion and the outer diffuser, and the inner end and the inner diffuser are fixed. In the strut structure of the exhaust part of the gas turbine provided with
A strut structure for an exhaust part of a gas turbine, wherein a strut cover is provided on a strut cover between a vehicle cabin wall and an outer diffuser so as to be extendable and contractible in an axial direction. The strut structure of a gas turbine exhaust part according to claim 1,
The stretching means,
A strut structure for an exhaust portion of a gas turbine, wherein the strut structure is a slide structure in which an inner end of an outer cover and an outer end of an inner cover are slidably fitted in an axial direction. The strut structure of a gas turbine exhaust part according to claim 1,
The stretching means,
A strut structure for an exhaust portion of a gas turbine, wherein the strut structure is a flexible structural member interposed between an inner end of an outer cover and an outer end of an inner cover and is capable of extending and contracting in the axial direction. The strut structure of a gas turbine exhaust part according to claim 1, 2 or 3,
A strut structure for an exhaust portion of a gas turbine, wherein a spring member for supporting a vehicle compartment wall and an outer diffuser so as to be relatively displaceable is provided over the vehicle compartment wall and the outer diffuser.

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