JP5498408B2 - Gas turbine rotor assembly - Google Patents

Description

  The present invention relates to a rotor assembly for a gas turbine, and more particularly to an improvement in a fitting portion between a rotor and a rotor blade that are components of the gas turbine.

  In recent years, in gas turbine facilities, an increase in output has been demanded in order to cope with an increase in power demand in summer, and an increase in efficiency for the purpose of energy saving has been demanded. As a means for increasing the output, the annular flow passage area, that is, the size of the gas turbine is increased. Further, as means for improving the efficiency, there is a tendency to increase the compressor pressure ratio and to improve the combustion temperature. As a result, the operating conditions and operating environment for turbine rotors are becoming stricter.

  A gas turbine is a compressor that adiabatically compresses air sucked from the atmosphere, a combustor that mixes fuel with compressed air and burns it to generate combustion gas, a turbine that expands combustion gas and generates rotational power, Drive. Further, the turbine has a turbine rotor that is rotated by combustion gas, and the rotor includes a rotor shaft and a rotor disk integrated with the rotor shaft. A rotor blade is fixed to the rotor disk. The moving blade is fixed to a groove or the like (moving blade implanting portion) provided in the rotor disk. The rotor assembly referred to in the present invention is composed of a rotor shaft, a rotor disk, and a moving blade implanted in the rotor disk.

  In order to prevent corrosion due to high temperature, Patent Document 1 describes that a coating for preventing corrosion is provided on a turbine engine. Patent Document 2 describes providing an abrasion resistant coating that provides abrasion resistance without compromising the resistance to corrosion fatigue.

  In patent document 3, the structure which covered the rotor shaft of the geothermal steam turbine rotor, the blade groove | channel, and the blade leg with the anticorrosion layer with respect to the corrosive component of geothermal steam is disclosed. As a material for the corrosion prevention layer, a mixture of flaky molybdenum disulfide powder and an epoxy resin binder is disclosed.

  In Patent Document 4, in a turbine, specifically, a steam turbine, a zinc layer is formed on a joint surface between a disk and a rotor blade, and the fact that the potential of zinc is lower than the potential of the disk material and the rotor blade material is utilized. It is described to prevent corrosion damage such as stress corrosion cracking, corrosion exposure and pitting corrosion of turbine materials.

  In patent document 5, what provided the sealing material in the clearance gap between the axial part of a steam turbine rotor and the fitting part of a disc part is disclosed. As the sealing material, thermal spraying, welding, rubber / oil and fat are described, and it is described that this is provided in the gap by press fitting or the like, but there is no specific description of the material.

JP 2007-169786 A JP 2006-329195 A JP 2004-204760 A JP 2000-204902 A JP 7-42503 A

  However, conventionally known countermeasures are not sufficient for suppressing crack generation in a high temperature and high stress environment in a gas turbine. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable gas turbine rotor assembly that can cope with higher temperatures and larger sizes.

  The present invention has been made in order to solve the above-described problems, and its features are a compressor that adiabatically compresses air sucked from the atmosphere, a combustor that mixes fuel with compressed air and burns to generate combustion gas, A gas turbine having a turbine that expands combustion gas, generates rotational power, and drives a generator, wherein the turbine is integrated with a rotor disk having a plurality of rotor blades fitted on an outer periphery thereof, and the rotor disk A turbine rotor blade having a rotor shaft formed, and the turbine rotor blade embedded portion of the turbine rotor disk has a thermal spray layer laminated in multiple layers made of nickel or chromium or an alloy of both formed by thermal spraying, The thermal spray layer is in a rotor assembly of a gas turbine that includes 25 to 33% oxide in cross-sectional area ratio. However, it is preferable that the sprayed layer of chromium or an alloy thereof does not contain hexavalent chromium.

  According to the present invention, the nickel layer or the chromium layer formed in the fitting portion between the moving blade and the rotor disk improves the oxidation resistance of the moving blade implantation portion, and the high stress of the gas turbine rotor generated during gas turbine operation. It is possible to prevent the oxidation of the part, extend the fatigue life of the rotor material, and improve the reliability of the equipment.

The schematic sectional drawing which showed the coating to the whole surface of the implantation part of the wing | blade of a gas turbine rotor disk. The figure which shows the result of having verified the fatigue life of Ni coating film construction material. Sectional drawing explaining the propagation mechanism of the crack of a thermal spray layer in the Example of this invention. Sectional drawing explaining the propagation mechanism of the crack in the sprayed layer of a comparative example. The schematic sectional drawing which formed the selective spraying layer to the stress concentration part of a gas turbine rotor disk. The schematic sectional drawing which formed the thermal spray layer in the convex part of a gas turbine rotor disk. Sectional drawing which shows the structure of a general gas turbine. The figure which shows the fitting part of a gas turbine rotor disk and a moving blade.

  A rotor assembly of a gas turbine according to the present invention is an object in which an oxidation resistant coating is provided on a high stress portion of a turbine rotor, such as an implanted portion of a gas turbine rotor rotor blade of a rotor disk. More specifically, thermal spraying made of nickel, chromium, or an alloy thereof in the implanted portion of the rotor blade of a gas turbine rotor disk made of Ni-base alloy or Fe-base alloy having a plurality of gas turbine rotor blades fitted on the outer periphery. It is the thing which constructed the layer. The turbine rotor assembly of the present invention is manufactured by applying the above-mentioned sprayed layer to the turbine rotor blade implantation portion of the Ni-based or Fe-based turbine rotor disk. This sprayed layer is formed by a powder or wire spraying method, and is a multilayer laminated film.

  The present invention is directed to a gas turbine rotor assembly, and therefore cannot be used in the corrosion resistant materials for steam turbines described in Patent Documents 3 to 5. Moreover, the oxide-containing nickel or chromium sprayed layer used in the present invention is superior in heat resistance to the thermoplastic aluminum powder coating described in Patent Document 1. Furthermore, the coating made of silicone (silicon organic compound) and alumina powder described in Patent Document 2 contains an organic substance. Therefore, there is a concern that it is thermally inferior to the oxygen-containing sprayed film of the present invention.

  In the present invention, spraying may include high-speed flame spraying (HVOF), flame spraying, plasma spraying, and arc spraying, but from the viewpoint of film deposition rate, cost, adhesion of the sprayed film, and denseness of the sprayed film, Thermal spraying is most suitable. However, HVOF spraying is also a preferable method because the performance of the sprayed film itself is excellent.

  The thermal spray layer in the present invention is a thermal spray layer laminated in a multilayer composed of nickel or chromium formed by thermal spraying or an alloy of both, and naturally does not include organic substances or low-melting point metals, and therefore at a high temperature. Has excellent heat resistance and corrosion resistance.

  In the present specification, the thermal spraying method itself is a technique well known as a coating method, and thus detailed description thereof is omitted.

  The nickel sprayed layer or the chromium sprayed layer formed by thermal spraying contains an oxide, and the oxide amount is particularly preferably 25 to 30% in terms of the cross-sectional area ratio. In addition, such a nickel layer or chromium layer is provided at least in a portion where stress is concentrated, such as only a concave portion of the rotor blade rotor portion of the rotor disk or a concave portion of the rotor blade shaft portion and the rotor shaft fitting portion. It is preferred that

  FIG. 6 shows a general structural sectional view of a gas turbine. The gas turbine is roughly composed of a compressor 1, a combustor 2 and a turbine 3. The compressor 1 adiabatically compresses air sucked into the gas path 4 from the atmosphere as a working fluid, and the combustor 2 mixes fuel with the compressed air supplied from the compressor 1 and burns to generate high-temperature and high-pressure gas. The turbine 3 generates rotational power when the combustion gas introduced from the combustor 2 is expanded. Exhaust gas from the turbine 3 is released into the atmosphere. The remaining power obtained by subtracting the power for driving the compressor 1 from the rotational power generated in the turbine 3 becomes the power generated by the gas turbine and drives a generator (not shown).

  FIG. 7 shows a structure for implanting the rotor blades into the turbine rotor disk 5. A plurality of blade grooves are provided on the outer periphery of the rotor disk, and the turbine rotor blade 6 having a matching implant portion is fitted. Since centrifugal force 11 is generated in the turbine rotor blade 6 during turbine operation, high stress due to stress concentration is generated in the joint between the rotor blade and the rotor disk. For this reason, a structure in which the shape and structure of the fitting portion is low stress has been studied.

  Therefore, as the turbine rotor material, a superalloy such as iron or Ni having excellent creep strength, or a material combining them is used. However, in these materials, an example in which the crack growth rate is accelerated by oxidation of the material has been reported. In particular, the stress concentration portion 8 of the blade implantation portion in the turbine rotor shown in FIG. 7 is a severe load condition in which the centrifugal force generated by the turbine blade is added to the high temperature environment. As a result, fatigue cracks tend to develop due to high temperature and high stress.

  Further, as the efficiency and output of the gas turbine are improved, the turbine wheel is increased in size and temperature, and accordingly, the fatigue life is reduced due to oxidation in the high stress load portion of the gas turbine rotor. By preventing oxidation of the blade implantation portion of the gas turbine rotor, it is possible to improve the oxidation resistance and realize a gas turbine rotor assembly with improved fatigue strength reliability.

  The oxidation resistant coating provided on the high stress load portion uses a layer formed by air plasma spraying of pure nickel powder, pure chromium powder, or an alloy powder thereof. This coating layer preferably contains 25 to 33% of an oxide in cross-sectional area ratio. Note that the nickel powder or chromium powder as the thermal spraying material may not be a pure metal, but may be an alloy thereof.

  The multilayer sprayed layer is more resistant to cracking than the sprayed layer is formed by a single spray. The mechanism will be described later with reference to FIGS. 3A and 3B. Therefore, the number of spraying is preferably 5 to 30 times, particularly 10 to 20 times. The total thickness of the sprayed layer is preferably in the range of 0.01 to 2 mm, and particularly preferably in the range of 0.02 to 1 mm.

  As described above, by forming the thermal spray layer, it is possible to prevent contact between the rotor base material and the air at the stress concentration portion of the turbine rotor, and to prevent a decrease in strength by suppressing oxidation. In particular, it is possible to increase the fatigue life of the turbine rotor blade-implanted portion and the fastening bolt hole, thereby improving the reliability of the entire turbine.

  FIG. 1 shows an example in which a Ni sprayed film 9 is applied as an oxidation resistant coating to the entire blade-implanted portion of the turbine rotor disk 5. Atmospheric plasma spraying was used as the method for spraying nickel powder. Thus, by providing a coating on the entire surface, an effect of improving oxidation resistance can be obtained.

  Of course, the present invention can also employ a reduced pressure spraying method. The reduced-pressure spraying method has a problem that the cost increases because the non-processed material is put in a vacuum vessel.

  In this example, two types of coatings were applied by changing the spraying speed. The thermal spray layer 9 was provided by overlapping 10 to 20 layers. As a result, as shown on the left side of FIG. 3A, a Ni coating layer having an oxide layer 10 on the surface of each layer during thermal spraying was obtained. The cross section of this coating layer was photographed, and the nickel portion 9 (white portion) and the oxide portion 10 (black portion) were image-recognized and the oxide layer was observed. The other contained 20% oxide in cross-sectional area ratio. The number of ruptures was evaluated on a test piece simulating this Ni-based rotor material with a fatigue load given a generated strain equivalent to the actual machine in a high temperature environment.

  FIG. 2 shows the effect of the above embodiment. Assuming that the evaluation result of a member having no coating in the conventional example is 1, the life of the member containing 30% oxide in the cross-sectional area ratio by applying nickel coating (the test piece considered as a turbine disk and its test piece) About 20% of the time taken for the fracture of the joint with the test piece assumed to be a rotor blade implanted in the plant). On the other hand, it was found that the lifetime of the nickel coating film having an oxide cross-sectional area ratio of 20% tends to decrease.

  Based on FIG. 3A and FIG. 3B, the life extension mechanism of each is demonstrated. As shown in FIG. 3A, when the oxide layer 10 is sufficiently included in the nickel coating, when the crack generated in the coating film reaches the substrate, the crack propagates in the direction in which the oxide is laminated. To do. Further, the bonding between the coating film and the substrate is not as strong as the substrate. As a result, it is possible to prevent the influence of crack propagation on the substrate. On the other hand, the coating film with few oxide layers 10 shown in FIG. 3B has high bonding strength with the base material. Further, since the strength of the coating film itself is weaker than that of the base material itself, cracks are likely to occur. As a result, since the crack generated in the coating film propagates to the base material as it is, the life is shortened. As a result of the study by the present inventors, it has been found that 25% or more (cross-sectional area ratio) of the coating film needs to be an oxide in order to extend the life of the turbine rotor.

  On the other hand, if there are too many oxides, the effect of suppressing crack propagation can be obtained, but the coating film itself tends to peel off, and oxidation resistance may not be imparted. Accordingly, it is preferable that the oxide be 1/3 or less of the coating film (the cross-sectional area ratio is 33% or less). Therefore, when thermal spraying nickel as an oxidation resistant coating, it is desirable that the oxide contained in the nickel coating is between 25% and 33% in terms of the cross-sectional area ratio. The amount of oxide can be appropriately adjusted by controlling the spraying temperature, speed, atmosphere, film thickness, and the like.

Further, the oxidation resistant coating nickel film 9 may be applied only to the stress concentration part 8 of the blade implantation part of the turbine rotor disk 5. FIG. 4 shows an example in which coating is applied to the disk-side recess of the blade-implanted portion where stress is concentrated. Thus, when coating a part, it coats in a square shape or a circle / oval shape centering on a stress concentration part. In a portion having a complicated uneven shape, it is difficult to spray a wide range uniformly. Therefore, if a coating layer is provided only in a part, the reliability is improved. Moreover, since the dimensional tolerance with a moving blade root is limited in a moving blade implantation part, it is easy to adjust film thickness and is preferable.

  In addition to the nickel used in this example, even when Cr or an alloy powder of Ni and Cr is coated by thermal spraying, a coating film having high temperature corrosion resistance and ductility can be provided in the same manner as the above nickel layer. is there. However, when Cr is used, a coating film containing an oxide layer is obtained in the same manner as Ni, and it is expected that a highly reliable turbine will be obtained as well.

  Next, an example in which a Ni spray coating is applied to a part of the turbine rotor disk in the same manner as in Example 1 will be described. FIG. 5 shows a part of the cross section of the turbine rotor disk (cross sectional view taken along the line AA ′ in FIG. 1). The turbine rotor disk has an annular shape rotated around BB ′ as a central axis, and is provided with a groove corresponding to each rotor blade. The turbine rotor disk has a convex portion that matches the surface of the turbine rotor in order to align the central axis with the turbine rotor. A nickel sprayed film 13 was applied as an oxidation resistant coating to the base of the convex portion.

  Note that the convex portion has a fastening bolt hole with a turbine rotor penetrating in the vertical direction of the drawing in FIG. A Ni coating film may also be provided on the fastening bolt hole at the same time as or separately from the root portion of the projection.

  By applying such a coating film, it is possible to extend the life of the turbine rotor disk.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Combustor 3 Turbine 4 Gas path 5 Turbine rotor disk 6 Turbine rotor blade 7 Turbine rotor shaft 8 Stress concentration part 9 Nickel sprayed film 10 Oxide layer 11 Centrifugal force 12 Turbine rotor 13 Nickel sprayed film

Claims (8)

A compressor that adiabatically compresses air sucked from the atmosphere, a combustor that mixes fuel with compressed air and burns it to generate combustion gas, a turbine that expands the combustion gas, generates rotational power, and drives a generator A gas turbine, the turbine having a rotor rotor having a rotor assembly having a rotor disk fitted with a plurality of rotor blades on an outer periphery and a rotor shaft integrated with the rotor disk;
The turbine rotor blade embedded portion of the turbine rotor disk has a multilayer sprayed layer formed of nickel or chromium formed by thermal spraying or an alloy layer of both, and the thermal sprayed layer has an oxidation ratio of 25 to 33% in cross-sectional area ratio. A rotor assembly for a gas turbine, comprising: an object. 2. The gas turbine rotor assembly according to claim 1, wherein a thickness of the sprayed sprayed layer is 0.02 to 1 mm. 2. The gas turbine rotor assembly according to claim 1, wherein the sprayed layer is provided in at least a part of a concave portion of a portion of the turbine rotor disk that contacts the moving blade of the moving blade implantation portion. Gas turbine rotor assembly. 2. The gas turbine rotor assembly according to claim 1, wherein the sprayed layer is further provided at the base of a convex portion in contact with the rotor shaft provided on the turbine rotor disk. . A rotor assembly of a turbine having a rotor shaft, a rotor disk fixed to the rotor shaft, and a moving blade fixed to the rotor disk,
It has a multilayer sprayed layer made of nickel formed by thermal spraying on at least a part of the rotor blade implantation portion of the rotor disk, and the thermal sprayed layer contains an oxide having a cross-sectional area ratio of 25 to 33%. rotor assembly features and to filter turbine. A turbine rotor assembly as claimed in claim 5, comprising:
The rotor assembly of a turbine, wherein the nickel sprayed layer is provided in a concave portion of a rotor blade implantation portion of the rotor disk. In the turbine rotor assembly according to claim 5, wherein the thermal sprayed layer further features and to filter turbine rotor assemblies that are disposed at the base of the convex portion in contact with the rotor shaft provided in a turbine rotor disk . In the turbine rotor assembly according to claim 5, rotor assembly features and to filter turbine a thickness of the sprayed layer is 0.02～1Mm.

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