Steam turbine rotor blade and modification method of steam turbine rotor blade

Abstract

To provide a steam turbine rotor blade for reducing a pump loss, and suppressed in erosion, and a modification method of the steam turbine rotor blade.SOLUTION: A steam turbine rotor blade comprises a back-side face, a belly-side face, a front edge, a rear edge, a blade root and a blade tip. Also, the steam turbine rotor blade comprises: a blade main body extending from the blade root up to the blade tip; an erosion shield attached to a blade main body recess which is formed at least at a back face side of the blade main body and extends in a blade height direction, the erosion shield having erosion resistance which is higher than that of the blade main body and forming a part of the front edge and a part of the back-side face of the steam turbine rotor blade; and an extension protrusion formed of at least the erosion shield and extending along a regulation direction which intersects with the blade height direction at the front edge and the back-side face.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to steam turbine blades and methods of retrofitting steam turbine blades. [Background technology]

[0002] Fine water droplets generated by condensation of a portion of the steam in the turbine casing grow and become a water film while absorbing surrounding fine water droplets. Collision of floating coarse water droplets with the steam turbine rotor blades can cause erosion of the steam turbine rotor blades. The steam turbine rotor blades disclosed in Patent Document 1 are provided with erosion prevention plates to prevent erosion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 58-057604 Summary of the Invention [Problem to be solved by the invention]

[0004] The water film that adheres to the suction side of the steam turbine blade moves on the suction side toward the blade tip due to centrifugal force. Also, some of the fine water droplets flying in the steam are collected on the suction side and ventral side of the blade, forming a water film, water vein, or hemispherical water droplets (hereinafter, the term water film applies regardless of the shape of the liquid phase), and the water film moves toward the blade tip due to centrifugal force. The longer the travel distance of the water film, the greater the pumping loss, which is classified as the wet loss of the steam turbine.

[0005] In recent years, there has been a trend for the length of the final stage moving blades of steam turbines to increase, and the tip peripheral speed increases in proportion to the radius of rotation. The initial speed of the water film detaching from the tip of the moving blade is the combined speed of the tip peripheral speed and the relative speed of the water film to the moving blade, so the water film is released into the steam at a very high speed. When this water film collides with the structure on the stationary side of the turbine, erosion can occur on the structure side.

[0006] An object of the present disclosure is to provide a steam turbine blade that reduces pumping losses and suppresses erosion, and a method for retrofitting a steam turbine blade. [Means for solving the problem]

[0007] A steam turbine blade according to at least one embodiment of the present disclosure comprises: 1. A steam turbine blade comprising a suction side, a pressure side, a leading edge, a trailing edge, a root, and a tip, a blade body extending from the blade root to the blade tip; an erosion shield attached to a blade body recess formed on at least the suction side of the blade body and extending in a blade height direction, the erosion shield having higher erosion resistance than the blade body and forming a part of the leading edge and a part of the suction side of the steam turbine blade; an extending convex portion extending along a prescribed direction intersecting the blade height direction at least on the leading edge and the suction side surface formed by the erosion shield; Equipped with.

[0008] A method for retrofitting a steam turbine blade in accordance with at least one embodiment of the present disclosure includes: 1. A method for retrofitting a steam turbine blade having a suction side, a pressure side, a leading edge, a trailing edge, a root, and a tip, comprising the steps of: The steam turbine blade comprises: a blade body extending from the blade root to the blade tip; a first erosion shield attached to a blade body recess formed on at least a suction side of the blade body and extending in a blade height direction, the first erosion shield having higher erosion resistance than the blade body and forming a part of the leading edge and a part of the suction side of the steam turbine blade; Equipped with The modification method includes: The method includes a replacement step of removing the first erosion shield and attaching an erosion shield to the blade main body recess, the erosion shield having an extending convex portion formed at least on the leading edge and the suction side surface, the extending convex portion extending along a specified direction intersecting the blade height direction. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a steam turbine rotor blade in which pumping losses are reduced and erosion is suppressed, and a method for retrofitting a steam turbine rotor blade. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating an internal structure of a steam turbine according to an embodiment. [Diagram 2] FIG. 2 is a schematic view showing the appearance of a rotor blade according to the first embodiment. [Diagram 3] FIG. 2 is a schematic view of a blade cross section of a rotor blade according to the first embodiment. [Figure 4] 2 is a schematic diagram showing a cross section of the erosion shield perpendicular to a prescribed direction according to the first embodiment. FIG. [Diagram 5] FIG. 6 is a schematic view showing the appearance of a rotor blade according to a second embodiment. [Figure 6] FIG. 11 is a schematic view of a blade cross section of a rotor blade according to a third embodiment. [Figure 7] FIG. 2 is a schematic diagram illustrating an appearance of a rotor blade before modification according to an embodiment. [Figure 8] 1 is a flowchart illustrating a method for modifying a blade according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0012] <Steam turbine 1> 1 is a cross-sectional view showing an internal structure of a steam turbine 1 according to an embodiment of the present disclosure. The steam turbine 1 includes a turbine rotor 12 and an internal casing 16 that accommodates at least a portion of the turbine rotor 12. In the following description, the rotation direction of the turbine rotor 12 may be referred to as the "circumferential direction," and the extension direction of an axis 12C of the turbine rotor 12 may be referred to as the "axial direction."

[0013] A plurality of diaphragms 17 are attached to the inner periphery of the inner casing 16. Each diaphragm 17 includes a diaphragm outer ring 18, a diaphragm inner ring 19, and a plurality of stator vanes 20 arranged in the circumferential direction. The number of stages of the diaphragms 17 forming the cascade of the stator vanes 20 is, for example, four.

[0014] The turbine rotor 12 includes a plurality of rotor disks 13 arranged side by side in the axial direction, and a plurality of steam turbine blades 30 arranged in the circumferential direction on each rotor disk 13. Each rotor disk 13 forms a row of the steam turbine blades 30. Hereinafter, the steam turbine blades 30 may be simply referred to as "blade 30".

[0015] The rotor disks 13 and the diaphragms 17 are arranged alternately in the axial direction. A cascade of stationary vanes 20 and a cascade of moving blades 30 adjacent to the cascade constitute one stage. In this example, a first stage (initial stage), a second stage, a third stage, and a fourth stage (final stage) of cascades are formed. Steam flowing into a main steam flow passage 9 formed in an internal casing 16 flows in the direction indicated by an arrow S and passes through the cascades constituted by each stage in order. Energy held by the steam is converted into mechanical work by the moving blades 30, causing the turbine rotor 12 to rotate.

[0016] As the steam moves downstream in the main steam flow passage 9, a part of the steam condenses to generate water droplets. When the water droplets attached to the rotor blades 30 move toward the blade tips 36 (see FIG. 2) due to centrifugal force, pumping loss may occur. In particular, a water film that collects on the blade tips 36 side and the leading edge 33 (see FIG. 2) side may cause pumping loss, and the high-speed water film detaching from the blade tips 36 may also cause erosion of the diaphragm outer ring 18 in the inner casing 16.

[0017] The inventors of the present application have devised a measure to suppress these problems at least for each rotor blade 30 in the final stage. The reason for applying the measure to the final stage is that water droplets are likely to adhere to the rotor blade 30 in the final stage where the steam pressure drops close to the steam saturation pressure. However, the measure may be applied not only to the final stage but also to each rotor blade 30 in, for example, the third stage. Hereinafter, when simply referring to "rotor blade 30," it refers to the rotor blade 30 in the final stage.

[0018] <Blade 30 (First embodiment)> A rotor blade 30A (30) according to the first embodiment will be described with reference to Figs. 2 to 4. As shown in Fig. 2, the rotor blade 30A (30) includes a leading edge 33, a trailing edge 34, a suction side surface 31, a pressure side surface 32, a blade root 35, and a blade tip 36. In any cross section perpendicular to the blade height direction of the rotor blade 30A (a blade cross section Ws shown in Fig. 3 as a more specific example), the suction side surface 31 is located downstream of the camber line M of the rotor blade 30A in the rotation direction of the rotor blade 30, and the pressure side surface 32 is located upstream of the camber line M in the rotation direction. The blade root 35 is connected to the rotor disk 13. The blade tip 36 is located on the opposite side of the rotor blade 30A to the blade root 35. The rotation direction of the rotor blade 30 is indicated by an arrow R in Fig. 2.

[0019] The rotor blade 30A (30) comprises a blade body 40 extending from a blade root 35 to a blade tip 36. A blade body suction surface 41 of the blade body 40 forms part of the suction side 31, and a blade body pressure surface 42 (see FIG. 3) of the blade body 40 forms at least part of the pressure side 32. A blade body recess 44A (44) extending in the blade height direction is formed in the blade body 40. The blade body recess 44A may be formed only on the blade body suction surface 41 side, or may be formed across the leading edge 33 on both the blade body suction surface 41 side and the blade body pressure surface 42 side.

[0020] The rotor blade 30A (30) includes an erosion shield 60A (60) according to the first embodiment. The erosion shield 60A is a plate-shaped member attached to the blade main body recess 44A, and has a thickness of 1 mm or more and 3 mm or less. The blade main body recess 44A has a shape in which the plate-shaped erosion shield 60A is fitted.

[0021] The material forming the erosion shield 60A has higher erosion resistance (erosion resistance) than the material forming the blade main body 40. For example, Stellite or a titanium alloy (more specifically, a β-type titanium alloy) is applied to the material of the erosion shield 60A.

[0022] The erosion shield 60A (60) of this example is attached to the blade body recess 44A via silver solder. The erosion shield 60A has a shield rear surface 61 that is substantially flush with the blade body rear surface 41 of the blade body 40. The shield rear surface 61 and the blade body rear surface 41 form the suction side surface 31 of the rotor blade 30A. Furthermore, the erosion shield 60A forms a part of the leading edge 33.

[0023] The rotor blade 30A (30) further includes an extended protrusion 50A (50) according to the first embodiment. The extended protrusion 50A (50) extends along a specified direction intersecting the blade height direction at least on the leading edge 33 and the suction side surface 31 (more specifically, the shield back surface 61). The specified direction in this example is a direction perpendicular to the blade height direction and the blade thickness direction.

[0024] The extending protrusion 50A may be integrally formed of the same material as the erosion shield 60A, or may be formed of a material different from that of the erosion shield 60A. In either embodiment, the material forming the extending protrusion 50A has a higher erosion resistance than the material forming the blade body 40.

[0025] At least a part of the extending protrusion 50A (50) smoothly extends along the blade shape on the shield back surface 61. As a more specific example, the extending protrusion 50A has a shield extending protrusion 55A extending along a specified direction on the shield back surface 61, and a blade body extending protrusion 56 extending on the blade body back surface 41 of the blade body 40. The shield extending protrusion 55A is joined to the blade body back surface 41. The blade body extending protrusion 56 is connected to the end of the shield extending protrusion 55A and abuts against the blade body back surface 41. The shield extending protrusion 55A and the blade body extending protrusion 56, which are integrally formed of the same material, extend in a straight line.

[0026] According to the above configuration, water droplets on the suction side surface 31 of the rotor blade 30 and radially inward of the extended protrusion 50A move toward the blade tip 36 side due to centrifugal force when the rotor blade 30 rotates, and reach the extended protrusion 50A. The water droplets then jump up from the extended protrusion 50A and leave the rotor blade 30 (symbol Wa in FIG. 4 indicates the jumped up water droplets). This makes it possible to suppress the water droplets on the suction side surface 31 from hindering the rotation of the rotor blade 30, and therefore the pumping loss of the steam turbine 1 can be reduced. In addition, since the erosion shield 60A attached to the blade main body 40 is replaceable (details will be described later), it is also possible to adjust the position of the extended protrusion 50A. Since the extended protrusion 50A can be arranged in a position that is favorable for reducing the pumping loss, the pumping loss is further reduced. In addition, according to the above configuration, the water droplets leave before reaching the blade tip 36, so that erosion caused by large water droplets colliding with the diaphragm outer ring 18 of the inner casing 16 can be avoided. As described above, the erosion shield 60A can suppress erosion and reduce pumping losses.

[0027] Moreover, since the extension protrusion 50A includes the blade main body extension protrusion 56, the extension protrusion 50A can be made even longer, so that the water droplets can be more reliably thrown up from the rotor blade 30. This more reliably achieves reduction in pumping loss and suppression of erosion.

[0028] The description of the extended protrusion 50A will be continued with reference to FIG. 2. In the example of FIG. 2, the entire extended protrusion 50A is located on the blade tip 36 side of the intermediate position between the blade root 35 and the blade tip 36 in the blade height direction. The intermediate position is a position equidistant from each of the blade root 35 and the blade tip 36 in the blade height direction, and is indicated by the two-dot chain line A. The reason why the extended protrusion 50A is preferably installed above the two-dot chain line A is as follows. As the water droplets attached to the rotor blade 30 move toward the blade tip 36 due to centrifugal force, they combine with other water droplets and their volume gradually increases. In other words, it is understood that most of the water film that causes pump loss is supplied from the lower half of the blade. For this reason, it is desirable to separate the water droplets and water film from the blade before they reach the blade tip 36. However, even if the water droplets are separated early, that is, even if the water droplets are separated at a position below the two-dot chain line A, the distance that the water droplets attached to the upper side reach the blade tip 36 will be long. As a result, the water droplets become large enough to increase the moment required to rotate the rotor blade 30, which increases the pumping loss. Therefore, it is preferable that the extending convex portion 50A is located closer to the blade tip 36 than to the intermediate position between the blade root 35 and the blade tip 36 in the blade height direction. According to the above configuration, the fine water droplets can detach from the rotor blade 30 and flow downstream in the main steam flow path 9 before becoming a water film. This makes it possible to more reliably suppress erosion.

[0029] 3 is a schematic diagram of a blade cross section Ws of the rotor blade 30A. The blade cross section Ws is a cross section of the rotor blade 30A cut along a direction perpendicular to the blade height direction of the rotor blade 30. The blade height direction position of the cross section is the same as the blade height direction position where both ends of the extended protrusion 50 (more specifically, one end 53 and the other end 54 described later) are disposed. That is, the blade cross section Ws includes the one end 53 and the other end 54.

[0030] The blade main body recesses 44A are formed on both the blade main body suction surface 41 side and the blade main body pressure surface 42 side, and the erosion shield 60A fitted into the blade main body recesses 44A further includes a shield pressure surface 62 forming part of the pressure surface 32 of the rotor blade 30. Furthermore, the erosion shield 60A has a shield pressure end 69. The shield pressure end 69 is located on the opposite side to the suction surface 31 across the camber line M in the blade thickness direction of the rotor blade 30. In other words, the shield pressure end 69 corresponds to the end of the erosion shield 60A on the shield pressure surface 62 side in the blade thickness direction of the rotor blade 30.

[0031] The shield back surface 61 and the shield ventral surface 62 are connected to each other at the leading edge 33, and the shield extending protrusion 55A of the extending protrusion 50A extends in a specified direction from the suction side surface 31 across the leading edge 33 to the ventral side surface 32. According to the above configuration, water droplets moving on the suction side surface 31 toward the blade tip 36 side and the leading edge 33 side can be more reliably captured by the extending protrusion 50A and can be made to fly up. This makes it possible to more reliably reduce pumping losses and suppress erosion near the leading edge 33.

[0032] 3, the extended protrusion 50A includes one end 53 located on the suction side 31 of the rotor blade 30 and the other end 54 located on the ventral side 32 of the rotor blade 30. The one end 53 is formed at an end of the blade main body extended protrusion 56, and the other end 54 is formed at an end of the shield extended protrusion 55A. The other end 54 is located between the shield ventral end 69 and the leading edge 33.

[0033] Generally, the curvature of the surface of the rotor blade 30 is relatively large near the leading edge 33 of the rotor blade 30. In this regard, according to the above-mentioned configuration, the length of the extended protrusion 50A on the ventral side surface 32 can be shortened, and the processing for forming the extended protrusion 50A can be simplified. As a specific example, in an embodiment in which the extended protrusion 50A is joined to the erosion shield 60A, a problem such as peeling of the extended protrusion 50A that is likely to occur on the surface of the erosion shield 60A with a large curvature can be suppressed. As another specific example, in an embodiment in which the extended protrusion 50A is formed by press processing, the processing step can be simplified by shortening the portion of the extended protrusion 50A with a large curvature.

[0034] The description of the extending protrusion 50A will continue with reference to Figure 3. In the blade cross section Ws, there is an outer end position Po on the suction side surface 31 of the rotor blade 30, where the tangent direction is parallel to the axial direction of the turbine rotor 12 (see Figure 1). The tangent line at the outer end position Po is the two-dot chain line B, which is parallel to the axis 12C of the turbine rotor 12. One end 53 of the extending protrusion 50A is located on the suction side surface 31 closer to the trailing edge 34 than the outer end position Po.

[0035] On the blade cross section Ws, on the leading edge 33 side of the outer end position Po, the normal direction of the suction side surface 31 faces the leading edge 33 side. Therefore, when the rotor blade 30 rotates, the force that moves the water droplets on the suction side surface 31 tends to face the leading edge 33 side as well as the blade tip 36 side. In this regard, according to the above configuration, since the extended convex portion 50A extends to the trailing edge 34 side of the outer end position Po, the water droplets moving toward the blade tip 36 side and the leading edge 33 side can be more reliably captured by the extended convex portion 50A and can be made to fly up. This more reliably realizes a reduction in pumping loss caused by water droplets generated in an area where erosion does not occur.

[0036] The description of the extended protrusion 50A will be continued with reference to Fig. 3. The camber line M of the rotor blade 30 has a maximum camber position Pc. Also, a first position P1 is located on the suction side surface 31 of the rotor blade 30. The first position P1 is a position where an imaginary straight line L passing through the maximum camber position Pc in a direction perpendicular to the axial direction intersects with the suction side surface 31. One end 53 of the extended protrusion 50A is located on the suction side surface 31 closer to the trailing edge 34 than the first position P1.

[0037] According to the above configuration, the extended protrusion 50A can be made even longer, so that the water droplets moving toward the blade tip 36 can be more reliably captured by the extended protrusion 50A and thrown up. This more reliably reduces pumping losses and suppresses erosion.

[0038] In the example of Fig. 3, the first position P1 is located between the outboard end position Po and the trailing edge 34, but the present disclosure is not limited to this. The rotor blade 30 may have a shape in which the first position P1 is located between the outboard end position Po and the leading edge 33, and the one end 53 may be located between the first position P1 and the outboard end position Po. Even in this case, the above-mentioned technical advantage is obtained by positioning the one end 53 closer to the trailing edge 34 than the first position P1. Furthermore, when the outboard end position Po is closer to the trailing edge 34 than the first position P1, the above-mentioned technical advantage is obtained by positioning the one end 53 closer to the trailing edge 34 than the outboard end position Po.

[0039] 4 is a schematic diagram showing a cross section Z of the erosion shield 60A perpendicular to the specified direction, with the lower side of the paper being the blade root 35 side and the upper side being the blade tip 36 side. The symbol Wa indicates a water droplet that has risen from the extended protrusion 50A and detached from the blade surface. The dimension D indicates the amount of protrusion of the extended protrusion 50A from the erosion shield 60A, and the dimension W indicates the dimension of the extended protrusion 50A in the width direction perpendicular to the protruding direction of the extended protrusion 50A. The width direction is also perpendicular to the specified direction.

[0040] In some embodiments, at least a portion of the extension protrusion 50A is configured so that 0.5 mm≦D≦3 mm is satisfied. In this example, 0.5 mm≦D≦3 mm is satisfied for each of the shield extension protrusion 55 and the blade main body extension protrusion 56.

[0041] According to the above configuration, since D is 0.5 mm or more, the R surface 37 having a sufficiently large radius can be formed on the side surface of the extended protrusion 50A on the blade tip 36 side and the side surface of the extended protrusion 50A on the blade root 35 side, and therefore, stress concentration on these sides can be suppressed. In addition, since the water film accumulates on the blade root 35 side of the extended protrusion 50A, the centrifugal force acting on the water film increases, and the interface due to surface tension is broken, so that the water film can be separated as water droplets in terms of wettability. In addition, since D is 3 mm or less, the protrusion amount of the extended protrusion 50A is suppressed from becoming excessive, and the rotation efficiency of the rotor blade 30 can be suppressed from being excessively reduced.

[0042] In some embodiments, at least a portion of the extension protrusion 50A is configured so that 1 mm≦W≦10 mm is satisfied. In this example, the shield extension protrusion 55 and the blade body extension protrusion 56 each satisfy 1 mm≦W≦10 mm.

[0043] According to the above configuration, since W is 1 mm or more, the strength of the extending protrusion 50A in the width direction can be secured. As a result, even if the phenomenon in which water droplets with a high peripheral speed collide with the extending protrusion 50A is repeated, fatigue failure of the extending protrusion 50A can be avoided. In addition, since W is 10 mm or less, the extending protrusion 50A is prevented from becoming excessively large, and the rotation efficiency of the rotor blade 30 is prevented from being excessively reduced.

[0044] As a more detailed example, at least a part of the extending convex portion 50A may be configured so that 1≦W / D≦20 is satisfied. This allows the shape of the extending convex portion 50A to be optimized.

[0045] <Blade 30 (Second embodiment)> A rotor blade 30B (30) according to a second embodiment will be described with reference to Fig. 5. In Fig. 5, the same components as those of the rotor blade 30A (see Fig. 2) are given the same reference numerals. The rotor blade 30B has an extension protrusion 50B (50) instead of the extension protrusion 50A (50). The extension protrusion 50B does not include the blade main body extension protrusion 56 (see Fig. 2) and only includes the shield extension protrusion 55A.

[0046] The erosion shield 60B (60) illustrated in FIG. 5 may be a pressed product formed from a single sheet metal member. The extending protrusion 50B may be a protrusion formed by pressing. In this case, the extending protrusion 50B is formed integrally with the erosion shield 60B. According to the above configuration, the configuration of the extending protrusion 50B can be further simplified.

[0047] <Blade 30 (Third embodiment)> A rotor blade 30C (30) according to a third embodiment will be described with reference to Fig. 6. In Fig. 6, the same components as those of the rotor blade 30A (see Fig. 2) are given the same reference numerals. In the rotor blade 30C, a blade main body recess 44C (44) is formed in the blade main body 40. Furthermore, the rotor blade 30C includes a block-shaped erosion shield 60C instead of the plate-shaped erosion shield 60A. The blade main body recess 44C has a shape into which the erosion shield 60C is fitted.

[0048] The erosion shield 60C is provided with an extended protrusion 50C. The shield extended protrusion 55C (55) constituting the extended protrusion 50C extends longer in the direction of the trailing edge 34 on the blade body pressure surface 42 side when viewed from the intersection of the camber line M and the leading edge 33 (the intersection corresponds to the reference symbol 33 in FIG. 3) compared to the shield extended protrusion 55A (see FIG. 3). This is because the erosion shield 60C is longer when comparing the erosion shields 60A and 60C present on the blade body pressure surface 42.

[0049] <How to modify the movable wing 30> A method for modifying the rotor blade 30 will be illustrated with reference to Figures 2, 7, and 8. Figure 7 is a schematic diagram showing the appearance of the rotor blade 30F (30) before modification according to one embodiment of the present disclosure. Figure 8 is a flowchart showing a method for modifying the rotor blade 30F according to one embodiment of the present disclosure. In this example, a method for modifying the rotor blade 30F to the rotor blade 30A is illustrated. In addition, in the following description, "step" may be abbreviated as "S".

[0050] As shown in Fig. 7, the rotor blade 30F is provided with a first erosion shield 110 instead of the erosion shield 60A. The first erosion shield 110 has the same configuration as the erosion shield 60A (60) except that the extended protrusion 50A (50) is not provided. The first erosion shield 110 is attached to the blade main body recess 44A.

[0051] As shown in FIG. 8, the method for modifying the rotor blade 30F includes a shield replacement step (S11) of replacing the first erosion shield 110 with the erosion shield 60A. In S11, the first erosion shield 110 is removed from the blade main body recess 44A. At this time, the silver solder that joins the first erosion shield 110 to the blade main body recess 44A is melted using a burner or the like, and the first erosion shield 110 is removed. Thereafter, the erosion shield 60A is attached to the blade main body recess 44A by silver solder welding in place of the first erosion shield 110. In this way, the rotor blade 30A (see FIG. 2) is produced, and the modification is completed. S11 can be performed by an operator, a robot arm, or a combination of these.

[0052] It is not necessary that the first erosion shield 110 and the erosion shield 60A are separate members. For example, the erosion shield 60A may be produced by joining the extending protrusion 50A to the detached first erosion shield 110.

[0053] <Summary> The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0054] 1) A steam turbine blade (30) according to at least one embodiment of the present disclosure comprises: A steam turbine blade (30) having a suction side (31), a pressure side (32), a leading edge (33), a trailing edge (34), a blade root (35), and a blade tip (36), a blade body (40) extending from the blade root to the blade tip; an erosion shield (60) attached to a blade body recess (44) extending in a blade height direction formed at least on a back surface (blade body back surface 41) side of the blade body, the erosion shield (60) having higher erosion resistance than the blade body and forming a part of the leading edge and a part of the back surface of the steam turbine blade; an extending protrusion (50) extending along a prescribed direction intersecting the blade height direction at least on the leading edge and the suction side surface formed by the erosion shield; Equipped with.

[0055] According to the above configuration 1), the water droplets on the suction side of the steam turbine rotor blade move toward the blade tip side and reach the extended convex portion. After that, the water droplets fly up from the extended convex portion and detach from the steam turbine rotor blade. Since the water droplets on the suction side can be prevented from hindering the rotation of the steam turbine rotor blade, the pumping loss of the steam turbine can be reduced. In addition, since the erosion shield attached to the blade body is replaceable, it is also possible to adjust the position of the extended convex portion. Since the extended convex portion can be arranged in a position that is favorable for reducing the pumping loss, the pumping loss is further reduced. In addition, according to the above configuration, the water droplets detach before reaching the blade tip, so that the water film detached from the rotor blade tip is split by the drag force from the gas phase and becomes coarse water droplets, which collide with the stationary part side. Erosion on the stationary part side caused by such coarse water droplets can also be avoided. As described above, a steam turbine rotor blade that reduces pumping loss and suppresses erosion can be obtained.

[0056] 2) In some embodiments, the steam turbine blade according to 1) above, The extending convex portion is located closer to the blade tip side than a midpoint (double-dotted chain line A) between the blade root and the blade tip in the blade height direction.

[0057] According to the above configuration 2), since the extended convex portion is located closer to the blade tip side than the intermediate position, the fine water droplets can detach from the steam turbine rotor blade and flow downstream in the turbine casing (9) before becoming a water film. This makes it possible to more reliably suppress erosion.

[0058] 3) In some embodiments, the steam turbine blade according to 1) or 2) above, The blade body recess is formed on each of the dorsal surface side and the pressure surface side of the blade body, The erosion shield further forms a portion of the ventral side surface that is connected to the portion of the dorsal side surface at the leading edge, The extending convex portion extends in the specified direction from the dorsal side surface across the front edge to the ventral side surface.

[0059] According to the above configuration 3), the water droplets moving on the suction side toward the blade tip and leading edge can be more reliably captured by the extended convex portion and thrown up, thereby more reliably realizing a reduction in pumping loss.

[0060] 4) In some embodiments, the steam turbine blade according to 3) above, The extending protrusion is One end (53) located on the rear side surface; The other end (54) located on the ventral side surface; Including, The other end is located between an end (shield pressure side end 69) of the erosion shield on the pressure side in the blade thickness direction of the steam turbine blade and the leading edge of the steam turbine blade.

[0061] Generally, the curvature of the surface of the steam turbine blade is relatively large near the leading edge of the steam turbine blade. In this regard, according to the configuration of 4) above, the length of the extended convex portion on the ventral surface side can be shortened, and the processing for forming the extended convex portion can be simplified. As a specific example, in an embodiment in which the extended convex portion is processed to be joined to the erosion shield, a problem such as peeling of the extended convex portion that is likely to occur on the surface of the erosion shield having a large curvature can be suppressed. As another specific example, in an embodiment in which the extended convex portion is formed by press processing, the processing step can be simplified by shortening the portion of the extended convex portion having a large curvature.

[0062] 5) In some embodiments, the steam turbine blade according to any one of 1) to 4) above, The extending protrusion includes one end (53) located on the back side surface, When a position on the suction side surface where a tangential direction is parallel to an axial direction of a turbine rotor (12) in a blade cross section (Ws) of the steam turbine blade perpendicular to the blade height direction and including the one end of the extended convex portion is defined as an outer end position (Po), In the blade cross section, the one end of the extending convex portion is located on the suction side surface closer to the trailing edge than the outer end position.

[0063] On the leading edge side of the outer end position in the blade cross section, the normal direction of the suction side surface faces the leading edge side. Therefore, when the steam turbine blade rotates, the force that moves the water droplets on the suction side surface tends to face the leading edge side as well as the blade tip side. In this regard, according to the configuration of 5) above, the extended convex portion extends to the trailing edge side of the outer end position, so that the water droplets moving toward the blade tip side and the leading edge side can be more reliably captured by the extended convex portion and thrown up. This more reliably achieves a reduction in pumping loss caused by water droplets generated in an area where erosion does not occur.

[0064] 6) In some embodiments, the steam turbine blade according to any one of 1) to 5) above, The extending protrusion includes one end (53) located on the back side surface, In a blade section (Ws) of the steam turbine blade perpendicular to the blade height direction including the one end of the extended convex portion, when a position where a virtual straight line (L) passing through a maximum camber position (Pc) on a camber line (M) of the steam turbine blade in a direction perpendicular to an axial direction of a turbine rotor (12) intersects with the suction side surface is defined as a first position (P1), In the blade cross section, the one end of the extended convex portion is located on the trailing edge side of the first position on the suction side surface.

[0065] According to the above-mentioned configuration 6), the extended convex portion can be made longer, so that the extended convex portion can more reliably capture water droplets moving toward the blade tip side and make them fly up, thereby more reliably realizing reduction in pumping loss and suppression of erosion.

[0066] 7) In some embodiments, the steam turbine blade according to any one of 1) to 6) above, The extending protrusion further includes a blade body extending protrusion (50) extending along the specified direction on the dorsal surface formed by the blade body.

[0067] According to the above configuration 7), the extended convex portion can be made longer, so that the water droplets can be more reliably caused to jump up from the steam turbine rotor blades, thereby more reliably realizing a reduction in pumping loss.

[0068] 8) In some embodiments, the steam turbine blade according to any one of 1) to 6) above, the erosion shield is a pressed product formed from a single sheet metal member, The extending protrusion is integrally formed with the erosion shield.

[0069] According to the above configuration 8), the configuration of the extended convex portion can be further simplified.

[0070] 9) In some embodiments, the steam turbine blade according to any one of 1) to 8) above, At least a portion of the extending protrusion is In a cross section (Z) of the erosion shield perpendicular to the extending direction of the extended convex portion, when the amount of protrusion of the extended convex portion from the erosion shield is defined as D, the cross section is configured so that 0.5 mm≦D≦3 mm holds.

[0071] According to the above configuration 9), by making D 0.5 mm or more, it is possible to form an R surface (37) having a sufficient radius on the side surface of the extended convex portion on the blade tip side and the side surface of the extended convex portion on the blade root side, and therefore it is possible to suppress stress concentration on these sides. In addition, by accumulating a water film on the blade root side of the convex portion, the centrifugal force acting on the water film increases, and the interface due to surface tension is broken, so that the water film can be separated as water droplets in terms of wettability. In addition, by making D 3 mm or less, it is possible to suppress the amount of protrusion of the extended convex portion from becoming excessive, and to suppress an excessive decrease in the rotation efficiency of the steam turbine rotor blade.

[0072] 10) In some embodiments, the steam turbine blade according to 9) above, At least a portion of the extending protrusion is In a cross section of the erosion shield perpendicular to the extension direction of the extended convex portion, when the dimension of the extended convex portion in the width direction perpendicular to the protruding direction of the extended convex portion is defined as W, the dimension of the extended convex portion is configured so that 1 mm≦W≦10 mm holds.

[0073] According to the above configuration 10), by making W 1 mm or more, it is possible to ensure the strength of the extending convex portion in the width direction. This makes it possible to avoid fatigue failure of the extending convex portion even if the phenomenon of water droplets with high peripheral speed colliding with the extending convex portion is repeated. In addition, by making W 10 mm or less, it is possible to prevent the extending convex portion from becoming excessively large, and to prevent an excessive decrease in the rotation efficiency of the steam turbine rotor blade.

[0074] 11) A method for retrofitting a steam turbine blade (30) according to at least one embodiment of the present disclosure, comprising: A method for modifying a steam turbine blade (30) having a suction side (31), a pressure side (32), a leading edge (33), a trailing edge (34), a blade root (35), and a blade tip (36), comprising the steps of: The steam turbine blade comprises: a blade body (40) extending from the blade root to the blade tip; a first erosion shield (60) attached to a blade body recess (44) extending in a blade height direction formed at least on a back surface (blade body back surface 41) side of the blade body, the first erosion shield (60) having higher erosion resistance than the blade body and forming a part of the leading edge and a part of the back surface of the steam turbine blade; Equipped with The modification method includes: The method includes a replacement step (S11) of removing the first erosion shield and attaching an erosion shield (110) to the blade body recess, the erosion shield having an extending protrusion (50) formed at least on the leading edge and the suction side surface, the extending protrusion (50) extending along a specified direction intersecting the blade height direction.

[0075] According to the configuration 11) above, the same technical advantages as those in 1) above can be obtained. [Explanation of symbols]

[0076] 1: Steam turbine 9: Main steam flow path 12: Turbine rotor 12C: Axis line 13:Rotor disc 16: Internal compartment 17: Diaphragm 18: Diaphragm outer ring 19: Diaphragm inner ring 20: Stator blade 30: Moving blade (steam turbine moving blade) 31: Dorsal side 32: Ventral aspect 33: Leading edge 34 : Trailing edge 35: Wing base 36: Wing tip 37 :R side 40: Wing body 41: Wing body back 42: Wing body ventral surface 44A: Blade body recess 44C: Blade body recess 50: Extended convex part 53: one end 54: Other end 55: Shield extension protrusion 56: Wing body extension convex part 60: Erosion Shield 61: Back of shield 62: Shield ventral surface 69: Ventral end of shield 110: First erosion shield A,B: Two-dot chain line L: Virtual line M: Camber line P1: 1st position Pc: Maximum camber position Po:Outer end position Ws: Wing cross section Z: Cross section

Claims

1. 1. A steam turbine blade comprising a suction side, a pressure side, a leading edge, a trailing edge, a root, and a tip, a blade body extending from the blade root to the blade tip; an erosion shield attached to a blade body recess formed on at least the suction side of the blade body and extending in a blade height direction, the erosion shield having higher erosion resistance than the blade body and forming a part of the leading edge and a part of the suction side of the steam turbine blade; an extending convex portion extending along a prescribed direction intersecting the blade height direction at least on the leading edge and the suction side surface formed by the erosion shield; Equipped Steam turbine blades.

2. The extending convex portion is located closer to the blade tip side than a middle position between the blade root and the blade tip in the blade height direction. The steam turbine blade of claim 1 .

3. The blade body recess is formed on each of the dorsal surface side and the pressure surface side of the blade body, The erosion shield further forms a portion of the ventral side surface that is connected to the portion of the dorsal side surface at the leading edge, The steam turbine blade according to claim 1 or 2, wherein the extending convex portion extends in the specified direction from the suction side surface to the pressure side surface across the leading edge.

4. The extending protrusion is One end located on the dorsal surface; The other end located on the ventral side surface; Including, The other end is located between an end of the erosion shield on a pressure surface side in a blade thickness direction of the steam turbine blade and the leading edge of the steam turbine blade. The steam turbine blade according to claim 3 .

5. The extending protrusion includes one end located on the back surface, When a position on the suction side surface where a tangential direction is parallel to an axial direction of a turbine rotor is defined as an outer end position in a blade cross section of the steam turbine blade perpendicular to the blade height direction and including the one end of the extended convex portion, In the airfoil cross section, the one end of the extending convex portion is located on the rear edge side of the outer end position on the suction side surface. The steam turbine blade according to claim 1 or 2.

6. The extending protrusion includes one end located on the back surface, When a position where a virtual straight line passing through a maximum camber position on a camber line of the steam turbine blade in a direction perpendicular to an axial direction of a turbine rotor intersects with the suction side surface in a blade cross section of the steam turbine blade perpendicular to the blade height direction and including the one end of the extended convex portion is defined as a first position, In the airfoil cross section, the one end of the extending convex portion is located on the rear edge side of the first position on the suction side. The steam turbine blade according to claim 1 or 2.

7. The extending protrusion further includes a blade body extending protrusion extending along the specified direction on the dorsal surface formed by the blade body. The steam turbine blade according to claim 1 or 2.

8. the erosion shield is a pressed product formed from a single sheet metal member, The extending protrusion is integrally formed with the erosion shield. The steam turbine blade according to claim 1 or 2.

9. At least a portion of the extending protrusion is In a cross section of the erosion shield perpendicular to the extending direction of the extending convex portion, when a protruding amount of the extending convex portion from the erosion shield is defined as D, 0.5 mm≦D≦3 mm is satisfied. The steam turbine blade according to claim 1 or 2.

10. At least a portion of the extending protrusion is In a cross section of the erosion shield perpendicular to the extending direction of the extending protrusion, when a dimension of the extending protrusion in a width direction perpendicular to the protruding direction of the extending protrusion is defined as W, 1 mm≦W≦10 mm is satisfied. The steam turbine blade of claim 9.

11. 1. A method for retrofitting a steam turbine blade having a suction side, a pressure side, a leading edge, a trailing edge, a root, and a tip, comprising the steps of: The steam turbine blade comprises: a blade body extending from the blade root to the blade tip; a first erosion shield attached to a blade body recess formed on at least the suction side of the blade body and extending in a blade height direction, the first erosion shield having higher erosion resistance than the blade body and forming a part of the leading edge and a part of the suction side of the steam turbine blade; Equipped with The remodeling method includes: A replacement step of removing the first erosion shield and attaching an erosion shield having an extending convex portion extending along a prescribed direction intersecting the blade height direction at least on the leading edge and the suction side surface to the blade main body concave portion is provided. A method for modifying steam turbine blades.

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