Shield member and turbine rotor blade

Abstract

To provide a shield member which can discharge drain in a turbine stage at an upstream side rather than a turbine stage of a final stage and can suppress corrosion of a rotor blade at the final stage, and a turbine rotor blade.SOLUTION: A shield member 10 has a rotor blade front edge part shape corresponding to a shape of a front edge lack part 60 in which a part of a front edge part of a rotor blade 40 is lacked over a blade tip 51, and is firmly adhered to the front edge lack part 60. The shield member 10 has: a front edge 11 extending in a longitudinal direction of the shield member 10; a back face 55 extending in a rear side of the shield member 10 from the front end face 11, and having a protrusive shape; a body face 13 extending in a rear side of the shield member 10 from the front edge 11, and having a recessive face; and a drain groove 14 formed at the back face 55 in the longitudinal direction of the shield member 10, extending up to a tip of the shield member 10 at one end, and discharging drain.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE An embodiment of the present invention relates to a shield member and a turbine blade. [Background technology]

[0002] One turbine stage in a steam turbine is composed of a stator vane row and a rotor blade row immediately downstream of the stator vane row. A steam turbine has multiple turbine stages in the axial direction of a turbine rotor. Here, the downstream side means the downstream side in the direction of the main flow of a working fluid in the central axial direction of the turbine rotor. The upstream side means the upstream side in the direction of the main flow of a working fluid in the central axial direction of the turbine rotor. The central axial direction of the turbine rotor will hereinafter be simply referred to as the axial direction.

[0003] Generally, in a turbine stage of a steam turbine, the temperature and pressure of steam decrease and the volume of steam expands as the stage progresses downstream. To introduce this expanded steam, the radial height of the steam passage in the turbine stage increases as the stage progresses downstream. As a result, the blade length of the turbine rotor blades increases as the stage progresses downstream. Furthermore, the centrifugal force acting on the turbine rotor blades during rotation increases as the stage progresses downstream. Note that the radial direction is the direction perpendicular to the central axis of the turbine rotor, with the central axis as the base point. Furthermore, hereinafter, turbine rotor blades will be referred to simply as rotor blades.

[0004] Steam flowing through the steam passage of a steam turbine becomes highly wet in the downstream turbine stages and contains a large amount of drainage. This drainage flows downstream as water droplets along with the main steam flow and turns into coarse water droplets. The coarse water droplets collide with the rotor blades rotating at high speed and erode the rotor blades. If the erosion of the rotor blades progresses, the rotor blades will be damaged.

[0005] In the conventional steam turbine rotor blades, the portion that is subject to erosion is made of cemented carbide to suppress erosion by drain. In addition, a rotor blade in which the leading edge of the rotor blade that is subject to erosion is made of cemented carbide and a drain groove is formed from the pressure side to the suction side of the leading edge is being considered. A part of this drain groove is formed in a direction perpendicular to the direction of the centrifugal force acting on the rotor blade when the rotor blade rotates.

[0006] These conventional rotor blades are configured to suppress erosion of the rotor blades themselves due to drainage. Therefore, in conventional steam turbines, the above-mentioned erosion suppression structure is mainly provided on the final stage rotor blades that are subject to erosion by drainage of coarse water droplets. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Utility Model Application Publication No. 60-39702 Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, the length of blades has increased the peripheral velocity, which has led to significant erosion caused by coarse water droplets. Therefore, it can be difficult to suppress erosion of the final stage blades using conventional erosion suppression techniques.

[0009] As described above, in conventional rotor blades, a part of the drain groove is formed in a direction perpendicular to the centrifugal force acting on the rotor blade. In such a rotor blade, if a microcrack occurs at the bottom of the drain groove, which is a stress concentration area due to erosion, the crack may grow due to centrifugal force, causing damage to the rotor blade.

[0010] In a steam turbine, the higher the wetness of the steam in the steam passage, the lower the enthalpy of the steam, and therefore the lower the internal efficiency. Therefore, when the drain contained in the steam is removed, the wetness of the steam decreases, the enthalpy of the steam increases, and the internal efficiency improves.

[0011] However, in conventional steam turbines, there has been no consideration of providing a drain groove for actively discharging drainage contained in steam in the rotor blades upstream of the last stage rotor blade. Therefore, it is not possible to improve the internal efficiency of the last stage turbine. In addition, in conventional steam turbines, the inflow of large water droplets into the last stage turbine stage is promoted.

[0012] The problem to be solved by the present invention is to provide a shield member and a turbine blade that can discharge drain in a turbine stage upstream of a final stage turbine stage and suppress erosion of the final stage blade. [Means for solving the problem]

[0013] A shield member according to an embodiment has a blade leading edge shape corresponding to a leading edge missing portion of a turbine blade in which a part of the leading edge of the turbine blade is missing from the blade tip, and is fixed to the leading edge missing portion. The shield member includes a shield leading edge extending in a longitudinal direction of the shield member, a shield back surface extending from the shield leading edge to a rear side of the shield member and having a convex surface, a shield ventral surface extending from the shield leading edge to the rear side of the shield member and having a concave surface, and a shield drain groove formed in the shield back surface in the longitudinal direction of the shield member, one end of which extends to a tip of the shield member for discharging drain. [Brief description of the drawings]

[0014] [Figure 1] 4 is a plan view showing a rear surface of an effective blade portion of a rotor blade to which a shield member according to an embodiment is fixed. FIG. [Diagram 2] 2 is a perspective view of a rotor blade having a leading edge notch to which a shield member of an embodiment is attached. FIG. [Diagram 3] FIG. 2 is a perspective view of a shield member according to an embodiment. [Figure 4] FIG. 2 is a perspective view of a rotor blade having a shield member fixed to a leading edge notched portion according to an embodiment. [Diagram 5] 1 shows a velocity triangle to explain the main flow of steam flowing from the stationary blades to the moving blades in a steam turbine. [Figure 6] 1 shows a velocity triangle to explain the flow of coarse water droplets from a stationary blade to a moving blade in a steam turbine. [Figure 7] FIG. 2 is a diagram showing a schematic view of the area where coarse water droplets collide at the inlet of a moving blade of a steam turbine. [Figure 8] 1 is a plan view of a blade having a shield member fixed to a leading edge notched portion according to an embodiment, as viewed from the blade tip. FIG. [Figure 9] FIG. 11 is a perspective view showing another configuration of a rotor blade to which a shield member according to an embodiment is fixed. [Figure 10] FIG. 11 is a plan view showing a rear surface of an effective blade portion in another configuration of a rotor blade to which a shield member according to an embodiment is fixed. [Figure 11] 11 is a cross-sectional view of the section AA in FIG. 10. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] Fig. 1 is a plan view showing the rear surface of the effective blade portion 50 of a rotor blade 40 to which a shielding member 10 of the embodiment is fixed. Fig. 2 is a perspective view of the rotor blade 40 having a leading edge notched portion 60 to which a shielding member 10 of the embodiment is fixed. Fig. 3 is a perspective view of the shielding member 10 of the embodiment. Fig. 4 is a perspective view of the rotor blade 40 to which a shielding member 10 of the embodiment is fixed to the leading edge notched portion 60. Figs. 2 and 4 show a part of the rotor blade 40 on the blade tip 51 side.

[0017] 1, the shield member 10 is fixed to a leading edge notch 60 formed in a part of the leading edge of a rotor blade 40 (turbine rotor blade). The shield member 10 is provided from a predetermined position on the leading edge of an effective blade portion 50 of the rotor blade 40 to a blade tip 51. The effective blade portion 50 is provided on the blade base end 52 side with a blade root portion (not shown) for attaching the rotor blade 40 to a turbine rotor.

[0018] First, the configuration of the rotor blade 40 having the leading edge notched portion 60 will be described.

[0019] As shown in Fig. 2, the rotor blade 40 includes a blade effective portion 50. The blade effective portion 50 includes a leading edge 53 and a trailing edge 54 extending in the height direction of the rotor blade. The leading edge 53 is located upstream in the steam flow direction, and the trailing edge 54 is located downstream in the steam flow direction. The blade effective portion 50 includes a back surface 55 forming a convex surface between the leading edge 53 and the trailing edge 54, and a pressure surface 56 opposing the back surface 55 and forming a concave surface. Thus, the blade effective portion 50 has an airfoil configuration including the leading edge 53, the trailing edge 54, the back surface 55, and the pressure surface 56.

[0020] As shown in FIG. 2, the leading edge of the blade effective portion 50 has a leading edge notch 60. The leading edge notch 60 is formed from a predetermined blade height position of the blade effective portion 50 to the blade tip 51. The leading edge notch 60 has an end face 61 on the trailing edge side and an end face 62 on the blade base side. The leading edge notch 60 is formed, for example, by cutting off a part of the leading edge of the blade effective portion 50 from a predetermined blade height position to the blade tip 51. Note that the leading edge notch 60 is not limited to being formed by cutting off the blade effective portion 50. For example, when the rotor blade 40 is formed by casting or the like, it may be formed to have the leading edge notch 60.

[0021] Here, as shown in Figures 1 and 2, an example is shown in which the end face 62 of the leading edge notch 60 is configured as a surface perpendicular to the blade height direction at a predetermined blade height position. Note that the configuration of the end face 62 is not limited to this configuration. The end face 62 of the leading edge notch 60 may be configured as an inclined surface that inclines toward the blade base end 52 toward the leading edge 53, for example. In this case, the inclined surface may be configured as, for example, a flat surface, or may be configured as a curved surface that is convex toward the blade base end 52.

[0022] Next, the configuration of the shield member 10 will be described.

[0023] 3, the shield member 10 has a blade leading edge shape that corresponds to the shape of the leading edge notch 60. By fixing the shield member 10 to the leading edge notch 60, the leading edge notch 60 is filled up, and the blade effective portion 50 has the original shape of the blade effective portion 50.

[0024] The shield member 10 includes a leading edge 11, a rear surface 12, a ventral surface 13, and a drain groove 14. The leading edge 11 functions as a shield leading edge, the rear surface 12 functions as a shield rear surface, the ventral surface 13 functions as a shield ventral surface, and the drain groove 14 functions as a shield drain groove.

[0025] Moreover, the shield member 10 has an end face 15 joined to an end face 61 of the leading edge notched portion 60, and an end face 16 joined to an end face 62 of the leading edge notched portion 60. Furthermore, the shield member 10 has an end face 17 at one end (tip) of the shield member 10. Note that, when the shield member 10 is fixed to the leading edge notched portion 60, the end face 17 constitutes the blade tip of the effective blade portion 50 together with the blade tip 51 of the effective blade portion 50. In this way, the shield member 10 has a cylindrical shape having the shape of the leading edge portion of the rotor blade.

[0026] The leading edge 11 constitutes an edge extending in the longitudinal direction of the shielding member 10. As shown in FIG. 4, when the shielding member 10 is fixed to the leading edge notch 60, the leading edge 11 extends in the height direction of the wing effective portion 50 (moving blade 40) and is continuous with the leading edge 53 of the wing effective portion 50. In other words, the leading edge 11 is configured to form an edge that smoothly continues with the leading edge 53 so as to form the original leading edge of the wing effective portion 50. Note that smoothly continuing means forming a continuous surface without any steps. As a result, the leading edge 11 and the leading edge 53 constitute the original leading edge of the wing effective portion 50. Note that the longitudinal direction of the shielding member 10 corresponds to the height direction of the wing effective portion 50 (moving blade 40) when the shielding member 10 is fixed to the leading edge notch 60.

[0027] The back surface 12 extends from the leading edge 11 to the end surface 15 side, which is the rear side of the shield member 10, and has a convex surface. As shown in FIG. 4, the back surface 12 extends from the leading edge 11 to the rear edge side of the wing effective portion 50 (moving blade 40) when the shield member 10 is fixed to the leading edge notch portion 60, and has a convex surface that continues to the back surface 55 of the wing effective portion 50. In other words, the back surface 12 is configured to form a convex surface that smoothly continues to the back surface 55 so as to form the original back surface of the wing effective portion 50. As a result, the back surface 12 and the back surface 55 form the original back surface of the wing effective portion 50. The rear side of the shield member 10 corresponds to the rear edge side of the wing effective portion 50 (moving blade 40) when the shield member 10 is fixed to the leading edge notch portion 60.

[0028] The pressure surface 13 extends from the leading edge 11 to the end surface 15 side, which is the rear side of the shield member 10, and has a concave surface. The pressure surface 13 is formed opposite the back surface 12. As shown in FIG. 4, when the shield member 10 is fixed to the leading edge notch 60, the pressure surface 13 extends from the leading edge 11 to the trailing edge side of the wing effective portion 50 (moving blade 40) and has a concave surface that continues to the pressure surface 56 of the wing effective portion 50. In other words, the pressure surface 13 is configured to form a concave surface that is smoothly continuous with the pressure surface 56 so as to form the original pressure surface of the wing effective portion 50. As a result, the pressure surface 13 and the pressure surface 56 form the original pressure surface of the wing effective portion 50.

[0029] The drain groove 14 is a groove for discharging water droplets (drainage) adhering to the rear surface 12 of the shield member 10. The drain groove 14 is formed in the rear surface 12 in the longitudinal direction of the shield member 10. As shown in FIG. 4, the drain groove 14 is formed in the rear surface 12 in the height direction of the effective blade portion 50 (moving blade 40) when the shield member 10 is fixed to the leading edge notch portion 60. The drain groove 14 is a concave groove formed in the rear surface 12. The cross-sectional shape of the drain groove 14 is not particularly limited. One end 14a (the end portion on the end surface 17 side) of the drain groove 14 is extended to the end surface 17, which is the tip of the shield member 10. That is, one end 14a of the drain groove 14 opens to the end surface 17.

[0030] Here, for example, in the rotor blade 40, when an integral cover is provided at the blade tip 51 of the blade effective portion 50, the integral cover is provided so as not to close one end 14a of the drain groove 14. For example, the integral cover is provided at the blade tip 51 of the blade effective portion 50 so as not to close one end 14a of the drain groove 14.

[0031] The other end 14b (the end on the end face 16 side) of the drain groove 14 extends, for example, to the end face 16. That is, here, an example is shown in which the other end 14b of the drain groove 14 opens to the end face 16.

[0032] The drain groove 14 is formed in the longitudinal direction of the shield member 10. The drain groove 14 is formed, for example, in the height direction of the effective blade portion 50 (moving blade 40). In other words, when the moving blade 40 is installed in a turbine rotor, the drain groove 14 is formed in the radial direction, which is a direction perpendicular to the central axial direction of the turbine rotor. The drain groove 14 is formed, for example, in a straight line.

[0033] Here, in the rotor blade 40, the chord length, which is the distance between the leading edge and the trailing edge, generally increases from the blade tip 51 to the blade base 52. In response to such a chord length, for example, the drain groove 14 may be formed so as to curve from the blade tip 51 to the blade base 52.

[0034] By forming the drain groove 14 in the above-mentioned direction, even if centrifugal force is generated by the rotation of the rotor blade 40, the centrifugal force is not applied in a direction perpendicular to the direction in which the drain groove 14 is formed. Therefore, even if a microcrack is generated in the bottom of the drain groove 14, the crack will not grow due to the centrifugal force. As a result, the effect of centrifugal force on the drain groove 14 is not an issue.

[0035] Here, an example in which three drain grooves 14 are provided is shown, but the present invention is not limited to this. It is sufficient that at least one drain groove 14 is provided. Two or four or more drain grooves 14 may be provided.

[0036] Shield member 10 is fixed to leading edge notch 60 by, for example, welding, as shown in Fig. 4. At this time, end face 15 is joined to end face 61 of leading edge notch 60, and end face 16 is joined to end face 62 of leading edge notch 60, as described above.

[0037] The shield member 10 is made of a material having excellent corrosion resistance. For example, the shield member 10 is made of a cemented carbide material. For example, the shield member 10 is made of Stellite (registered trademark).

[0038] Here, Fig. 5 shows a velocity triangle for explaining the main flow of steam flowing from the stator blade 80 to the rotor blade 90 in a steam turbine. Fig. 6 shows a velocity triangle for explaining the flow of coarse water droplets flowing from the stator blade 80 to the rotor blade 90 in a steam turbine. Fig. 7 is a schematic diagram showing the range where coarse water droplets collide at the inlet of the rotor blade 90 of the steam turbine.

[0039] As shown in Figure 5, the mainstream flow of steam is designed so that the relative inflow velocity W, determined by the absolute velocity C at the outlet of the stator blade 80 and the peripheral velocity U of the rotor blade 90, flows in in a direction that matches the inlet shape of the rotor blade 90.

[0040] On the other hand, since the mass of the coarse water droplets is large, the absolute velocity Ca of the coarse water droplets at the outlet of the stator blade 80 is smaller than the absolute velocity C of the main stream of steam, as shown in Fig. 6. Therefore, the direction of the inflow velocity Wa into the rotor blade 90 is the direction in which the coarse water droplets collide with the suction surface of the leading edge of the rotor blade 90, as shown in Fig. 7. In Fig. 7, the region on the suction surface of the leading edge where the coarse water droplets collide is indicated by a dashed line.

[0041] For example, geothermal steam turbine power generation is becoming more common as an effective use of renewable energy. In geothermal steam turbines, the steam tends to have a high degree of wetness. In addition, the circumferential speed of rotor blades has increased due to the recent trend toward longer turbine blades. For this reason, as shown in FIG. 7, even in rotor blades upstream of the final stage of a turbine stage, large water droplets collide with the back surface of the leading edge of the rotor blade 90.

[0042] Therefore, in the shield member 10 of this embodiment, as shown in Figure 4, the drain groove 14 is formed so that when the shield member 10 is fixed to the leading edge notched portion 60 of the rotor blade 40, the drain groove 14 is located on the back surface 12 of the leading edge portion of the blade effective portion 50 (rotor blade 40).

[0043] As a result, in a steam turbine equipped with the rotor blade 40 to which the shield member 10 is fixed, water droplets including coarse water droplets adhering to the back surface of the leading edge of the rotor blade flow into the drain groove 14. The water droplets that have flowed into the drain groove 14 flow radially outward through the drain groove 14 due to centrifugal force generated by the rotation of the rotor blade 40. The water droplets are then discharged from one end 14a of the drain groove 14 to the outside of the steam passage.

[0044] In this way, the rotor blade 40 equipped with the shield member 10 discharges coarse water droplets flowing through the steam passage to the outside via the drain groove 14, thereby preventing the collision of the coarse water droplets with the rotor blade in the final stage. In other words, the rotor blade 40 equipped with the shield member 10 prevents the rotor blade in the final stage from being eroded by the coarse water droplets. Therefore, the rotor blade 40 equipped with the shield member 10 of this embodiment is applied to a rotor blade upstream of the rotor blade 40 in the final stage. For example, the rotor blade 40 equipped with the shield member 10 is applied to a rotor blade one stage upstream of the rotor blade 40 in the final stage, or to a rotor blade one and two stages upstream of the rotor blade 40 in the final stage.

[0045] 8 is a plan view of the rotor blade 40 having the shield member 10 of the embodiment fixed to the leading edge notched portion 60, as viewed from the blade tip 51. The range in which the drain groove 14 is formed will be described with reference to FIG.

[0046] As shown in FIG. 8, the range along the back surface 12 from the leading edge 11 toward the trailing edge 54, in which the drain grooves 14 are formed on the back surface 12, is defined as a drain groove forming range A. The drain groove forming range A functions as a shield drain groove forming range. The drain grooves 14 are formed within this drain groove forming range A. Even in the case where multiple drain grooves 14 are provided, all of the drain grooves 14 are formed within the drain groove forming range A. The drain groove forming range A shown in FIG. 8 is a range along the back surface 12 at a position where the blade height of the rotor blades 40 is the same.

[0047] 8, the length from the leading edge 11 to the trailing edge 54 along the rear surface 12, 55 is denoted as L. The drain groove forming range A is preferably within a range between the leading edge 11 and a position that is 15% of the length L from the leading edge 11 toward the trailing edge 54. In other words, the drain groove forming range A is preferably located between the leading edge 11 and a position that is 0.15L from the leading edge 11 along the rear surface 12. Furthermore, it is more preferable that the drain groove forming range A is located between a position that is 0.03L from the leading edge 11 along the rear surface 12 and a position that is 0.12L from the leading edge 11 along the rear surface 12.

[0048] As described above, even when the drain groove 14 is formed in a straight line or when the drain groove 14 is formed to curve from the blade tip 51 to the blade base 52, the drain groove formation range A is located in the above-mentioned range at each blade height of the rotor blade 40, regardless of any deviation.

[0049] Here, the shield member 10 is designed to include a drain groove forming area A on the back surface 12 of the shield member 10. This allows the shield member 10, which is made of a material with excellent corrosion resistance, to collide with coarse water droplets and to collect and discharge the coarse water droplets.

[0050] The shield member 10 is provided from a predetermined position on the leading edge of the effective blade portion 50 of the rotor blade 40 to the blade tip 51. This predetermined position corresponds to the position of the end face 62 of the leading edge notched portion 60. In the rotor blade 40 equipped with the shield member 10, this predetermined position also corresponds to the end face 16 of the shield member 10.

[0051] 1, the blade height of the effective blade portion 50 of the rotor blade 40 is defined as H1. Also, the height in the blade height direction from the blade tip 51 of the effective blade portion 50 to the end face 62 of the leading edge notched portion 60, in other words, the height in the blade height direction from the end face 17 of the shield member 10 to the end face 16 of the shield member 10, is defined as H2.

[0052] Here, the height H2 is preferably 10 to 50% of the blade height H1. That is, the height H2 is preferably 0.1H1 to 0.5H1. Furthermore, the height H2 is more preferably 0.15H1 to 0.35H1.

[0053] Here, for example, if end face 62 of leading edge notched portion 60 is configured as an inclined surface that inclines toward blade base end 52 toward leading edge 53, end face 16 of shield member 10 will have a shape that corresponds to the shape of end face 62 of leading edge notched portion 60. In this case, the height in the blade height direction from end face 17 of shield member 10 to end face 16 of shield member 10 increases toward leading edge 11. When such end face 62 is configured as an inclined surface, the height H2 described above applies to the height in the blade height direction at leading edge 11, where the height in the blade height direction is the highest.

[0054] The above-mentioned drain groove formation range A and height H2 range are regions where a large amount of coarse water droplets adhere when the steam turbine is operated. This range is also a region where the large amount of adhered coarse water droplets flow radially outward due to centrifugal force generated by the rotation of the rotor blades 40. Therefore, by forming the drain grooves 14 in these ranges of the back surface 12, the large amount of adhered coarse water droplets can be discharged radially outward of the steam passage through the drain grooves 14.

[0055] As described above, the shield member 10 of the embodiment is fixed to the leading edge notched portion 60 of the rotor blade 40 to form the rotor blade leading edge portion that collides with a large amount of water droplets including coarse water droplets. By providing the drain grooves 14 on the back surface 12 of the shield member 10 that collides with a large amount of coarse water droplets, it is possible to discharge the large amount of coarse water droplets that adhere to the back surface 12 radially outward of the steam passage.

[0056] By removing a large amount of coarse water droplets from the steam passage, it is possible to improve the internal efficiency of turbine stages downstream of the turbine stage having the rotor blades 40 equipped with this shield member 10. Furthermore, it is possible to suppress erosion of the rotor blades of the downstream turbine stages due to coarse water droplets. Furthermore, collision of coarse water droplets with the rotor blades of the final stage is suppressed, and erosion of the rotor blades of the final stage due to coarse water droplets is suppressed.

[0057] (Other embodiments) Fig. 9 is a perspective view showing another configuration of the rotor blade 40 to which the shield member 10 of the embodiment is fixed. Fig. 10 is a plan view showing the back surface of the effective blade portion 50 in another configuration of the rotor blade 40 to which the shield member 10 of the embodiment is fixed. Fig. 11 is a view showing the AA cross section of Fig. 10. In the other embodiments, the same components as those in the above-mentioned embodiment are given the same reference numerals, and duplicated explanations will be omitted or simplified.

[0058] In other embodiments, the back surface 55 of the blade effective portion 50 is also provided with a drain groove 100. The other configurations are the same as those of the rotor blade 40 to which the shield member 10 is fixed in the above-mentioned embodiment. Therefore, the configuration of the drain groove 100 will be mainly described here.

[0059] 9 and 10, a drain groove 100 communicating with the drain groove 14 of the shield member 10 is formed on the back surface 55 of the blade effective portion 50 (rotor blade 40). The drain groove 100 functions as a rotor blade drain groove. Like the drain groove 14, the drain groove 100 is formed so as to be located on the back surface 55 of the leading edge portion of the blade effective portion 50 (rotor blade 40).

[0060] The drain grooves 100 are provided corresponding to the drain grooves 14 formed in the shield member 10. For example, when three drain grooves 14 are formed, three drain grooves 100 corresponding to the respective drain grooves 14 are formed.

[0061] The drain groove 100 is formed in the back surface 55 in the height direction of the blade effective portion 50 (rotor blade 40). The drain groove 100 is a concave groove, similar to the drain groove 14. The cross-sectional shape of the drain groove 100 is not particularly limited. One end 100a (the end on the leading edge notch 60 side) of the drain groove 100 extends to the end face 62 of the leading edge notch 60. In other words, the one end 100a of the drain groove 100 opens to the end face 62. The one end 100a of the drain groove 100 is connected to the other end 14b of the drain groove 14 to form a drain groove that is continuous in the height direction of the blade effective portion 50.

[0062] As shown in FIG. 10, the height in the blade height direction from the end face 17 of the shield member 10 to the end face 16 of the shield member 10 is H2, and the height in the blade height direction of the drain groove 100 is H3. The height H2 plus the height H3 is H4. In the shield member 10 shown in FIG. 10, the height H2 in the blade height direction from the end face 17 of the shield member 10 to the end face 16 of the shield member 10 corresponds to the height in the blade height direction of the drain groove 14. The height H3 is the height in the blade height direction from one end 100a of the drain groove 100 to the other end 100b of the drain groove 100 in the blade height direction. That is, the height H4 is the height obtained by adding the height in the blade height direction of the drain groove 14 and the height in the blade height direction of the drain groove 100.

[0063] Here, the height H4 is preferably 15 to 80% of the blade height H1. That is, the height H4 is preferably 0.15H1 to 0.8H1. The height H4 is more preferably 0.35H1 to 0.8H1. In addition, in any range of the height H4, as described above, the height H2 is preferably 0.1H1 to 0.5H1. The height H2 is more preferably 0.15H1 to 0.35H1. For example, when the height H4 is 0.15H1 to 0.8H1, the height H2 is preferably 0.1H1 to 0.5H1. In addition, when the height H4 is 0.35H1 to 0.8H1, the height H2 is more preferably 0.15H1 to 0.35H1.

[0064] Height H3 is set based on height H4 and height H2. That is, height H3 is set to a height obtained by subtracting height H2 from height H4. The region to which coarse water droplets adhere varies depending on the turbine stage to which rotor blade 40 is provided. Therefore, heights H2, H3, and H4 are set based on the range in the blade height direction of rotor blade 40 to which coarse water droplets adhere depending on the turbine stage to which rotor blade 40 is provided.

[0065] Heights H2, H3 and H4 are set, for example, as follows. Height H4 is set based on the range in the blade height direction of the rotor blade 40 to which coarse water droplets adhere. It is preferable to provide a shield member 10 in an area where a large amount of coarse water droplets adhere, even within this set range of height H4. Height H2 is then set based on the range in the blade height direction to which a large amount of coarse water droplets adhere, within the range of height H4. Height H3 is then set by subtracting height H2 from height H4.

[0066] For example, in the rotor blade 40, if the height H4 at which coarse water droplets adhere is in the range of 0.8H1, and the height H2 at which the inner shield member 10 having the height H4 is provided is in the range of 0.5H1, the height H3 is 0.3H1, which is the value (height) obtained by subtracting the height H2 from the height H4. In this manner, the height H4 and the height H2 are appropriately set within the above-mentioned range according to the turbine stage at which the rotor blade 40 is provided. Then, the height H3 is set based on the set height H4 and height H2.

[0067] 11, a range along the back surface 55 from the leading edge 53 to the trailing edge 54, in which the drain groove 100 is formed on the back surface 55, is defined as a drain groove forming range A1. The drain groove forming range A1 functions as a blade drain groove forming range. The drain groove 100 is formed within the drain groove forming range A1, similar to the drain groove 14. The drain groove forming range A1 shown in FIG. 11 is a range along the back surface 55 at a position where the blade height of the blade 40 is the same.

[0068] 11, the length from the leading edge 53 to the trailing edge 54 along the back surface 55 is defined as L1. The drain groove forming range A1 is preferably within a range between the leading edge 53 and a position that is 15% of the length L1 from the leading edge 53 toward the trailing edge 54. That is, the drain groove forming range A1 is preferably located between the leading edge 53 and a position that is 0.15L from the leading edge 53 along the back surface 55. Furthermore, the drain groove forming range A1 is more preferably located between a position that is 0.03L1 from the leading edge 53 along the back surface 55 and a position that is 0.12L1 from the leading edge 53 along the back surface 55.

[0069] As described above, even when the drain groove 100 is formed in a straight line or when the drain groove 100 is formed curved from one end 100a to the other end 100b, the drain groove formation range A1 is located within the above-mentioned range at each blade height of the rotor blade 40.

[0070] By forming the drain groove 100 in the above-mentioned direction, even if centrifugal force is generated by the rotation of the rotor blade 40, the centrifugal force is not applied in a direction perpendicular to the direction in which the drain groove 100 is formed. Therefore, even if a microcrack is generated in the bottom of the drain groove 100, the crack will not grow due to the centrifugal force. As a result, the effect of centrifugal force on the drain groove 100 is not an issue.

[0071] The drain groove formation range A1 and the range of height H4 described above are areas where coarse water droplets adhere when the steam turbine is operated. This range is also an area where the adhered coarse water droplets flow radially outward due to centrifugal force generated by the rotation of the rotor blades 40. The range of height H3 is an area where coarse water droplets may adhere, although the amount of the adhered coarse water droplets is smaller than that of the range where the shield member 10 is provided. Therefore, by forming the drain groove 100 in the range of the drain groove formation range A1 and the range of height H3 on the back surface 55, the adhered coarse water droplets can be discharged radially outward of the steam passage through the drain groove 100 and the drain groove 14.

[0072] As described above, in the other embodiments, the effects of providing the drain groove 14 on the rear surface 12 of the shield member 10 are the same as those described above.

[0073] In another embodiment, a drain groove 100 is provided on the back surface 55 of the blade effective portion 50, so that large water droplets adhering to the blade base end 52 side rather than the area where the shield member 10 is provided can be discharged radially outward of the steam passage.

[0074] According to the embodiment described above, it is possible to discharge drain in a turbine stage upstream of the final turbine stage, and to suppress erosion of the rotor blades in the final stage.

[0075] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0076] 10...shield member, 11, 53...leading edge, 12, 55...rear surface, 13, 56...ventral surface, 14, 100...drain groove, 14a, 100a...one end, 14b, 100b...other end, 15, 16, 17, 61, 62...end surface, 40, 90...moving blade, 50...effective blade portion, 51...blade tip, 52...blade base, 54...trailing edge, 60...leading edge missing portion, 80...stationary blade, A, A1...drain groove forming area.

Claims

1. A shield member having a rotor blade leading edge shape corresponding to a leading edge missing portion in which a part of a leading edge of a turbine rotor blade is missing over a blade tip, the shield member being fixed to the leading edge missing portion, a shield leading edge extending in a longitudinal direction of the shield member; a shield rear surface extending from the shield front edge toward the rear side of the shield member and having a convex surface; a shield ventral surface extending from the shield front edge toward the rear side of the shield member and having a concave surface; a shield drain groove for discharging drain, the shield drain groove being formed on the rear surface of the shield in the longitudinal direction of the shield member and having one end extending to the tip of the shield member; A shield member comprising:

2. 2. The shield member of claim 1, wherein the shield member is made of a cemented carbide material.

3. an effective wing portion including a leading edge, a trailing edge, a back surface forming a convex surface between the leading edge and the trailing edge, and a pressure surface forming a concave surface between the leading edge and the trailing edge, the effective wing portion having a leading edge missing portion in which a part of the leading edge portion is missing over a wing tip; The shield member according to claim 1 or 2, which is fixed to the front edge notch portion. Equipped with The shield leading edge extends in a wing height direction of the wing effective portion and is continuous with the leading edge of the wing effective portion, The shield back surface extends from the shield leading edge toward the trailing edge side of the wing effective portion and is continuous with the back surface of the wing effective portion, The shield ventral surface extends from the shield leading edge toward the trailing edge side of the wing effective portion and is continuous with the ventral surface of the wing effective portion, 2. A turbine rotor blade, comprising: a shield drain groove formed on a rear surface of the shield in a blade height direction of the effective blade portion.

4. The shield drain groove is formed in a shield drain groove forming area of ​​the rear surface of the shield, When the length from the leading edge of the shield to the trailing edge of the wing effective portion along the rear surface of the shield and the rear surface of the wing effective portion is L, 4. The turbine blade according to claim 3, wherein the shield drain groove forming area is within a range between the leading edge of the shield and a position 15% of a length L from the leading edge of the shield toward the trailing edge of the blade effective portion.

5. When the wing height of the effective wing portion is H1 and the height of the shield member in the wing height direction is H2, 4. The turbine blade according to claim 3, wherein the height H2 is 10 to 50% of the blade height H1.

6. 4. The turbine rotor blade according to claim 3, wherein a rotor blade drain groove communicating with said shield drain groove is formed on said back surface of said blade effective portion.

7. the rotor blade drain groove is formed in a rotor blade drain groove forming range of the back surface of the blade effective portion, When the length from the leading edge of the wing effective portion to the trailing edge of the wing effective portion along the back surface of the wing effective portion is L1, 7. The turbine blade according to claim 6, wherein the blade drain groove forming range is within a range between the leading edge of the blade effective portion and a position 15% of a length L1 from the leading edge of the blade effective portion toward the trailing edge of the blade effective portion.

8. When the blade height of the effective blade portion is H1, the height of the shield member in the blade height direction is H2, the height of the rotor blade drain groove in the blade height direction is H3, and the sum of the heights H2 and H3 is H4, The height H4 is 15 to 80% of the wing height H1, 7. The turbine rotor blade according to claim 6, wherein the height H2 is 10 to 50% of the blade height H1.

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