Steam turbine blade and steam turbine

Abstract

To enable suppression of erosion and braking loss due to water droplets detached from a blade surface on a back side of a steam turbine blade.SOLUTION: A steam turbine blade includes a blade-shaped part and is used for a steam turbine. The blade-shaped part includes a groove that is provided within a range from a leading edge of a back-side blade surface to a first position on the back-side blade surface which corresponds to a maximum camber position.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a steam turbine blade and a steam turbine. [Background technology]

[0002] Steam passing through a steam turbine loses energy as it travels from upstream to downstream, resulting in a drop in temperature and pressure. As a result, in the downstream stages of the steam turbine, some of the steam condenses into tiny water droplets that exist in the airflow. Some of these droplets adhere to the surface of the turbine stator blades and grow on the blade surface to form a liquid film. As this liquid film grows further and thickens, some of it is torn off by the steam flow and scattered as coarse droplets. When these scattered droplets collide with the turbine rotor blades downstream, they impede the rotation of the turbine rotor blades, causing braking loss and causing erosion.

[0003] For this reason, for example, a minute slit is formed in the blade surface of a hollow stator vane, connecting the internal space inside the stator vane with the outside of the stator vane, and water (liquid phase) adhering to the surface of the stator vane is sucked into the internal space through this slit by a pressure difference, thereby suppressing the scattering of water droplets (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-181773 Summary of the Invention [Problem to be solved by the invention]

[0005] When slits such as those described in Patent Document 1 are provided on both the pressure side and the suction side of the stator blade, if the pressure at the suction side and the pressure side are not equal, water droplets sucked into the internal space of the stator blade through the pressure side slit will spray out from the suction side slit. For this reason, slits are often provided only on the pressure side of the stator blade. On the other hand, if no slits are provided on the suction side of the stator blade, the liquid film (water film) that grows on the suction side blade surface will reach the trailing edge of the stator blade, and the water droplets that detach from there will collide with the rotor blade, causing erosion and braking loss.

[0006] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a steam turbine blade and a steam turbine that can suppress erosion and braking loss caused by water droplets detached from the suction side blade surface of the steam turbine blade. [Means for solving the problem]

[0007] In order to solve the above problems, a steam turbine blade according to at least one embodiment of the present disclosure comprises: A steam turbine blade for use in a steam turbine, comprising: an airfoil portion; The airfoil has a groove disposed on the suction surface from the leading edge to a first location on the suction surface corresponding to a maximum camber position.

[0008] In order to solve the above problem, a steam turbine according to at least one embodiment of the present disclosure includes: A steam turbine blade according to at least one embodiment of the present disclosure is provided. [Effects of the Invention]

[0009] According to at least one embodiment of the present disclosure, it is possible to provide a steam turbine blade and a steam turbine that can suppress erosion and braking loss caused by water droplets detached from the blade surface on the suction side of the steam turbine blade. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic cross-sectional view of a steam turbine taken along an axial direction according to an embodiment of the present disclosure; [Figure 2] FIG. 2 is a diagram showing a plurality of stator vanes arranged at intervals in the circumferential direction in FIG. 1, spread out in the circumferential direction together with a plurality of rotor blades arranged downstream in the axial direction. [Figure 3] 3 is a diagram showing the external shape of the cross section of the airfoil portion of the stator vane of FIG. 2 as viewed from the blade height direction. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the vicinity of the groove in FIG. 3. [Figure 5] This is a modified example of FIG. [Figure 6] FIG. 10 is a diagram showing the relationship between the absolute velocity of a water droplet detached from the groove position and the relative velocity of the water droplet with respect to the rotor blade. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the configurations described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0012] First, the overall configuration of a steam turbine 1 according to at least one embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view taken along the axial direction of a steam turbine 1 according to one embodiment of the present disclosure.

[0013] The steam turbine 1 includes a rotor 2 supported by bearings 6 for rotation about a central axis O, multiple stages of moving blades 8 attached to the rotor 2, an inner casing 10 that houses the rotor 2 and the moving blades 8, and multiple stages of stator blades 9 attached to the inner casing 10 so as to face the moving blades 8. An outer casing 12 is provided outside the inner casing 10. In this steam turbine 1, when steam is introduced into the inner casing 10 from the steam inlet 3, the steam expands and accelerates as it passes through the stator blades 9, and does work on the moving blades 8 to rotate the rotor 2.

[0014] The steam turbine 1 also includes an exhaust chamber 14. The exhaust chamber 14 is located downstream of the rotor blades 8 and the stator blades 9. Steam (steam flow) that has passed through the rotor blades 8 and the stator blades 9 inside the inner casing 10 flows into the exhaust chamber 14 from an exhaust chamber inlet 11, passes through the inside of the exhaust chamber 14, and is discharged to the outside of the steam turbine 1 from an exhaust chamber outlet 13 provided on the lower side of the exhaust chamber 14. In some embodiments, a condenser (not shown) is provided below the exhaust chamber 14. In this case, the steam that has finished working on the rotor blades 8 in the steam turbine 1 flows from the exhaust chamber 14 to the condenser via the exhaust chamber outlet 13.

[0015] The stator blades 9 arranged in each stage are arranged at intervals in the circumferential direction centered on the central axis O. Each stator blade 9 has an airfoil portion 101 extending in the blade height direction, i.e., in the radial direction centered on the central axis O.

[0016] In the following description, the circumferential direction centered on the central axis O will be referred to as the "circumferential direction" as appropriate, the radial direction centered on the central axis O will be referred to as the "radial direction" as appropriate, and the axial direction centered on the central axis O will be referred to as the "axial direction" as appropriate.

[0017] Next, the configuration of the airfoil portion 101 of each stator vane 9 will be described with reference to Figures 2 and 3. Figure 2 is a diagram showing the multiple stator vanes 9 arranged at intervals in the circumferential direction in Figure 1, expanded in the circumferential direction together with the multiple rotor blades 8 arranged downstream in the axial direction, and Figure 3 is a diagram showing the external shape of the airfoil portion 101 of the stator vane 9 in Figure 2 in cross section as seen from the blade height direction.

[0018] 3 also illustrates the chord line and camber of the airfoil portion 101 for the purpose of explaining each part, which will be described later. In the following description, unless otherwise specified, the stator blade 9 is the stator blade 9 at the downstream stage among multiple stages of stator blades 9.

[0019] The stator blade 9 has an airfoil portion 101. The airfoil portion 101 has a suction surface 103 and a pressure surface 104.

[0020] As described above, the liquid film (water film) grown on the suction blade surface 103 separates from the suction blade surface 103 as water droplets and collides with the rotor blade 8 arranged downstream of the stator blade 9, which can cause erosion and braking loss in the rotor blade 8. In order to suppress such erosion and braking loss, the stator blade 9 has the following configuration.

[0021] The airfoil portion 101 of the stator vane 9 has a groove 114 formed in a concave shape on the suction side blade surface 103. The suction side blade surface 103 has a convex shape when viewed in the blade height direction (radial direction). Therefore, by providing the groove 114 on the suction side blade surface 103, when a liquid film (water film) that has grown on the suction side blade surface 103 reaches the groove 114 from the leading edge 105 side, the groove 114 makes it easier for the liquid film to separate from the suction side blade surface 103.

[0022] 4 is an enlarged cross-sectional view of the vicinity of the groove 114 in FIG. 3. The groove 114 is formed concavely with respect to the outer surface of the suction blade surface 103. Specifically, the leading edge side end 114a thereof is composed of an outer surface 114a1 adjacent to the leading edge 105 and an inner surface 114a2 adjacent to the outer surface 114a1. In particular, the angle θ formed by the outer surface 114a1 and the inner surface 114a2 constituting the leading edge side end 114a is configured to be an acute angle (i.e., less than 90 degrees). This makes it easier for the water film adhering to the suction blade surface 103 to detach when it reaches the groove 114.

[0023] The airfoil portion 101 is formed by forming grooves 114 in plate material by machining using a drill, cutter, or the like, and then molding the formed material with sheet metal. The airfoil portion 101 configured in this manner has a hollow space 116 inside, and the grooves 114 are not connected to the hollow space 116. In other words, the depth of the grooves 114 is less than the thickness of the plate material constituting the airfoil portion 101. This prevents water from being sucked into the inner hollow space 116 from the suction side blade surface 103 through the grooves 114, and allows the water film to be efficiently removed from the suction side blade surface 103 by the grooves 114.

[0024] The depth of the groove 114 formed in the plate material constituting the airfoil portion 101 may or may not be constant. The groove 114 may have a bottom 115 that includes an R-shape. In the configuration example shown in FIG. 4, a pair of corners 115a, 115b with an approximately 90-degree angle are provided at both ends of the bottom 115 of the groove 114 that is located on the hollow space 116 side. However, as shown in the modified example in FIG. 5, the angles of these corners 115a, 115b may be R-shaped (curved in cross section). In this case, vortices are less likely to form at the bottom 115, and as a result, the size of the vortices generated in most of the hollow space 116 is stabilized. This reduces the randomness of water droplets scattering outward from the groove 114, making it easier to control the scattering of water droplets into the mainstream.

[0025] The grooves 114 are configured to extend along the blade length direction (blade height direction) on the suction blade surface 103. This allows the water film to be suitably separated from the suction blade surface 103 over a wide range of the airfoil portion 101.

[0026] Furthermore, the grooves 114 may be provided over the entire area in the blade height direction on the suction blade surface 103 of the stator blade 9, or may be provided over a partial area in the blade height direction. In one embodiment, the grooves 114 are provided over at least a portion of the range from the mid-span position of the airfoil portion 101 to the tip (tip of the blade). Water droplets that cause erosion are likely to be caused by a water film that detaches from the area on the suction blade surface 103 from the mid-span position of the airfoil portion 101 to the tip. Therefore, by providing the grooves 114 over at least a portion of that range on the airfoil portion 101, the occurrence of erosion can be effectively prevented.

[0027] The groove 114 having the above configuration is provided within a range from the leading edge 105 of the suction surface 103 of the airfoil portion 101 to a first position P1 on the suction surface 103 corresponding to the maximum camber position Pcmax. The maximum camber position Pcmax is the position where the camber height (maximum camber Cmax) relative to the chord line is maximum.

[0028] By having the grooves 114 in the range from the leading edge 105 to the first position P1 in this way, the position (detachment position) at which the water film adhering to the suction side blade surface 103 detaches from the suction side blade surface 103 can be brought closer to the leading edge 105, compared to when the grooves 114 are located closer to the trailing edge 106 than the first position P1. Therefore, compared to when the grooves 114 are located closer to the trailing edge 106 than the first position P1, the distance from the detachment position of the water film to the rotor blade 8 located downstream of the stator blade 9, i.e., the travel distance of the detached water droplets, can be ensured to be longer.

[0029] The size of the water droplets that reach the rotor blade 8 depends on the distance traveled from the detachment position to the rotor blade 8. Specifically, the longer the travel distance, the more the water droplets become atomized. This is because the longer the liquid phase is exposed to a high-speed airflow environment, the more atomized it becomes due to the gas-liquid shear force. Therefore, by increasing the travel distance from the detachment position to the rotor blade 8 located downstream of the stator blade 9 compared to when the groove 114 is located closer to the trailing edge 106 than the first position P1, the size of the water droplets that reach the rotor blade 8 can be reduced, and erosion and braking loss caused by water droplets detached from the suction blade surface 103 of the stator blade 9 can be effectively suppressed.

[0030] 6 is a diagram showing the relationship between the absolute velocity of water droplets detached from the position of the groove 114 and the relative velocity of the water droplets with respect to the rotor blade 8. FIG. 6 shows a vector V1 corresponding to the absolute velocity cd of water droplets released from the stator blade 9 when the groove 114 is located closer to the trailing edge 106 than the first position P1, and a vector V2 corresponding to the absolute velocity cd' of water droplets released from the stator blade 9 when the groove 114 is located in the range from the leading edge 105 to the first position P1. As described above, when the groove 114 is located in the range from the leading edge 105 to the first position P1, the size of the detached water droplets is smaller than when the groove 114 is located closer to the trailing edge 106 than the first position P1. Therefore, the absolute velocity cd' corresponding to the vector V2 is greater than the absolute velocity cd corresponding to the vector V1.

[0031] 6 shows a vector V4 corresponding to the airflow (flow velocity cg) flowing from the upstream side to the downstream side. Furthermore, since the water droplets detached from the suction blade surface 103 are rectified by the airflow toward the rotor blade 8 regardless of the position of the groove 114, vectors V1 and V2 are shown to be approximately parallel in FIG.

[0032] Vector V1', which corresponds to the relative velocity wd of the water droplets detached from the stator vane 9 with respect to the rotor blade 8, is calculated as a resultant vector of the above-mentioned vector V1 and vector V3, which corresponds to the rotational speed u of the rotor blade 8 along the circumferential direction. Vector V2', which corresponds to the relative velocity wd' of the water droplets detached from the stator vane 9 with respect to the rotor blade 8, is calculated as a resultant vector of the above-mentioned vector V2 and vector V3, which corresponds to the rotational speed u of the rotor blade 8. Comparing the vectors V1' and V2' calculated in this manner, vector V2' has a smaller circumferential component, which is a cause of erosion and braking loss, than vector V1'. From this perspective, it is also shown that when the groove 114 is located in the range from the leading edge 105 to the first position P1, erosion and braking loss can be more effectively suppressed than when the groove 114 is located closer to the trailing edge 106 than the first position P1.

[0033] 3, the groove 114 may be located between a position spaced apart in the chord direction from the second position P2 on the suction side blade surface 103 corresponding to the maximum blade thickness position Ptmax where the blade thickness of the airfoil portion 101 becomes the maximum blade thickness Tmax by 10% (0.1Lc) of the chord length Lc of the airfoil portion 101 toward the leading edge 105, and a position spaced apart in the chord direction from the second position P2 by 10% (0.1Lc) of the chord length toward the trailing edge 106. By providing the groove 114 within the above-mentioned range (±0.1Lc) centered on the second position P2 in this way, the water film becomes more easily detached and the travel distance of the detached water droplets can be secured to be large, thereby more suitably reducing erosion and braking loss.

[0034] The groove 114 may be located closer to the trailing edge 106 than the point of contact TP between the suction blade surface 103 and an imaginary straight line Lv that is a tangent to the suction blade surface 103 and extends in the axial direction.

[0035] The airflow flowing from the upstream side of the stator vane 9 toward the stator vane 9 flows in at an angle close to the pressure side blade surface 104 of the stator vane 9. Therefore, the water film adhering to the suction side blade surface 103 is likely to detach from the suction side blade surface 103 in a region closer to the trailing edge 106 than the contact point TP. Therefore, by setting the groove 114 closer to the trailing edge 106 than the contact point TP, the water film adhering to the suction side blade surface 103 is more likely to detach from the suction side blade surface 103 in a region closer to the trailing edge 106 than the contact point TP.

[0036] 3, the airfoil portion 101 may be formed with slits 107 for recovering liquid water on the pressure-side blade surface 104. This makes it possible to suppress erosion and braking loss caused by water droplets detached from the pressure-side blade surface 104.

[0037] The contents described in each of the above embodiments can be understood, for example, as follows.

[0038] (1) A steam turbine blade according to at least one embodiment of the present disclosure includes: A steam turbine blade for use in a steam turbine, comprising: an airfoil portion; The airfoil has a groove disposed on the suction surface from the leading edge to a first location on the suction surface corresponding to a maximum camber position.

[0039] According to the above aspect (1), at least one aspect of the present disclosure provides a steam turbine blade including an airfoil portion for use in a steam turbine. The airfoil portion has a groove on a suction surface. The groove is provided so that at least a portion of the groove is included within a range from a leading edge of the suction surface to a first position on the suction surface corresponding to a maximum camber position.

[0040] The suction surface of a steam turbine blade has a convex shape when viewed from the blade height direction. By providing the grooves, water arriving from the leading edge of the suction surface can easily separate and scatter from the suction surface. The grooves are provided within a range from the leading edge to a first position on the suction surface corresponding to the maximum camber position. This allows the water film to separate (or scatter) from the suction surface. This allows the separation position of the water film (separation position) to be closer to the leading edge. Therefore, compared with a case where the grooves are located further toward the trailing edge than the range, the distance from the separation position to other steam turbine blades downstream of the steam turbine blade, i.e., the travel distance of the detached water droplets, can be increased. This reduces the difference between the direction of travel of the detached water droplets and the gas flow direction compared with a case where the grooves are located further toward the trailing edge than the range. This reduces the difference between the direction of travel of the detached water droplets and the gas flow direction, thereby suppressing erosion and braking loss caused by water droplets detached from the suction surface of the steam turbine blade.

[0041] (2) In another embodiment, in the above embodiment (1), The groove is present between a position spaced apart in the chord direction from a second position on the suction surface corresponding to a maximum thickness position of the airfoil portion toward the leading edge by 10% of the chord length of the airfoil portion, and a position spaced apart in the chord direction from the second position by 10% of the chord length toward the trailing edge.

[0042] According to the above aspect (2), by providing the groove in the range, the water film becomes easy to detach, and when the water film adhering to the suction blade surface in the vicinity of the groove detaches, the difference between the moving direction of the detached water droplets and the flow direction of the gas phase can be reduced, thereby reducing erosion and braking loss.

[0043] (3) In another aspect, in the above aspect (1) or (2), the steam turbine blade is a turbine stator blade, The groove is located on the trailing edge side of a point of contact between the suction side blade surface and an imaginary line that is a tangent to the suction side blade surface and extends in the axial direction of the rotor of the steam turbine.

[0044] The airflow flowing from the upstream side of the turbine stator blade toward the turbine stator blade flows in at an angle close to the pressure side surface of the stator blade. Therefore, the water film adhering to the suction side surface is likely to detach from the suction side surface in a region closer to the trailing edge than the contact point. According to the above aspect (3), the water film adhering to the suction side surface is even more likely to detach from the suction side surface in a region closer to the trailing edge than the contact point.

[0045] (4) In another embodiment, in any one of the above (1) to (3), The groove has a leading edge side end portion where an acute angle is formed between an outer surface of the suction side blade surface adjacent to the groove on the leading edge side and an inner surface of the groove adjacent to the outer surface.

[0046] According to the above aspect (4), the groove provided on the suction blade surface has an acute angle formed between the outer surface adjacent to the groove on the leading edge side and the inner surface adjacent to the outer surface, so that the water film adhering to the suction blade surface can be easily and suitably separated by the groove provided on the suction blade surface.

[0047] (5) In another embodiment, in any one of the above (1) to (4), The groove has a bottom that includes a radius.

[0048] According to the above aspect (5), the groove has a bottom including a rounded portion, which stabilizes the size of the vortex generated in most of the hollow space of the groove. This reduces the randomness of the water droplets scattering outward from the groove, making it easier to control the scattering of water droplets into the main stream.

[0049] (6) In another embodiment, in any one of the above (1) to (5), The airfoil portion has an internal hollow space, The groove does not communicate with the hollow space.

[0050] According to the above aspect (6), the grooves formed on the suction surface of the airfoil are recessed relative to the airfoil surface and are formed so as not to communicate with the hollow space formed inside the airfoil. This prevents water from being sucked from the suction surface into the hollow space inside the grooves, and allows the water film to be efficiently removed from the suction surface.

[0051] (7) In another embodiment, in any one of the above (1) to (6), The groove extends along the span of the airfoil.

[0052] According to the above aspect (7), the grooves provided on the suction surface extend along the length of the airfoil, thereby enabling the water film to be suitably separated from the suction surface over a wide range of the airfoil.

[0053] (8) In another embodiment, in the above embodiment (7), The groove extends at least partially from a mid-span position to the tip of the airfoil.

[0054] Water droplets that cause erosion tend to originate from a water film that detaches from the suction blade surface in the area from the midspan position of the airfoil to the tip (tip of the airfoil). According to the above aspect (8), by providing the grooves over at least a portion of the area in question in the airfoil, the occurrence of erosion can be effectively prevented.

[0055] (9) In another embodiment, in any one of the above (1) to (8), The airfoil portion is formed with slits for recovering liquid water on the pressure side of the airfoil surface.

[0056] According to the above aspect (9), it is possible to suppress erosion and braking loss caused by water droplets detached from the pressure side blade surface.

[0057] (10) A steam turbine according to one aspect includes: The steam turbine blade according to any one of the above aspects (1) to (9) is provided.

[0058] According to the above aspect (10), erosion and braking loss caused by water droplets detached from the suction side blade surface of the steam turbine blade can be suppressed, thereby improving the durability and efficiency of the steam turbine. [Explanation of symbols]

[0059] 1. Steam turbine 2 rotors 3 Steam inlet 8 Moving blades 9 Stator blades 10 Inner casing 12 outer casing 11 Exhaust chamber entrance 13 Exhaust chamber outlet 14 Exhaust chamber 101 Airfoil 103 Dorsal wing surface 104 Ventral wing surface 105 leading edge 106 Trailing edge 114 Groove 114a Leading edge end 114a1 outer surface 114a2 Inner 115 Bottom 115a, 115b corner 116 Hollow space Pcmax Maximum camber position Ptmax Maximum blade thickness position P1 1st position P2 2nd position

Claims

1. A steam turbine blade for use in a steam turbine, comprising: an airfoil portion; the airfoil portion has a groove disposed on a suction surface within a range from a leading edge to a first location on the suction surface corresponding to a maximum camber position; Steam turbine blades.

2. the groove is present between a position spaced apart in the chord direction from a second position on the suction surface corresponding to a maximum thickness position of the airfoil portion toward a leading edge by a length that is 10% of the chord length of the airfoil portion, and a position spaced apart in the chord direction from the second position toward a trailing edge by a length that is 10% of the chord length. The steam turbine blade of claim 1 .

3. the steam turbine blade is a turbine stator blade, the groove is located on the trailing edge side of a point of contact between the suction side blade surface and an imaginary line that is a tangent to the suction side blade surface and extends in an axial direction of the rotor of the steam turbine. The steam turbine blade according to claim 1 or 2.

4. the groove has a leading edge side end portion, and an angle formed between an outer surface of the suction side blade surface adjacent to the groove on the leading edge side and an inner surface of the groove adjacent to the outer surface is an acute angle. The steam turbine blade according to claim 1 or 2.

5. The steam turbine blade according to claim 1 or 2, wherein the groove has a bottom portion including an R-shape.

6. The airfoil portion has an internal hollow space, The groove is not connected to the hollow space. The steam turbine blade according to claim 1 or 2.

7. the groove extends along the span of the airfoil; The steam turbine blade according to claim 1 or 2.

8. the groove extends over at least a portion of the airfoil from a midspan position to a tip; The steam turbine blade of claim 7.

9. The airfoil portion is formed with a slit for recovering liquid water on the pressure side airfoil surface. The steam turbine blade according to claim 1 or 2.

10. A steam turbine comprising the steam turbine blade according to claim 1 or 2.

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