Fir tree type blade root structure with force unloading function for water feed pump turbine

Abstract

The utility model discloses a fir tree type blade root structure with a force unloading function for a water feeding pump turbine, and relates to the technical field of turbines. The structure comprises a blade root; the wheel groove is connected with the blade root; and the force unloading groove is formed in the joint of the blade root and the wheel groove. The inwards-concave arc-shaped force unloading groove is additionally formed in the round corner where the wheel groove of the fir-tree-shaped blade root is connected with the blade root in a targeted mode, and by optimizing geometric parameters, concentrated stress at the traditional round corner is transferred to the smooth transition area of the force unloading groove; meanwhile, the force unloading grooves can be distributed in the wave-shaped connecting positions of all the contact surfaces in pairs, a multi-stage stress dissipation structure is formed, the stress peak value at the fillet position is effectively reduced, cracks are avoided, the fatigue life of the blade root and the wheel groove is remarkably prolonged, and the operation reliability of the blade root and the wheel groove is remarkably improved.

Description

Technical Field

[0001] This application relates to the field of steam turbine technology, and in particular to a fir-shaped blade root structure with a stress-relief function for a feedwater pump steam turbine. Background Technology

[0002] Steam turbines are key power equipment that converts the kinetic and thermal energy of high-temperature, high-pressure steam into mechanical energy. Their internal rotating blades transfer energy through their connection with the rotor. The blade root, as the core structure connecting the blade to the rotor groove, directly bears the enormous centrifugal force generated by the high-speed rotation of the blade. With the development of steam turbines towards higher speeds and variable operating conditions, especially for feedwater pump turbines used in deep peak-shaving operations, the loads on the blades and rotor have increased significantly. This places higher demands on the connection strength and reliability between the blade root and the rotor groove. If the force transmitted at the blade root exceeds the material's limit, it can lead to cracks in the rotor groove or even complete failure, causing serious safety hazards and economic losses.

[0003] Fir-shaped blade roots are a widely used connection structure, which disperses loads through multi-tooth meshing, providing good load-bearing capacity and maintainability. However, this structure is prone to stress concentration in the rounded corner area where the blade root teeth contact the rotor wheel groove. Over long-term operation, this can lead to crack propagation and ultimately structural failure. Existing technologies mainly alleviate stress concentration by optimizing the contact angle, tooth curvature, or rounding radius, but these methods require repeated trial and error adjustments and do not disperse peak stress at the structural root. Utility Model Content

[0004] In view of this, this application provides a fir-shaped blade root structure with stress relief function for a feedwater pump turbine. The main purpose is to solve the technical problem that the existing technology mainly alleviates stress concentration by optimizing the contact angle, tooth curvature or rounding radius, but these methods require repeated trial and error adjustments and do not disperse the stress peak from the structural root.

[0005] This application provides a fir-shaped blade root structure with stress-relief function for a feedwater pump turbine, comprising:

[0006] Leaf roots;

[0007] Wheel groove, the wheel groove being connected to the blade root;

[0008] The stress relief groove is located at the connection between the blade root and the wheel groove.

[0009] In one feasible implementation, the structure further includes:

[0010] The contact surface is located at the connection between the blade root and the wheel groove. There are multiple contact surfaces, and the stress relief grooves are provided in pairs on each contact surface.

[0011] In one feasible implementation, the blade root engages with the wheel groove, and the connection between the blade root and the wheel groove is wavy.

[0012] In one feasible implementation, the structure further includes:

[0013] The wheel groove fillet is provided on the wheel groove and is a concave arc shape. The wheel groove fillet is used to connect with the convex blade root.

[0014] In one feasible implementation, the stress relief groove is disposed within the fillet of the wheel groove.

[0015] In one feasible implementation, the structure further includes:

[0016] The blade root rounded corner is located on the wheel groove and is a concave arc shape. The blade root rounded corner is used to connect with the convex wheel groove.

[0017] In one feasible implementation, the stress relief groove is located within the fillet of the blade root.

[0018] In one feasible implementation, the stress relief groove is a concave arc shape.

[0019] In one feasible implementation, the radius of the stress relief groove has a predetermined relationship with the length of the straight segment at the connection between the blade root and the wheel groove.

[0020] In one feasible implementation, the stress relief groove is tangent to the profile of the blade root and the wheel groove.

[0021] This application provides a fir-shaped blade root structure with stress relief function for a feedwater pump turbine, comprising: a blade root; a wheel groove connected to the blade root; and a stress relief groove disposed at the connection between the blade root and the wheel groove.

[0022] This application adds a concave arc-shaped stress relief groove at the rounded corner where the wheel groove of the fir-shaped blade root connects to the blade root. By optimizing the geometric parameters, the concentrated stress at the traditional rounded corner is transferred to the smooth transition area of ​​the stress relief groove. At the same time, the stress relief grooves can be distributed in pairs at the wavy connection of each contact surface to form a multi-level stress dissipation structure, effectively reducing the stress peak at the rounded corner, avoiding crack generation, and significantly improving the fatigue life and operational reliability of the blade root and wheel groove.

[0023] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0024] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0026] Figure 1 This illustration shows a structural diagram of a fir-shaped leaf root structure with stress-relief function for a feedwater pump turbine, provided in an embodiment of this application.

[0027] Figure 2 This paper shows a schematic diagram of the wheel groove fillet and blade root fillet provided in an embodiment of this application;

[0028] Figure 3 A schematic diagram of the unloading groove provided in an embodiment of this application is shown;

[0029] Figure 4 A schematic diagram of an existing blade root stress relief structure is shown.

[0030] Figure 5 This illustration shows a geometric diagram of a fir-shaped blade root structure with stress-relief function for a feedwater pump turbine, provided in an embodiment of this application.

[0031] In the picture:

[0032] 1. Blade root; 2. Wheel groove; 3. Wheel groove fillet; 4. Blade root fillet; 5. Contact surface; 6. Unloading groove. Detailed Implementation

[0033] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0035] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] As the energy structure shifts towards higher efficiency and cleaner energy sources, steam turbines, as key power equipment in thermal power, nuclear power, and combined cycle units, are facing increasingly complex operating conditions. Especially under deep peak-shaving scenarios, variable-speed feedwater pump turbines need to frequently respond to changes in grid load, leading to a significant increase in alternating loads on the moving blades and rotor grooves. Long-term operation at high speeds and under varying conditions exacerbates the stress concentration problem at the blade root and the rounded corners of the rotor groove, creating a weak point in the traditional fir-tree blade root structure. These stress peaks easily trigger the initiation and propagation of microcracks, ultimately leading to rotor groove cracking or even overall failure, seriously threatening the safety and economy of the unit. (See also...) Figure 4 The diagram shows a schematic of an existing blade root stress relief structure. Although existing technologies alleviate stress concentration by optimizing the contact surface angle or transition circle radius, it is still difficult to balance structural strength and stress distribution under high dynamic loads. An innovative design that is adapted to industrial needs is urgently needed.

[0037] See Figure 1 This document illustrates a structural schematic diagram of a fir-shaped leaf root structure with stress-relief function for a feedwater pump turbine, provided in an embodiment of this application. The structure includes:

[0038] Leaf root 1;

[0039] Wheel groove 2, wheel groove 2 is connected to blade root 1;

[0040] Unloading groove 6 is located at the connection between blade root 1 and wheel groove 2.

[0041] In the above embodiment, the blade root 1 is curved and its end is fitted and connected to the wheel groove 2; the wheel groove 2 is provided with a groove structure that matches the shape of the blade root 1 for fixing the blade root 1; the unloading groove 6 is embedded in the connection transition area between the blade root 1 and the wheel groove 2, and its tortuous groove-shaped profile extends along the connecting line.

[0042] By embedding the stress relief groove 6 at the connection point, the concentrated stress in the joint area between the blade root 1 and the wheel groove 2 is dispersed along the groove contour. The tortuous shape of the stress relief groove 6 increases the stress release area through geometric extension, avoiding local load accumulation and thus significantly reducing the risk of crack propagation. This application achieves stress optimization without changing the main connection form between the blade root 1 and the wheel groove 2, making it suitable for dynamic stability requirements under high-speed conditions.

[0043] Furthermore, the structure also includes:

[0044] Contact surface 5 is located at the connection between blade root 1 and wheel groove 2. There are multiple contact surfaces 5, and unloading grooves 6 are provided in pairs on each contact surface 5.

[0045] In the above embodiment, the blade root 1 and the wheel groove 2 are connected by multiple contact surfaces 5. The contact surfaces 5 are distributed at intervals along the axial direction of the blade root 1, and stress relief grooves 6 are symmetrically arranged in the rounded transition area of ​​each pair of contact surfaces 5. The arc segment of the stress relief groove 6 smoothly transitions with the profile of the contact surface 5, forming a continuous load transfer path.

[0046] By working in tandem with the paired stress relief grooves 6 and the contact surface 5, the concentrated load of the traditional single contact surface 5 is distributed to multiple pairs of contact areas, significantly reducing the stress peak at the tooth root fillet. At the same time, the symmetrical distribution of the stress relief grooves 6 avoids local plastic deformation caused by eccentric loading, improves the load uniformity of the blade root 1 and the wheel groove 2, and is especially suitable for alternating load conditions at high speeds.

[0047] Furthermore, the blade root 1 is engaged with the wheel groove 2, and the connection between the blade root 1 and the wheel groove 2 is wavy.

[0048] In the above embodiment, the blade root 1 and the wheel groove 2 are connected by a wave-shaped connection structure. The crests and troughs at the connection point are respectively matched with the protrusions and depressions of the wheel groove 2 and the blade root 1, and a stress relief groove 6 is opened at the rounded corners of the transition between the crests and troughs.

[0049] The wavy connection structure increases the contact area, and combined with the stress-relieving function of the stress-relieving groove 6, the load is evenly transferred along the wavy contour. This not only enhances the bending stiffness of the structure, but also absorbs some vibration energy through the elastic deformation of the waveform, reducing the stress fluctuation amplitude under dynamic conditions and lowering the risk of fatigue crack initiation.

[0050] See Figure 2 The diagram shows a structural schematic of the rounded corners of the wheel groove 2 and the blade root 1 provided in an embodiment of this application. Further, the structure also includes:

[0051] The wheel groove fillet 3 is located on the wheel groove 2 and is a concave arc shape. The wheel groove fillet 3 is used to connect with the convex blade root 1.

[0052] In the above embodiment, the rounded corner of the wheel groove 2 is a concave arc structure, the curvature of which is adapted to the profile of the convex part of the blade root 1. The unloading groove 6 extends along the arc segment of the rounded corner of the wheel groove 2 and forms a nested fit with the rounded corner of the blade root 1.

[0053] The nested design of the concave wheel groove fillet 3 and the convex blade root 1 optimizes the assembly clearance and eliminates the edge stress caused by traditional right-angle contact. The combination of the stress relief groove 6 and the rounded arc segment further disperses the contact stress, while the geometric adaptation limits the relative displacement between the blade root 1 and the wheel groove 2, avoiding crack propagation caused by fretting wear.

[0054] Furthermore, the stress relief groove 6 is located inside the rounded corner 3 of the wheel groove.

[0055] In the above embodiment, the unloading groove 6 is embedded inside the rounded corner 3 of the wheel groove, and its arc radius matches the curvature of the rounded corner 3 of the wheel groove. Furthermore, the two ends of the unloading groove 6 are tangent to the profile of the contact surface of the blade root 1, forming a transition without abrupt changes.

[0056] The matching design of the arc radius and fillet curvature of the stress relief groove 6 ensures a smooth stress transition and eliminates secondary stress concentration points, making it particularly suitable for strength protection of material creep-sensitive areas under high temperature and high pressure steam environments.

[0057] Furthermore, the structure also includes:

[0058] The blade root fillet 4 is located on the wheel groove 2 and is a concave arc shape. The blade root fillet 4 is used to connect with the convex wheel groove 2.

[0059] In the above embodiment, the blade root fillet 4 is a concave arc-shaped structure, which is opened in the transition area connecting the wheel groove 2 and the blade root 1. Its radius of curvature is geometrically adapted to the convex profile of the wheel groove 2 to form a nested fit.

[0060] The concave arc design of the blade root fillet 4 eliminates edge stress concentration in traditional right-angle connections, while providing a geometrical fit for the integration of the stress relief groove 6. This structure allows the load to be evenly transferred along the arc surface to the convex area of ​​the wheel groove 2, avoiding the initiation of microcracks caused by local stress peaks.

[0061] Furthermore, the unloading groove 6 is located inside the blade root fillet 4.

[0062] In the above embodiment, the stress relief groove 6 is embedded in the concave arc segment of the blade root fillet 4, and the two ends of the arc of the stress relief groove 6 are strictly tangent to the profile of the blade root fillet 4.

[0063] The stress relief groove 6 is built into the structure of the blade root fillet 4. Through a double-arc transition, the concentrated stress in the original blade root fillet 4 area is dispersed along the curvature of the stress relief groove 6. The tangential connection design ensures a continuous stress transmission path and avoids secondary stress concentration, making it particularly suitable for high-cycle fatigue load conditions.

[0064] See Figure 3 The diagram shows a structural schematic of the stress relief groove 6 provided in the embodiment of this application. Further, the stress relief groove 6 is a concave arc shape.

[0065] See Figure 5 The diagram shows a geometric relationship of a blade root 1 unloading structure provided in an embodiment of this application. Furthermore, the radius of the unloading groove 6 has a preset relationship with the length of the straight segment at the connection between the blade root 1 and the wheel groove 2.

[0066] In the above embodiment, the stress relief groove 6 is a concave arc-shaped structure, which is opened at the end of the straight segment of the contact surface 5 between the blade root 1 and the wheel groove 2. The geometric design relationship of the stress relief groove 6 satisfies: the length of the straight segment of the contact surface 5 between the blade root 1 and the wheel groove 2 is L, and the radius of the arc segment of the stress relief groove 6 is R, which is limited to 0.2L < R < 0.6L.

[0067] When R > 0.6L, the curvature of the stress relief groove 6 is too small, the stress dispersion effect is insufficient, and it cannot effectively reduce the peak stress.

[0068] When R < 0.2L, the curvature of the unloading groove 6 is too large, which will excessively weaken the connection strength between the blade root 1 and the wheel groove 2;

[0069] Within the range of 0.2L < R < 0.6L, the stress relief groove 6 can smoothly transition the concentrated stress at the end of the contact surface 5 along the groove body through the arc curvature, and can also avoid the decrease in structural strength caused by excessive material removal, thus achieving a balance between stress optimization and load-bearing capacity.

[0070] Furthermore, the unloading groove 6 is tangent to the profiles of the blade root 1 and the wheel groove 2.

[0071] In the above embodiment, the arc segment of the stress relief groove 6 is strictly tangent to the profile of the blade root 1 and the wheel groove 2, and forms a gradual transition in the extension direction of the contact surface 5 to avoid abrupt curvature changes.

[0072] Strict tangential connection and gradual transition design eliminate local stress gradients and prevent secondary stress concentration. This structure homogenizes the stress field through geometric continuity optimization, significantly improving the durability of blade root 1 and wheel groove 2 under high-cycle fatigue conditions.

[0073] This application provides a schematic diagram of a fir-tree-shaped blade root structure with stress-relief function for a feedwater pump turbine, comprising: a blade root 1; a wheel groove 2 connected to the blade root 1; and a stress-relief groove 6 located at the connection between the blade root 1 and the wheel groove 2. This application specifically adds a concave arc-shaped stress-relief groove at the rounded corner where the wheel groove connects to the blade root of the fir-tree-shaped blade root. By optimizing geometric parameters, the concentrated stress at the traditional rounded corner is transferred to the smooth transition area of ​​the stress-relief groove. Simultaneously, the stress-relief grooves can be distributed in pairs at the wavy connections of each contact surface, forming a multi-level stress dissipation structure, effectively reducing the stress peak at the rounded corner, preventing crack formation, and significantly improving the fatigue life and operational reliability of the blade root and wheel groove.

[0074] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the apparatus of the embodiment can be distributed within the apparatus of the embodiment as described, or can be modified to be located in one or more apparatuses different from this embodiment. The modules of the above-described embodiment can be combined into one module, or further divided into multiple sub-modules.

[0075] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A fir-tree blade root structure with load shedding function for a water pump turbine, characterized in that, include: Leaf root (1); Wheel groove (2), the wheel groove (2) is connected to the blade root (1); The stress relief groove (6) is located at the connection between the blade root (1) and the wheel groove (2).

2. The structure of claim 1, wherein The structure also includes: The contact surface (5) is located at the connection between the blade root (1) and the wheel groove (2). There are multiple contact surfaces (5), and the unloading grooves (6) are provided in pairs on each contact surface (5).

3. The structure of claim 1, wherein The blade root (1) is engaged with the wheel groove (2), and the connection between the blade root (1) and the wheel groove (2) is wavy.

4. The structure of claim 1, wherein The structure also includes: The wheel groove fillet (3) is provided on the wheel groove (2) and is an inwardly concave arc shape. The wheel groove fillet (3) is used to connect with the outwardly convex leaf root (1).

5. The structure of claim 4, wherein The unloading groove (6) is located inside the rounded corner (3) of the wheel groove.

6. The structure of claim 1, wherein The structure also includes: The blade root rounded corner (4) is provided on the wheel groove (2) and is a concave arc shape. The blade root rounded corner (4) is used to connect with the convex wheel groove (2).

7. The structure of claim 6, wherein The unloading groove (6) is located inside the fillet (4) at the blade root.

8. The structure of claim 1, wherein The unloading groove (6) is a concave arc shape.

9. The structure of claim 8, wherein The radius of the unloading groove (6) has a predetermined relationship with the length of the straight segment at the connection between the blade root (1) and the wheel groove (2).

10. The structure of claim 9, wherein The unloading groove (6) is tangent to the profile of the blade root (1) and the wheel groove (2).

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