Blade root weight reduction structure of steam turbine moving blade, steam turbine moving blade and manufacturing method of steam turbine moving blade

Abstract

The invention discloses a turbine rotor blade root weight reduction structure, a turbine rotor blade and a manufacturing method of the turbine rotor blade root weight reduction structure, the turbine rotor blade root weight reduction structure comprises a fir tree type blade root and a blade root middle body connecting a blade body and the fir tree type blade root, and a weight reduction groove is formed in the inner arc side of the blade root middle body; the opening area of the weight reduction groove accounts for 60%-40% of the area of the inner arc side without the weight reduction groove; after the adjacent blades are assembled, the contact area of the inner arc side of the blade root middle body accounts for 40%-60% of the contact area of the inner arc side of the blade root middle body when the weight reduction groove is not formed. The method has the advantages that the average stress level of the blade root area can be effectively reduced, the manufacturing cost of the blade is reduced, the machining difficulty of the blade is not increased, the weight of the blade root can be reduced, and the strength and rigidity of the blade root can be effectively guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbines, and in particular relates to a steam turbine rotor blade root weight reduction structure, a steam turbine rotor blade and a manufacturing method thereof. Background Art

[0002] In the field of steam turbine technology, blade design and structural optimization are important links in improving unit stability.

[0003] The blade root is the key connection between the blade and the rotor, and its strength and rigidity directly impact the safe operation of the blade. Traditional fir-tree blade root designs often make the blade root area heavier to ensure sufficient strength and rigidity. This not only increases material costs but also increases the inertia of rotating components, negatively impacting unit stability.

[0004] Existing Solutions: Several existing solutions exist to address the aforementioned issues. For example, reducing blade root weight by changing its shape and size or using different materials. However, these methods often compromise blade root strength and rigidity or increase manufacturing costs.

[0005] Although existing technologies have provided some solutions, there are still some problems and limitations.

[0006] First, existing solutions often fail to achieve significant weight reduction while ensuring blade root strength and stiffness.

[0007] Secondly, existing solutions may increase manufacturing costs or make blade processing more difficult.

[0008] Furthermore, existing solutions may negatively impact the strength properties of the blades, for example increasing the risk of blade vibration.

[0009] Therefore, how to achieve effective weight reduction while ensuring the strength and stiffness of the blade root is an urgent problem to be solved in the current field of turbine blade design. Summary of the Invention

[0010] The purpose of the present invention is to provide a turbine blade root weight reduction structure, a turbine blade and a manufacturing method thereof, which can effectively reduce the average stress level in the blade root area without increasing the processing difficulty of the blade, and can achieve blade root weight reduction and effectively ensure the strength and rigidity of the blade root, in response to the shortcomings of the existing technology.

[0011] The technical objectives of the present invention are achieved through the following technical solutions: A steam turbine blade root weight reduction structure includes a fir-tree-shaped blade root and a blade root intermediate body connecting the blade body and the fir-tree-shaped blade root. A weight reduction groove is defined on the inner arc side of the blade root intermediate body. The opening area of ​​the weight reduction groove accounts for 60% to 40% of the area of ​​the inner arc side without the weight reduction groove. When adjacent blades are assembled, the contact area of ​​the inner arc side of the blade root intermediate body accounts for 40% to 60% of the contact area of ​​the inner arc side of the blade root intermediate body without the weight reduction groove.

[0012] Preferably, the weight-reducing groove is a U-shaped groove with an open lower end, and the corners of the U-shaped groove are arc transitions.

[0013] Preferably, the length L of the U-shaped groove satisfies: 20 mm ≤ L ≤ 30 mm, the width W satisfies: 10 mm ≤ W ≤ 15 mm, and the depth H satisfies: 3 mm ≤ H ≤ 5 mm.

[0014] Preferably, the arc radius R of the U-shaped groove satisfies: 3mm ≤ R ≤ 5mm.

[0015] Preferably, the arc of the U-shaped groove and the groove wall transition through a continuous smooth curved surface.

[0016] Preferably, the fir-tree-shaped blade root has a structure with three to five pairs of teeth.

[0017] Preferably, the symmetry axis of the weight-reducing groove coincides with the radial centerline of the blade.

[0018] A steam turbine blade comprises a fir-tree-shaped blade root and a blade root intermediate body connecting the blade body and the fir-tree-shaped blade root; the above-mentioned steam turbine blade blade root weight reduction structure is provided on the inner arc side of the blade root intermediate body.

[0019] A method for manufacturing the above-mentioned turbine rotor blades comprises the following steps: Step 1: Selecting alloy steel materials with low density and high tensile strength to make fir-tree-shaped blade roots, blade root intermediates, and blade bodies; Step 2: Process a weight-reducing groove on the inner arc side of the blade root intermediate body, and dynamically adjust the opening area of ​​the weight-reducing groove according to the size of the blade root intermediate body to meet the following requirements: (Total surface area of ​​the inner arc side of the middle of the blade root - opening area of ​​the weight-reducing groove) / Total surface area of ​​the inner arc side of the middle of the blade root × 100% = 40%~60%.

[0020] Preferably, after the weight-reducing grooves are opened in step three, the shape, size and distribution of the weight-reducing grooves are adjusted through simulation calculation and experimental verification so that the centrifugal force distribution of the blades during rotation is more uniform.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention's steam turbine blade root weight-reduction structure features a weight-reduction groove located on the inner arc side of the blade root midbody. By providing this groove on the inner arc side of the blade root midbody, the average stress level in the blade root region can be effectively reduced, thereby achieving blade root weight reduction. This structure not only reduces material costs but also reduces the inertial forces of rotating components. Unlike existing methods that reduce blade root weight by changing the blade root's shape and dimensions or using different materials, this structure achieves weight reduction without compromising the blade root's strength and rigidity. This is because the weight-reduction groove is located in the blade root midbody, where the strength and rigidity of the entire blade root are less affected. Compared to methods that reduce blade root weight by changing the blade root's shape and dimensions or using different materials, this structure is less difficult to implement and does not increase blade processing complexity. Therefore, the present invention offers the advantages of effectively reducing the average stress level in the blade root region, lowering blade manufacturing costs, while not increasing blade processing complexity, achieving blade root weight reduction, and effectively ensuring blade root strength and rigidity.

[0022] 2. In the specific implementation of the turbine blade root weight-reduction structure manufactured by this invention, the symmetry axis of the weight-reduction grooves coincides with the radial centerline of the blade. This technical measure aligns the layout of the weight-reduction grooves with the force direction of the blade. During blade rotation, centrifugal force acts primarily radially. This symmetrical design ensures a more uniform stress distribution on the weight-reduced blades after force application, avoiding problems such as excessive localized stress or uneven deformation caused by offset weight-reduction grooves. This ensures balanced blade strength and stiffness in all directions, maintaining smooth and reliable turbine operation and reducing the risk of vibration and imbalance.

[0023] 3. The steam turbine rotor blade of the present invention features a blade root weight-reducing structure on the inner arc side of the blade root intermediate body. This effectively reduces blade root strength and rigidity while achieving weight reduction, which is crucial for improving turbine stability. Furthermore, this reduces blade manufacturing costs and the inertia of rotating components, positively impacting energy consumption and extending equipment life.

[0024] In addition, it can also improve the dynamic performance of the blades and reduce the risk of blade root cracks, which is of great value in improving the operational safety of the equipment.

[0025] 4. The turbine rotor blades manufactured by the method of the present invention can achieve effective weight reduction of the blades while ensuring the strength, stiffness and dynamic performance of the blades, reducing the manufacturing cost of the blades, and also improving the dynamic performance of the blades, reducing the risk of blade root cracks, and improving the operating safety of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a structural schematic diagram of the present invention; Figure 2 yes Figure 1 Front view of Figure 3 yes Figure 2 Side view of Reference numerals: 1—fir-tree blade root; 2—blade root intermediate body; 21—inner arc side; 3—blade body; 4—weight-reducing groove. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. In addition, the terms "first," "second," etc. are used only to distinguish the descriptions and are not to be understood as indicating or implying relative importance.

[0030] Example 1 like Figure 1 — Figure 3As shown, a turbine blade root weight reduction structure comprises a fir-tree-shaped blade root 1 and a blade root intermediate body 2 connecting the blade body 3 and the fir-tree-shaped blade root 1. A weight reduction groove 4 is defined on the inner curved side 21 of the blade root intermediate body 2. The opening area of ​​the weight reduction groove 4 accounts for 60% to 40% of the area of ​​the inner curved side 21 of the blade root intermediate body 2 without the weight reduction groove 4. When adjacent blades are assembled, the contact area of ​​the inner curved side 21 of the blade root intermediate body 2 accounts for 40% to 60% of the contact area of ​​the inner curved side 21 of the blade root intermediate body 2 without the weight reduction groove 4. By providing the weight reduction groove 4 on the inner curved side 21 of the blade root intermediate body 2, the average stress level in the blade root area can be effectively reduced, thereby achieving blade root weight reduction. This structure not only reduces material costs but also reduces the inertial force of rotating components. Unlike existing methods that reduce blade root weight by changing the shape and size or using different materials, this structure achieves weight reduction without compromising the strength and rigidity of the blade root. This is because the weight-reducing grooves 4 are located in the blade root midsection 2, where the strength and stiffness of the entire blade root are less affected. Compared to reducing the weight of the blade root by changing its shape and dimensions or using different materials, this structure is less difficult to implement and does not increase the blade's machining complexity. Therefore, this technical measure effectively reduces the average stress level in the blade root area, lowering blade manufacturing costs without increasing blade machining complexity, while achieving blade root weight reduction and effectively maintaining blade root strength and stiffness.

[0031] like Figure 1 — Figure 3 As shown, the blade includes a fir-tree-shaped blade root 1 and a blade root intermediate body 2 connecting the blade body 3 and the fir-tree-shaped blade root 1. A weight-reducing groove 4 is provided on the inner arc side 21 of the blade root intermediate body 2. The opening area of ​​the weight-reducing groove 4 accounts for 60% to 40% of the area of ​​the inner arc side 21 without the weight-reducing groove 4; that is, the opening area of ​​the weight-reducing groove 4 = the area of ​​the inner arc side 21 of the blade root intermediate body 2 without the weight-reducing groove 4 × (60% to 40%). When adjacent blades are assembled, the contact area of ​​the inner arc side 21 of the blade root intermediate body 2 accounts for 40% to 60% of the contact area of ​​the inner arc side 21 of the blade root intermediate body 2 without the weight-reducing groove 4. This technical measure can achieve the purpose of weight reduction by reducing the contact area, reduce the average stress of the wheel groove, reduce stress concentration, and improve the overall fatigue life of the blade; it can also avoid insufficient blade connection stiffness due to too small a contact area, which affects the operating stability and reliability of the turbine, and achieve a balanced optimization of weight reduction and blade performance. like Figure 1 — Figure 3As shown, the fir-tree blade root 1 has three to five pairs of teeth. This technical measure ensures excellent connection strength and rigidity. Combined with the weight-reducing grooves 4, this reduces blade root weight while ensuring a secure connection between the blade and the wheel rim. This ensures the blade can withstand complex loads such as centrifugal force and steam forces generated by high-speed rotation, maintaining the dynamic balance and stable operation of the turbine rotor and providing strong support for the overall performance of the turbine.

[0032] In practice, the axis of symmetry of the weight-reducing grooves 4 coincides with the radial centerline of the blade. This technical measure aligns the arrangement of the weight-reducing grooves 4 with the direction of force acting on the blade. During blade rotation, centrifugal force primarily acts radially. This symmetrical design ensures a more uniform stress distribution on the weight-reduced blades after force application, avoiding problems such as excessive localized stress or uneven deformation caused by offset weight-reducing grooves 4. This ensures balanced blade strength and stiffness in all directions, maintaining the smooth and reliable operation of the turbine and reducing the risk of vibration and imbalance.

[0033] In practice, the weight-reducing groove 4 is a U-shaped groove with an open bottom end, and the corners of the U-shaped groove are rounded. By designing the weight-reducing groove 4 as a U-shaped groove with a rounded corner, the rounded corner effectively reduces the stress concentration factor around the weight-reducing groove 4 compared to other shapes (such as sharp corners), preventing crack initiation and propagation caused by stress concentration. This enhances the blade's fatigue resistance under high-frequency vibration and complex stress environments, thereby improving the blade's reliability and service life. In practice, if the U-shaped groove is open at the top end, stress concentration will occur in the blade root area. By designing the groove with an open bottom end, stress concentration in the blade root area is avoided. The relatively regular shape of the U-shaped groove facilitates precise machining using existing machining processes (such as milling), ensuring the dimensional accuracy and surface quality of the weight-reducing groove 4. It also facilitates quality inspection and control, reducing manufacturing complexity and costs. Furthermore, the one-way open structure of the U-shaped groove allows the use of a standard taper milling cutter for single-step forming. This eliminates multiple finishing steps compared to a closed groove, effectively reducing machining time and tool wear.

[0034] Therefore, the adoption of this structure can effectively reduce the average stress level in the blade root area, has low processing costs and can effectively reduce manufacturing difficulty.

[0035] In practice, the arc of the U-shaped groove transitions to the groove wall through a continuous, smooth curved surface. This structure avoids stress concentration caused by sudden changes in cross-section, allowing stress to gradually change and disperse along the smooth curved surface, further reducing the risk of fatigue crack initiation during blade use and improving blade reliability and service life.

[0036] In this embodiment, the length L of the U-shaped groove satisfies: 20 mm ≤ L ≤ 30 mm, the width W satisfies: 10 mm ≤ W ≤ 15 mm, and the depth H satisfies: 3 mm ≤ H ≤ 5 mm.

[0037] Preferably, the length L of the U-shaped groove is 26 mm; the width W is 12.8 mm; and the depth H is 4 mm. Within this size range, the weight-reducing groove 4 can remove sufficient material to meet weight reduction requirements, reducing blade weight, centrifugal force, and groove stress. It also ensures the structural integrity of the remaining blade portion, meeting strength and rigidity requirements. This prevents deformation and cracking caused by excessive weight reduction under complex operating conditions such as high-speed rotation, high temperature, and high pressure, thereby ensuring safe and stable operation of the steam turbine.

[0038] In a specific implementation, the arc radius R of the U-shaped groove satisfies: 3mm ≤ R ≤ 5mm.

[0039] Preferably, the arc radius R is 4 mm. A suitable arc radius helps to better disperse stress, reduce local stress peaks, reduce the risk of stress concentration, improve the fatigue resistance and overall mechanical properties of the blade while ensuring the weight reduction effect, and ensure the blade has good reliability and durability in long-term operation.

[0040] Example 2 A steam turbine rotor blade comprises a fir-tree-shaped blade root 1 and a blade root intermediate body 2 connecting a blade body 3 and the fir-tree-shaped blade root 1; an inner arc side 21 of the blade root intermediate body 2 is provided with the steam turbine rotor blade blade root weight reduction structure of embodiment 1.

[0041] In specific implementation, by providing the steam turbine rotor blade root weight reduction structure of embodiment 1 on the inner arc side 21 of the blade root intermediate body 2, effective weight reduction can be achieved while ensuring the blade root strength and rigidity, which is of great significance for improving the stability of the steam turbine.

[0042] Secondly, it can reduce the manufacturing cost of blades and the inertia force of rotating parts, which has a positive effect on reducing energy consumption and increasing the service life of equipment.

[0043] In addition, it can also improve the dynamic performance of the blades and reduce the risk of blade root cracks, which is of great value in improving the operational safety of the equipment.

[0044] A method for manufacturing the above-mentioned turbine rotor blades comprises the following steps: Step 1: Select an alloy steel material with low density and high tensile strength to manufacture the fir-tree-shaped blade root 1, the blade root intermediate body 2 and the blade body 3.

[0045] In practice, 14NiCr18 alloy steel, with a density of 7.80 g / cm³ and a strength exceeding 1000 MPa, can be selected as a low-density, high-tensile-strength alloy steel. Low density reduces blade weight and centrifugal forces, while high tensile strength ensures the blades are sufficiently resistant to deformation and fracture under complex stresses. This approach ensures that the reduced-weight blades possess excellent comprehensive mechanical properties, meeting the operational requirements of steam turbines under harsh operating conditions such as high temperature, high pressure, and high speed.

[0046] Step 2: Process the weight-reducing groove 4 on the inner arc side 21 of the blade root intermediate body 2, and dynamically adjust the opening area of ​​the weight-reducing groove 4 according to the size of the blade root intermediate body 2 to meet the following requirements: (Total surface area of ​​the inner arc side 21 of the blade root intermediate body 2 - opening area of ​​the weight-reducing groove 4) / Total surface area of ​​the inner arc side 21 of the blade root intermediate body 2 × 100% = 40% to 60%.

[0047] In practice, the weight-reducing grooves 4 are machined using multi-axis CNC milling, with the arc-shaped sections formed using a ball-end milling cutter to ensure a continuous and smooth curved transition. The opening area of ​​the weight-reducing grooves 4 is dynamically adjusted based on the dimensions of the blade root intermediate body 2 to meet the required contact area ratio. This design approach can adapt to the manufacturing needs of blades of varying specifications and sizes, ensuring that each blade achieves maximum weight reduction while maintaining sufficient strength and rigidity. This improves versatility and adaptability during production, reducing production costs.

[0048] Step 3: After the weight-reducing grooves 4 are opened, the shape, size and distribution of the weight-reducing grooves 4 are adjusted through simulation calculation and experimental verification, so that the centrifugal force distribution of the blades during rotation is more uniform.

[0049] During specific implementation, after the weight-reducing groove 4 is opened, through simulation calculation and experimental verification, we can gain an in-depth understanding of the actual centrifugal force distribution of the blade during rotation, and adjust the shape, size and distribution of the weight-reducing groove 4 in a targeted manner according to the verification results, further optimize the uniformity of the centrifugal force distribution of the blade, reduce the overall stress level of the blade root area, reduce the vibration risk, and improve the reliability and service life of the blade, ensuring that the performance of the blade after weight reduction reaches the best state and meets the requirements of safe and stable operation of the turbine.

[0050] Therefore, this method can effectively reduce the weight of the blades while ensuring the strength, stiffness and dynamic performance of the blades, reduce the manufacturing cost of the blades, improve the dynamic performance of the blades, reduce the risk of blade root cracks, and improve the operating safety of the equipment.

[0051] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A turbine blade root weight reduction structure, comprising a fir-tree-shaped blade root and a blade root intermediate connecting the blade body and the fir-tree-shaped blade root, characterized in that: A weight-reducing groove is provided on the inner arc side of the blade root intermediate body; The opening area of ​​the weight-reducing groove accounts for 60% to 40% of the area of ​​the inner arc side when the weight-reducing groove is not set; when the adjacent blades are assembled, the contact area of ​​the inner arc side of the blade root intermediate body accounts for 40% to 60% of the contact area of ​​the inner arc side of the blade root intermediate body when the weight-reducing groove is not set.

2. The steam turbine rotor blade root weight reduction structure according to claim 1, characterized in that: The weight-reducing groove is a U-shaped groove with an open lower end, and the corners of the U-shaped groove are arc transitions.

3. The steam turbine rotor blade root weight reduction structure according to claim 2, characterized in that: The length L of the U-shaped groove satisfies: 20 mm ≤ L ≤ 30 mm, the width W satisfies: 10 mm ≤ W ≤ 15 mm, and the depth H satisfies: 3 mm ≤ H ≤ 5 mm.

4. The steam turbine rotor blade root weight reduction structure according to claim 3, characterized in that: The arc radius R of the U-shaped groove satisfies: 3mm ≤ R ≤ 5mm.

5. The steam turbine rotor blade root weight reduction structure according to claim 2, characterized in that: The arc of the U-shaped groove and the groove wall transition through a continuous smooth curved surface.

6. The steam turbine rotor blade root weight reduction structure according to claim 1, characterized in that: The fir-tree-shaped leaf root has a structure of three to five pairs of teeth.

7. The steam turbine rotor blade root weight reduction structure according to claim 1, characterized in that: The symmetry axis of the weight-reducing groove coincides with the radial center line of the blade.

8. A steam turbine rotor blade, characterized in that: It comprises a fir-tree-shaped blade root and a blade root intermediate body connecting the blade body and the fir-tree-shaped blade root; the inner arc side of the blade root intermediate body is provided with the turbine rotor blade blade root weight reduction structure according to any one of claims 1-7.

9. A method for manufacturing a turbine blade according to claim 8, characterized in that , including the following steps: Step 1: Selecting alloy steel materials with low density and high tensile strength to make fir-tree-shaped blade roots, blade root intermediates, and blade bodies; Step 2: Process a weight-reducing groove on the inner arc side of the blade root intermediate body, and dynamically adjust the opening area of ​​the weight-reducing groove according to the size of the blade root intermediate body to meet the following requirements: (Total surface area of ​​the inner arc side of the middle of the blade root - opening area of ​​the weight-reducing groove) / Total surface area of ​​the inner arc side of the middle of the blade root × 100% = 40%~60%.

10. The method for manufacturing a turbine blade according to claim 9, characterized in that , also includes the following steps: Step 3, after the weight-reducing groove is opened, the shape, size and distribution of the weight-reducing groove are adjusted through simulation calculation and experimental verification so that the centrifugal force distribution of the blade during rotation is more uniform.

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