A method for manufacturing a low specific speed Francis turbine runner blade in sections

Abstract

The invention belongs to the field of low specific speed mixed flow water turbine, and discloses a kind of low specific speed mixed flow water turbine runner blade split manufacturing method. The runner is divided into four parts of upper crown blade disc, lower ring inner blade disc, lower ring outer blade disc and short blade casting and processing. Long blade is divided into upper and lower two parts along the rotation cutting surface of the fitting center line of upper crown and lower ring flow channel, and the middle short blade is the remaining part of the short blade after removing the upper crown side short blade root transition step, the lower ring inner ring side short blade root transition step and the lower ring outer ring side short blade root transition step. First, the long blade is welded with radial split welding seam without short blade, then the short blade related welding seam is welded without lower ring outer blade disc, and finally the lower ring outer blade disc is assembled and welded at the runner water inlet edge. The invention can greatly improve the process accessibility of low specific speed mixed flow water turbine runner with small opening, long flow channel and multiple blades, and the design length of short blade flow channel is not limited by the runner manufacturing process, and the blade connection welding seam avoids the high stress area, improving the runner manufacturing quality and operation safety margin.

Description

Technical Field

[0001] This invention relates to the field of low-specific-speed mixed-flow turbines, and more particularly to a method for manufacturing a low-specific-speed mixed-flow turbine runner by welding and assembling four independently manufactured parts: an upper crown blade disk, a lower inner ring blade disk, a lower outer ring blade disk, and a middle section short blade. Background Technology

[0002] To reduce unit and powerhouse vibration caused by dynamic-static interference (RSI), low-specific-speed mixed-flow turbine runners typically employ a maximum of 15+15 long-short blades. However, due to the hydraulic characteristics of the runner's long flow channel and small opening, conventional manufacturing methods are increasingly unable to simultaneously achieve both manufacturability and excellent hydraulic design specifications. The disadvantages of conventional manufacturing methods for low-specific-speed mixed-flow turbine runners are:

[0003] 1) The internal flow channel space of the impeller is narrow, and the accessibility for welding, grinding and non-destructive testing is poor.

[0004] 2) The connecting weld is located in the transition arc part at the root of the blade. The high stress area of ​​the runner and the weld connection part are highly overlapped. The residual stress of the weld and the operating stress are superimposed and act on the weak link inside the weld, which poses a risk to the safe and stable operation of the component.

[0005] 3) When the short blades are installed after the process is improved to improve the process accessibility of long blades, the process accessibility of short blades and deformation control cannot be taken into account at the same time. At the same time, this manufacturing process also limits the design of the flow channel length of short blades. Generally, the flow channel length of short blades cannot exceed 1 / 3 of the flow channel length of long blades.

[0006] 4) The welding of the T-joint between the blade and the upper crown and lower ring, as well as the grinding of the transition arc, is difficult and labor-intensive.

[0007] In summary, conventional manufacturing methods for low-specific-speed mixed-flow turbine runners have poor accessibility in welding, grinding, and non-destructive testing, making it increasingly difficult to balance the manufacturability of the runner with excellent hydraulic design parameters. At the same time, welding and grinding are difficult and time-consuming, and the safety margin of component manufacturing and operation is low. Therefore, it is necessary to develop a new method for manufacturing segmented blades of low-specific-speed mixed-flow turbine runners. Summary of the Invention

[0008] Therefore, this invention employs a novel method for manufacturing segmented blades of low-specific-speed mixed-flow turbine runners, which can replace the conventional manufacturing method for low-specific-speed mixed-flow turbine runners. This method primarily solves the problem of process accessibility in the manufacturing of low-specific-speed mixed-flow turbine runners, while simultaneously improving the manufacturing quality and operational safety margin of low-specific-speed mixed-flow turbine runners.

[0009] The technical solution of this invention is as follows: the runner is composed of an upper crown blade disk, a lower inner ring blade disk, a lower outer ring blade disk, and a middle section short blade, which are independently cast and CNC machined. Weld C is the connecting weld between the upper crown blade disk and the lower inner ring blade disk. The position of weld C is the rotating cutting surface of the fitting centerline between the upper crown and lower ring flow channels in the axial cross section of the runner. Weld D is the connecting weld between the middle section short blade and the upper crown blade disk. Weld E is the connecting weld between the middle section short blade and the lower inner ring blade disk. Weld F is the radial connecting weld between the lower outer ring blade disk and the upper crown blade disk. Weld G is the connecting weld between the lower outer ring blade disk and the middle section short blade. Weld H and weld... Seam I is the axial connection weld between the lower outer impeller and the lower inner impeller. Weld H is the mating surface of the long blades on the inner and outer ring sides of the lower ring, which are integrally cast with the lower inner impeller and the lower outer impeller, respectively. Weld I is the mating surface of the root transition step of the short blades on the inner and outer ring sides of the lower ring, which are integrally cast with the lower inner impeller and the lower outer impeller, respectively. Weld J is the circumferential connection weld between the lower outer impeller and the lower inner impeller. By welding the above welds, the impeller is welded into a whole. This invention is achieved through the following steps:

[0010] S1. The upper crown blade disk, lower inner ring blade disk, lower outer ring blade disk, and middle short blades are cast and CNC machined independently.

[0011] S2. Assemble the upper crown blade disk, the lower inner ring blade disk, and the lower outer ring blade disk into a whole using convex positioning blocks and concave positioning blocks;

[0012] S3. Remove the lower ring outer blade disk and weld weld C;

[0013] S4. Assemble the middle section short blades and weld welds D and E. Reinstall the lower ring outer blade disk and weld welds G and F in sequence.

[0014] S5. Weld weld seam H, weld seam I, and weld seam J in sequence.

[0015] In the above-mentioned method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine, S1 further includes the fact that the transition steps at the root of the upper crown blade disk and the long blades and short blades on the upper crown side are integrally cast and CNC machined.

[0016] In the above-mentioned method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine, S1 further includes the fact that the transition steps at the root of the inner blade disk of the lower ring and the long blades and short blades of the inner ring side of the lower ring are integrally cast and CNC machined.

[0017] In the above-mentioned method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine, S1 further includes the fact that the transition steps at the root of the lower outer ring blade disk, the long blades on the lower outer ring side, and the short blades on the lower outer ring side are integrally cast and CNC machined.

[0018] In the above-mentioned method for manufacturing segmented blades of low-specific-speed mixed-flow turbines, S1 further includes the following: the middle short blade is the remaining part of the short blade after removing the transition steps at the root of the short blade on the upper crown side, the transition steps at the root of the short blade on the inner ring side of the lower ring, and the transition steps at the root of the short blade on the outer ring side of the lower ring, which is separately cast and CNC machined.

[0019] In the above-mentioned method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine, step S2 further includes the following: concave positioning blocks are distributed at the same theoretical position on the upper crown blade disk, the lower inner ring blade disk, and the lower outer ring blade disk. The concave positioning blocks are welded on after the flow channels of the upper crown blade disk, the lower inner ring blade disk, and the lower outer ring blade disk are precision machined, while the convex positioning blocks are manufactured separately.

[0020] In the above-mentioned method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine, step S4 further includes that the distance between the positions of welds D, E, and G and the edge of the root transition arc is ≥ 0.3 times the radius of the root transition arc.

[0021] In the above-mentioned method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine, step S5 further includes that the radial distance between weld J and the runner inlet edge is no more than 600 mm, and that weld J is offset from weld H and weld I by at least 50 mm in radial distance.

[0022] The advantages of this invention compared to the prior art are:

[0023] 1. This invention greatly improves the accessibility of wheel welding, grinding, and non-destructive testing.

[0024] 2. This invention allows the weld seam connecting the rotor blades to avoid the high-stress zone during operation, thereby improving the manufacturing quality and operational safety margin of the rotor.

[0025] 3. This invention allows the flow channel design length of short blades to be free from the limitations of the impeller manufacturing process, and the flow channel length of short blades can reach about 70% of the flow channel length of long blades.

[0026] 4. This invention transforms the T-joint between the blade and the upper crown and lower ring into a butt joint, reducing the difficulty and workload of blade welding and grinding. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a conventional segmented manufacturing scheme for a rotor.

[0028] Figure 2 This is a schematic diagram of the overall assembly of a novel segmented manufacturing scheme for turbine blades.

[0029] Figure 3 A schematic diagram of the removal of the outer blade disk of the lower ring in the new segmented manufacturing scheme of the turbine blade.

[0030] Figure 4A schematic diagram of inserting short blades for a novel segmented manufacturing scheme of turbine blades.

[0031] Figure 5 A schematic diagram of the reinstallation of the lower ring outer blade disk for a novel segmented manufacturing scheme of the turbine blade.

[0032] Figure 6 A schematic diagram showing the completed welding of a novel segmented manufacturing scheme for turbine blades.

[0033] Figure 7 This is a general drawing of a novel segmented manufacturing scheme for turbine blades.

[0034] The markings in the diagram are as follows: 1-Upper crown; 2-Lower ring; 3-Long blade; 4-Short blade; 5-Weld A; 6-Weld B; 7-Concave positioning block; 8-Convex positioning block; 9-Upper crown blade disk; 10-Lower ring inner blade disk; 11-Lower ring outer blade disk; 12-Long blade on the upper crown side; 13-Long blade on the lower ring inner side; 14-Long blade on the lower ring outer side; 15-Weld C; 16-Middle section short blade; 17-Transition step at the root of the short blade on the upper crown side; 18-Transition step at the root of the short blade on the lower ring inner side; 19-Weld D; 20-Weld E; 21-Weld F; 22-Weld G; 23-Weld H; 24-Weld I; 25-Transition step at the root of the short blade on the lower ring outer side; 26-Weld J. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that the positional relationships indicated by terms such as "upper", "lower", "long", "short", "inner", "outer", "convex", and "concave" are only based on the positional relationships shown in the accompanying drawings and are used only for the convenience of describing this invention, and are not intended to indicate or imply that the components referred to have a specific orientation, or are constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Specific implementation method one: as follows Figure 1 As shown, in the conventional segmented manufacturing scheme of the rotor, the rotor is divided into four parts: upper crown 1, lower ring 2, long blade 3, and short blade 4. The upper crown 1 and the blade form a connecting weld A, and the lower ring 2 and the blade form a connecting weld B. Figure 7As shown, in the novel segmented manufacturing scheme of the runner blade, the runner is divided into four parts: upper crown blade disk 9, lower inner ring blade disk 10, lower outer ring blade disk 11, and middle short blade 16. The connecting welds are weld C, weld D, weld E, weld F, weld G, weld H, weld I, and weld J. The runner consists of an upper crown blade disk 9, a lower inner ring blade disk 10, a lower outer ring blade disk 11, and a middle section short blade 16, all of which are independently cast and CNC machined. Weld C is the connecting weld between the upper crown blade disk 9 and the lower inner ring blade disk 10. The location of weld C is the rotating cutting surface of the fitting centerline between the flow channels of the upper crown 1 and the lower ring 2 in the axial cross-section of the runner. The purpose of selecting the location of weld C is to ensure that the connecting weld of the long blade 3 of the runner avoids the high-stress zone during operation, and to transform the connecting weld of the long blade 3 from a T-joint to a butt joint, reducing the difficulty and workload of welding and grinding the long blade 3. Weld D is the connecting weld between the middle section short blade 16 and the upper crown blade disk 9. Weld E is the connecting weld between the middle section short blade 16 and the lower inner ring blade disk 10. Weld F is the connecting weld between the lower outer ring blade disk 11 and the upper crown blade disk 9. The radial connection welds between the blades 9 are as follows: weld G is the connection weld between the lower outer blade 11 and the middle short blade 16; welds H and I are the axial connection welds between the lower outer blade 11 and the lower inner blade 10; weld H is located at the mating surfaces of the lower inner ring side long blade 13, which is integrally cast with the lower inner blade 10, and the lower outer ring side long blade 14, which is integrally cast with the lower outer blade 11; weld I is located at the mating surfaces of the lower inner ring side short blade root transition step 18, which is integrally cast with the lower inner blade 10, and the lower outer ring side short blade root transition step 25, which is integrally cast with the lower outer blade 11; and weld J is the circumferential connection weld between the lower outer blade 11 and the lower inner blade 10. The runner is welded into a whole by welding the above welds. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner provided in this embodiment is achieved through the following steps:

[0038] like Figure 7 As shown, S1 and the runner are divided into four parts: the upper crown blade disk 9, the lower inner ring blade disk 10, the lower outer ring blade disk 11, and the middle short blades 16, which are cast and CNC machined independently.

[0039] like Figure 2 As shown in Figure S2, the upper crown blade disk 9, the lower inner ring blade disk 10, and the lower outer ring blade disk 11 are first assembled into a whole using concave positioning blocks 7 and convex positioning blocks 8. The use of concave positioning blocks 7 and convex positioning blocks 8 in this step to assemble the upper crown blade disk 9, the lower inner ring blade disk 10, and the lower outer ring blade disk 11 greatly simplifies the impeller assembly and dimensional adjustment processes, reduces difficulty, shortens the cycle time, and improves accuracy.

[0040] like Figure 3As shown, in step S3, the lower outer blade disk 11 is removed, and the weld C between the upper crown blade disk 9 and the lower inner blade disk 10 is welded. The welding sequence adopted in this step provides more operational space for welding, non-destructive testing, and grinding of weld C in the absence of the middle short blade 16 and the lower outer blade disk 11, thus meeting its accessibility requirements.

[0041] like Figure 4 As shown, S4, assemble the middle section short blade 16 and weld welds D and E; as Figure 5 As shown, the lower outer ring blade disk 11 is reinstalled, and welds G and F are welded sequentially. The welding sequence adopted in this step provides more operating space for welding, non-destructive testing, and grinding of welds D and E in the open state without the lower outer ring blade disk 11 being reinstalled, meeting their accessibility requirements, and allowing the flow channel design length of the short blade 4 to be unrestricted by the impeller manufacturing process; the purpose of first welding the radial segmented welds of the blades, such as welds D, E, F, and G, is to allow the impeller to freely contract in the opening height direction, releasing the high load capacity of the impeller.

[0042] like Figure 5 and Figure 6 As shown, weld seam S5, weld seam H, weld seam I, and weld seam J are welded in sequence.

[0043] The purpose of the welding sequence adopted in this step is that the radial segmented welds of the blades, such as welds D, E, F, and G, which are welded first, can limit the welding shrinkage of the axial segmented welds of the blades, such as welds H and I. The same principle applies to the final weld J, which is beneficial for controlling the welding dimensions of the runner.

[0044] Specific implementation method two: such as Figure 2 , Figure 4 As shown, this embodiment further defines S1 as described in Specific Embodiment 1. In this embodiment, in S1, the upper crown blade disk 9, the upper crown side long blade 12, and the upper crown side short blade root transition step 17 are integrally cast and CNC machined.

[0045] Specific implementation method three: such as Figure 2 , Figure 4 As shown, this embodiment further defines S1 as described in Specific Embodiment 1. In this embodiment, the lower ring inner blade disk 10, the lower ring inner ring side long blade 13, and the lower ring inner ring side short blade root transition step 18 are integrally cast and CNC machined.

[0046] Specific implementation method four: such as Figure 2 , Figure 7As shown, this embodiment further defines S1 as described in Specific Embodiment 1. In this embodiment, the lower ring outer blade disk 11, the lower ring outer ring side long blade 14, and the lower ring outer ring side short blade root transition step 25 are integrally cast and CNC machined.

[0047] Specific implementation method five: such as Figure 4 As shown, this embodiment further defines S1 as described in Specific Embodiment 1. In this embodiment, the middle short blade 16 is the remaining part of the short blade 4 after removing the transition step 17 at the root of the short blade on the upper crown side, the transition step 18 at the root of the short blade on the inner ring side of the lower ring, and the transition step 25 at the root of the short blade on the outer ring side of the lower ring, and is separately cast and CNC machined.

[0048] In this step, a special mid-section short blade 16 structure is adopted to transform the connection weld of the mid-section short blade 16 of the runner from a T-joint to a butt joint, which reduces the difficulty and workload of welding and grinding the mid-section short blade 16.

[0049] Specific implementation method six: such as Figure 2 As shown, this embodiment further defines S2 as described in Specific Embodiment 1. In this embodiment, the concave positioning block 7 is distributed at the same theoretical position on the upper crown blade disk 9, the lower inner ring blade disk 10, and the lower outer ring blade disk 11. The concave positioning block 7 is welded after the flow channels of the upper crown blade disk 9, the lower inner ring blade disk 10, and the lower outer ring blade disk 11 are precision machined, while the convex positioning block 8 is manufactured separately.

[0050] Specific implementation method seven: such as Figure 4 , Figure 7 As shown, this embodiment further defines S4 as described in Specific Embodiment 1. In this embodiment, the distance between the positions of weld D, weld E, and weld G and the edge of the root transition arc is ≥ 0.3 times the radius of the root transition arc.

[0051] The purpose of selecting the positions of weld D, weld E, and weld G in this step is to ensure that the connecting welds of the short blades 16 in the middle section of the runner avoid the high-stress zone during operation.

[0052] Specific implementation method eight: such as Figure 7 As shown, this embodiment further limits step five of the specific embodiment one. In this embodiment, the radial distance between weld J and the water inlet edge of the impeller is no more than 600mm, and it is offset from weld H and weld I by at least 50mm in radial distance.

[0053] The purpose of limiting the maximum radial distance between weld J and the runner inlet edge in this step is to ensure that the accessibility requirements of welds F, G, H, and I can be met even after the outer blade disk 11 of the lower ring is reinstalled; the purpose of limiting the minimum offset distance between weld J and welds H and I is to avoid through welds.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner, characterized in that: The runner consists of an upper crown blade disk (9), a lower ring inner blade disk (10), a lower ring outer blade disk (11), and a middle section short blade (16), which are independently cast and CNC machined. Weld C (15) is the connecting weld between the upper crown blade disk (9) and the lower ring inner blade disk (10). The position of weld C (15) is the rotating cutting surface of the fitting center line between the upper crown (1) and the lower ring (2) flow channels in the axial cross section of the runner. Weld D (19) is the connecting weld between the middle section short blade (16) and the upper crown blade disk (9). Weld E (20) is the connecting weld between the middle section short blade (16) and the lower ring inner blade disk (10). Weld F (21) is the radial connecting weld between the lower ring outer blade disk (11) and the upper crown blade disk (9). Weld G (22) is the connecting weld between the lower ring outer blade disk (11) and the middle section short blade (16). Weld H (23) and weld I (24) are axial connection welds between the lower ring outer blade disk (11) and the lower ring inner blade disk (10). Weld H (23) is located at the joint surface of the lower ring inner ring side long blade (13) integrally cast with the lower ring inner blade disk (10) and the lower ring outer ring side long blade (14) integrally cast with the lower ring outer blade disk (11). Weld I (24) is located at the joint surface of the lower ring inner ring side short blade root transition step (18) integrally cast with the lower ring inner blade disk (10) and the lower ring outer ring side short blade root transition step (25) integrally cast with the lower ring outer blade disk (11). Weld J (26) is the circumferential connection weld between the lower ring outer blade disk (11) and the lower ring inner blade disk (10). The impeller is welded into a whole by welding the above welds. The method is achieved by the following steps: S1. The upper crown blade disk (9), the lower inner ring blade disk (10), the lower outer ring blade disk (11), and the middle short blades (16) of the runner are independently cast and CNC machined. S2. Assemble the upper crown blade disk (9), the lower inner ring blade disk (10), and the lower outer ring blade disk (11) into a whole using the convex positioning block (8) and the concave positioning block (7); S3. Remove the lower ring outer blade disk (11) and weld weld C (15); S4. Assemble the middle section short blade (16) and weld weld D (19) and weld E (20). Reassemble the lower ring outer blade disk (11) and weld weld G (22) and weld F (21) in sequence. S5. Weld seam H (23), seam I (24), and seam J (26) in sequence.

2. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S1 also includes the fact that the upper crown leaf disc (9), the upper crown side long leaf (12), and the upper crown side short leaf root transition step (17) are integrally cast and CNC machined.

3. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S1 also includes the fact that the lower ring inner blade disk (10), the lower ring inner side long blade (13), and the lower ring inner side short blade root transition step (18) are integrally cast and CNC machined.

4. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S1 also includes the fact that the lower outer blade disk (11), the lower outer ring side long blade (14), and the lower outer ring side short blade root transition step (25) are integrally cast and CNC machined.

5. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S1 further includes the middle section short blade (16), which is the remaining part of the short blade (4) after removing the transition step (17) at the root of the short blade on the upper crown side, the transition step (18) at the root of the short blade on the inner ring side of the lower ring, and the transition step (25) at the root of the short blade on the outer ring side of the lower ring, which is separately cast and CNC machined.

6. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S2 further includes a concave positioning block (7) distributed at the same theoretical position on the upper crown blade disk (9), the lower inner ring blade disk (10), and the lower outer ring blade disk (11). The concave positioning block (7) is installed and welded after the flow channels of the upper crown blade disk (9), the lower inner ring blade disk (10), and the lower outer ring blade disk (11) are precision machined, while the convex positioning block (8) is made separately.

7. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S4 further includes that the distance between the positions of weld D (19), weld E (20), and weld G (22) and the edge of the root transition arc is ≥ 0.3 times the radius of the root transition arc.

8. The method for manufacturing segmented blades of a low-specific-speed mixed-flow turbine runner according to claim 1, characterized in that: The S5 further includes that the radial distance between weld J (26) and the water inlet side of the impeller is no more than 600 mm, and that the weld J (23) and weld I (24) are offset by a radial distance of at least 50 mm.

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