Wheel, engine, and methods to improve wheel fatigue life

Abstract

This invention discloses a wheel, comprising a first blade disk, a second blade disk, a third blade disk, and a connecting part. The first blade disk has a first mounting hole, the second blade disk has a second mounting hole, and the third blade disk has a third mounting hole. The connecting part includes a connecting rod with a fixing cap at one end and a nut for use with the connecting rod. The outer surface of the other end of the connecting rod has external threads. The connecting rod passes sequentially through the first mounting hole, the second mounting hole, and the third mounting hole and is fixed by the nut on the external threads of the connecting rod. Several annularly arranged shoulders are provided on the outer surface of the connecting rod between the nut and the fixing cap. The shoulders have a clearance fit with the first and / or second mounting holes, and a clearance fit with the third mounting hole. This invention also discloses an engine including the above-described wheel and a method for improving the fatigue life of the wheel. This invention can solve the technical problem of low wheel fatigue life caused by high stress in the bolt holes at the blade disk spokes of existing wheel designs.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and in particular, to a wheel and an engine comprising the wheel. Furthermore, this invention also relates to a method for improving the fatigue life of a wheel comprising the aforementioned wheel or engine. Background Technology

[0002] Multi-stage axial-flow gas turbine compressors extensively employ a disc-drum structure, where the blade discs are connected by a cylindrical drum structure, and the blade discs at each stage are connected by bolts. Figure 1 As shown, each stage of a bladed disk typically has four structural features: blades, hub, spokes, and wheel center. Blades are the power-operating components of the compressor, located at the outermost edge of the bladed disk, ranging in number from a dozen to several dozen. During rotation, the blades compress the airflow. The hub is a complete ring structure. For an integral bladed disk, the blades and hub are a single entity; for a tenon-and-groove design, the hub has tenons, and the blades have tenons, with the blades mounted to the hub via tenon joints. Due to centrifugal force, if a single-stage bladed disk only has blades and a hub, the hub will break under the immense centrifugal force during engine operation. Therefore, a solid structure with spokes and a wheel center is needed to constrain the blades and hub. The spokes are thinner than the wheel center because for the same mass, a larger radius generates greater centrifugal force than a smaller radius. If the spokes had the same thickness as the wheel center, not only would they not provide greater constraint for the blades and hub, but the centrifugal force generated by the spokes themselves would cause the wheel center to break. Typical axial flow bladed disks all have the above-mentioned obvious structural features.

[0003] like Figure 1 As shown, the middle stage blade disk is fixed to the mounting edges of the front and rear blade disks using bolts. Bolt holes are designed on the spokes of the middle blade disk. As mentioned above, under centrifugal force, the spokes themselves bear enormous stress on the middle blade disk. Drilling holes in the spokes will cause stress concentration around the holes, especially for high-speed, high-load blade disk designs with very strict weight reduction requirements. The stress at the bolt holes often approaches the material's inherent limit. Ideally, the bolts should be positioned in the center of the bolt holes. Figure 2 As shown. When the engine is running, due to centrifugal force, the bolt will be thrown away from the engine axis. For example... Figure 3 As shown, in the threaded holes of the blade disk and the mounting edge, the bolt shank will be adjacent to the edge of the bolt hole. For example... Figure 4As shown, at high speeds, because the bolt heads and nuts are suspended on both sides, centrifugal force acting on the bolt heads and nuts will cause the bolt shank to bend. If the bending reaches a certain extent, it may even press against the bolt hole wall at the middle stage blade disk spoke, generating a squeezing effect and reducing the fatigue life of the disk at the threaded hole. As mentioned earlier, the bolt holes at the spokes are already areas of high stress; the bolt shank squeezing the hole wall will further increase the stress in the hole. For blade disks whose static strength meets design requirements, the stress in the bolt holes will be within the allowable stress range of the material. However, for fatigue life, higher stress will reduce the fatigue life of the component. Summary of the Invention

[0004] This invention provides a wheel, an engine, and a method for improving the fatigue life of the wheel, in order to solve the technical problem of low wheel fatigue life caused by high stress in the bolt holes at the blade disc spokes of existing wheel.

[0005] According to one aspect of the present invention, a wheel is provided, comprising a first blade disk, a second blade disk, a third blade disk, and a connecting portion. The spokes of the second blade disk are clamped between the flanges of the first and third blade disks. The flange of the first blade disk is provided with a first mounting hole, the spokes of the second blade disk are provided with a second mounting hole, and the flange of the third blade disk is provided with a third mounting hole. The first, second, and third mounting holes have the same diameter and are coaxially arranged. The connecting portion includes a connecting rod with a fixing cap at one end and a nut for use with the connecting rod. The outer surface of the other end of the connecting rod is provided with an external thread. The connecting rod passes through the first, second, and third mounting holes in sequence to connect the first, second, and third blade disks in sequence and is fixed by the nut being sleeved on the external thread of the connecting rod. The outer surface of the connecting rod between the nut and the fixing cap is provided with a plurality of annularly arranged shoulders. The first and / or second mounting holes are in clearance fit with the shoulders, and the third mounting hole is in clearance fit with the shoulders.

[0006] As a further improvement to the above technical solution: the protrusion height of the shoulder protruding from the surface of the connecting rod is 0.4 to 0.8 mm.

[0007] Furthermore, the clearance between the shoulder and mounting hole one and / or mounting hole two and / or mounting hole three is 0.04 to 0.11 mm.

[0008] Furthermore, the plurality of said shoulders includes at least one shoulder 1 that mates with mounting hole 1 and at least one shoulder 3 that mates with mounting hole 3, and the diameter of shoulder 1 is equal to the diameter of shoulder 3.

[0009] Furthermore, the axial length of the side of the first shoulder is equal to any value within the range of 1 / 3 of the shoulder diameter to the axial length of the first mounting hole, and the axial length of the side of the third shoulder is equal to any value within the range of 1 / 3 of the shoulder diameter to the axial length of the third mounting hole.

[0010] Furthermore, the plurality of shoulders also include at least one shoulder two that mates with the mounting hole two. The axial length of the side of the shoulder two is any value within the range of 1 mm to 1 / 2 of the axial length of the mounting hole two. The shoulder two is disposed in the opening at one end of the mounting hole two.

[0011] Further, the second shoulder is disposed within the opening of the second mounting hole near the first mounting hole. The axial length of the side of the first shoulder is any value within the range of 1 mm to 1 / 2 of the axial length of the first mounting hole, and the axial length of the third shoulder is any value within the range of 1 / 3 of the shoulder diameter to the axial length of the third mounting hole; or, the second shoulder is disposed within the opening of the second mounting hole near the third mounting hole, and the axial length of the side of the first shoulder is any value within the range of 1 / 3 of the shoulder diameter to the axial length of the first mounting hole, and the axial length of the third shoulder is any value within the range of 1 mm to 1 / 2 of the axial length of the third mounting hole. Further, the width of the shoulder gradually increases radially towards the central axis.

[0012] In the above discussion of the wheel of this invention, when the axial length of the shoulder is more than one-third of the shoulder diameter, it can be considered a wide-shoulder design. The maximum length of a wide-shoulder design cannot exceed the length of the mounting hole it occupies, to avoid the shoulder crossing two holes and becoming susceptible to shearing. When the axial length of the shoulder is less than one-third of the diameter, it is considered a narrow-shoulder design. However, in actual design, the axial length of a narrow shoulder is generally designed to be less than 1 / 2 of the axial length of the mounting hole it occupies (generally, 1 / 2 of the axial length of the mounting hole is definitely less than one-third of the shoulder diameter), and should not be less than 1mm. A length less than 1mm would greatly increase the processing difficulty and easily cause pressure damage to the hole.

[0013] The main purpose of the wheel design in this invention is to add a shoulder to the screw to suppress deformation during operation. As shown in the figure below, under centrifugal force, the suspended part on the right deforms. Due to the presence of the wide shoulder, the deformation of the connecting rod is greatly suppressed. Shoulder one and shoulder two together effectively function as a wide shoulder. Therefore, when shoulder two is removed, shoulder one must be a wide shoulder. Similarly, if shoulder three is changed to a narrow shoulder design, a narrow shoulder must be added near the right side of the mounting hole two.

[0014] According to another aspect of the invention, an engine is also provided, which includes the aforementioned disc.

[0015] According to another aspect of the present invention, a method for improving the fatigue life of a wheel is also provided, comprising the wheel described above or comprising an engine described above, specifically comprising the following steps:

[0016] S1. Determine the diameter of the connecting rod based on the existing nut model, and determine the height of the shoulder based on the diameter of the connecting rod;

[0017] S2. Align the mounting edge of blade disk one, the spokes of blade disk two, and the mounting edge of blade disk three closely, and use drilling equipment to sequentially process mounting holes one, two, and three with diameters that meet the design requirements.

[0018] S3. Determine the number of shoulders, and determine the width and position of each shoulder based on the number of shoulders and the axial length of mounting hole one, mounting hole two and mounting hole three;

[0019] S4. Based on the result of step S2, use a turning machine to process a connecting rod with a shoulder and external thread. Insert the connecting rod into mounting hole one, mounting hole two and mounting hole three in sequence, and use a nut to put on the external thread and tighten the nut to fix it.

[0020] The present invention has the following beneficial effects:

[0021] (1) The wheel of the present invention is connected to three blade disks through a connecting part with a shoulder. By setting the shoulder and making the shoulder fit with the mounting hole with a clearance, the presence of the shoulder can ensure that when the connecting rod of the wheel is deformed in a predetermined manner during operation, it only contacts the specific low stress area of ​​the mounting hole (the position inside the mounting hole corresponding to the shoulder), avoiding the high stress area, thereby avoiding the stress of the mounting hole from exceeding the limit, which is beneficial to improving the low cycle life of the wheel. In addition, the presence of the shoulder and the small clearance fit with the mounting hole can effectively suppress the bending deformation of the connecting rod when the engine is working, avoiding the increase in stress of the mounting hole caused by the connecting rod squeezing the mounting hole, which can further improve the low cycle life of the wheel.

[0022] (2) The wheel of the present invention only needs to change the size and structure of the connecting part and the mounting hole of the existing wheel structure to greatly improve the fatigue life of the wheel. The structural modification of the existing wheel is small and the application cost is low. In addition, the structure of the connecting part and the structure of the mounting hole in the present invention have the advantages of simple structure, simple processing and convenient installation. It can be widely used in gas turbine engines and is easy to promote and apply.

[0023] (3) The method of improving the fatigue life of the wheel in this invention only requires changing the size and structure of the connection part and mounting hole of the existing wheel structure to greatly improve the fatigue life of the wheel. It requires little modification to the existing wheel structure, has low application cost, and is simple to operate.

[0024] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

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

[0026] Figure 1 This is a schematic diagram of the existing roulette wheel;

[0027] Figure 2 This is a schematic diagram of the existing wheel in a non-ideal working state, showing the bolt rod located in the bolt hole.

[0028] Figure 3 This is a schematic diagram of the existing wheel disc in its working state, with the bolt rod located in the bolt hole.

[0029] Figure 4 This is a schematic diagram of the existing wheel when the bolt rod presses against the wall of the bolt hole during operation;

[0030] Figure 5 This is a schematic diagram of the structure of the wheel in Embodiment 1 of the present invention;

[0031] Figure 6 This is a schematic diagram of the structure of the wheel in Embodiment 2 of the present invention;

[0032] Figure 7 This is a schematic diagram of the wheel under force in Embodiment 2 of the present invention.

[0033] Legend:

[0034] 1. Blade disk one; 11. Mounting hole one; 2. Blade disk two; 21. Mounting hole two; 3. Blade disk three; 31. Mounting hole three; 4. Connecting part; 41. Fixing cap; 42. Connecting rod; 43. Nut; 5. Shoulder; 51. Shoulder one; 52. Shoulder two; 53. Shoulder three. Detailed Implementation

[0035] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0036] Example 1:

[0037] like Figure 5 As shown, the wheel in this embodiment includes a first blade disk 1, a second blade disk 2, a third blade disk 3, and a connecting part 4. The spokes of the second blade disk 2 are clamped between the flange of the first blade disk 1 and the flange of the third blade disk 3. The flange of the first blade disk 1 has a mounting hole 11, the spokes of the second blade disk 2 have a mounting hole 21, and the flange of the third blade disk 3 has a mounting hole 31. The mounting holes 11, 21, and 31 have the same diameter and are coaxially arranged. The connecting part 4 includes a connecting rod 42 with a fixing cap 41 at one end and a connecting rod 42 with the connecting rod 42. 2. The nut 43 used in the matching assembly has an external thread on the outer surface of the other end of the connecting rod 42. The connecting rod 42 passes through the mounting hole 11, mounting hole 21 and mounting hole 31 in sequence to connect the blade disk 1, blade disk 2 and blade disk 3 in sequence. The nut 43 is sleeved on the external thread of the connecting rod for fixation. The outer surface of the connecting rod 42 between the nut 43 and the fixing cap has a number of annularly arranged shoulders 5. The shoulders 5 are clearance-fitted with the mounting hole 11 and mounting hole 31. The nut 43 in this embodiment is a common model in the prior art.

[0038] In this embodiment, due to the small design clearance between the shoulder 5 and the mounting hole, the positional tolerance of the mounting holes for each wheel needs to be controlled, requiring the positional tolerance not to exceed Φ0.04mm. A 0.5mm chamfer needs to be designed at the opening of all three mounting holes to avoid stress concentration. The edge of the shoulder 5 needs to maintain a distance of 0.2mm to 0.5mm from the opening.

[0039] In this embodiment, the wheel is connected to three blade disks via a connecting part 4 with a shoulder 5. The shoulder 5 is provided and is fitted with a clearance fit between the shoulder 5 and the mounting hole. The presence of the shoulder 5 ensures that when the connecting rod 42 deforms in a predetermined manner during operation, it only contacts a specific low-stress area of ​​the mounting hole (the position inside the mounting hole corresponding to the shoulder 5), avoiding high-stress areas. This prevents the stress in the mounting hole from exceeding the limit, which helps to improve the low-cycle life of the wheel. In addition, the presence of the shoulder 5 and the small clearance fit with the mounting hole can effectively suppress the bending deformation of the connecting rod 42 during engine operation, avoiding the increase in stress in the mounting hole caused by the connecting rod 42 pressing against the mounting hole, which can further improve the low-cycle life of the wheel.

[0040] The wheel in this embodiment only needs to change the size and structure of the connecting part 4 and the mounting hole of the existing wheel structure to greatly improve the fatigue life of the wheel. The structural changes to the existing wheel are small and the application cost is low. In addition, the structure of the connecting part 4 and the mounting hole in this embodiment have the advantages of simple structure, simple processing and convenient installation. It can be widely used in gas turbine engines and is easy to promote and apply.

[0041] In this embodiment, the protrusion height of the shoulder 5 protruding from the surface of the connecting rod 42 is 0.4–0.8 mm, preferably 0.5 mm. This 0.4–0.8 mm distance ensures that even if the connecting rod 42 deforms during engine operation, it will not compress the mounting hole of the wheel disc. The shoulder 5 exists to suppress bolt bending deformation. Even with the shoulder 5, the connecting rod will still undergo slight deformation due to centrifugal force when the engine rotor rotates. The height of the shoulder 5 is essentially the gap between the connecting rod 42 and the mounting hole. Generally, a gap of at least 0.4 mm is sufficient to ensure that the connecting rod will not contact the hole wall even after deformation. If the height of the shoulder 5 is too small, there is a possibility that the connecting rod 42 will contact the hole wall, thus rendering it ineffective. Since the external threads of the nut 43 and the connecting rod 42 are generally standard, if the height of the shoulder 5 is too high, it means that either the diameter of the mounting hole is too large, causing the contact area between the nut 43 and the mounting edge to become smaller, affecting the normal tightening of the nut 43; or the diameter of the thin rod part in the middle of the connecting rod 42 is too small, causing the strength of the connecting rod 42 to decrease. Under the tightening force of the nut 43, the connecting rod 42 is easily stretched, resulting in a decrease in the reliability of the clamping of the parts.

[0042] In this embodiment, the fit clearance between the shoulder 5 and the mounting hole 11 and / or mounting hole 21 and / or mounting hole 31 is 0.04 to 0.11 mm. Analysis shows that when the shoulder 5 and the mounting hole adopt this design clearance, the bending deformation of the connecting rod 42 can be effectively suppressed.

[0043] In this embodiment, the shoulder 5 includes one (or two or three in other embodiments) shoulder 51 that mates with mounting hole 11 and one (or two or three in other embodiments) shoulder 53 that mates with mounting hole 31, and the diameter of shoulder 51 is equal to the diameter of shoulder 53. The purpose of designing both shoulder 51 and shoulder 53 as a single unit is to reduce processing difficulty and cost. Using the same diameter for shoulder 51 and shoulder 53 also reduces processing difficulty and cost.

[0044] In this embodiment, the axial length of the side of shoulder 51 is equal to any value within the range of 1 / 3 of the shoulder diameter to the axial length of mounting hole 11, and the axial length of shoulder 53 is equal to any value within the range of 1 / 3 of the shoulder diameter to the axial length of mounting hole 31. When the axial length of shoulder 5 is more than one-third of the diameter of shoulder 5, it can be considered as a wide shoulder design. The maximum length of the wide shoulder design cannot exceed the length of the mounting hole where it is located, so as to avoid shoulder 5 crossing two holes and being easily sheared. Both shoulder 51 and shoulder 53 are wide shoulders.

[0045] In this embodiment, the width of the shoulder 5 gradually increases in the radial direction towards the central axis, which can form a force transition, so that the connecting rod 42 deforms uniformly when under force, and is less likely to cause stress concentration, thereby reducing the pressure of the connecting rod 42 on the wheel.

[0046] In this embodiment, the outer surface of the shoulder, the inner wall of mounting hole one, the inner wall of mounting hole two, and the inner wall of mounting hole three are all smooth structures to avoid stress concentration and reduce damage to the mounting holes.

[0047] The engine in this embodiment includes the aforementioned wheel.

[0048] The method for improving the fatigue life of the wheel in this embodiment includes the wheel described above or the engine described above, and specifically includes the following steps:

[0049] S1. Determine the diameter of the connecting rod 42 based on the existing nut 43 model, and determine the height of the shoulder 5 based on the diameter of the connecting rod 42;

[0050] S2. Align the mounting edge of blade disk 1, the spokes of blade disk 2, and the mounting edge of blade disk 3 tightly, and use drilling equipment to sequentially process mounting holes 11, 21 and 31 with diameters conforming to the design requirements.

[0051] S3. Determine whether the number of shoulders 5 is two or three, and determine the width and position of each shoulder 5 according to the number of shoulders 5 and the axial length of mounting hole 11, mounting hole 21 and mounting hole 31.

[0052] S4. Based on the result of step S2, use a turning machine to process a connecting rod 42 with a shoulder 5 and an external thread. Insert the connecting rod 42 into the mounting hole 11, mounting hole 21 and mounting hole 31 in sequence. Use a nut 43 to fit on the external thread and tighten the nut 43 to fix it.

[0053] Example 2:

[0054] like Figure 6 and 7 As shown, the difference between this embodiment and Embodiment 1 is that:

[0055] In this embodiment, the shoulder 5 includes one (or two or three in other embodiments) shoulder 51 that mates with mounting hole 11, one (or two or three in other embodiments) shoulder 52 that mates with mounting hole 21, and one (or two or three in other embodiments) shoulder 53 that mates with mounting hole 31. Shoulder 52 is disposed in one end opening of mounting hole 21, and the axial length of the side of shoulder 52 is any value within the range of 1mm to 1 / 2 of the axial length of mounting hole 21.

[0056] In this embodiment, shoulder 2 52 is disposed in the end opening of mounting hole 21 near mounting hole 11. The axial length of shoulder 1 51 is any value within the range of 1 mm to 1 / 2 of the axial length of mounting hole 11. The axial length of shoulder 3 53 is any value within the range of 1 / 3 of the shoulder diameter to the axial length of mounting hole 3 31. Alternatively, shoulder 2 52 is disposed in the end opening of mounting hole 21 near mounting hole 3 31. The axial length of shoulder 1 51 is any value within the range of 1 / 3 of the shoulder diameter to the axial length of mounting hole 11. The axial length of shoulder 3 53 is any value within the range of 1 mm to 1 / 2 of the axial length of mounting hole 3 31.

[0057] In this embodiment, the position of shoulder 51 can be close to the left side of the mounting hole opening in blade disk 1. In other embodiments, it can be close to the right side of the opening, or any position in between. The design principle of shoulder 53 is the same as that of shoulder 51. The positions of shoulder 51 and shoulder 53 can adopt any of the above structural forms and can be randomly combined with each other. However, the position of shoulder 52 can be close to the left side of the mounting hole opening in blade disk 2, or close to the right side of the opening. The position can only be one of the above and cannot be placed in the middle. This is because: when the engine is working, the position of mounting hole 21 of blade disk 2 is a high stress area. In principle, it is necessary to avoid designing shoulder 5 at mounting hole 21. That is, the design of eliminating shoulder 52 is adopted, and both shoulder 51 and shoulder 53 are designed as wide shoulders. The high stress area of ​​mounting hole 21 of blade disk 2 is mainly located in the middle of the hole, and the stress at the two opening positions is relatively low. Therefore, shoulder 52 should be designed as narrow as possible and can only be placed at the opening position of mounting hole 21.

[0058] In the above discussion of the wheel in this embodiment, when the axial length of the shoulder 5 is more than one-third of its diameter, it can be considered a wide-shoulder design. The maximum length of a wide-shoulder design cannot exceed the length of its mounting hole to avoid the shoulder 5 spanning two holes and becoming susceptible to shearing. When the axial length of the shoulder 5 is less than one-third of its diameter, it is considered a narrow-shoulder design. However, in actual design, the axial length of a narrow shoulder is generally designed to be less than half the axial length of its mounting hole (generally, half the axial length of the mounting hole is definitely less than one-third of the diameter of the shoulder 5), and should not be less than 1mm. A length less than 1mm would greatly increase the processing difficulty and easily cause damage to the hole.

[0059] The main purpose of the design of the wheel in this invention is to add a shoulder 5 to the screw to suppress deformation during operation. For example... Figure 7 As shown, under centrifugal force, the suspended part on the right deforms. Due to the presence of the wide shoulder, the deformation of the connecting rod 42 is greatly suppressed. Shoulder 1 51 and Shoulder 2 52 together effectively function as a wide shoulder. Therefore, when Shoulder 2 52 is removed, Shoulder 1 51 must be a wide shoulder. Similarly, if Shoulder 3 53 is changed to a narrow shoulder design, a narrow shoulder must be added near the right opening of mounting hole 21.

[0060] The remaining structure and method are the same as in Example 1.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wheel, comprising a first blade disk (1), a second blade disk (2), a third blade disk (3), and a connecting part (4), wherein the spokes of the second blade disk (2) are clamped between the flange of the first blade disk (1) and the flange of the third blade disk (3), the flange of the first blade disk (1) is provided with a first mounting hole (11), the spokes of the second blade disk (2) are provided with a second mounting hole (21), and the flange of the third blade disk (3) is provided with a third mounting hole (31). The connecting part (4) includes a connecting rod (42) with a fixing cap (41) at one end and a nut (43) used in conjunction with the connecting rod (42). The outer surface of the other end of the connecting rod (42) is provided with an external thread. The connecting rod (42) passes through mounting hole one (11), mounting hole two (21) and mounting hole three (31) in sequence to connect blade disk one (1), blade disk two (2) and blade disk three (3) in sequence, and is fixed by the nut (43) sleeved on the external thread of the connecting rod. The mounting hole 1 (11), the mounting hole 2 (21) and the mounting hole 3 (31) have the same diameter and are arranged coaxially. The outer surface of the connecting rod (42) between the nut (43) and the fixing cap is provided with several annularly arranged shoulders (5), and the mounting hole one (11) and / or mounting hole two (21) are clearance-fitted with the shoulders (5), and the mounting hole three (31) is clearance-fitted with the shoulders (5); The shoulder (5) in the first mounting hole (11) is 0.2 to 0.5 mm away from the opening of the first mounting hole (11); the shoulder (5) in the second mounting hole (21) is 0.2 to 0.5 mm away from the opening of the second mounting hole (21); the shoulder (5) in the third mounting hole (31) is 0.2 to 0.5 mm away from the opening of the third mounting hole (31). The protrusion height of the shoulder (5) protruding from the surface of the connecting rod (42) is 0.4 to 0.8 mm; The fitting clearance between the shoulder (5) and mounting hole one (11) and / or mounting hole two (21) is 0.04 to 0.11 mm, and the fitting clearance between the shoulder (5) and mounting hole three (31) is 0.04 to 0.11 mm; The shoulder (5) includes a shoulder one (51) that mates with the mounting hole one (11), a shoulder two (52) that mates with the mounting hole two (21), and a shoulder three (53) that mates with the mounting hole three (31). The axial length of the side of the shoulder two (52) is any value within the range of 1 mm to 1 / 2 of the axial length of the mounting hole two (21). The second shoulder (52) is disposed in the end opening of the second mounting hole (21) near the first mounting hole (11). The axial length of the side of the first shoulder (51) is any value within the range of 1 mm to 1 / 2 of the axial length of the first mounting hole (11). The axial length of the side of the third shoulder (53) is any value within the range of 1 / 3 of the diameter of the shoulder to the axial length of the third mounting hole (31). Alternatively, the second shoulder (52) is disposed in the end opening of the second mounting hole (21) near the third mounting hole (31), the lateral axial length of the first shoulder (51) is equal to any value within the range of 1 / 3 of the shoulder diameter to the axial length of the first mounting hole (11), and the lateral axial length of the third shoulder (53) is equal to any value within the range of 1 mm to 1 / 2 of the axial length of the second mounting hole (21).

2. The roulette wheel according to claim 1, characterized in that, The width of the shoulder (5) gradually increases radially toward the central axis.

3. An engine, characterized in that, The roulette wheel included in any one of claims 1-2 above.

4. A method for improving the fatigue life of a wheel, characterized in that, The method includes the wheel according to any one of claims 1-2 or the engine according to claim 3, specifically comprising the following steps: S1. Determine the diameter of the connecting rod (42) according to the model of the existing nut (43), and determine the height of the shoulder (5) according to the diameter of the connecting rod (42); S2. Align the mounting edge of blade disk one (1), the spoke of blade disk two (2), and the mounting edge of blade disk three (3) tightly, and use drilling equipment to process mounting holes one (11), two (21) and three (31) with the hole diameters meeting the design requirements in sequence. S3. Determine the number of shoulders (5), and determine the width and position of each shoulder (5) based on the number of shoulders (5) and the axial length of mounting hole one (11), mounting hole two (21) and mounting hole three (31); S4. Based on the result of step S2, use a turning machine to process a connecting rod (42) with a shoulder (5) and an external thread. Insert the connecting rod (42) into the mounting hole one (11), mounting hole two (21) and mounting hole three (31) in sequence. Use a nut (43) to fit on the external thread and tighten the nut (43) to fix it.

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