Turbine tail blade locking structure and turbine

Abstract

The invention relates to the technical field of turbine blade installation, in particular to a turbine tail blade locking structure and a turbine. Wherein the two side portions, in the width direction, of the first blade root are each provided with a plurality of lock teeth which are arranged at intervals in the length direction of the first blade root, every two adjacent lock teeth are smoothly connected, and each lock tooth is provided with a force bearing face facing the first blade body; in the direction from the tail end of the first blade root to the head end of the first blade root, the distance between the force bearing surface of the first first blade root and the force bearing surface of the second first blade root is larger than the distance between the force bearing surfaces of the other two adjacent first blade roots; the first blade root is provided with a pin hole penetrating and extending in the thickness direction of the first blade root. A plurality of locking grooves distributed at intervals in the length direction of the second blade root are formed in the side portion of the second blade root, all the locking grooves are meshed with all the locking teeth in a one-to-one correspondence mode, and the second blade body is connected to the tail end of the second blade root. The locking structure for the tail blade of the steam turbine can prevent the pin from being broken, and safe operation of the steam turbine is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine blade installation, and in particular to a steam turbine last blade locking structure and a steam turbine. Background Art

[0002] Blades are important parts of steam turbines. Blades mainly include blade roots and blade bodies. Blade roots are the connecting part for installing blades on impellers. Blade roots include T-type blade roots, fork-type blade roots, and longitudinal tree-shaped blade roots. Among them, T-type blade roots have a simple structure and are relatively easy to process, so they are widely used.

[0003] When installing blades with T-shaped blade roots, first insert all blades with T-shaped blade roots from the impeller rim notch into the impeller rim installation groove one by one, then move them circumferentially to the corresponding position, and finally install a blade with T-shaped blade root at the rim notch to form a complete blade circle. Among them, the blade located in the rim installation groove is the standard blade, and the blade installed at the rim notch is the final blade, which can squeeze all standard blades circumferentially to make the whole circle of blades rotate stably.

[0004] The traditional T-shaped blade root of the last blade is fixedly connected to the rim of the impeller by a pin, and due to its own size limitation, the diameter of the pin and the pin hole is relatively small. However, during the high-speed rotation of the last blade, the last blade will apply a radial outward pulling force to the pin, and the pulling force is large, which causes the pin to bear excessive stress. Under high-speed rotation and high temperature conditions, this high stress can easily lead to material fatigue of the pin, accelerate the wear and cracks of the pin, and cause the pin to break easily, affecting the safe operation of the turbine. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that the pin connected to the last blade is prone to breakage under high-speed rotation and high temperature conditions.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a locking structure for a last blade of a steam turbine, which comprises: a last blade, the last blade comprises a first blade body and a first blade root which is set as a T-shaped blade root, the first blade body is connected to the end of the first blade root, and the two sides of the first blade root in the width direction are respectively provided with a plurality of locking teeth arranged at intervals along the length direction of the first blade root, the adjacent locking teeth are smoothly connected, and the locking teeth have a bearing surface facing the first blade body; in the direction from the end of the first blade root to its head end, the distance between the bearing surface of the first first blade root and the bearing surface of the second first blade root is greater than the distance between the bearing surfaces of the other two adjacent first blade roots; the first blade root is provided with a pin hole extending through along the thickness direction thereof; two locking blades, the two locking blades are respectively located on both sides of the last blade in the width direction, the locking blade comprises a second blade body and a second blade root which is set as a T-shaped blade root, the side of the second blade root is provided with a plurality of locking grooves which are spaced apart along the length direction thereof, all the locking grooves are engaged with all the locking teeth in a one-to-one correspondence, and the second blade body is connected to the end of the second blade root.

[0007] In some embodiments, the locking tooth has a locking surface facing the head end of the first blade root; in the direction from the tooth root to the tooth top of the locking tooth, the distance between the load-bearing surface and the locking surface along the length direction of the first blade root gradually decreases.

[0008] In some embodiments, five locking teeth are respectively provided on both sides of the first blade root in the width direction; and in the direction from the end of the first blade root to its head end, the spacing between the load-bearing surface of the first locking tooth and the load-bearing surface of the second locking tooth is a first spacing t1, the spacing between the load-bearing surface of the second locking tooth and the load-bearing surface of the third locking tooth is a second spacing t2, the spacing between the load-bearing surface of the third locking tooth and the load-bearing surface of the fourth locking tooth is a third spacing t3, the spacing between the load-bearing surface of the fourth locking tooth and the load-bearing surface of the fifth locking tooth is a third spacing t3, the first spacing t1 is greater than the second spacing t2, and the second spacing t2 is greater than the third spacing t3; and a plane parallel to the head end face of the first blade root is defined as a first reference plane, and the angle α between the load-bearing surface of the locking tooth and the first reference plane is in the range of 0° to 5.5°.

[0009] In some embodiments, a plane parallel to the head end surface of the first blade root is defined as a first reference plane, and an angle α between the load-bearing surface of the locking tooth and the first reference plane is in a range of 20° to 45°.

[0010] In some embodiments, four locking teeth are respectively provided on both sides in the width direction of the first blade root; and in the direction from the end to the head end of the first blade root, the spacing between the bearing surface of the first locking tooth and the bearing surface of the second locking tooth is a first spacing t1, the spacing between the bearing surface of the second locking tooth and the bearing surface of the third locking tooth is a second spacing t2, and the spacing between the bearing surface of the third locking tooth and the bearing surface of the fourth locking tooth is a third spacing t3, the first spacing t1 is greater than the second spacing t2, and the second spacing t2 is greater than the third spacing t3; and in the length direction of the first blade root, the calculation formula for the total length h of all the locking teeth is:

[0011] In some embodiments, the length of the first interval t1 ranges from 6 mm to 7 mm, the length of the second interval t2 ranges from 5 mm to 5.5 mm, and the length of the third interval t3 ranges from 3.25 mm to 5 mm.

[0012] In some embodiments, the bottom side of the bearing surface of the locking tooth is smoothly connected to the side surface of the first blade root through the first arc surface, and the first arc surface is tangent to the side surface of the first blade root; projected in the thickness direction of the first blade root, the length range of the radius R1 of the first arc surface is 0.5 mm to 1.2 mm; in the direction from the end of the first blade root to its head end, the calculation formula of the first length h1 of the first arc surface in the length direction of the first blade root is: The top side of the locking surface is smoothly connected to the top side of the load-bearing surface through a second arc surface (144); when projected in the thickness direction of the first blade root, the length range of the radius R2 of the second arc surface (144) is 0.6 mm to 1.3 mm; the radius R2 of the second arc surface (144) is greater than the radius R1 of the first arc surface, and the difference between the two is 0.1 mm; the bottom side of the locking surface is smoothly connected to the side surface of the first blade root through a third arc surface, and the third arc surface is tangent to the side surface of the first blade root; the adjacent first arc surface and the third arc surface are cocentric and smoothly connected.

[0013] In some embodiments, the dimension of the locking tooth in the width direction of the first blade root is defined as width B; projected in the thickness direction of the first blade root, the calculation formula for the load-bearing surface length b of the locking tooth is: b = (B-R1-R2) / cosα+(R1+R2)×tanα.

[0014] On the other hand, the present invention provides a steam turbine, which includes a pin, an impeller, a plurality of standard blades and the turbine last blade locking structure of the above-mentioned embodiment, wherein the plurality of standard blades are installed in the rim mounting groove of the impeller, the turbine last blade locking structure is arranged at the rim notch of the impeller, and the turbine last blade locking structure squeezes all the standard blades circumferentially, and the pin is passed through the pin hole and the rim of the impeller.

[0015] In some embodiments, a gasket is provided between two adjacent standard blades, and the gasket is welded to the adjacent standard blades.

[0016] The above technical solution of the present application has the following beneficial effects:

[0017] The locking blade is used to be installed in the rim installation groove of the impeller, and the last blade is used to be installed in the notch of the impeller rim. The last blade and the locking blade can be firmly engaged through the locking teeth and the locking groove, so the last blade can not only be fixedly connected to the rim of the impeller through the pin, but also can be further fixed to the locking blade through the mutually engaged locking teeth and the locking groove. When the last blade is running under high-speed rotation and high temperature conditions, the mutually engaged locking teeth and the locking groove can bear part of the radial outward pulling force, so that the radial outward pulling force applied by the last blade to the pin will be greatly reduced, reducing the stress on the pin, thereby avoiding material fatigue of the pin, avoiding wear and cracks on the pin, and preventing the pin from breaking, ensuring the safe operation of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the assembly of the locking structure of the last blade of a steam turbine in one embodiment of the present invention;

[0019] Figure 2 is a front view schematic diagram of the last blade in one embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of the spacing between adjacent locking teeth in one embodiment of the present invention;

[0021] Figure 4 is a partial schematic diagram of a lock tooth in one embodiment of the present invention;

[0022] Figure 5 is a three-dimensional schematic diagram of a last blade in another embodiment of the present invention;

[0023] Figure 6 is a front view schematic diagram of a last blade in another embodiment of the present invention;

[0024] Figure 7 is a partial schematic diagram of a lock tooth in another embodiment of the present invention;

[0025] Figure 8 is a schematic diagram of the spacing between adjacent locking teeth in another embodiment of the present invention;

[0026] Fig. 9 is the normal component of the centrifugal force F in one embodiment of the present invention n Schematic diagram of

[0027] Fig.10 is a schematic diagram of a first length h1 in one embodiment of the present invention;

[0028] Fig.11 Schematic diagram of the second length h2 in one embodiment of the present invention.

[0029] Description of Reference Numerals

[0030] 1. Last blade; 11. First blade body; 12. First blade root; 13. Pin hole; 14. Locking tooth; 141. Load-bearing surface; 142. Locking surface; 143. First arc surface; 144. Second arc surface; 145. Third arc surface; 15. First reference surface;

[0031] 2. Locking blade; 21. Second blade body; 22. Second blade root; 23. Locking groove;

[0032] 3. Pins;

[0033] 4. Standard blades;

[0034] 5. Gasket. DETAILED DESCRIPTION

[0035] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention, rather than to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention.

[0036] like Figures 1 to 8As shown, the present invention provides a locking structure for a last blade of a steam turbine, which includes a last blade 1 and two locking blades 2. The last blade 1 includes a first blade body 11 and a first blade root 12 set as a T-shaped blade root, the first blade body 11 is connected to the end of the first blade root 12, and the two sides in the width direction of the first blade root 12 are respectively provided with a plurality of locking teeth 14 arranged at intervals along the length direction of the first blade root 12, and the adjacent locking teeth 14 are smoothly connected, and the locking teeth 14 have a bearing surface 141 facing the first blade body 11; in the direction from the end of the first blade root 12 to its head end, the distance between the bearing surface 141 of the first first blade root 12 and the bearing surface 141 of the second first blade root 12 is greater than the distance between the bearing surfaces 141 of the other two adjacent first blade roots 12; the first blade root 12 is provided with a pin hole 13 extending through it in the thickness direction. The two locking blades 2 are respectively located on both sides of the width direction of the last blade 1. The locking blade 2 includes a second blade body 21 and a second blade root 22 set as a T-shaped blade root. The side of the second blade root 22 is provided with a plurality of locking grooves 23 spaced along its length direction. All locking grooves 23 are engaged with all locking teeth 14 one by one. The second blade body 21 is connected to the end of the second blade root 22.

[0037] Specifically, the last blade 1 is located between the two locking blades 2, and the second blade roots 22 of the two locking blades 2 are respectively fitted with the first blade roots 12. The side of the second blade root 22 of the locking blade 2 is provided with a plurality of locking grooves 23, and the side of the first blade root 12 of the last blade 1 is provided with a plurality of locking teeth 14, and all the locking teeth 14 are inserted into all the locking grooves 23 one by one and bite, so that the last blade 1 and the locking blade 2 are tightly matched. Of course, the locking groove 23 has a suitable depth and opening so that it can be fully adapted and fitted with the corresponding locking teeth 14.

[0038] In this embodiment, the locking blade 2 is used to be installed in the rim installation groove of the impeller, and the last blade 1 is used to be installed in the rim notch of the impeller. The last blade 1 and the locking blade 2 can be firmly engaged through the locking teeth 14 and the locking groove 23, so the last blade 1 can not only be fixedly connected to the rim of the impeller through the pin 3, but also can be further fixed to the locking blade 2 through the mutually engaged locking teeth 14 and the locking groove 23. When the last blade 1 is running under high-speed rotation and high temperature conditions, the mutually engaged locking teeth 14 and the locking groove 23 can bear a part of the radial outward pulling force, so that the radial outward pulling force applied by the last blade 1 to the pin 3 will be greatly reduced, reducing the stress borne by the pin 3, thereby avoiding material fatigue of the pin 3, avoiding wear and cracks of the pin 3, and preventing the pin 3 from breaking, thereby ensuring the safe operation of the steam turbine.

[0039] like Figure 2 and Figure 6As shown, in some embodiments of the present invention, the locking tooth 14 has a locking surface 142 facing the head end of the first blade root 12; in the direction from the root of the locking tooth 14 to the top of its tooth, the distance between the load-bearing surface 141 and the locking surface 142 along the length direction of the first blade root 12 gradually decreases.

[0040] Specifically, when projected in the thickness direction of the first blade root 12, the lock tooth 14 is roughly triangular. This arrangement allows the root of the lock tooth 14 to have a larger size, thereby being able to bear a larger force, so that the pulling force applied to the pin 3 by the last blade 1 during rotation is greatly reduced. Moreover, compared with setting the lock tooth 14 in a semi-cylindrical shape or the like, the lock tooth 14 in the above-mentioned form also has the advantages of simple structure and easy manufacturing. Preferably, the angle between the load-bearing surface 141 and the locking surface 142 ranges from 40° to 135°.

[0041] like Figures 2 to 4 As shown, in some embodiments of the present invention, five locking teeth 14 are respectively provided on both sides of the first blade root 12 in the width direction; and in the direction from the end to the head end of the first blade root 12, the distance between the bearing surface 141 of the first locking tooth 14 and the bearing surface 141 of the second locking tooth 14 is a first distance t1, the distance between the bearing surface 141 of the second locking tooth 14 and the bearing surface 141 of the third locking tooth 14 is a second distance t2, and the distance between the bearing surface 141 of the third locking tooth 14 and the bearing surface 141 of the third locking tooth 14 is a second distance t3. The spacing between the load-bearing surfaces 141 of the four locking teeth 14 is the third spacing t3, the spacing between the load-bearing surface 141 of the fourth lock tooth 14 and the load-bearing surface 141 of the fifth lock tooth 14 is the third spacing t3, the first spacing t1 is greater than the second spacing t2, and the second spacing t2 is greater than the third spacing t3; and a plane parallel to the head end face of the first blade root 12 is defined as the first reference plane 15, and the angle α between the load-bearing surface 141 of the lock tooth 14 and the first reference plane 15 is in the range of 0° to 5.5°.

[0042] Specifically, by setting the above spacing, the connection surface S at the root of the first lock tooth 14 is the largest, the connection surface S at the root of the second lock tooth 14 is the second largest, and the connection surface S at the root of the third lock tooth 14, the connection surface S at the root of the fourth lock tooth 14, and the connection surface S at the root of the fifth lock tooth 14 are the smallest. This structural form matches the extrusion force exerted on each lock tooth 14, prevents the lock tooth 14 from failing, and enables the last blade 1 to operate stably for a long time. For example, the first lock tooth 14 is subjected to the largest extrusion force; at the same time, the connection surface S at the root of the first lock tooth 14 is the largest, so that the first lock tooth 14 can withstand the corresponding extrusion force. For another example, the fifth lock tooth 14 is subjected to the smallest extrusion force; at the same time, the connection surface S at the root of the fifth lock tooth 14 is the smallest, so that the fifth lock tooth 14 can withstand the corresponding extrusion force. In addition, the angle α between the bearing surface 141 of the lock tooth 14 and the first reference surface 15 ranges from 0° to 5.5°, that is, the bearing surface 141 of the lock tooth 14 and the first reference surface 15 are substantially parallel to facilitate the engagement between the lock tooth 14 and the lock groove 23 .

[0043] Of course, the first reference plane 15 is parallel to the thickness direction of the first blade root 12 .

[0044] like Figures 5 to 9 As shown, in some embodiments of the present invention, a plane parallel to the head end surface of the first blade root 12 is defined as the first reference plane 15, and the angle α between the bearing surface 141 of the locking tooth 14 and the first reference plane 15 is in the range of 20° to 45°. Preferably, the angle α is 30°.

[0045] Specifically, it has been verified through experiments that, under the condition of meeting the load-bearing requirements, no matter four lock teeth 14, five lock teeth 14 or a greater number of lock teeth 14 are designed, the force carried by the first lock tooth 14 (counted along the direction from the end of the first blade root 12 to its head end) is the largest, and the centrifugal force on the load-bearing surface 141 of the first lock tooth 14 is substantially the same. Then, under the premise that the centrifugal force F on the load-bearing surface 141 of the first lock tooth 14 is substantially the same, the angle α between the load-bearing surface 141 of the lock tooth 14 and the first reference plane 15 increases, and the normal component of the centrifugal force F on the load-bearing surface 141 of the first lock tooth 14 increases. n The smaller the F n =F×cosα. The locking blade 2 exerts a squeezing force on the bearing surface 141 of the first locking tooth 14. The squeezing force is equal to the normal component of the centrifugal force and opposite in direction. The normal component of the centrifugal force F nThe smaller the angle α is, the smaller the extrusion pressure on the bearing surface 141 is, thereby reducing the stress on the bearing surface 141. Referring to the description of the first locking tooth 14, the second to fourth locking teeth 14 can also achieve stress reduction. In addition, when designing the locking tooth 14, the tooth height of the locking tooth 14 in the width direction of the first blade root 12 is basically constant, so when the angle α between the bearing surface 141 of the locking tooth 14 and the first reference plane 15 increases, the area of ​​the bearing surface 141 of the locking tooth 14 will also increase, further reducing the stress on the bearing surface 141, so that the last blade 1 can operate stably for a long time.

[0046] like Figures 5 to 9 As shown, in some embodiments of the present invention, four locking teeth 14 are respectively provided on both sides in the width direction of the first blade root 12; and in the direction from the end to the head end of the first blade root 12, the spacing between the bearing surface 141 of the first locking tooth 14 and the bearing surface 141 of the second locking tooth 14 is a first spacing t1, the spacing between the bearing surface 141 of the second locking tooth 14 and the bearing surface 141 of the third locking tooth 14 is a second spacing t2, and the spacing between the bearing surface 141 of the third locking tooth 14 and the bearing surface 141 of the fourth locking tooth 14 is a third spacing t3, the first spacing t1 is greater than the second spacing t2, and the second spacing t2 is greater than the third spacing t3; and in the length direction of the first blade root 12, the calculation formula for the total length h of all the locking teeth 14 is: Of course, the length H of the first blade root 12 is greater than the total length h of all locking teeth 14 .

[0047] Specifically, by setting the above spacing, the connection surface S at the root of the first lock tooth 14 is the largest, the connection surface S at the root of the second lock tooth 14 is the second largest, and the connection surface S at the root of the third lock tooth 14 and the connection surface S at the root of the fourth lock tooth 14 are the smallest. This structural form matches the extrusion force on each lock tooth 14. For example, the first lock tooth 14 is subjected to the largest extrusion force; at the same time, the connection surface S at the root of the first lock tooth 14 is the largest, so that the first lock tooth 14 can withstand the corresponding extrusion force. For another example, the fourth lock tooth 14 is subjected to the smallest extrusion force; at the same time, the connection surface S at the root of the fourth lock tooth 14 is the smallest, so that the fourth lock tooth 14 can withstand the corresponding extrusion force. At the same time, as the angle α between the bearing surface 141 of the lock tooth 14 and the first reference plane 15 increases, the bearing surface 141 of the lock tooth 14 will also increase, further reducing the stress on the bearing surface 141, which is helpful to achieve stress equalization, and because the last blade 1 reduces the pressure on the pin 3, the last blade 1 can further operate stably for a long time. In addition, by adjusting the angle α between the bearing surface 141 and the first reference surface 15 and changing the spacing between adjacent locking teeth 14, the number of locking teeth 14 can be reduced to four while fully ensuring the performance of the locking teeth 14, thereby simplifying the structure of the last blade 1 and reducing costs.

[0048] In addition, in order to facilitate understanding of the calculation process of the total length h of all the locking teeth 14, it is assumed that there is a fifth locking tooth 14, that is, the fifth locking tooth 14 is a virtual locking tooth that does not actually exist. Figure 8 and Fig.11 As shown, at this time, the first arc surface 143 at the bearing surface 141 of the fifth locking tooth 14 is the last first arc surface 143, and the calculation formula of the second length h2 of the last first arc surface 143 in the length direction of the first blade root 12 is: At this time, in the length direction of the first blade root 12, the calculation formula for the total length h of all the locking teeth 14 is:

[0049] like Figure 8 As shown, in some embodiments of the present invention, the length range of the first spacing t1 is 6 mm to 7 mm, the length range of the second spacing t2 is 5 mm to 5.5 mm, and the length range of the third spacing t3 is 3.25 mm to 5 mm.

[0050] Specifically, by setting the above spacing, the connection surface S at the root of the first locking tooth 14 is the largest, the connection surface S at the root of the second locking tooth 14 is the second largest, and the connection surface S at the root of the third locking tooth 14 and the connection surface S at the root of the fourth locking tooth 14 are the smallest. This structural form matches the extrusion force on each locking tooth 14. In addition, four locking teeth 14 are formed on the side of the first blade root 12, which simplifies the number of the last blades 1 and reduces the cost.

[0051] like Figures 7 to 10 As shown, in some embodiments of the present invention, the bottom side of the bearing surface 141 of the locking tooth 14 is smoothly connected to the side surface of the first blade root 12 through the first arc surface 143, and the first arc surface 143 is tangent to the side surface of the first blade root 12; projected in the thickness direction of the first blade root 12, the length range of the radius R1 of the first arc surface 143 is 0.5mm to 1.2mm; in the direction from the end of the first blade root 12 to its head end, the calculation formula of the first length h1 of the first arc surface 143 in the length direction of the first blade root 12 is: The top side of the locking surface 142 is smoothly connected to the top side of the load-bearing surface 141 through the second arc surface 144; projected in the thickness direction of the first blade root 12, the length range of the radius R2 of the second arc surface 144 is 0.6mm~1.3mm; the radius R2 of the second arc surface 144 is greater than the radius R1 of the first arc surface 143, and the difference between the two is 0.1mm; the bottom side of the locking surface 142 is smoothly connected to the side of the first blade root 12 through the third arc surface 145, and the third arc surface 145 is tangent to the side of the first blade root 12; the adjacent first arc surface 143 and the third arc surface 145 are cocentric and smoothly connected.

[0052] Specifically, by providing the first arc surface 143 and the third arc surface 145, stress concentration can be prevented at the root of the lock tooth 14, and the lock tooth 14 and the lock groove 23 can be closely fitted. By providing the second arc surface 144, stress concentration can be prevented at the tooth top of the lock tooth 14, and the lock tooth 14 and the lock groove 23 can be closely fitted. Moreover, by providing the first arc surface 143 and the third arc surface 145 within the above range, the area of ​​the bearing surface 141 can be maximized while avoiding stress concentration at the root and the tooth top of the lock tooth 14, thereby reducing the stress at the bearing surface 141. In addition, the adjacent first arc surface 143 and the third arc surface 145 are cocentric and smoothly connected, that is, the adjacent first arc surface 143 and the third arc surface 145 extend on the same arc surface, thereby avoiding stress concentration between two adjacent lock teeth 14. In addition, the radius R2 of the second arc surface 144 is 0.1 mm larger than the radius R1 of the first arc surface 143, so the second arc surface 144 is relatively flat. Therefore, when assembling the last blade 1, interference between the tooth top of the locking tooth 14 and the bottom of the locking groove 23 can be avoided, so that the load-bearing surface 141 and the locking surface 142 can be fully fitted with the groove wall of the locking groove 23.

[0053] like Figure 8 As shown, in some embodiments of the present invention, the dimension of the locking tooth 14 in the width direction of the first blade root 12 is defined as width B; projected in the thickness direction of the first blade root 12, the calculation formula for the load-bearing surface length b of the locking tooth 14 is: b = (B-R1-R2) / cosα+R1+R2×tanα.

[0054] Specifically, the length of the bearing surface 141 of the lock tooth 14 is set by the above calculation method, so that the length b of the bearing surface 141 of the lock tooth 14 is larger, which helps to reduce the stress on the bearing surface 141.

[0055] In some embodiments, a dimension of the locking tooth 14 in the width direction of the first blade root 12 is a width B, and the width B is in a range of 3 mm to 6 mm.

[0056] Below, the effects of five lock teeth 14 and four lock teeth 14 are compared, and all lock teeth 14 are made of the same metal material. Among them, the first group is five lock teeth 14, the angle α between the load-bearing surface 141 of the lock teeth 14 and the first reference surface 15 is 0°, and the spacing between the load-bearing surfaces 141 of adjacent lock teeth 14 is 5mm; the radius R2 of the second arc surface 144 is 0.6mm, and the radius R1 of the first arc surface 143 is 0.5mm. Among them, the second group is four lock teeth 14, the angle α between the load-bearing surface 141 of the lock teeth 14 and the first reference surface 15 is 30°, the length of the first spacing t1 is 7mm, the length of the second spacing t2 is 5.5mm, and the length of the third spacing t3 is 5mm; the radius R2 of the second arc surface 144 is 0.9mm, and the radius R1 of the first arc surface 143 is 0.8mm. Table 1 shows the stress test results of the two groups. Combined with Table 1, it can be seen that in the second group, the stress of the bearing surface 141 of the lock tooth 14 has decreased significantly, and the stress concentration has been effectively solved. It is generally believed that the stress at the bearing surface 141 of the last lock tooth 14 must be less than 50MPa, otherwise another lock tooth 14 must be added to ensure safe operation. In the first group, the stress of the bearing surface 141 of the fourth lock tooth 14 is greater than 50MPa, and the stress of the bearing surface 141 of the fifth lock tooth 14 is less than 50MPa, so five lock teeth 14 need to be set in the first group, but the stress at the first and second lock teeth 14 is relatively large. In the second group, the stress of the bearing surface 141 of the third lock tooth 14 is greater than 50MPa, and the stress of the bearing surface 141 of the fourth lock tooth 14 is less than 50MPa, so only four lock teeth 14 need to be set in the second group, and the stress at the first and second lock teeth 14 is relatively small. Obviously, by changing the spacing of the locking teeth 14 , increasing the angle α, increasing the radius R1 of the first arc surface 143 and increasing the radius R2 of the second arc surface 144 , the stress on the bearing surface 141 of the locking teeth 14 can be reduced, and the number of the locking teeth 14 can also be reduced.

[0057] Table 1

[0058] Group 1 Group 2 Stress at the bearing surface of the first locking tooth 538.02MPa 381.94MPa Stress at the bearing surface of the second locking tooth 371.13MPa 205.54MPa Stress at the bearing surface of the third locking tooth 146.56MPa 78.59MPa Stress at the bearing surface of the fourth locking tooth 67.718MPa 46.29MPa Stress at the bearing surface of the fifth locking tooth 35.711MPa /

[0059] like Figure 1 As shown, on the other hand, the present invention provides a steam turbine, which includes a pin 3, an impeller, a plurality of standard blades 4 and the turbine last blade locking structure of the above-mentioned embodiment, the plurality of standard blades 4 are installed in the rim mounting groove of the impeller, the turbine last blade locking structure is arranged at the rim notch of the impeller, and the turbine last blade locking structure squeezes all the standard blades 4 circumferentially, and the pin 3 is passed through the pin hole 13 and the rim of the impeller.

[0060] Specifically, the steam turbine adopts the steam turbine last blade locking structure of the above embodiment, so it can also achieve the above technical effects.

[0061] like Figure 1 As shown, in some embodiments of the present invention, a gasket 5 is provided between two adjacent standard blades 4, and the gasket 5 is welded to the adjacent standard blades 4 to make the blade ring stable and firm.

[0062] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above are only preferred implementation methods of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the present invention to other occasions without improvement, should be regarded as the protection scope of the present invention.

Claims

1. A steam turbine last blade locking structure, characterized in that: include: A last blade (1), the last blade (1) comprising a first blade body (11) and a first blade root (12) configured as a T-shaped blade root, the first blade body (11) being connected to the end of the first blade root (12), a plurality of locking teeth (14) arranged at intervals along the length direction of the first blade root (12) being respectively provided at both sides in the width direction of the first blade root (12), adjacent locking teeth (14) being smoothly connected, and the locking teeth (14) having a bearing surface (141) facing the first blade body (11); in the direction from the end of the first blade root (12) to its head end, the distance between the bearing surface (141) of the first first blade root (12) and the bearing surface (141) of the second first blade root (12) is greater than the distance between the bearing surfaces (141) of the other two adjacent first blade roots (12); the first blade root (12) is provided with a pin hole (13) extending through it in the thickness direction; and Two locking blades (2), the two locking blades (2) are respectively located on both sides of the width direction of the last blade (1), the locking blade (2) comprises a second blade body (21) and a second blade root (22) arranged as a T-shaped blade root, the side of the second blade root (22) is provided with a plurality of locking grooves (23) spaced apart along its length direction, all the locking grooves (23) are engaged with all the locking teeth (14) in a one-to-one correspondence, and the second blade body (21) is connected to the end of the second blade root (22).

2. The steam turbine last blade locking structure according to claim 1, characterized in that: The locking tooth (14) has a locking surface (142) facing the head end of the first blade root (12); in the direction from the tooth root of the locking tooth (14) to its tooth top, the distance between the load-bearing surface (141) and the locking surface (142) along the length direction of the first blade root (12) gradually decreases.

3. The locking structure of the last blade of a steam turbine according to claim 2, characterized in that: Five locking teeth (14) are respectively provided on both sides in the width direction of the first blade root (12); and in the direction from the end to the head end of the first blade root (12), the distance between the bearing surface (141) of the first locking tooth (14) and the bearing surface (141) of the second locking tooth (14) is a first distance t1, the distance between the bearing surface (141) of the second locking tooth (14) and the bearing surface (141) of the third locking tooth (14) is a second distance t2, the distance between the bearing surface (141) of the third locking tooth (14) and the bearing surface (141) of the fourth locking tooth (14) is a third distance t3, the distance between the bearing surface (141) of the fourth locking tooth (14) and the bearing surface (141) of the fifth locking tooth (14) is a third distance t3, the first distance t1 is greater than the second distance t2, and the second distance t2 is greater than the third distance t3; A plane parallel to the head end face of the first blade root (12) is defined as a first reference plane (15), and an angle α between a load-bearing surface (141) of the locking tooth (14) and the first reference plane (15) is in the range of 0° to 5.5°.

4. The steam turbine last blade locking structure according to claim 2, characterized in that: A plane parallel to the head end face of the first blade root (12) is defined as a first reference plane (15), and an angle α between a load-bearing surface (141) of the locking tooth (14) and the first reference plane (15) is in the range of 20° to 45°.

5. The steam turbine last blade locking structure according to claim 4, characterized in that: Four locking teeth (14) are respectively provided on both sides in the width direction of the first blade root (12); and in the direction from the end to the head end of the first blade root (12), the distance between the bearing surface (141) of the first locking tooth (14) and the bearing surface (141) of the second locking tooth (14) is a first distance t1, the distance between the bearing surface (141) of the second locking tooth (14) and the bearing surface (141) of the third locking tooth (14) is a second distance t2, and the distance between the bearing surface (141) of the third locking tooth (14) and the bearing surface (141) of the fourth locking tooth (14) is a third distance t3, the first distance t1 is greater than the second distance t2, and the second distance t2 is greater than the third distance t3; and in the length direction of the first blade root (12), the total length h of all the locking teeth (14) is calculated as follows:

6. The steam turbine last blade locking structure according to claim 5, characterized in that: The length range of the first interval t1 is 6 mm to 7 mm, the length range of the second interval t2 is 5 mm to 5.5 mm, and the length range of the third interval t3 is 3.25 mm to 5 mm.

7. The steam turbine last blade locking structure according to claim 6, characterized in that: The bottom side of the load-bearing surface (141) of the locking tooth (14) is smoothly connected to the side surface of the first blade root (12) through a first arc surface (143), and the first arc surface (143) is tangent to the side surface of the first blade root (12); when projected in the thickness direction of the first blade root (12), the length range of the radius R1 of the first arc surface (143) is 0.5 mm to 1.2 mm; In the direction from the end of the first blade root (12) to its head end, a first length h1 of the first arc surface (143) in the length direction of the first blade root (12) is calculated by the formula: The top side of the locking surface (142) is smoothly connected to the top side of the load-bearing surface (141) via a second arc surface (144); when projected in the thickness direction of the first blade root (12), the length range of the radius R2 of the second arc surface (144) is 0.6 mm to 1.3 mm; the radius R2 of the second arc surface (144) is greater than the radius R1 of the first arc surface (143), and the difference between the two is 0.1 mm; The bottom side of the locking surface (142) is smoothly connected to the side surface of the first blade root (12) through a third arc surface (145), and the third arc surface (145) is tangent to the side surface of the first blade root (12); the adjacent first arc surface (143) and the third arc surface (145) are cocentric and smoothly connected.

8. The steam turbine last blade locking structure according to claim 7, characterized in that: The dimension of the locking tooth (14) in the width direction of the first blade root (12) is defined as width B; Projected in the thickness direction of the first blade root (12), the calculation formula for the load-bearing surface length b of the locking tooth (14) is: b=(B-R1-R2) / cosα+(R1+R2)×tanα.

9. A steam turbine, characterized in that: The invention comprises a pin (3), an impeller, a plurality of standard blades (4) and a turbine last blade locking structure as described in any one of claims 1 to 8, wherein the plurality of standard blades (4) are installed in the rim mounting groove of the impeller, the turbine last blade locking structure is arranged at the rim notch of the impeller, and the turbine last blade locking structure squeezes all the standard blades (4) circumferentially, and the pin (3) is passed through the pin hole (13) and the rim of the impeller.

10. The steam turbine according to claim 9, characterized in that A gasket (5) is provided between two adjacent standard blades (4), and the gasket (5) is welded to the adjacent standard blades (4).

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