A three-shell steam turbine steam inlet structure and steam turbine

Abstract

The present application provides a three-layer shell steam turbine steam inlet structure and a steam turbine, wherein the steam inlet structure includes a steam inlet valve, a three-layer shell and a plug. The steam inlet valve includes a valve housing and a valve diffuser. The three-layer shell includes an outer shell, an outer inner shell and an inner shell. The outer shell is sealed with the valve housing flange. The plug includes an inner ring part, an outer ring part and a through hole. The first end of the outer ring part is in close contact with the valve housing through a sealing ring, and the second end is in close contact with the outer inner shell flange. The first end of the inner ring part is in close contact with the valve diffuser through a sealing ring, and the second end is in close contact with the inner shell through a sealing ring. The plug, the valve housing and the valve diffuser enclose a first interlayer cavity, and the plug, the outer inner shell and the inner shell enclose a second interlayer cavity. The through hole connects the first and second interlayer cavities. The first and second interlayer cavities and the through hole constitute a first sealed cavity. The valve housing, the outer shell, the plug and the outer inner shell enclose a second sealed cavity. The present application can improve the service conditions of the valve diffuser, the inner shell and the outer inner shell, increase the upper limit of the pressure bearing capacity, and reduce the risk of failure.

Description

Technical Field

[0001] The present application relates to the technical field of power station steam turbines, and in particular to a three-shell steam turbine steam inlet structure and a steam turbine. Background Art

[0002] A steam turbine is a turbine that uses steam as a medium. Its main purpose is to convert thermal energy into mechanical energy. The working medium of a steam turbine is high-temperature and high-pressure steam. Therefore, when the steam turbine is working, it is always in a high-temperature and high-pressure working condition. The high-temperature and high-pressure environment may bring a greater risk of failure to the structure. Therefore, in order to reduce this risk, the steam turbines in the prior art generally use double-shell steam turbines and triple-shell steam turbines.

[0003] In a double-shell steam turbine, the inner shell is arranged around the rotor, and the outer shell is arranged around the inner shell. Due to temperature changes, the inner shell moves relative to the valve. The valve includes a valve housing and a valve diffuser arranged in the valve. During operation, high stress may cause the valve diffuser to deform, which affects the working performance of the steam turbine. Therefore, an angular sealing ring is arranged between the valve diffuser and the inner shell to balance the thermal displacement between the valve diffuser and the inner shell.

[0004] However, as the operating parameters of the steam turbine, such as pressure and temperature, become higher and higher, due to strength and material limitations, the double-shell steam turbine can no longer meet the needs of the work, and a three-shell structure must be adopted to reduce the temperature gradient in the thickness direction of the cylinder and the use of expensive high-temperature materials.

[0005] Generally, a three-shell steam turbine includes an inner shell, an outer shell, and an outer inner shell between the inner shell and the outer shell. The outer inner shell also undergoes thermal displacement due to thermal changes, and this thermal displacement may interfere with the valve diffuser. In addition, the space between the inner shell and the outer inner shell, and the space between the outer inner shell and the outer shell should be sealed, and excessive mechanical stress due to thermal displacement should be avoided.

[0006] In the prior art, the patent document with publication number CN104033190A discloses a steam inlet structure of a three-layer shell steam turbine, in which the sealing cavity formed between the outer inner shell and the inner shell extends to between the valve housing and the valve diffuser, thereby reducing the pressure difference and temperature difference borne by the valve diffuser, thereby reducing the high stress caused by the high pressure difference and the high temperature difference. However, in the patent document CN104033190A, the inner shell and the valve diffuser are connected only by an angular sealing ring, and the steam pressure and temperature range that can be tolerated are limited. When the pressure difference and temperature difference between the inner and outer walls of the valve diffuser and the inner and outer walls of the inner shell are too large, the sealing line established at the connection between the inner shell and the valve diffuser is at risk of failure. Summary of the invention

[0007] The purpose of the embodiments of the present application is to provide a three-shell steam turbine steam inlet structure, which can effectively improve the working environment of the valve diffuser, inner shell and outer inner shell, reduce the risk of structural failure and sealing line failure, and at the same time increase the pressure and temperature bearing upper limits of the valve diffuser, inner shell and outer inner shell.

[0008] The second purpose of the embodiment of the present application is to provide a steam turbine using the above-mentioned steam inlet structure.

[0009] In a first aspect, a three-layer shell steam turbine steam inlet structure is provided, comprising a steam inlet valve, a three-layer shell and a plug pipe.

[0010] The steam inlet valve includes a valve housing and a valve diffuser located inside the valve housing. The three-layer shell includes an outer shell, an outer inner shell and an inner shell arranged in sequence, and the outer shell is sealed and connected to the outer side of the valve housing through a flange structure. The insert includes an inner ring part, an outer ring part and a through hole. The outer ring part includes a first end and a second end, the first end of the outer ring part is sealed and connected to the valve housing through a first sealing ring, and the second end of the outer ring part is sealed and connected to the outer inner shell through a flange structure. The inner ring part includes a first end and a second end, the first end of the inner ring part is sealed and connected to the valve diffuser through a second sealing ring, and the second end of the inner ring part is sealed and connected to the inner shell through a third sealing ring. The insert, the valve housing and the valve diffuser together enclose a first interlayer cavity, and the insert, the outer inner shell and the inner shell together enclose a second interlayer cavity. The through hole connects the first interlayer cavity and the second interlayer cavity. The first interlayer cavity, the through hole and the second interlayer cavity constitute a first sealed cavity. The valve housing, the outer shell and the insert, the outer inner shell together enclose a second sealed cavity.

[0011] In an implementable scheme, the steam pressure passing through the channel formed by the valve diffuser, the insert tube and the inner side of the inner shell is P0, steam is introduced into the first sealed cavity and the second sealed cavity, the steam pressure in the first sealed cavity is P1, and the steam pressure in the second sealed cavity is P2, and P0, P1 and P2 satisfy P0>P1>P2.

[0012] In one feasible solution, the plurality of through holes are evenly or unevenly distributed along the circumference between the inner ring portion and the outer ring portion of the insertion tube.

[0013] In an implementable scheme, the first sealing ring, the second sealing ring and the third sealing ring all include a movable end and a fixed end; the end face of the first end of the outer ring part of the insert tube is provided with a first ring groove, the end face of the first end of the inner ring part of the insert tube is provided with a second ring groove, and the end face of the inner shell for connecting with the insert tube is provided with a third ring groove; the fixed end of the first sealing ring is sealedly connected to the valve housing, the movable end of the first sealing ring is inserted into the first ring groove, and the movable end of the first sealing ring is slidably sealed with the first ring groove; the fixed end of the second sealing ring is sealedly connected to the valve diffuser, the movable end of the second sealing ring is inserted into the second ring groove, and the movable end of the second sealing ring is slidably sealed with the second ring groove; the fixed end of the third sealing ring is sealedly connected to the second end of the inner ring part of the insert tube, the movable end of the third sealing ring is inserted into the third ring groove, and the movable end of the third sealing ring is slidably sealed with the third ring groove.

[0014] In an implementable solution, it also includes a first threaded ring, and the first end of the outer ring part of the insert is threadedly fastened and sealed with the first threaded ring; the first threaded ring is provided with a first ring groove that cooperates with the movable end of the first sealing ring.

[0015] In an implementable solution, a second threaded ring is further included, and the first end of the inner ring portion of the insert is threadedly fastened and sealed with the second threaded ring; the second threaded ring is provided with a second ring groove that cooperates with the movable end of the second sealing ring.

[0016] In an implementable solution, a third threaded ring is further included, and one end of the inner shell connected to the insert tube is threadedly fastened and sealed with the third threaded ring; the third threaded ring is provided with a third ring groove that cooperates with the movable end of the third sealing ring.

[0017] In an implementable scheme, it also includes at least two of the first threaded ring, the second threaded ring and the third threaded ring; the first end of the inner ring part of the insert tube is threadedly fastened and sealed with the second threaded ring; the second threaded ring is provided with a second ring groove that cooperates with the movable end of the second sealing ring; the first end of the inner ring part of the insert tube is threadedly fastened and sealed with the second threaded ring; the second threaded ring is provided with a second ring groove that cooperates with the movable end of the second sealing ring; one end of the inner shell used for connecting to the insert tube is threadedly fastened and sealed with the third threaded ring; the third threaded ring is provided with a third ring groove that cooperates with the movable end of the third sealing ring.

[0018] In an implementable scheme, it also includes a first threaded bushing, a second threaded bushing and a third threaded bushing; the first threaded bushing is threadedly fastened and sealed with the downstream end of the valve housing in the steam flow direction, and the body of the first threaded bushing and the end face of the downstream end of the valve housing in the steam flow direction form an annular groove for fixing the first sealing ring; the second threaded bushing is threadedly fastened and sealed with the downstream end of the valve diffuser in the steam flow direction, and the body of the second threaded bushing and the end face of the downstream end of the valve diffuser in the steam flow direction form an annular groove for fixing the second sealing ring; the third threaded bushing is threadedly fastened and sealed with the second end of the inner ring part of the insert, and the body of the third threaded bushing and the end face of the second end of the inner ring part form an annular groove for fixing the third sealing ring.

[0019] According to a second aspect of the present application, there is also provided a steam turbine, comprising the three-shell steam turbine steam inlet structure in the above-mentioned solution.

[0020] Compared with the prior art, the beneficial effects of this application are:

[0021] In the technical solution of the present application, the function of gradually taking over the pressure difference and temperature difference is realized through the second sealed cavity and the first sealed cavity, basically avoiding the harsh working conditions of high pressure difference and high temperature difference, reducing mechanical stress and thermal stress, thereby effectively improving the working environment of the valve diffuser, inner shell and outer inner shell, and reducing the risk of structural failure.

[0022] At the same time, a structural coupling is formed between the inner shell and the valve diffuser with the help of the inner ring part of the insert tube, and the original one sealing ring is changed into two sealing rings. In this way, the thermal displacement of the inner shell and the valve diffuser can be better borne through the two connections, effectively reducing the failure risk of the sealing line at the sealing ring.

[0023] Compared with the original structure in which the sealing rings are independent of each other, the present application connects the three sealing rings with the help of a plug tube, so as to better bear the thermal displacement of each component in a synergistic manner, which can relatively reduce the amount of thermal displacement borne by each sealing ring and reduce the pressure of a single sealing ring, thereby reducing the risk of failure of the sealing line of the sealing ring.

[0024] The first interlayer cavity of the first sealed cavity and the second interlayer cavity of the second sealed cavity are connected by steam through the through hole, forming a self-regulating pressure inside the first sealed cavity, so that the thermal displacement of the inner shell and the valve diffuser is first self-adjusted and self-buffered through the first sealed cavity, and then transmitted to the valve shell and the outer shell, so that the adjustment of the entire pressure difference and temperature difference is smoother. In addition, the self-regulating and self-buffering structure of the first sealed cavity can withstand greater steam pressure and temperature, improve the pressure and temperature bearing upper limit of the valve diffuser, inner shell, and outer inner shell, and further expand the applicable steam parameter range. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a schematic diagram of a steam inlet structure of a three-shell steam turbine according to an embodiment of the present application;

[0027] Figure 2 It is a schematic diagram of a steam inlet structure of a three-layer shell steam turbine using three threaded rings according to an embodiment of the present application;

[0028] Figure 3 It is a schematic diagram of a steam inlet structure of a three-layer shell steam turbine using a threaded ring according to an embodiment of the present application;

[0029] Figure 4 It is a schematic diagram of a steam inlet structure of a three-layer shell steam turbine using two threaded rings according to an embodiment of the present application;

[0030] Figure 5 It is a schematic diagram of a pipe inserting structure of a three-layer shell steam turbine steam inlet structure according to an embodiment of the present application;

[0031] Figure 6 It is a schematic structural diagram of a sealing ring of a three-shell steam turbine steam inlet structure according to an embodiment of the present application.

[0032] In the figure: 11, valve housing; 12, valve diffuser; 21, outer shell; 22, outer inner shell; 23, inner shell; 231, third annular groove; 30, insert tube; 31, inner ring part; 311, second annular groove; 32, outer ring part; 321, first annular groove; 33, through hole; 41, first sealing ring; 42, second sealing ring; 43, third sealing ring; 401, movable end; 402, fixed end; 51, first sealing cavity; 511, first interlayer cavity; 512, second interlayer cavity; 52, second sealing cavity; 61, first threaded ring; 62, second threaded ring; 63, third threaded ring; 71, first threaded bushing; 72, second threaded bushing; 73, third threaded bushing; 100, steam inlet center line; 200, steam inlet direction. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0035] It should be noted that Figures 1 to 4 It is only a schematic diagram of the upper half of the cross-sectional view of the steam inlet structure. The steam inlet centerline 100 is the central axis of the steam inlet valve, and the steam inlet direction 200 indicates the flow direction of the high-temperature and high-pressure steam.

[0036] According to the first aspect of the present application, Figure 1 , 5 As shown in FIG. 6 , a three-layer shell steam turbine steam inlet structure is first provided, including a steam inlet valve, a three-layer shell and a plug pipe 30 .

[0037] The steam inlet valve includes a valve housing 11 and a valve diffuser 12 located inside the valve housing 11. The three-layer shell includes an outer shell 21, an outer inner shell 22 and an inner shell 23 arranged in sequence, and the outer shell 21 is sealed and connected to the outer side of the valve housing 11 through a flange structure.

[0038] The insert tube 30 includes an inner ring portion 31, an outer ring portion 32 and a through hole 33. The outer ring portion 32 includes a first end and a second end. The first end of the outer ring portion 32 is sealed and connected to the valve housing 11 through a first sealing ring 41, and the second end of the outer ring portion 32 is sealed and connected to the outer inner shell 22 through a flange structure. The inner ring portion 31 includes a first end and a second end. The first end of the inner ring portion 31 is sealed and connected to the valve diffuser 12 through a second sealing ring 42, and the second end of the inner ring portion 31 is sealed and connected to the inner shell 23 through a third sealing ring 43. The insert tube 30, the valve housing 11, and the valve diffuser 12 together enclose a first interlayer cavity 511, and the insert tube 30, the outer inner shell 22, and the inner shell 23 together enclose a second interlayer cavity 512. The through hole 33 connects the first interlayer cavity 511 and the second interlayer cavity 512. The first interlayer cavity 511, the through hole 33, and the second interlayer cavity 512 constitute a first sealed cavity 51. The valve housing 11 , the outer shell 21 , the insert tube 30 , and the outer and inner shells 22 together enclose a second sealed chamber 52 .

[0039] It should be noted that the first sealing ring 41 , the second sealing ring 42 and the third sealing ring 43 are all angular sealing rings.

[0040] During operation of the steam inlet structure of the steam turbine in the above-mentioned embodiment, high-temperature and high-pressure steam passes through the channel formed by the valve diffuser 12, the insert pipe 30 and the inner shell 23, which brings a large pressure difference and temperature difference to the inner and outer walls of the valve diffuser 12 and the inner and outer walls of the inner shell 23. In order to alleviate this pressure difference and temperature difference, a first sealed cavity 51 and a second sealed cavity 52 are sequentially arranged on the outside of the valve diffuser 12. The pressure and temperature in the first sealed cavity 51 are equivalent to the internal steam pressure and temperature, or are lower than the internal steam pressure and temperature, thereby reducing the pressure difference and temperature difference between the inner and outer walls of the valve diffuser 12, and also reducing the pressure difference and temperature difference between the inner and outer walls of the inner shell 23, thereby reducing the high stress caused by the high temperature difference and the high pressure difference, thereby improving the service conditions of the valve diffuser 12 and the inner shell 23, and reducing the risk of structural failure.

[0041] At the same time, the pressure and temperature in the second sealed cavity 52 are equivalent to the steam pressure and temperature in the first sealed cavity 51, or lower than the temperature of the steam pressure in the first sealed cavity 51, thereby reducing the temperature difference and pressure difference borne by the outer and inner shells 22, reducing the high stress generated thereby, improving the service condition of the outer and inner shells 22, and reducing the risk of failure.

[0042] As can be seen from the above, the second sealed cavity 52 and the first sealed cavity 51 can realize the function of gradually taking over the pressure difference and temperature difference, basically avoiding the adverse working conditions of high pressure difference and high temperature difference, reducing mechanical stress and thermal stress, thereby effectively improving the working environment of the valve diffuser 12, the inner shell 23 and the outer inner shell 22, and reducing the risk of structural failure.

[0043] At the same time, the inner shell 23 and the valve diffuser 12 are structurally coupled by means of the inner ring portion 31 of the insert tube 30, and the original one sealing ring is changed into two sealing rings. This can better bear the thermal displacement caused by the thermal deformation of the inner shell 23 and the valve diffuser 12, and effectively reduce the failure risk of the entire sealing line at the sealing ring.

[0044] Compared with the original structure in which the sealing rings are independent of each other, the present application connects the three sealing rings with the help of a tube 30, so as to better bear the thermal displacement of each component in a synergistic manner, which can relatively reduce the amount of thermal displacement borne by each sealing ring and reduce the pressure of a single sealing ring, thereby reducing the risk of failure of the entire sealing line of the sealing ring.

[0045] Furthermore, the first sealed cavity 51 is further optimized to be a first interlayer cavity 511 and a second interlayer cavity 512 connected through the through hole 33. When the inner shell 23 slightly expands along its circumferential direction, the cavity volume of the second interlayer cavity 512 will be slightly reduced. In order to maintain the balance of the internal pressure of the first sealed cavity 51, a small amount of steam in the second interlayer cavity 512 will enter the first interlayer cavity 511 through the through hole 33. However, since the total pressure and temperature of the first sealed cavity 51 are basically unchanged, the pressure of the internal steam on the inner shell 23 will be quickly taken over by the pressure in the second interlayer cavity 512. When the first interlayer cavity 511 at the outer wall of the valve diffuser 12 is affected by the thermal displacement of the valve diffuser 12, the cavity volume of the first interlayer cavity 511 is slightly reduced. In order to maintain the balance of the internal pressure of the first sealed cavity 51, a small amount of steam in the first interlayer cavity 511 will enter the second interlayer cavity 512 through the through hole 33. However, since the total pressure and temperature of the first sealed cavity 51 are basically unchanged, the pressure of the internal steam on the valve diffuser 12 will be quickly taken over by the pressure in the first interlayer cavity 511. It can be seen that the first interlayer cavity 511 and the second interlayer cavity 512 of the first sealed cavity 51 realize steam communication through the through hole 33, forming a self-regulating pressure inside the first sealed cavity 51, so that the thermal displacement of the inner shell 23 and the valve diffuser 12 is first self-adjusted and self-buffered through the first sealed cavity 51, and then transmitted to the valve shell 11 and the outer shell 21, so that the regulation of the entire pressure difference and temperature difference is smoother, and the self-regulating and self-buffering functions of the first sealed cavity 51 can withstand greater steam pressure and temperature, thereby improving the upper limit of the pressure bearing of the valve diffuser 12, the inner shell 23, etc.

[0046] It should be noted that the flange structure connection between the valve housing 11 and the outer shell 21, and the flange structure connection between the insert pipe 30 and the outer and inner shells 22 are common structures, which have been omitted in the drawings, and the position of the flange structure is only indicated by a center line.

[0047] It should be noted that the inner wall of the valve diffuser 12, the inner wall of the insert tube 30 and the inner wall of the inner shell 23 are of the same height, the contours are smoothly transitioned, and there are basically no protrusions and edges that block the flow of steam, so as to reduce the generation of turbulence as much as possible.

[0048] In one embodiment, Figure 1As shown, the steam pressure passing through the channel formed by the valve diffuser 12, the insert 30 and the inner side of the inner shell 23 is P0, and steam is introduced into the first sealed cavity 51 and the second sealed cavity 52. ​​The steam pressure in the first sealed cavity 51 is P1, and the steam pressure in the second sealed cavity 52 is P2. P0, P1 and P2 satisfy P0>P1>P2. This step-by-step decreasing pressure optimizes the mechanical stress and thermal stress load of the valve diffuser 12, the inner shell 23 and the outer inner shell 22, and reduces the risk of structural failure or fatigue damage caused by excessive stress generated by the valve diffuser 12 during the startup, shutdown and variable load operation stages. At the same time, the pressure characteristics of P0>P1>P2 make the valve diffuser 12, the inner shell 23 and the outer inner shell 22 all bear a pressure difference within a certain controllable range, so that these components have a certain tendency to expand outward, thereby making the connection of the sealing ring tighter and maintaining a good sealing effect for the entire circle of sealing lines established.

[0049] In one embodiment, when P0 is 28MPa, the temperature is 600℃, the steam pressure in the first sealing cavity 51 is P1, the temperature is 480℃, and the steam pressure in the second sealing cavity 52 is P2, which is 5.5MPaa and the temperature is 400℃, the structure of this embodiment can still maintain good stability without generating excessive mechanical and thermal stresses, which can reduce the possibility of structural and sealing failure. In the solution of the patent document mentioned in the background technology, the internal steam pressure, i.e., the operating pressure of P0, is low and the scope of use is limited. When P0 is increased, the anisotropic expansion and thermal displacement of the structure will increase significantly, and the risk of failure of the structure and the entire sealing line will increase.

[0050] In one embodiment, the plurality of through holes 33 are evenly or uniformly distributed along the circumference between the inner ring portion 31 and the outer ring portion 32 of the cannula 30, preferably evenly distributed around the circumference to make the steam flow between the first interlayer cavity 511 and the second interlayer cavity 512 as smooth as possible.

[0051] In one embodiment, Figure 1 and Figure 6As shown, the first sealing ring 41, the second sealing ring 42 and the third sealing ring 43 all include a movable end 401 and a fixed end 402; the end surface of the first end of the outer ring portion 32 of the insert tube 30 is provided with a first annular groove 321, the end surface of the first end of the inner ring portion 31 of the insert tube 30 is provided with a second annular groove 311, and the end surface of the inner shell 23 for connecting with the insert tube 30 is provided with a third annular groove 231; the fixed end 402 of the first sealing ring 41 is sealed and connected to the valve housing 11, the movable end 401 of the first sealing ring 41 is inserted into the first annular groove 321, and the first sealing ring 41 The movable end 401 of the second sealing ring 42 is slidably sealed with the first annular groove 321; the fixed end 402 of the second sealing ring 42 is sealedly connected with the valve diffuser 12, the movable end 401 of the second sealing ring 42 is inserted into the second annular groove 311, and the movable end 401 of the second sealing ring 42 is slidably sealed with the second annular groove 311; the fixed end 402 of the third sealing ring 43 is sealedly connected with the second end of the inner ring portion 31 of the cannula 30, the movable end 401 of the third sealing ring 43 is inserted into the third annular groove 231, and the movable end 401 of the third sealing ring 43 is slidably sealed with the third annular groove 231.

[0052] In the above scheme, the sliding seal of the movable ends 401 of the first, second and third sealing rings in the ring grooves is to accommodate the thermal displacement of the valve diffuser 12, the inner shell 23, the outer inner shell 22 and other components along the steam flow direction, provide a buffer for the displacement changes caused by the thermal displacement and ensure a better sealing effect.

[0053] For the ring groove position matched with the movable end 401 of the sealing ring, because it needs to withstand sliding friction, increase the wear resistance of the seal, and ensure sliding sealing, the area where the ring groove is located needs to be treated with special processes, such as surfacing or spraying and subsequent heat treatment, etc., but such treatment generally requires the entire component to be subjected to relevant process operations, which seriously increases the processing time. At the same time, if a large area of ​​defects occurs in the surfacing, the entire component may be scrapped. Therefore, in order to solve this problem, the inventor further proposes the following solution.

[0054] In one embodiment, Figure 2 As shown, it also includes a first threaded ring 61 , and the first end of the outer ring portion 32 of the insert 30 is threadedly sealed with the first threaded ring 61 ; the first threaded ring 61 is provided with a first ring groove 321 that cooperates with the movable end 401 of the first sealing ring 41 .

[0055] In one embodiment, Figure 2 As shown, it also includes a second threaded ring 62 , and the first end of the inner ring portion 31 of the insert tube 30 is threadedly sealed with the second threaded ring 62 ; the second threaded ring 62 is provided with a second annular groove 311 that cooperates with the movable end 401 of the second sealing ring 42 .

[0056] In one embodiment, Figure 2As shown, it also includes a third threaded ring 63, and one end of the inner shell 23 used for connecting with the insert tube 30 is threadedly sealed with the third threaded ring 63; the third threaded ring 63 is provided with a third ring groove 231 that cooperates with the movable end 401 of the third sealing ring 43.

[0057] The structural designs of the first threaded ring 61, the second threaded ring 62 and the third threaded ring 63 may use only any one of them, for example Figure 3 As shown; you can use all three, for example Figure 2 As shown; any combination of two of them can also be used, for example Figure 4 shown. Figure 2 , Figure 3 and Figure 4 This is only a schematic diagram of the arrangement of the threaded ring and is not limited to this embodiment. Figure 2 to Figure 4 Schematic scheme.

[0058] For components that do not use threaded rings, the annular groove for cooperating with the movable end 401 of the sealing ring can be directly opened on the corresponding component.

[0059] For the processes such as surfacing welding, spraying and post-heat treatment of the ring groove, it can be performed only on the first threaded ring 61, the second threaded ring 62 and the third threaded ring 63, transferring the original risk of damage to the components to the threaded rings, and the structural volume of the threaded rings is much smaller than the volume of the inner shell 23 and other structures, so it is more convenient to perform related surfacing welding, spraying and other processes. In addition, if the structures of the first threaded ring 61, the second threaded ring 62 and the third threaded ring 63 are damaged and fail, the replacement cost is relatively low.

[0060] In one embodiment, due to the high steam pressure and temperature inside the valve diffuser 12, the insert 30 and the inner shell 23, the working conditions are more severe, the amplitude of thermal displacement is larger, and the sliding friction between the movable end 401 of the sealing ring and the ring groove will be relatively more frequent, and the possibility of failure of the seal at the ring groove position will increase. In order to facilitate the subsequent maintenance, it is preferred to adopt Figure 4 The solution in the embodiment uses the second threaded ring 62 and the third threaded ring 63, so when the second annular groove 311 and the third annular groove 231 are damaged, the second threaded ring 62 and the third threaded ring 63 can be directly replaced.

[0061] If we want to further reduce the assembly complexity of the structure, such as Figure 3 As shown, the insert pipe 30 is convenient for surfacing, spraying and heat treatment, and the third threaded ring 63 can be used only at the matching position between the inner shell 23 and the third sealing ring 43.

[0062] In one embodiment, if the assembly complexity is not considered, such as Figure 2 As shown, the first threaded ring 61 , the second threaded ring 62 and the third threaded ring 63 may be used simultaneously.

[0063] like Figures 1 to 4 As shown, it also includes a first threaded bushing 71, a second threaded bushing 72 and a third threaded bushing 73. The first threaded bushing 71 is threadedly sealed with the downstream end of the valve housing 11 in the steam flow direction, and the body of the first threaded bushing 71 and the end surface of the downstream end of the valve housing 11 in the steam flow direction form an annular groove for fixing the first sealing ring 41. The second threaded bushing 72 is threadedly sealed with the downstream end of the valve diffuser 12 in the steam flow direction, and the body of the second threaded bushing 72 and the end surface of the downstream end of the valve diffuser 12 in the steam flow direction form an annular groove for fixing the second sealing ring 42. The third threaded bushing 73 is threadedly sealed with the second end of the inner ring part 31 of the insert 30, and the body of the third threaded bushing 73 and the end surface of the second end of the inner ring part 31 form an annular groove for fixing the third sealing ring 43. The annular grooves formed by the first threaded bushing 71, the second threaded bushing 72 and the third threaded bushing 73 and the corresponding end faces are convenient for fixing the fixed end of the sealing ring on the one hand, and are used to balance the relative thermal displacement perpendicular to the steam flow direction between the outer inner shell 22, the valve diffuser 12, the inner shell 23 and the valve housing 11 on the other hand.

[0064] The first to third sealing rings are adapted to the axial expansion and thermal displacement of the valve housing 11, the insert tube 30, the valve diffuser 12, the outer inner shell 22 and the inner shell 23 under the combined effect of the pressure difference and thermal stress of each sealing chamber, and with the help of the deformability and resettability of their own structures, so as to ensure that the sealing surface of the entire circle can always be maintained during operation.

[0065] In one embodiment, sealing rings may be provided at the flange structural connection between the outer shell 21 and the valve housing 11 and at the flange structural connection between the outer inner shell 22 and the insert pipe 30 to ensure the sealing performance of the joint surface.

[0066] In addition, sealing rings may be provided at the connection between the first threaded bushing 71 and the valve housing 11 , the connection between the second threaded bushing 72 and the valve diffuser 12 , and the connection between the third threaded bushing 73 and the cannula 30 to ensure the sealing performance of the joint surfaces.

[0067] Furthermore, sealing rings may be provided at the connection between the first threaded ring 61 and the insert tube 30 , the connection between the second threaded ring 62 and the insert tube 30 , and the connection between the third threaded ring 63 and the inner shell 23 to ensure the sealing performance of the joint surfaces.

[0068] According to a second aspect of the present application, there is also provided a steam turbine, comprising the three-shell steam turbine steam inlet structure in the above-mentioned solution.

[0069] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A three-layer shell steam turbine steam inlet structure, characterized in that: include: A steam inlet valve, comprising a valve housing (11) and a valve diffuser (12) located inside the valve housing (11); A three-layer shell, comprising an outer shell (21), an outer inner shell (22) and an inner shell (23) arranged in sequence, wherein the outer shell (21) is sealedly connected to the outer side of the valve housing (11) via a flange structure; The cannula (30) comprises an inner ring portion (31), an outer ring portion (32) and a through hole (33); The outer ring part (32) comprises a first end and a second end, the first end of the outer ring part (32) is sealedly connected to the valve housing (11) via a first sealing ring (41), and the second end of the outer ring part (32) is sealedly connected to the outer inner shell (22) via a flange structure; The inner ring portion (31) comprises a first end and a second end, the first end of the inner ring portion (31) is sealedly connected to the valve diffuser (12) via a second sealing ring (42), and the second end of the inner ring portion (31) is sealedly connected to the inner shell (23) via a third sealing ring (43); The insert pipe (30), the valve housing (11), and the valve diffuser (12) together enclose a first interlayer cavity (511), and the insert pipe (30), the outer inner shell (22), and the inner shell (23) together enclose a second interlayer cavity (512); The through hole (33) communicates with the first interlayer cavity (511) and the second interlayer cavity (512); The first interlayer cavity (511), the through hole (33) and the second interlayer cavity (512) constitute a first sealed cavity (51); The valve housing (11), the outer shell (21), the insert tube (30), and the outer and inner shells (22) together enclose a second sealed cavity (52).

2. The three-shell steam turbine steam inlet structure according to claim 1, characterized in that: The steam pressure passing through the channel formed by the valve diffuser (12), the insert pipe (30) and the inner side of the inner shell (23) is P0, steam is introduced into the first sealed cavity (51) and the second sealed cavity (52), the steam pressure in the first sealed cavity (51) is P1, the steam pressure in the second sealed cavity (52) is P2, and P0, P1 and P2 satisfy P0>P1>P2.

3. The three-shell steam turbine steam inlet structure according to claim 1 is characterized in that: The plurality of through holes (33) are evenly or unevenly distributed along the circumference between the inner ring portion (31) and the outer ring portion (32) of the insertion tube (30).

4. The three-shell steam turbine steam inlet structure according to claim 1, characterized in that: The first sealing ring (41), the second sealing ring (42) and the third sealing ring (43) all include a movable end (401) and a fixed end (402); The end surface of the first end of the outer ring portion (32) of the insert tube (30) is provided with a first annular groove (321), the end surface of the first end of the inner ring portion (31) of the insert tube (30) is provided with a second annular groove (311), and the end surface of the inner shell (23) for connecting with the insert tube (30) is provided with a third annular groove (231); The fixed end (402) of the first sealing ring (41) is sealedly connected to the valve housing (11), the movable end (401) of the first sealing ring (41) is inserted into the first annular groove (321), and the movable end (401) of the first sealing ring (41) and the first annular groove (321) are slidably sealed; The fixed end (402) of the second sealing ring (42) is sealedly connected to the valve diffuser (12), the movable end (401) of the second sealing ring (42) is inserted into the second annular groove (311), and the movable end (401) of the second sealing ring (42) and the second annular groove (311) are slidably sealed; The fixed end (402) of the third sealing ring (43) is sealedly connected to the second end of the inner ring portion (31) of the insert tube (30), and the movable end (401) of the third sealing ring (43) is inserted into the third annular groove (231), and the movable end (401) of the third sealing ring (43) is slidably sealed with the third annular groove (231).

5. The three-shell steam turbine steam inlet structure according to claim 4 is characterized in that: It also includes a first threaded ring (61), and the first end of the outer ring portion (32) of the cannula (30) is threadedly fastened and sealed with the first threaded ring (61); The first threaded ring (61) is provided with the first ring groove (321) which cooperates with the movable end (401) of the first sealing ring (41).

6. The three-shell steam turbine steam inlet structure according to claim 4, characterized in that: It also includes a second threaded ring (62), and the first end of the inner ring portion (31) of the cannula (30) is threadedly fastened and sealed with the second threaded ring (62); The second threaded ring (62) is provided with the second ring groove (311) that cooperates with the movable end (401) of the second sealing ring (42).

7. The three-shell steam turbine steam inlet structure according to claim 4, characterized in that: It also includes a third threaded ring (63), and one end of the inner shell (23) used for connecting with the cannula (30) is threadedly fastened and sealed with the third threaded ring (63); The third threaded ring (63) is provided with the third ring groove (231) that cooperates with the movable end (401) of the third sealing ring (43).

8. The three-shell steam turbine steam inlet structure according to claim 4, characterized in that: Also includes at least two of a first threaded ring (61), a second threaded ring (62) and a third threaded ring (63); The first end of the outer ring portion (32) of the insert tube (30) is threadedly fastened and sealed with the first threaded ring (61); the first threaded ring (61) is provided with the first ring groove (321) that cooperates with the movable end (401) of the first sealing ring (41); The first end of the inner ring portion (31) of the insert tube (30) is threadedly fastened and sealed with the second threaded ring (62); the second threaded ring (62) is provided with the second ring groove (311) that cooperates with the movable end (401) of the second sealing ring (42); One end of the inner shell (23) connected to the insert tube (30) is threadedly fastened and sealed with the third threaded ring (63); the third threaded ring (63) is provided with the third ring groove (231) that cooperates with the movable end (401) of the third sealing ring (43).

9. The three-layer shell steam turbine steam inlet structure according to any one of claims 4 to 8, characterized in that: Also includes a first threaded bushing (71), a second threaded bushing (72) and a third threaded bushing (73); The first threaded bushing (71) is threadedly fastened and sealed with the downstream end of the valve housing (11) in the steam flow direction, and the body of the first threaded bushing (71) and the end surface of the downstream end of the valve housing (11) in the steam flow direction form an annular groove for fixing the first sealing ring (41); The second threaded bushing (72) is threadedly fastened and sealed with the downstream end of the valve diffuser (12) in the steam flow direction, and the body of the second threaded bushing (72) and the end surface of the downstream end of the valve diffuser (12) in the steam flow direction form an annular groove for fixing the second sealing ring (42); The third threaded bushing (73) is threadedly fastened and sealed with the second end of the inner ring portion (31) of the insert tube (30), and the body of the third threaded bushing (73) and the end surface of the second end of the inner ring portion (31) form an annular groove for fixing the third sealing ring (43).

10. A steam turbine, characterized in that: It comprises a three-shell steam turbine steam inlet structure as described in any one of claims 1-9.

Images