A tip steam seal structure

Abstract

The present invention relates to the technical field of flow-through sealing, and in particular to a tip steam seal structure, comprising: a stator shroud arranged at the top of the stator blade, a rotor shroud arranged at the top of the rotor blade, and a plurality of steam seal teeth. By arranging a stepped structure at the ends of the rotor shroud and the stator shroud, a tortuous geometric channel is formed between the rotor shroud and the stator shroud and the steam seal teeth respectively. When steam enters therein, the airflow is effectively guided to turn and rotate. Under the influence of the swirling flow, it collides with the subsequent incoming airflow, effectively reducing the kinetic energy of the steam, forming a steam flow seal steam flow, and achieving a sealing effect. At the same time, by arranging steps with different heights through the stepped structure, each step cooperates with the corresponding steam seal tooth, solving the technical problem that when the axial expansion difference is greater than the width of the rotor shroud, the steam seal teeth and the rotor shroud rub against each other, thereby causing the steam seal teeth to fail or damage the rotor shroud at the top of the rotor blade, thus ensuring the safe operation of the steam turbine unit.

Description

Technical Field

[0001] The present invention relates to the technical field of flow-through sealing, and particularly to a tip steam seal structure. Background Art

[0002] In recent years, with the increasing demand for energy conservation and environmental protection, it has become extremely urgent to improve the performance of thermal power plants, and reducing the steam leakage of steam turbines is one of the key technologies to solve the above problems. The amount of steam leakage is mainly determined by the clearance of the steam seal, the effective number of teeth, and the chamber structure. However, in the actual design of steam turbines, the clearance and number of teeth of the steam seal are often restricted by constraints such as radial expansion difference and axial expansion difference, especially for the low-pressure cylinders of large-capacity units. Therefore, the most effective way to reduce steam leakage is to optimize the steam seal chamber structure. For example, the labyrinth steam seal widely used in the tip and diaphragm of steam turbines at present works on the principle that the air flow forms vortices in the steam seal chamber through throttling expansion, and the fluid domain is controlled by the chamber structure. By enhancing the vortices through the chamber structure, the steam leakage can be greatly reduced under the condition that the steam seal clearance and the number of teeth are the same. However, for steam turbines with a large axial expansion difference, such as the low-pressure cylinders of large-capacity units, which are far from the thrust bearing, the axial expansion difference during start-up and shutdown is greater than the width of the tip shroud. When using a conventional labyrinth steam seal, the steam seal teeth and the moving blade shroud will rub against each other, resulting in the failure of the steam seal teeth or damage to the top shroud of the moving blade, causing operating accidents.

[0003] There are various types of steam seals for steam turbines, and the existing steam seal structures include labyrinth, honeycomb, brush, etc. The labyrinth has been widely used in the tip steam seal and diaphragm steam seal of steam turbines. Generally, there are three methods to reduce the steam leakage loss of the steam seal: changing the steam seal structure, reducing the steam seal clearance, and increasing the number of steam seal teeth. Among them, changing the steam seal structure and reducing the steam seal clearance have a more obvious effect on reducing the steam leakage loss. For example, the traditional design of large steam turbine low-pressure cylinders all uses flat tooth steam seal structures. In recent years, cursor steam seal teeth structures have been used in low-pressure cylinders, that is, bosses similar to steam seal teeth are machined on the top shroud of the moving blade, and together with the steam seal installed at the diaphragm, they form a rectangular steam seal chamber. This type of steam seal is not restricted by the axial expansion difference. Compared with the traditional flat teeth, it can increase the expansion space of the leakage steam flow, enhance the vortex strength of the leakage air flow to a certain extent, reduce the air leakage loss, and achieve certain energy-saving effects. However, there are many deficiencies in the control measures for the steam leakage loss of steam turbines, and there is still a certain potential for energy conservation. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a tip steam seal structure, which solves the technical problem of large steam leakage of steam turbines.

[0006] (II) Technical Solutions

[0007] To achieve the above object, the main technical solutions adopted by the present invention include:

[0008] A tip steam seal structure, comprising:

[0009] A stationary blade shroud arranged at the top of the stationary blade, a moving blade shroud arranged at the top of the moving blade, and a plurality of steam seal teeth;

[0010] The steam seal teeth are sequentially arranged on the side walls of the steam turbine rotor and the steam turbine casing;

[0011] The end of the stationary blade shroud is provided with a stationary blade shroud sealing surface with a stepped structure. The stationary blade shroud faces the steam turbine rotor, so that after the steam flow passes through the gap formed by the stationary blade shroud sealing surface and the steam seal teeth on the steam turbine rotor, the gas can continuously change direction;

[0012] The end of the moving blade shroud is provided with a moving blade shroud sealing surface with a stepped structure. The moving blade shroud faces the steam turbine casing, so that after the steam flow passes through the gap formed by the moving blade shroud sealing surface and the steam seal teeth on the steam turbine casing, the gas can continuously change direction.

[0013] The stepped structure of the stationary blade shroud sealing surface is provided with a plurality of steps from high to low according to the height in the extending direction of the stationary blade. The height difference and width of adjacent steps are the same.

[0014] The stepped structure of the moving blade shroud sealing surface is provided with a plurality of steps from high to low according to the height in the extending direction of the moving blade. The height difference and width of adjacent steps are the same.

[0015] The circumferential side wall of the steam turbine rotor is provided with a rotor sealing surface. The rotor sealing surface is arranged in a stepped structure corresponding to the stationary blade shroud sealing surface. The stepped structure of the rotor sealing surface is provided with a plurality of steps from low to high according to the height in the vertical direction of the rotor sealing surface.

[0016] The circumferential side wall of the steam turbine casing is provided with a casing sealing surface. The casing sealing surface is arranged in a stepped structure corresponding to the moving blade shroud sealing surface. The stepped structure of the casing sealing surface is provided with a plurality of steps from low to high according to the height in the vertical direction of the casing sealing surface.

[0017] The stepped structure has a plane and a vertical surface, and a perpendicular fold angle is formed between the plane and the vertical surface.

[0018] The steam seal teeth include: a plurality of rotor sealing pieces and casing sealing pieces;

[0019] The rotor sealing pieces are vertically arranged on the rotor sealing surface in sequence, and the retainer ring sealing pieces are vertically arranged on the retainer ring sealing surface in sequence.

[0020] The end of the rotor sealing piece is arranged corresponding to the middle of each step on the shroud seal surface of the stationary blade, or the rotor sealing pieces are arranged at equal intervals corresponding to the width of each step on the shroud seal surface of the stationary blade.

[0021] The end of the retainer ring sealing piece is arranged corresponding to the middle of each step on the shroud seal surface of the moving blade, or the retainer ring sealing pieces are arranged at equal intervals corresponding to the width of the steps on the shroud seal surface of the moving blade.

[0022] (III) Beneficial effects

[0023] The beneficial effects of the present invention are as follows: The present invention provides a tip steam seal structure. By arranging a stepped structure at the ends of the shroud of the moving blade and the shroud of the stationary blade, a tortuous geometric channel is formed between the shroud of the moving blade and the shroud of the stationary blade and the steam seal teeth respectively. When steam enters it, the airflow is effectively guided to turn and rotate. Under the influence of the swirling flow, it collides with the subsequent incoming airflow, effectively reducing the kinetic energy of the steam, forming a steam flow to seal the steam flow, and achieving a sealing effect.

[0024] Meanwhile, by arranging steps with different heights through the stepped structure, each step cooperates with the corresponding steam seal tooth, solving the technical problem that when the axial expansion difference is greater than the width of the shroud of the moving blade, the steam seal teeth and the shroud of the moving blade rub against each other, resulting in the failure of the steam seal teeth or damage to the shroud of the moving blade at the top of the moving blade, thereby ensuring the safe operation of the steam turbine unit. Description of the drawings

[0025] Figure 1 It is a schematic cross-sectional view of the steam seal structure of the stationary blade of the tip steam seal structure of the present invention (the first embodiment);

[0026] Figure 2 It is a schematic cross-sectional view of the steam seal structure of the moving blade of the tip steam seal structure of the present invention (the first embodiment);

[0027] Figure 3 It is a schematic cross-sectional view of the steam seal structure of the stationary blade of the tip steam seal structure of the present invention (the second embodiment);

[0028] Figure 4 It is a schematic cross-sectional view of the steam seal structure of the moving blade of the tip steam seal structure of the present invention (the second embodiment).

[0029]

Description of the reference numerals

[0030] 11: Stationary blade;

[0031] 12: Moving blade;

[0032] 21: shroud of stationary blade

[0033] 22: shroud of moving blade

[0034] 31: steam turbine rotor

[0035] 32: steam turbine diaphragm

[0036] 311: rotor sealing strip

[0037] 321: diaphragm sealing strip

[0038] 331: plane

[0039] 341: elevation Detailed implementation manners

[0040] For better explaining the present invention for easy understanding, the present invention will be described in detail below in conjunction with the accompanying drawings through specific implementation manners.

[0041] For better understanding the above technical solutions, the exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and the scope of the present invention can be fully conveyed to those skilled in the art.

[0042] The present invention provides a tip steam seal structure applied to the moving blades 12, stationary blades 11, steam turbine diaphragm 32 and steam turbine rotor 31 of a steam turbine. The tip steam seal structure includes: a shroud of stationary blade 21 provided at the top of the stationary blade 11, a shroud of moving blade 22 provided at the top of the moving blade 12, and a plurality of steam seal teeth.

[0043] The bottom end of the stationary blade 11 is inserted into the steam turbine diaphragm 32, the bottom end of the moving blade 12 is inserted into the steam turbine rotor 31, the tops of the moving blade 12 and the stationary blade 11 face in opposite directions, and are arranged at intervals along the axial direction of the steam turbine rotor 31.

[0044] In this embodiment, the top of the stationary blade 11 is arranged facing downward, that is, the top of the stationary blade 11 faces the steam turbine rotor 31, the bottom end of the stationary blade 11 is inserted into the steam turbine diaphragm 32, and the steam turbine diaphragm 32 is located outside the bottom end of the stationary blade 11. The top of the moving blade 12 is arranged facing upward, that is, the top of the moving blade 12 faces the steam turbine diaphragm 32. The moving blade 12 is arranged between two stationary blades 11, the bottom end of the moving blade 12 is inserted into the steam turbine rotor 31, and the rotor is located inside the top end of the stationary blade 11, so as to form a gap between the top end of the stationary blade 11 and the steam turbine rotor 31.

[0045] During the startup of the steam turbine, steam flows through the interior of the steam turbine, heating the steam turbine body and causing the expansion of various components of the steam turbine. Due to differences in the materials, thicknesses, etc. of the various components of the steam turbine, uneven expansion occurs. This application relates to the axial differential expansion, that is, the shortening of the axial distance between the rotor 31 part (rotating part) and the casing retainer 32 part (stationary part) of the steam turbine due to uneven expansion. When the spacing is too short, faults are likely to occur. Therefore, a gap is left between the stationary blades 11 and the steam turbine rotor 31, and a gap is also left between the moving blades 12 and the casing retainer 32.

[0046] See Figure 1 , a casing band 21 is provided at the top of the stationary blade 11. One end of the casing band 21 is fixedly connected to the stationary blade 11, and a sealing surface of the casing band is provided at the other end of the casing band 21. The sealing surface of the casing band is arranged in a stepped structure. The stepped structure is provided with several steps from high to low according to the height. In this embodiment, the number of steps of the stepped structure of the sealing surface of the casing band is 3. The setting of the number of 3 steps makes the shape of the casing band 21 moderate in processing difficulty and can achieve a better air flow deflection effect. By providing the stepped sealing surface of the casing band, the steam flow generated during the operation of the steam turbine can be continuously deflected along with the stepped structure, reducing the flow velocity and hindering the occurrence of laminar flow. The height of the step is the height in the extending direction of the stationary blade 11, or Figure 1 in the vertical direction, the height of the sealing surface of the casing band downward.

[0047] Optionally, see Figure 3 , the stepped structure of the sealing surface of the casing band can also be provided with steps from low to high according to the height.

[0048] A rotor sealing surface is provided on the circumferential side wall of the steam turbine rotor 31. The rotor sealing surface corresponds to the sealing surface of the casing band and is arranged in a stepped structure. The stepped structure of the rotor sealing surface is provided with several steps from low to high according to the height. The number of steps of the stepped structure of the rotor sealing surface is less than the number of steps of the sealing surface of the casing band. In this embodiment, the number of steps of the stepped structure of the rotor sealing surface is 2. The setting of the number of 2 steps can make the gland teeth on the rotor sealing surface better cooperate with the stepped structure of the sealing surface of the casing band. The height of the step is the height in the vertical direction of the rotor sealing surface, or Figure 1 in the vertical direction, the height of the rotor sealing surface upward.

[0049] Optionally, see Figure 3 , the stepped structure of the rotor sealing surface can also be provided with steps from high to low according to the height. During the actual setting process, it is necessary to select a matching one according to the height trend of the sealing surface of the casing band.

[0050] The gland teeth include: several rotor sealing pieces 311 and casing retainer sealing pieces 321.

[0051] A number of rotor sealing pieces 311 are arranged in sequence on the rotor sealing surface. The rotor sealing pieces 311 are used to cooperate with the stepped structure on the shroud sealing surface of the stationary blade. The stepped structure has a plane 331 and a vertical surface 341, and a fold angle is formed between the plane 331 and the vertical surface 341. The fold angle is vertically arranged, or the fold angle can be set according to actual design requirements. Through the setting of the fold angle, the steam flow can be deflected when flowing through the fold angle.

[0052] As a preferred embodiment of the present invention, 4 rotor sealing pieces 311 are arranged on the rotor sealing surface. One rotor sealing piece 311 is arranged in the middle of the first step of the stepped structure corresponding to the shroud sealing surface of the stationary blade, one rotor sealing piece 311 is arranged in the middle of the second step of the stepped structure corresponding to the shroud sealing surface of the stationary blade, and two rotor sealing pieces 311 are arranged at equal intervals corresponding to the width of the third step of the stepped structure of the shroud sealing surface of the stationary blade.

[0053] The end of the rotor sealing piece 311 is arranged corresponding to the middle of each step of the stepped structure, or the end of the rotor sealing piece 311 is arranged at equal intervals corresponding to the width of the step, so as to facilitate the deflection flow of the air flow. The width of the step is Figure 1 the width in the left-right direction of the middle step, and the middle of the step is the midpoint position in the width direction of the step.

[0054] The high-speed steam generated during the operation of the steam turbine, the air flow passes through the gap between the rotor sealing surface and the shroud sealing surface of the stationary blade. Through the action of the fold angle of the stepped structure on the shroud sealing surface of the stationary blade, the flow direction of the air flow is deflected, and enters the gap formed between the side of the rotor sealing piece 311 and the vertical surface 341 of the stepped structure. The air flow is deflected again and enters the gap formed between the end of the rotor sealing piece 311 and the plane 331 of the stepped structure. The air flow passes through the gaps between the stepped structure and the multiple rotor sealing pieces 311 in sequence until it flows out from the gap between the last rotor sealing piece 311 and the stepped structure, and continues to deflect and enter the moving and stationary gap space for expansion. That is, because the gap between the rotor sealing surface and the shroud sealing surface of the stationary blade is extremely small, the moving and stationary gap space entered after the air flow passes through is much larger relative to it, so the gas expands. Subsequently, the air flow flows into the next-stage tip steam seal structure.

[0055] Among them, the moving and stationary gap is the flow path formed between the single-stage moving blade and the stationary blade of the steam turbine.

[0056] So far, because the air flow continuously rotates in the opposite direction in a limited space and forms turbulence, which hinders the occurrence of laminar flow and reduces the flow velocity, forming the phenomenon of "sealing" the air flow by the air flow, the amount of air flowing into from this channel is reduced to the minimum state, so as to achieve the purpose of reducing the steam leakage of the steam turbine.

[0057] SeeFigure 2 , a moving blade shroud 22 is provided at the top of the moving blade 12. One end of the moving blade shroud 22 is fixedly connected to the moving blade 12, and a moving blade shroud sealing surface is provided at the other end of the moving blade shroud 22. The moving blade shroud sealing surface is arranged in a stepped structure, and several steps are provided according to the height from high to low. In this embodiment, the number of steps of the stepped structure of the moving blade shroud sealing surface is 3. The setting of the 3 steps makes the shape of the moving blade shroud 22 moderate in processing difficulty and can achieve a better air flow deflection effect. By setting the stepped moving blade shroud sealing surface, the steam flow generated during the operation of the steam turbine can be continuously deflected along with the stepped structure, reducing the flow velocity and hindering the occurrence of laminar flow. The height of the step is the height in the extending direction of the moving blade 12, or Figure 2 the height of the moving blade shroud sealing surface upward in the vertical direction in

[0058] Optionally, referring to Figure 4 , the stepped structure of the moving blade shroud sealing surface can also be provided with steps according to the height from low to high.

[0059] A retaining ring sealing surface is provided on the circumferential side wall of the turbine retaining ring 32. The retaining ring sealing surface corresponds to the moving blade shroud sealing surface and is arranged in a stepped structure. The stepped structure of the retaining ring sealing surface is provided with several steps according to the height from low to high. The number of steps of the retaining ring sealing surface is less than the number of steps of the moving blade shroud sealing surface. In this embodiment, the number of steps of the retaining ring sealing surface is 2. The setting of the 2 steps can make the gland teeth on the retaining ring sealing surface better cooperate with the stepped structure of the moving blade shroud sealing surface. The height of the step is the height in the vertical direction of the retaining ring sealing surface, or Figure 2 the height of the retaining ring sealing surface downward in the vertical direction in

[0060] Optionally, referring to Figure 4 , the stepped structure of the retaining ring sealing surface can also be provided with steps according to the height from high to low. In the actual setting process, it is necessary to select a matching one according to the step height trend of the moving blade shroud sealing surface.

[0061] A number of retaining ring sealing pieces 321 are sequentially arranged on the retaining ring sealing surface, and the retaining ring sealing pieces 321 are used to cooperate with the stepped structure on the moving blade shroud sealing surface.

[0062] As a preferred embodiment of the present invention, 4 retaining ring sealing pieces 321 are provided on the retaining ring sealing surface. One retaining ring sealing piece 321 is provided in the middle of the first step of the stepped structure corresponding to the moving blade shroud sealing surface, one retaining ring sealing piece 321 is provided in the middle of the second step of the stepped structure corresponding to the moving blade shroud sealing surface, and two retaining ring sealing pieces 321 are arranged at equal intervals corresponding to the width of the third step of the stepped structure of the moving blade shroud sealing surface.

[0063] The end of the holding ring sealing piece 321 is arranged corresponding to the middle part of each step of the stepped structure, or the end of the holding ring sealing piece 321 is arranged at equal intervals corresponding to the width of the step, so as to facilitate the deflection flow of the air flow. The width of the step is the Figure 1 width of the middle step in the left - right direction, and the middle part of the step is the mid - point position in the width direction of the step.

[0064] During the operation of the steam turbine, high - speed steam is generated. The air flow passes through the gap between the shroud seal surface of the moving blade and the holding ring seal surface, and the air flow deflects through the fold angle of the stepped structure on the shroud seal surface of the moving blade, and enters the gap formed between the holding ring sealing piece 321 and the vertical surface 341 of the stepped structure. The air flow deflects again and enters the gap formed between the holding ring sealing piece 321 and the plane 331 of the stepped structure. The air flow passes through the gaps between the stepped structure and the multiple holding ring sealing pieces 321 in turn until it flows out from the gap between the last holding ring sealing piece 321 and the stepped structure, continues to deflect and enters the moving - static gap space for expansion. Subsequently, the air flow flows into the next - stage tip steam seal structure. The air flow continuously rotates in opposite directions in a limited space and forms a turbulent flow, which hinders the occurrence of laminar flow and reduces the flow velocity, forming a phenomenon of "sealing" the air flow by the air flow, so that the amount of gas flowing into from this channel is reduced to the minimum state.

[0065] The present invention provides a tip steam seal structure. By arranging a stepped structure at the ends of the shroud of the moving blade 22 and the shroud of the stationary blade 21, a tortuous geometric channel is formed between the shroud of the moving blade 22 and the shroud of the stationary blade 21 and the steam seal teeth respectively. When the steam enters it, the air flow is effectively guided to turn and rotate. Under the influence of the swirling flow, it collides with the subsequent incoming air flow, effectively reducing the kinetic energy of the steam, forming a steam flow to seal the steam flow, and achieving the sealing effect.

[0066] At the same time, through the steps with different heights arranged by the stepped structure, each step cooperates with the corresponding steam seal teeth, solving the technical problem that when the axial expansion difference is greater than the width of the shroud of the moving blade 22, the steam seal teeth and the shroud of the moving blade 22 rub against each other, resulting in the failure of the steam seal teeth or damage to the shroud of the moving blade 22 at the top of the moving blade 12, thus ensuring the safe operation of the steam turbine unit.

[0067] The tip steam seal structure of this embodiment is applicable to the scenario with a relatively low rotational speed, a relatively small aspect ratio of the blade, and a relatively wide blade width. In this scenario, the complex shapes of the shroud of the stationary blade 21 and the shroud of the moving blade 22 will not cause problems of blade strength caused by excessive centrifugal force. Among them, the aspect ratio of the blade is the ratio of the height and chord length of the moving and stationary blades of the steam turbine.

[0068] When selecting the direction of the step, that is, when selecting whether the step is arranged from high to low or from low to high, it is necessary to clarify the expansion direction of the stationary blade 11 and the moving blade 12 of this stage to prevent the rubbing problem caused by the too - fast expansion of the steam turbine rotor 31 and the too - slow expansion of the cylinder.

[0069] After steam enters the turbine, it mainly flows through the channel between the moving and stationary blades, thereby heating the inside of the turbine. According to the principle of heat transfer, the transfer of heat also starts from the flow channel and transfers to other locations. Metals have strong thermal conductivity and expand rapidly, but due to the difference in the amount of heat received, the expansion rate will also vary significantly. The rotor part (rotating parts) is closer to the steam and expands faster, while the stationary parts such as the ring and the cylinder are larger, thicker, and made of relatively poor material. They are far away from the heat source and therefore expand slowly.

[0070] The most fundamental principle of the steam seal method formed by the cooperation of the blade top shroud and the steam seal teeth in this embodiment is: to allow the steam flow to continuously turn in the flow channel formed by the shroud and the steam seal ruler to form a high-speed vortex, affecting the flow pattern of the airflow, and generating a vortex in the opposite direction when passing through each "step", thereby forming turbulence, hindering the occurrence of laminar flow, reducing the kinetic energy of the steam, and ultimately reducing the amount of leakage.

[0071] Compared with traditional steam seal types, the design concept of traditional steam seals is more concerned with reducing the flow gap and the absolute mass flow of steam flowing into the steam seal. The disadvantages of the traditional solution are obvious. The excessive number of steam seal teeth and the small steam seal gap will cause the steam seal teeth to rub against the sealing surface during the restart and shutdown process, and in severe cases, the machine cannot be started. The cost is increased, the installation difficulty increases, it is not conducive to adjustment, and the operation and maintenance costs are increased.

[0072] The proposal of this embodiment negates the design concept of the traditional steam seal in principle. By establishing a fluid mechanics analysis of the air flow channel, the steam flow is "sealed" to interrupt the occurrence of laminar flow as much as possible, forming a steam vortex in the opposite direction, and combining the characteristics of the flow channel geometry to hinder the flow of steam, thereby reducing the amount of steam leakage. First, the problem of the steam seal installation gap being too small is solved. The steam seal installation gap can be greater than 0.5mm. At the same time, considering the problem of expansion direction, two types of shrouds are designed to meet the needs of two degrees of freedom axial expansion. At the same time, the density of the steam seal teeth is comparable to that of most sealing types, and there is no additional cost. The blade tip shroud is not difficult to process.

[0073] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0074] In the present invention, unless otherwise clearly defined or limited, terms such as "installed", "connected", "linked", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium; it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] In the present invention, unless otherwise clearly defined or limited, when the first feature is "on" or "under" the second feature, it may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, when the first feature is "above", "over" and "on top of" the second feature, it may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. When the first feature is "under", "below" and "beneath" the second feature, it may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0076] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0077] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A tip steam seal structure, characterized in that, it includes: a stationary blade shroud (21) arranged at the top of a stationary blade (11), a moving blade shroud (22) arranged at the top of a moving blade (12), and a plurality of steam seal teeth; the steam seal teeth are sequentially arranged on the side walls of a steam turbine rotor (31) and a steam turbine casing (32); the end of the stationary blade shroud (21) is provided with a stepped structure of a stationary blade shroud sealing surface, and the stepped structure of the stationary blade shroud sealing surface is provided with a plurality of steps from high to low according to the height in the extending direction of the stationary blade (11). The stationary blade shroud (21) faces the steam turbine rotor (31). A rotor sealing surface is arranged on the circumferential side wall of the steam turbine rotor (31). The rotor sealing surface is arranged in a stepped structure corresponding to the stationary blade shroud sealing surface. The stepped structure of the rotor sealing surface is provided with a plurality of steps from low to high according to the height in the vertical direction of the rotor sealing surface. The number of steps of the rotor sealing surface is less than the number of steps of the stationary blade shroud sealing surface, so that after the steam flow passes through the gap formed by the stationary blade shroud sealing surface and the steam seal teeth on the steam turbine rotor (31), the gas can continuously turn; the end of the moving blade shroud (22) is provided with a stepped structure of a moving blade shroud sealing surface, and the stepped structure of the moving blade shroud sealing surface is provided with a plurality of steps from high to low according to the height in the extending direction of the moving blade (12). The moving blade shroud (22) faces the steam turbine casing (32). A casing sealing surface is arranged on the circumferential side wall of the steam turbine casing (32). The casing sealing surface is arranged in a stepped structure corresponding to the moving blade shroud sealing surface. The stepped structure of the casing sealing surface is provided with a plurality of steps from low to high according to the height in the vertical direction of the casing sealing surface. The number of steps of the casing sealing surface is less than the number of steps of the moving blade shroud sealing surface, so that after the steam flow passes through the gap formed by the moving blade shroud sealing surface and the steam seal teeth on the steam turbine casing (32), the gas can continuously turn; the steam seal teeth include: a plurality of rotor sealing pieces (311) and casing sealing pieces (321); a plurality of rotor sealing pieces (311) are sequentially arranged on the rotor sealing surface, and the rotor sealing pieces (311) are used to cooperate with the stepped structure on the stationary blade shroud sealing surface; a plurality of casing sealing pieces (321) are sequentially arranged on the casing sealing surface, and the casing sealing pieces (321) are used to cooperate with the stepped structure on the moving blade shroud sealing surface; the end of the casing sealing piece (321) is arranged corresponding to the middle of each step on the moving blade shroud sealing surface, or the casing sealing piece (321) is arranged at equal intervals corresponding to the width of the steps on the moving blade shroud sealing surface.

2. The tip steam seal structure according to claim 1, characterized in that, the height difference and width of adjacent steps of the stepped structure of the stationary blade shroud sealing surface are the same.

3. The tip steam seal structure according to claim 2, characterized in that, the height difference and width of adjacent steps of the stepped structure of the moving blade shroud sealing surface are the same.

4. The tip steam seal structure according to claim 1, characterized in that, the stepped structure has a plane (331) and a vertical surface (341), and a perpendicular fold angle is formed between the plane (331) and the vertical surface (341).

5. The tip steam seal structure according to claim 4, characterized in that, the rotor sealing pieces (311) are sequentially arranged vertically on the rotor sealing surface, and the retainer ring sealing pieces (321) are sequentially arranged vertically on the retainer ring sealing surface.

6. The tip steam seal structure according to claim 5, characterized in that, the end of the rotor sealing piece (311) is arranged corresponding to the middle of each step on the shroud seal surface of the stationary blade, or the rotor sealing piece (311) is arranged at equal intervals corresponding to the width of each step on the shroud seal surface of the stationary blade.

7. The tip steam seal structure according to claim 1, characterized in that, the bottom end of the stationary blade (11) is inserted into the steam turbine retainer ring (32), the bottom end of the moving blade (12) is inserted into the steam turbine rotor (31), the tops of the moving blade (12) and the stationary blade (11) face in opposite directions, and they are arranged at intervals along the axial direction of the steam turbine rotor (31).

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