A design method for adjustable steam seal and spring leaf of steam turbine

Abstract

The present invention provides a design method for an adjustable steam seal and spring sheet for a steam turbine, and relates to the field of steam seals for steam turbines. The scheme adopted is: comprising a steam seal body and a steam seal ring, the steam seal ring is a segmented structure, comprising at least 4 steam seal arc segments, the steam seal body is provided with a mounting groove, a spring sheet is provided between the steam seal body and the steam seal ring, the spring sheet comprises a fixed end, a middle part and a free end in sequence, the widths of the fixed end, the middle part and the free end are all the same, the fixed end and the free end are both arc-shaped structures, the middle part is a straight structure, a slot is provided on the steam seal arc segment, the fixed end is inserted into the slot, the fixed end and the free end are both in contact with the top of the steam seal body cavity, the middle part can slide along the steam seal arc segment, a limiting plate is also provided on the steam seal arc segment, and the two ends of the limiting plate can be in contact with the steps of the mounting groove. The present invention can effectively maintain the minimum gap between the dynamic and static parts of the steam turbine, the good yield and sealing properties of the steam seal ring, and at the same time, the spring sheet is not easy to break and has a long service life.

Description

Technical Field

[0001] The invention relates to the field of steam turbine steam seals, and in particular to a design method for an adjustable steam turbine steam seal and a spring sheet. Background Art

[0002] The high-temperature and high-pressure steam used for doing work inside the steam turbine is sealed by a steam seal composed of a steam seal body and a steam seal ring. The most common type is a labyrinth steam seal. Among the labyrinth steam seals, tree-shaped steam seals and comb-tooth steam seals are commonly used according to the shape of the cross-section. Among them, the comb-tooth steam seal is widely used due to its low steam seal cost, simple structure, safety and reliability, and easy installation. The sealing mechanism of the comb-tooth labyrinth steam seal is that there are many mutually matching comb teeth and concave and convex shoulders on the inner circle of the steam seal ring and the outer circle of the steam seal sleeve (the high-temperature part is the rotor shaft), forming a tiny steam seal gap and a steam expansion chamber to prevent steam leakage; each steam seal ring is divided into multiple steam seal arc segments, and a spring sheet is installed between each steam seal arc segment and the steam seal body, so that the steam seal block is elastically pressed toward the center, thereby maintaining the minimum gap between the moving and static parts.

[0003] The prior art uses diamond-shaped spring sheets, such as the attached Figure 1 and attached Figure 2 As shown, the elastic effect is used to quickly restore the position of the steam seal ring. However, due to the sudden change in cross-section of the diamond-shaped spring sheet, the stress concentration coefficient is large, it is easy to break, and the service life is short, which increases the frequency of turbine shutdown to replace the spring sheet, affecting the working efficiency of the steam turbine. At the same time, the diamond-shaped spring sheet and the steam seal ring are supported by a single point or two points, which can easily cause uneven force on the steam seal arc segment. On the one hand, the yield of the steam seal arc segment is not stable enough. On the other hand, when the steam seal arc segment is returned to its position, it causes a slight deflection of the steam seal arc segment, resulting in poor sealing.

[0004] Therefore, in view of the current status of the above-mentioned prior art, it is an urgent problem to develop a design method for an adjustable steam seal and a spring leaf of a steam turbine. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art such as the easy breakage of the diamond-shaped spring leaves, the poor yield of the steam seal arc segment and the insufficient sealing effect, the present invention provides a design method for an adjustable steam seal and spring leaf of a steam turbine, which can effectively maintain the minimum gap between the dynamic and static parts of the steam turbine, the good yield and sealing of the steam seal ring, and at the same time, the spring leaf is not easy to break and has a long service life.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a steam turbine adjustable steam seal, including a steam seal body and a steam seal ring, the steam seal ring is a segmented structure, the steam seal ring includes at least 4 steam seal arc segments, the steam seal body is provided with a mounting groove, a spring sheet is provided between the steam seal body and the steam seal ring, the spring sheet includes a fixed end, a middle part and a free end in sequence, the fixed end, the middle part and the free end have the same width, the fixed end and the free end are both arc-shaped structures, the middle part is a straight structure, a slot is provided on the steam seal arc segment, the fixed end is inserted in the slot, the fixed end and the free end are both abutted against the top of the steam seal body cavity, the middle part can slide along the steam seal arc segment, the mounting groove is in an inverted convex shape, and a limiting plate is also provided on the steam seal arc segment, and the two ends of the limiting plate can abut against the steps of the mounting groove. Through the effect of the spring plate limit plate in the adjustable steam seal, the steam seal ring has good yield and stably maintains the minimum gap. At the same time, the middle part of the spring plate in the adjustable steam seal is in line contact with the steam seal arc segment and the contact position occurs in the middle of the middle part, which will not cause the steam seal arc segment to deflect, thereby ensuring the sealing effect and good yield. At the same time, the stress concentration coefficient of the spring plate is lower than that of the diamond spring plate, it is not easy to break and has a longer service life.

[0007] Furthermore, the central angle of the fixed end is c, 120°<c<160°. On the one hand, it can be elastically deformed immediately upon receiving the force of the steam seal arc segment, thereby improving the agility of the response, and on the other hand, it can be more firmly installed in the slot to avoid falling off.

[0008] Furthermore, the central angle of the free end is b, 55°<b<65°. When the middle part slides, the free end will also slide along the steam seal body, and setting it into an arc can transform the resistance of the steam seal body to the spring sheet into the elastic deformation of the free end, reduce the resistance to the sliding of the middle part, and make the middle part generate sufficient force on the steam seal arc segment.

[0009] Furthermore, the limit plate is detachably mounted on the steam seal arc segment, and an adjustment gasket is arranged between the limit plate and the steam seal arc segment, so as to adjust the minimum clearance of the steam turbine as required.

[0010] Furthermore, the limit plate is installed on the steam seal arc segment by fastening bolts, and the head of the fastening bolt is provided with an anti-loosening steel wire, and the anti-loosening steel wire is connected in series with the head of the fastening bolt on the adjacent steam seal arc segment. The limit plate and the adjustment gasket can be easily disassembled and assembled by the fastening bolts and the anti-loosening steel wire, while maintaining the fastening effect on the limit plate and the adjustment gasket.

[0011] Furthermore, the thickness of the spring sheet is h, 1.5 mm < h < 2.6 mm, which can make the spring sheet have a certain strength and extend the service life without affecting the yield of the steam seal ring.

[0012] Furthermore, the spring sheet is made of 3Cr13 material or GH2136 material.

[0013] The present solution also provides a spring sheet design method, wherein the spring sheet comprises a fixed end, a middle portion and a free end in sequence, the widths of the fixed end, the middle portion and the free end are the same, the fixed end and the free end are both arc-shaped structures, the middle portion is a straight structure, the length of the middle portion is L, the arc radius of the fixed end and the free end is r, the width of the spring sheet is x, the thickness of the spring sheet is t, the deformation of the spring sheet along the radial direction of the corresponding steam seal ring after installation is δ, the top radius of the installation groove of the steam seal body corresponding to the spring sheet is R, the radial clearance between the top of the steam seal ring and the top of the installation groove is d, and the spring sheet calculation method comprises the following steps:

[0014] S01: Calculate the weight W of the steam seal body of the corresponding arc segment;

[0015] S02: assign initial values ​​to L, r, x and t, and assign a constraint value δ0 to δ;

[0016] S03: Calculate the actual deformation δ1 of the spring sheet after installation,

[0017]

[0018] δ1=(Rr)*(1-cosa)+t*cosa-d

[0019] If δ1<δ0, increase L and calculate the actual deformation of the spring after installation again until δ1≥δ0;

[0020] S04: Calculate the spring constant k,

[0021]

[0022] Wherein, E is the elastic modulus of the spring at the working temperature;

[0023] S05: Calculate the installation stress σ0 of the spring leaf,

[0024]

[0025] If σ0 is greater than the allowable stress of the spring leaf, increase t until σ0 is no greater than the allowable stress of the spring leaf;

[0026] S06: Calculate the spring leaf relaxation stress σr,

[0027]

[0028] If σr is greater than the allowable stress of the spring leaf, increase t until σr is no greater than the allowable stress of the spring leaf;

[0029] S07: using three-dimensional software to establish an assembly model of a spring sheet, a steam seal body and a steam seal ring of the same arc segment, wherein the size of the spring sheet is the size finally determined in S06;

[0030] S08: Use finite element software to analyze the stress and deformation of the spring leaf;

[0031] S09: If the local stress of the spring sheet is greater than its yield strength in the finite element software analysis results, reduce r until the local stress of the spring sheet is less than its yield strength. By combining the spring sheet analysis calculation with the finite element analysis, the corresponding spring sheet structure that meets the use requirements can be designed comprehensively and accurately.

[0032] Furthermore, in S03 to S08, the spring sheet is treated as a simply supported beam for force analysis.

[0033] It can be seen from the above technical solutions that the present invention has the following advantages:

[0034] The present scheme provides a design method for an adjustable steam seal and spring leaf of a steam turbine. Through the action of the spring leaf limit plate in the adjustable steam seal, the steam seal ring has good yield and can stably maintain a minimum gap. At the same time, the spring leaf in the adjustable steam seal is in line contact with the steam seal arc segment and the contact position occurs in the middle part, which will not cause the steam seal arc segment to deflect, thereby ensuring the sealing effect and good yield. At the same time, the stress concentration coefficient of the spring leaf is lower than that of the diamond spring leaf, and it is not easy to break and has a long service life. By setting the center angle of the fixed end, the reaction agility can be improved and the spring leaf can be prevented from falling off. By setting the center angle of the free end, the resistance to the sliding of the middle part can be reduced, so that the middle part can generate sufficient force on the steam seal arc segment. By adjusting the gasket, the minimum dynamic and static gap of the steam turbine can be adjusted as needed. By combining the analysis and calculation of the spring leaf with the finite element analysis, the corresponding spring leaf structure that meets the use requirements can be designed comprehensively and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0036] Figure 1The present invention is a schematic diagram of the assembly structure of a diamond-shaped spring leaf, a steam seal arc segment and a steam seal body in the prior art.

[0037] Figure 2 It is a structural schematic diagram of a diamond-shaped spring sheet in the prior art.

[0038] Figure 3 It is a structural schematic diagram of a specific implementation manner of the present invention.

[0039] Figure 4 It is a schematic diagram of the assembly structure of the spring sheet and the steam seal arc segment when the steam seal arc segment retreats in a specific implementation manner of the present invention.

[0040] Figure 5 The structure of the spring sheet in the specific embodiment of the present invention is schematically shown. Figure 1 .

[0041] Figure 6 It is a schematic diagram of the mechanical model of the spring sheet in a specific implementation manner of the present invention.

[0042] Figure 7 It is a flow chart of the spring leaf design method in a specific embodiment of the present invention.

[0043] In the figure, 1, spring sheet, 2, fixed end, 3, middle part, 4, free end, 5, slot, 6, adjustment gasket, 7, anti-loosening wire, 8, fastening bolt, 9, limit plate, 10, steam seal arc segment, 11, steam seal body, 12, rotor shaft, 13, diamond-shaped spring sheet, 14, installation groove. DETAILED DESCRIPTION

[0044] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in this specific embodiment. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0045] like Figures 3 to 5As shown, this specific embodiment provides an adjustable steam seal for a steam turbine, including a steam seal body 11 and a steam seal ring. The steam seal ring is a segmented structure. The steam seal ring includes at least 4 steam seal arc segments 10. In this specific embodiment, 6 steam seal arc segments 10 are arranged. The steam seal body 11 is provided with a mounting groove 14. A spring sheet 1 is arranged between the steam seal body 11 and the steam seal ring. The spring sheet 1 includes a fixed end 2, a middle part 3 and a free end 4 in sequence. The widths of the fixed end 2, the middle part 3 and the free end 4 are all the same. The fixed end 2 and the free end 4 are both arc-shaped structures. The middle part 3 is a straight structure. A slot 5 is arranged on the steam seal arc segment 10. The fixed end 2 is inserted into the slot 5. The fixed end 2 and the free end 4 are both in contact with the top of the steam seal body 11 cavity. The middle part 3 can slide along the steam seal arc segment 10. The mounting groove 14 is in an inverted convex shape. A limit plate 9 is also arranged on the steam seal arc segment 10. The two ends of the plate 9 can abut against the steps of the mounting groove 14, and the spring sheet 1 is set to an equal-width structure with curvature at both ends and a straight middle. Compared with the diamond-shaped spring sheet 13, the stress concentration coefficient of the spring sheet 1 can be reduced, and at the same time, the contact with the steam seal body 11 and the steam seal arc segment 10 is line contact, so that the steam seal arc segment 10 is evenly stressed and will not deflect, so that the steam seal ring has good yieldability, stably maintains the minimum gap and good sealing performance; in order to make the spring sheet 1 maintain a certain strength while being compressed by the steam seal arc segment 10, the thickness of the spring sheet 1 is h, 1.5mm<h<2.6mm, and the spring sheet 1 is made of 3Cr13 or GH2136 material, which can be determined according to the operating temperature of the turbine. When its operating temperature is below 450℃, 3Cr13 is used, and when the operating temperature is 450℃~700℃, GH2136 is used.

[0046] like Figure 5 As shown, in order to better fix the spring leaf 1 and prevent deformation when the steam seal arc segment 10 retreats, the central angle of the fixed end 2 is c, 120°<c<160°, and in this specific embodiment, c is 155°.

[0047] like Figure 5 As shown, in order to reduce the resistance during translation of the middle portion 3, the central angle of the free end 4 is b, 55°<b<65°. In the present specific embodiment, b is 60°. The resistance of the steam sealing ring 10 can make the free end 4 easily elastically deformed, thereby reducing the resistance to the translation of the middle portion 3.

[0048] like Figure 3As shown, in order to be able to adjust the minimum clearance of the steam turbine as needed, the limit plate 9 is detachably mounted on the steam seal arc segment 10, and the limit plate 9 is mounted on the steam seal arc segment 10 by means of a fastening bolt 8, and an anti-loosening steel wire 7 is provided at the head of the fastening bolt 8, and the anti-loosening steel wire 7 is connected in series with the head of the fastening bolt 8 on the adjacent steam seal arc segment 10, and an adjusting gasket 6 is provided between the limit plate 9 and the steam seal arc segment 10; when it is necessary to reduce the value of the minimum clearance, the thickness of the adjusting gasket 6 can be increased.

[0049] The working principle of the adjustable steam seal of the steam turbine is:

[0050] When the steam seal arc segment 10 is moved toward the spring sheet 1 by an external force, the fixed end 2 is compressed first, so that the steam seal arc segment 10 has good pushing properties. Since the fixed end 2 is compressed and its radius becomes smaller, the middle part 3 slides obliquely downward along the circumference of the steam seal arc segment 10, generating a downward pressure on the steam seal arc segment 10. When the external force disappears, the steam seal arc segment 10 moves toward the rotor shaft 12 under the action of the middle part 3, and is limited by the limit plate 9. When the limit plate 9 abuts against the step of the mounting groove 14, it stops moving, and the steam seal arc segment 10 reaches the set minimum gap position and remains there. When the minimum gap needs to be reduced, the thickness of the adjustment gasket 6 can be increased.

[0051] like Figure 6 and Figure 7 As shown, this specific embodiment also provides a design method for a spring sheet, which is used to design the spring sheet of the above structure, wherein the length of the middle portion is L, the arc radius of the fixed end and the free end is r, the width of the spring sheet is x, the thickness of the spring sheet is t, the deformation amount of the spring sheet along the radial direction of the corresponding steam seal ring after installation is δ, the top radius of the installation groove of the steam seal body corresponding to the spring sheet is R, and the radial clearance between the top of the steam seal ring and the top of the installation groove is d. The calculation method of the spring sheet includes the following steps:

[0052] S01: Calculate the weight W of the steam seal body corresponding to the arc segment;

[0053] S02: assign initial values ​​of L, r, x and t and a constraint value of δ0;

[0054] S03: Calculate the actual deformation δ1 of the spring after installation.

[0055]

[0056] δ1=(Rr)*(1-cosα)+t*cosα-d

[0057] If δ1<δ0, increase L and calculate the actual deformation of the spring after installation again until δ1≥δ0;

[0058] S04: Calculate the spring constant k,

[0059]

[0060] Wherein, E is the elastic modulus of the spring at the working temperature;

[0061] S05: Calculate the installation stress σ0 of the spring leaf,

[0062]

[0063] If σ0 is greater than the allowable stress of the spring leaf, increase t until σ0 is no greater than the allowable stress of the spring leaf;

[0064] S06: Calculate the spring leaf relaxation stress σr,

[0065]

[0066] If σr is greater than the allowable stress of the spring leaf, increase t until σr is no greater than the allowable stress of the spring leaf;

[0067] S07: Use 3D software to establish an assembly model of the spring sheet, steam seal body and steam seal ring of the same arc segment. The size of the spring sheet is the size finally determined in S06;

[0068] S08: Use finite element software to analyze the stress and deformation of the spring leaf;

[0069] S09: If the local stress of the spring leaf is greater than its yield strength in the finite element software analysis results, reduce r until the local stress of the spring leaf is less than its yield strength.

[0070] Among them, in S03 to S08, the spring sheet is treated as a simply supported beam for force analysis. When assigning values ​​in S02, the width x of the spring sheet is determined according to a set ratio with the slot width, and δ0 is 2.5 mm.

[0071] From the above specific implementations, it can be seen that the present invention has the following beneficial effects:

[0072] 1. Through the action of the limit plate 9 of the spring piece 1 in the adjustable steam seal, the steam seal ring has good yield and stably maintains the minimum gap. At the same time, the spring piece 1 in the adjustable steam seal is in line contact with the steam seal arc segment 10 and the contact position occurs in the middle of the middle part 3, which will not cause the steam seal arc segment 10 to deflect, thereby ensuring the sealing effect and good yield. At the same time, the stress concentration coefficient of the spring piece 1 is lower than that of the diamond spring piece 1, so it is not easy to break and has a longer service life;

[0073] 2. By setting the center angle of the fixed end 2, the reaction agility can be improved and the spring sheet 1 can be prevented from falling off;

[0074] 3. By setting the degree of the center angle of the free end 4, the resistance to the sliding of the middle part 3 can be reduced, so that the middle part 3 can generate sufficient force on the steam seal arc segment 10;

[0075] 4. The minimum clearance between the turbine and the static turbine can be adjusted as needed by adjusting the gasket 6;

[0076] 5. The limit plate 9 and the adjustment pad can be easily disassembled and assembled by tightening the bolts 8 and the anti-loosening wire 7;

[0077] 6. By combining the analysis and calculation of the spring sheet 1 with the finite element analysis, the corresponding spring sheet structure that meets the use requirements can be designed comprehensively and accurately.

[0078] The terms "upper", "lower", "outer side", "inner side", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish the relative relationship in position without giving qualitative description. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0079] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A spring leaf calculation method, characterized in that: The spring sheet comprises a fixed end, a middle part and a free end in sequence, the widths of the fixed end, the middle part and the free end are the same, the fixed end and the free end are both arc-shaped structures, the middle part is a straight structure, the length of the middle part is L, the arc radius of the fixed end and the free end is r, the width of the spring sheet is x, the thickness of the spring sheet is t, the deformation of the spring sheet along the radial direction of the corresponding steam seal ring after installation is δ, the top radius of the installation groove of the steam seal body corresponding to the spring sheet is R, the radial gap between the top of the steam seal ring and the top of the installation groove is d, and the spring sheet calculation method comprises the following steps: S01: Calculate the weight W of the steam seal body corresponding to the arc segment; S02: assign initial values ​​of L, r, x and t and a constraint value of δ0; S03: Calculate the actual deformation δ1 of the spring after installation. δ1=(Rr)*(1-cosα)+t* cosα-d If δ1<δ0, increase L and calculate the actual deformation of the spring after installation again until δ1≥δ0; S04: Calculate the spring constant k, Wherein, E is the elastic modulus of the spring at the working temperature; S05: Calculate the installation stress σ0 of the spring leaf, If σ0 is greater than the allowable stress of the spring leaf, increase t until σ0 is no greater than the allowable stress of the spring leaf; S06: Calculate the spring leaf relaxation stress σr, If σr is greater than the allowable stress of the spring leaf, increase t until σr is no greater than the allowable stress of the spring leaf; S07: Use 3D software to establish an assembly model of the spring sheet, steam seal body and steam seal ring of the same arc segment. The size of the spring sheet is the size finally determined in S06; S08: Use finite element software to analyze the stress and deformation of the spring leaf; S09: If the local stress of the spring leaf is greater than its yield strength in the finite element software analysis results, reduce r until the local stress of the spring leaf is less than its yield strength.

2. The spring leaf calculation method according to claim 1, characterized in that: In S03 to S08, the spring leaf is treated as a simply supported beam for force analysis.

3. An adjustable steam seal for a steam turbine, comprising a steam seal body (11) and a steam seal ring, wherein the steam seal ring is a segmented structure, the steam seal ring comprises at least four steam seal arc segments (10), the steam seal body (11) is provided with a mounting groove (14), a spring sheet (1) is provided between the steam seal body (11) and the steam seal ring, and characterized in that: The spring sheet (1) is designed using the spring sheet calculation method as claimed in claim 2, a slot (5) is provided on the steam seal arc segment (10), the fixed end (2) is inserted into the slot (5), the fixed end (2) and the free end (4) are both in contact with the top of the steam seal body (11) cavity, the middle part (3) can slide along the steam seal arc segment (10), the installation groove (14) is in an inverted convex shape, and a limit plate (9) is also provided on the steam seal arc segment (10), and both ends of the limit plate (9) can be in contact with the steps of the installation groove (14).

4. The adjustable steam seal of a steam turbine according to claim 3, characterized in that: The central angle of the fixed end (2) is c, 120°<c<160°.

5. The adjustable steam seal of a steam turbine according to claim 4, characterized in that: The central angle of the free end (4) is b, 55°<b<65°.

6. The adjustable steam seal of a steam turbine according to claim 3, characterized in that: The limiting plate (9) is detachably mounted on the steam seal arc segment (10), and an adjusting gasket (6) is provided between the limiting plate (9) and the steam seal arc segment (10).

7. The adjustable steam seal of a steam turbine according to claim 6, characterized in that: The limit plate (9) is mounted on the steam seal arc segment (10) via a fastening bolt (8); a head of the fastening bolt (8) is provided with an anti-loosening steel wire (7); and the anti-loosening steel wire (7) is connected in series with the head of the fastening bolt (8) on the adjacent steam seal arc segment (10).

8. The adjustable steam seal of a steam turbine according to claim 3, characterized in that: The spring sheet (1) is made of 3Cr13 or GH2136.

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