Bridge seal structure of steam turbine and steam leakage control method
Patent Information
- Application Number
- CN202611338242.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-31
- Publication Date
- 2026-10-20
Smart Images
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Figure FT_2 
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of steam turbine technology and relates to a steam turbine bridge steam seal structure and a method for controlling steam leakage. Background Technology
[0002] See Figure 1 Traditionally, the turbine overpass seal is a core sealing structure connecting the high and low pressure flow sections of the turbine and separating different pressure chambers, used to reduce the flow of high-pressure steam to the low-pressure area. However, due to structural limitations and the large pressure difference between the two ends, its leakage is often substantial, directly affecting unit efficiency. Furthermore, steam leaking from the overpass seal to the low-pressure side directly enters the space between the first-stage moving and stationary blades at low pressure. This portion of steam fails to complete its thermal conversion by flowing through the first-stage stationary blades, resulting in energy waste.
[0003] Secondly, the leaked steam disrupts the mainstream flow field between the first-stage moving and stationary blades, severely impacting the main steam flow state and indirectly exacerbating flow efficiency losses. Under normal operating conditions, the mainstream steam flows orderly along the blade passage, with a uniform and stable flow field, enabling efficient energy conversion by conforming to the blade profile. However, when the high-speed, high-pressure leaked steam merges into the mainstream, the deviation in velocity, pressure, and flow direction compared to the mainstream steam disrupts the original stable flow field. On one hand, the leaked steam induces turbulence in the mainstream airflow, generating local eddies and secondary flows, leading to flow separation and streamline distortion, disrupting the matching of airflow at the blade inlet and outlet, and significantly increasing eddy current losses, friction losses, and impact losses. On the other hand, the temperature and pressure parameters of the leaked steam differ from those of the mainstream steam, causing uneven local flow field parameters after merging, resulting in local overload and airflow angle deviation on some blades, reducing blade working efficiency.
[0004] Furthermore, the pressure formed between the first-stage moving and stationary components due to the leakage of steam will change significantly as the bridge steam seal wears out during operation, which in turn affects the force on the low-pressure first-stage impeller, causing the unit thrust to deviate from the design value, and in severe cases, it will pose a threat to the safety of the unit.
[0005] Traditional design solutions can only reduce steam leakage by increasing the number of steam seal teeth on the bridge, thus keeping leakage losses, mainstream disturbances, and thrust effects within acceptable limits. However, the axial span of the unit is limited by rotor dynamics requirements and cannot be increased arbitrarily. The space for adding steam seal teeth is also limited, making it difficult to effectively solve the above problems. Therefore, new structures and control methods are urgently needed. Summary of the Invention
[0006] The purpose of this invention is to provide a steam turbine bridge steam seal structure and a steam leakage control method to solve the technical problems in the existing steam turbine bridge steam seal structure, which are caused by high-pressure steam leakage directly entering the space between the low-pressure first-stage moving and stationary blades, resulting in wasted steam leakage heat energy, reduced low-pressure first-stage flow efficiency, and impaired unit thrust stability.
[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a turbine overpass steam seal structure, including an inner cylinder and a rotor. The overpass steam seal structure is axially divided into a high-pressure overpass steam seal section and a low-pressure side last ring overpass steam seal section. A first drainage hole is provided on the inner cylinder at a position between the high-pressure overpass steam seal section and the low-pressure side last ring overpass steam seal section. The first drainage hole is used to guide steam leaking through the high-pressure overpass steam seal section to the front of the low-pressure first-stage stationary blades. The number of the first drainage holes is specified. Satisfying 6≤ ≤30; the diameter of the first drainage hole The leakage rate, specific volume of the leaking steam, number of first drainage holes, and steam velocity within the first drainage hole are determined by calculation using the bridge steam seal theory.
[0008] Furthermore, the diameter of the first drainage hole Determined by the following formula:
[0009] in, The diameter of the first drainage hole, The leakage rate for the bridge steam seal is calculated theoretically, with units of kg / s. The specific volume of leaking steam is expressed in m³ / kg. This refers to the number of the first drainage holes; The steam velocity in the first inlet hole is expressed in m / s.
[0010] Furthermore, the first drainage hole is opened around the entire circumference of the inner cylinder.
[0011] Furthermore, the axial direction of the first drainage hole is consistent with the radial direction of the inner cylinder; the cross-sectional shape of the first drainage hole is circular, elliptical, or oblong.
[0012] Furthermore, the steam flow rate within the first drainage hole The range of values is 10≤ ≤100, in m / s.
[0013] Furthermore, the high-pressure bridge steam seal section and the last ring of the low-pressure side bridge steam seal section are two independent structural sections.
[0014] Furthermore, a second drainage hole is provided on the side of the last ring of the low-pressure side steam seal section away from the high-pressure side steam seal section. The second drainage hole is used to guide the steam leaking through the last ring of the low-pressure side steam seal section to the space between the low-pressure first stage stationary blade and the low-pressure first stage moving blade.
[0015] Furthermore, the number of the second drainage holes is multiple and they are evenly arranged along the circumference of the inner cylinder.
[0016] Secondly, the present invention provides a method for controlling steam leakage at a turbine bridge steam seal, characterized by employing a turbine bridge steam seal structure and comprising the following steps: High-pressure steam leaks through the gap between the steam seal teeth of the high-pressure bridge steam seal section; The leaked steam is discharged through the first drain hole on the inner cylinder to the front of the low-pressure first stage stationary vane; The leaked steam is mixed with the low-pressure main steam flow in the cavity before the first stage low-pressure stationary vane; The mixed steam enters a low-pressure flow path to perform work.
[0017] Furthermore, the leaked steam, after being guided through the first inlet hole, mixes with the low-pressure main steam flow in the cavity before the first stage low-pressure stationary blade; the mixed steam, together with the low-pressure main steam flow, enters the low-pressure flow path of each stage blade to perform work.
[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention divides the bridge steam seal structure axially into a high-pressure bridge steam seal section and a low-pressure side last ring bridge steam seal section. A first drainage hole is set on the inner cylinder between the two sections to guide the steam leaking through the high-pressure bridge steam seal section to the front of the low-pressure first-stage stationary blade. The leaked steam completes the heat energy conversion of the low-pressure first-stage stationary blade before doing work, realizing the recovery and utilization of leaked steam heat energy. This avoids the leakage steam directly rushing into the low-pressure first-stage moving and stationary blades, causing flow field turbulence, eddies, and secondary flows, and eliminates interference with the flow field. At the same time, by limiting the number of first drainage holes n to 6≤n≤30 and quantitatively determining the hole diameter d by calculating the leakage steam volume, specific volume of leaked steam, number of first drainage holes, and steam flow velocity in the first drainage hole based on the bridge steam seal theory, the leakage steam is stably and quantitatively guided to the front of the low-pressure first-stage stationary blade. This avoids the formation of dynamic pressure fluctuating with the wear of the steam seal between the first-stage moving and stationary blades, thereby maintaining the stability of the pressure on the low-pressure first-stage moving blade and controlling the rotor thrust of the unit.
[0019] The method of this invention allows high-pressure steam to leak through the gap between the steam seal teeth of the high-pressure bridge steam seal section, and then be guided through the first drainage hole on the inner cylinder to the front of the low-pressure first-stage stationary vane. There, it mixes with the main low-pressure inlet steam in the cavity before entering the low-pressure flow path to perform work. This achieves active interception, directional drainage, and effective recovery of the leaked steam. The leaked steam completes its thermal energy conversion before performing work after passing through the low-pressure first-stage stationary vane, avoiding the direct influx of leaked steam into the space between the low-pressure first-stage moving and stationary vanes, thus eliminating interference with the flow field. Simultaneously, the pressure between the low-pressure first-stage moving and stationary vanes is unaffected by changes in the amount of leaked steam, maintaining a controlled rotor thrust. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of a traditional bridge steam seal. Figure 2 This is a schematic diagram of the bridge steam seal of the present invention; Figure 3 This is a cross-sectional view of the drainage hole of the present invention; Figure 4 This is a diagram of the present invention.
[0021] The components are: 1. Inner cylinder; 2. Rotor; 3. Overpass steam seal ring; 301. High-pressure overpass steam seal section; 302. Low-pressure side last overpass steam seal section; 401. Low-pressure first stage stationary vane; 402. Low-pressure first stage moving vane; 5. First drainage hole; 6. Second drainage hole. Detailed Implementation
[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0023] It should be noted that the terms "first," "second," etc., used in the specification and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0024] Example 1: The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 2This invention discloses a steam turbine overpass sealing structure, including an inner cylinder 1 and a rotor 2. The overpass sealing structure is axially divided into a high-pressure overpass sealing section 301 and a low-pressure side last-ring overpass sealing section 302. A first drainage hole 5 is provided on the inner cylinder 1 at a position between the high-pressure overpass sealing section 301 and the low-pressure side last-ring overpass sealing section 302. The first drainage hole 5 is used to divert steam leaking through the high-pressure overpass sealing section 301 to before the low-pressure first-stage stationary vane 401. The number of first drainage holes 5 is specified. Satisfying 6≤ ≤30; the diameter of the first drainage hole 5 The leakage rate, specific volume of the leaking steam, number of first drainage holes, and steam velocity within the first drainage hole are determined by calculation using the bridge steam seal theory.
[0025] In this embodiment of the invention, the diameter of the first drainage hole 5 is... Determined by the following formula:
[0026] in, The diameter of the first drainage hole 5 is... The leakage rate for the bridge steam seal is calculated theoretically, with units of kg / s. The specific volume of leaking steam is expressed in m³ / kg. This refers to the number of the first drainage holes; The steam velocity in the first inlet hole is expressed in m / s.
[0027] See Figure 3 In this embodiment of the invention, the first drainage hole 5 is opened around the entire circumference of the inner cylinder 1. The axial direction of the first drainage hole 5 is consistent with the radial direction of the inner cylinder 1; the cross-sectional shape of the first drainage hole 5 is circular, elliptical, or oblong.
[0028] In this embodiment of the invention, the steam flow rate in the first drainage hole is... The range of values is 10≤ ≤100, in m / s.
[0029] In this embodiment of the invention, the high-pressure bridge steam seal section 301 and the last ring of the low-pressure side bridge steam seal section 302 are two independent structural sections.
[0030] In this embodiment of the invention, a second drainage hole 6 is provided on the side of the last ring of the low-pressure side steam seal section 302 away from the high-pressure side steam seal section 301 on the inner cylinder 1. The second drainage hole 6 is used to guide the steam leaking through the last ring of the low-pressure side steam seal section 302 to the space between the low-pressure first stage stationary blade 401 and the low-pressure first stage moving blade 402.
[0031] In this embodiment of the invention, the number of the second drainage holes 6 is multiple and they are evenly arranged along the circumference of the inner cylinder 1.
[0032] See Figure 4 The present invention also discloses a method for controlling steam leakage of a turbine bridge steam seal, which adopts the above-mentioned turbine bridge steam seal structure and includes the following steps: S1, high-pressure steam leaks through the gap between the steam seal teeth of the high-pressure bridge steam seal section 301; S2, the leaked steam is discharged through the first drain hole 5 on the inner cylinder 1 to the front of the low-pressure first stage stationary vane 401; S3, the leaked steam is mixed with the low-pressure main steam flow in the cavity before the low-pressure first stage stationary vane 401; S4, the mixed steam enters the low-pressure flow path to do work.
[0033] In this embodiment of the invention, the leaked steam is guided through the first drainage hole 5 and then mixed with the low-pressure main steam flow in the cavity before the low-pressure first stage stationary vane 401; the mixed steam enters the low-pressure flow stage blades together with the low-pressure main steam flow to do work.
[0034] Example 2: See Figure 2 This invention provides a high-efficiency turbine cross-bridge steam seal structure. A pre-designed first drainage hole 5 is pre-installed before the last cross-bridge steam seal section 302 on the low-pressure side of the cross-bridge steam seal ring 3. This guides the leaking steam from the cross-bridge steam seal to the front of the low-pressure first-stage stationary blade 401, where it mixes with the mainstream steam entering the low-pressure zone. The mixture then undergoes thermal energy conversion through the low-pressure first-stage stationary blade 401 before flowing into the low-pressure first-stage moving blade 402 to perform work, thus achieving steam leakage recovery and utilization. Simultaneously, because the leaking steam from the cross-bridge steam seal is introduced into the mainstream before the low-pressure first-stage stationary blade 401, the amount of leaking steam entering the mainstream between the low-pressure first-stage stationary blade 401 and the low-pressure first-stage moving blade 402 is drastically reduced. The influence of the leaking steam on the mainstream between the low-pressure first-stage stationary blade 401 and the low-pressure first-stage moving blade 402 is essentially eliminated. The efficiency of the first-stage flow is no longer affected by the leaking steam from the cross-bridge steam seal, significantly improving the first-stage flow efficiency. Finally, since the leakage steam from the bridge steam seal is introduced to the main flow before the low-pressure first-stage stationary vane 401 in advance, the pressure between the low-pressure first-stage stationary vane 401 and the low-pressure first-stage moving vane 402 is no longer affected by the change in leakage steam, and the unit rotor thrust is more controlled, reducing the unit's operating risk.
[0035] This invention can effectively utilize the steam leakage capacity of the bridge steam seal to perform work through the low-pressure first stage; it can also eliminate the impact of the steam leakage of the bridge steam seal on the main flow of the low-pressure first stage, thereby improving efficiency; finally, it can also ensure that the rotor thrust of the unit is controlled, reducing the safety risks of operation.
[0036] This invention divides the traditional cross-bridge steam seal into two sections: a high-pressure cross-bridge steam seal section 301 and a low-pressure side last-ring cross-bridge steam seal section 302. Simultaneously, between the two cross-bridge steam seal sections, at the corresponding position in the inner cylinder 1, a reasonably configured first drainage hole 5 with n-φd is opened around the circumference. This guides the high-pressure steam passing through the cross-bridge steam seal to the front of the low-pressure first-stage stationary vane 401, allowing the steam leaking from the cross-bridge steam seal to mix with the mainstream low-pressure steam before entering the unit's low-pressure flow to perform work.
[0037] This invention can effectively prevent leakage steam from the bridge steam seal from disrupting the mainstream flow field between the low-pressure first-stage stationary blade 401 and the low-pressure first-stage moving blade 402. Moreover, the leaking steam is led to mix with the low-pressure mainstream steam before entering the low-pressure flow path to do work, thus effectively recovering energy. Finally, this invention can effectively control the pressure between the low-pressure first-stage stationary blade 401 and the low-pressure first-stage moving blade 402, avoiding changes in rotor thrust caused by changes in leakage steam from the bridge steam seal.
[0038] The first drainage hole 5 is evenly distributed circumferentially on the inner cylinder 1 according to the AA sectional view, and the number of holes is set to 6≤ ≤30; its orifice diameter should be calculated and determined based on the leakage rate of the bridge steam seal, and the calculation method is as follows:
[0039] in, The diameter of the first drainage hole 5 is... The leakage rate for the bridge steam seal is calculated theoretically, with units of kg / s. The specific volume of leaking steam is expressed in m³ / kg. This refers to the number of the first drainage holes; The steam velocity in the first inlet hole is expressed in m / s.
[0040] During actual unit operation, the high-pressure steam leaking through the gap in the high-pressure bridge steam seal section 301 no longer directly enters the gap between the low-pressure first-stage stationary blade 401 and the low-pressure first-stage moving blade 402. Instead, it is directed out through the pre-designed inter-section first drainage hole 5 and guided to the main flow channel at the front end of the low-pressure first-stage stationary blade 401. The leaked high-pressure steam is fully mixed and uniformly integrated with the low-pressure main inlet steam in the cavity in front of the low-pressure first-stage stationary blade 401. After completing the gradient matching of airflow parameters and the homogenization adjustment of the flow field, it enters the low-pressure flow path blades of each stage along with the low-pressure main steam to participate in expansion and work.
[0041] Compared to the traditional integral bridge steam seal structure, the segmented, pre-diverted bridge steam seal structure of this invention possesses multiple significant technical advantages and engineering benefits. First, this structure completely isolates the flow path of high-pressure leaking steam from directly impacting the main flow field of the low-pressure first-stage moving and stationary blades. This fundamentally avoids the destructive effect of leaking steam turbulence on the main flow field of the low-pressure first-stage flow path, effectively optimizing the aerodynamic flow field quality of the low-pressure first-stage blade cascade, reducing irreversible flow losses such as eddy current losses and secondary flow losses, and improving the aerodynamic efficiency of the low-pressure flow unit. Second, this invention directionally recovers and reuses the high-pressure leaking steam that would otherwise be directly lost, integrating the waste leaking steam into the low-pressure power process. This achieves efficient recovery and full conversion of leaking steam heat and pressure energy, significantly reducing steam leakage losses in the unit and effectively improving the overall cycle thermal efficiency and operating economy of the turbine. Finally, through the directional pressure stabilization and diversion effect of the first diversion hole 5, the pressure range between the low-pressure first-stage stationary blade 401 and the low-pressure first-stage moving blade 402 can be constantly controlled, effectively reducing the pressure disturbance caused by the leakage of steam from the bridge steam seal and the fluctuation of steam parameters, stabilizing the axial force state of the rotor 2, avoiding problems such as shaft vibration and thrust bearing load fluctuation caused by frequent changes in rotor thrust, and significantly improving the stability and reliability of the turbine unit under variable operating conditions.
[0042] This invention has a simple structure, makes full use of the original structure, and basically does not make major changes. Only a reasonable first leakage hole 5 is opened on the inner cylinder 1 at the bridge steam seal, which realizes the improvement of leakage efficiency and controllable rotor thrust of the unit. It is an effective solution to improve the efficiency and safety performance of the bridge steam seal.
[0043] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.
Claims
1. A steam turbine bridge steam seal structure, characterized in that, Including an inner cylinder (1) and a rotor (2), the bridge steam seal structure is divided axially into a high-pressure bridge steam seal section (301) and a low-pressure side last ring bridge steam seal section (302). A first drainage hole (5) is provided on the inner cylinder (1) at a position between the high-pressure bridge steam seal section (301) and the low-pressure side last ring bridge steam seal section (302). The first drainage hole (5) is used to guide the steam leaking through the high-pressure bridge steam seal section (301) to the front of the low-pressure first stage stationary vane (401); the number of the first drainage holes (5) is as follows: Satisfying 6≤ ≤30; the diameter of the first drainage hole (5) The leakage rate, specific volume of the leaking steam, number of first drainage holes, and steam velocity within the first drainage hole are determined by calculation using the bridge steam seal theory.
2. The turbine bridge steam seal structure according to claim 1, characterized in that, The diameter of the first drainage hole (5) Determined by the following formula: in, The diameter of the first drainage hole (5) is The leakage rate for the bridge steam seal is calculated theoretically, with units of kg / s. The specific volume of leaking steam is expressed in m³ / kg. This refers to the number of the first drainage holes; The steam velocity in the first inlet hole is expressed in m / s.
3. The turbine bridge steam seal structure according to claim 1, characterized in that, The first drainage hole (5) is opened along the entire circumference of the inner cylinder (1).
4. The turbine bridge steam seal structure according to claim 1, characterized in that, The axial direction of the first drainage hole (5) is consistent with the radial direction of the inner cylinder (1); the cross-sectional shape of the first drainage hole (5) is circular, elliptical or waist-shaped.
5. The steam turbine bridge steam seal structure according to claim 1, characterized in that, Steam flow rate in the first drainage hole The range of values is 10≤ ≤100, in m / s.
6. The turbine bridge steam seal structure according to claim 1, characterized in that, The high-pressure bridge steam seal section (301) and the last ring of the low-pressure side bridge steam seal section (302) are two independent structural sections.
7. The turbine bridge steam seal structure according to claim 1, characterized in that, The inner cylinder (1) is provided with a second drainage hole (6) on the side of the last ring of the low-pressure side bridge steam seal section (302) away from the high-pressure bridge steam seal section (301). The second drainage hole (6) is used to guide the steam leaking through the last ring of the low-pressure side bridge steam seal section (302) to the space between the low-pressure first stage stationary blade (401) and the low-pressure first stage moving blade (402).
8. The steam turbine bridge steam seal structure according to claim 7, characterized in that, The number of the second drainage holes (6) is multiple and they are evenly arranged around the inner cylinder (1).
9. A method for controlling steam leakage at the steam seal of a steam turbine bridge, characterized in that, The turbine bridge steam seal structure according to any one of claims 1 to 8 includes the following steps: High-pressure steam leaks through the gap between the steam seal teeth of the high-pressure bridge steam seal section (301); The leaked steam is discharged through the first drain hole (5) on the inner cylinder (1) to the front of the low-pressure first stage stationary vane (401); The leaked steam is mixed with the low-pressure inlet steam mainstream in the cavity before the first stage low-pressure stationary vane (401); The mixed steam enters a low-pressure flow path to perform work.
10. The method for controlling steam leakage at the turbine bridge steam seal according to claim 9, characterized in that, The leaked steam is guided through the first drainage hole (5) and mixed with the low-pressure steam mainstream in the cavity in front of the low-pressure first stage stationary blade (401); the mixed steam enters the low-pressure flow stage blades together with the low-pressure steam mainstream to do work.