Thrust balancing system of large heat supply steam turbine and design method of thrust balancing system

Abstract

The invention discloses a large heat supply turbine thrust balance system and a design method thereof, the large heat supply turbine thrust balance system comprises a high-medium pressure cylinder provided with a high-medium pressure rotor, a high pressure section comprises a high-row first section, a high-row second section and a high-row third section, and the diameter of the high-row first section is larger than the diameter of the high-row second section is larger than the diameter of the high-row third section; a high-exhaust first-section steam leakage sealing ring and a high-exhaust second-section steam leakage sealing ring are respectively arranged on the outer sides of the high-exhaust first section and the high-exhaust second section; the side wall, close to one side of the high-exhaust first section, of the high-exhaust second section steam leakage sealing ring, the outer side of the high-exhaust second section and the side wall, facing one side of the high-exhaust second section steam leakage sealing ring, of the high-exhaust first section jointly form a balance step. One end of a high-exhaust first-section steam leakage pipeline is arranged at the position of the balance step, and the other end of the high-exhaust first-section steam leakage pipeline leads high-exhaust first-section leakage steam to a third steam extraction pipeline or a fourth steam extraction pipeline of the high-medium-pressure cylinder. The invention has the advantages of small steam leakage, good economical efficiency, high reliability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of steam turbines, and in particular relates to a thrust balance system of a large-scale heating steam turbine and a design method thereof. Background Art

[0002] When large-scale heating steam turbine units are operating in pure condensing, heating and abnormal full cut-off conditions, various thermal conditions are complex, resulting in large changes in axial thrust. It is difficult to meet the axial thrust requirements under various conditions at the same time by structural adjustment alone, resulting in thrust exceeding the limit; it may even cause damage to the thrust bearing and the unit cannot operate safely.

[0003] Chinese patent literature discloses "A system for adjusting axial thrust of a steam turbine under variable operating conditions and its use method" (publication number CN112412548A, publication date February 26, 2021). This technology proposes to adjust the thrust by changing the direction of the steam flow interface, but it uses a high-pressure exhaust port upstream of the turbine flow and a low-pressure exhaust port downstream, which causes the high-exhaust first-stage steam leakage to flow back during switching operation, which is poor in economy. The pressure difference of the high-exhaust second-stage steam leakage increases dramatically, and the steam leakage volume is comparable to that of the conventional design only after the number of steam seal teeth is increased by more than 30 times. However, the axial length is limited and the number of steam seal teeth is difficult to make sufficient. During operation, there will be a series of problems such as large steam leakage, poor economy, and even high-temperature steam leakage and safety hazards. Therefore, this method loses one thing while taking another into account, and its implementation feasibility is poor. Summary of the invention

[0004] The purpose of the present invention is to provide a large-scale heating steam turbine thrust balance system and a design method thereof with small steam leakage, good economy and high reliability in view of the deficiencies in the prior art.

[0005] The technical purpose of the present invention is achieved by the following technical solutions:

[0006] A thrust balancing system for a large-scale heating steam turbine comprises a high-pressure cylinder provided with a high-pressure rotor, the high-pressure section comprising a high-pressure first section, a high-pressure second section and a high-pressure third section, and the diameter of the high-pressure first section>the diameter of the high-pressure second section>the diameter of the high-pressure third section; a high-pressure first section leakage steam seal ring and a high-pressure second section leakage steam seal ring are respectively arranged on the outer sides of the high-pressure first section and the high-pressure second section; the side wall of the high-pressure second section leakage steam seal ring close to the high-pressure first section, the outer side of the high-pressure second section and the side wall of the high-pressure first section facing the high-pressure second section leakage steam seal ring together form a balancing step; one end of a high-pressure first section leakage steam pipeline is arranged at the balancing step, and the other end of the high-pressure first section leakage steam pipeline leads the high-pressure first section leakage steam to the third steam extraction pipeline or the fourth steam extraction pipeline of the high-pressure cylinder.

[0007] Preferably, the high pressure exhaust first section steam leakage pipeline comprises a first branch pipe and a second branch pipe respectively connected to the third steam extraction pipeline and the fourth steam extraction pipeline of the high and medium pressure cylinders, and the first branch pipe and the second branch pipe are respectively provided with shut-off valves.

[0008] Preferably, the steam leakage from the second section of the high row and the first section of the middle row is led to the shaft seal main pipe through a pipeline; the steam leakage from the third section of the high row and the second section of the middle row is led to the steam seal heater through a pipeline.

[0009] A design method for a large-scale heating steam turbine thrust balance system, based on the large-scale heating steam turbine thrust balance system described above, comprises the following steps:

[0010] S1. A balancing step is provided at the steam leakage of the first section of the high-pressure exhaust of the high-pressure section, and a balancing plate is provided at the balancing step; the balancing plate area A is optimized and designed according to the thrust requirements when the steam leakage goes to the fourth steam extraction pipeline under pure condensing and full cut-off conditions of the high-pressure heater and goes to the third steam extraction pipeline under heating conditions;

[0011] S2, the steam seal rings of the first section of the high-pressure section and the second section of the high-pressure section are designed according to the total number of teeth and the maximum pressure difference under the limited length;

[0012] S3. Combine S1 and S2, and on the basis of meeting the design requirements of optimizing the steps of each shaft section and optimizing the number of steam seal teeth of each section, the steam seal teeth of the first section of the high-row steam leakage seal ring and the second section of the high-row steam leakage seal ring are arranged reasonably and the economy of the whole machine is excellent, and the steps of each shaft section and the number of steam seal teeth of each section are preferably determined;

[0013] S4. According to the thrust balance of the unit under pure condensing and heating conditions, the destination of the first stage steam leakage of the high exhaust is selected optimally;

[0014] S5. Calculate the thrust under each operating condition, the step size of each shaft section, and the steam leakage parameters according to the final optimal solution, and select and design the first high exhaust steam leakage pipeline and the shut-off valve installed on the branch line.

[0015] Preferably, in S2, the number of teeth of the high-pressure exhaust first-stage steam leakage steam sealing ring is designed according to the pressure difference between the high-pressure exhaust first-stage steam leakage and the fourth-stage steam extraction port under the fully open condition of the pure condensing valve; the number of teeth of the high-pressure exhaust second-stage steam leakage steam sealing ring is designed according to the pressure difference between the third-stage steam extraction port and the steam seal mother pipe under the heating condition; the number of teeth of the high-pressure exhaust first-stage steam leakage steam sealing ring and the high-pressure exhaust second-stage steam leakage steam sealing ring are optimized and allocated according to a certain principle of the total number of teeth.

[0016] Preferably, in S3, the optimization of the steps of each shaft section includes reasonably determining the size and position of the balancing step on the first-section leakage rotor of the high-row according to the design requirements of the balancing step, so as to ensure that the axial thrust balance requirements are met under different working conditions; the optimization of the number of teeth of each section of the steam seal includes optimizing the distribution of the number of teeth of the two sections of the steam seal ring according to the design requirements of the first-section leakage steam seal ring of the high-row and the second-section leakage steam seal ring of the high-row, under a limited length, according to the principle of a constant total number of teeth and maximum pressure difference.

[0017] Preferably, in S4, the destination of the first-stage steam leakage from the high-pressure exhaust is preferably selected to include leading the first-stage steam leakage from the high-pressure exhaust to the third steam extraction pipeline or the fourth steam extraction pipeline, leading the first-stage steam leakage from the high-pressure exhaust to the third steam extraction pipeline and the fourth steam extraction pipeline or the third steam extraction pipeline and the fifth steam extraction pipeline respectively, and the first-stage steam leakage from the high-pressure exhaust is connected to the third steam extraction pipeline, the fourth steam extraction pipeline and the fifth steam extraction pipeline and is provided with a switching device for switching according to actual operating conditions.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The thrust balancing system of a large-scale heating steam turbine of the present invention sets a balancing step at the steam leakage of the first section of the high-discharge shaft seal, controls the steam leakage of the first section of the high-discharge shaft seal to switch to different downstream flow interfaces, and adjusts the thrust by changing the pressure in front of the balancing step, so as to achieve thrust that meets the requirements under various complex working conditions such as pure condensation, full cut-off of high-pressure heaters and heating. The design of the full downstream switching interface prevents the steam leakage of the first section of the high-discharge from backflowing, the pressure difference between the two sections changes little, and the number of steam seal teeth is appropriate under a limited axial length, which solves a series of problems such as large steam leakage, poor economy, high-temperature steam leakage, and safety hazards. It has the advantages of small steam leakage, good economy, and high reliability.

[0020] 2. The design method of the thrust balance system of a large-scale heating steam turbine of the present invention can improve the operating efficiency and safety of the equipment, reduce the operating cost, and enhance the adaptability and economy of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention;

[0022] Figure markings: 1—high and medium pressure cylinder; 11—first stage steam extraction port; 12—second stage steam extraction port; 13—third stage steam extraction port; 131—third steam extraction pipeline; 14—fourth stage steam extraction port; 141—fourth steam extraction pipeline; 15—fifth stage steam extraction port; 21—high pressure section; 211—first section of high exhaust; 212—second section of high exhaust; 213—third section of high exhaust; 22—medium pressure section; 31—steam leakage seal ring of first section of high exhaust; 32—steam leakage seal ring of second section of high exhaust; 4—balancing step; 5—steam leakage pipeline of first section of high exhaust; 51—first branch pipe; 52—second branch pipe; SSR-shaft seal mother pipe; CF-steam seal heater. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0026] like Figure 1As shown, a large-scale heat supply steam turbine thrust balance system includes a high-pressure cylinder 1 provided with a high-pressure rotor, and a high-pressure section 21 and a medium-pressure section 22 of the high-pressure rotor are respectively arranged on the left and right sides of the high-pressure cylinder 1; the high-pressure section 21 includes a high-row first section 211, a high-row second section 212 and a high-row third section 213 from right to left, and the diameter of the high-row first section 211 is greater than the diameter of the high-row second section 212 and the diameter of the high-row third section 213; the outer sides of the high-row first section 211 and the high-row second section 212 are respectively provided with a high-row third section 213; The first stage steam leakage sealing ring 31 and the second stage steam leakage sealing ring of the high exhaust; the side wall of the second stage steam leakage sealing ring 32 of the high exhaust close to the first stage 211 of the high exhaust, the outer side of the second stage 212 of the high exhaust and the side wall of the first stage 211 of the high exhaust facing the second stage steam leakage sealing ring 32 together constitute a balance step 4; one end of the first stage steam leakage pipeline 5 of the high exhaust is arranged at the balance step 4, and the other end of the first stage steam leakage pipeline 5 of the high exhaust leads the first stage steam leakage to the third steam extraction pipeline 131 or the fourth steam extraction pipeline 141 of the high and medium pressure cylinder 1. By setting a balancing step 4 at the steam leakage of the first section 211 of the high-pressure exhaust, and controlling the steam leakage of the first section 211 of the high-pressure exhaust to switch to different downstream flow interfaces, the thrust is adjusted by the pressure change in front of the balancing step 4, so as to meet the thrust requirements under various complex working conditions such as pure condensation, full cut-off of high-pressure heater and heating. The design of the full downstream switching interface prevents the steam leakage of the first section of the high-pressure exhaust from backflowing, the pressure difference between the two sections changes little, and the number of steam seal teeth is appropriate under a limited axial length, which solves a series of problems such as large steam leakage, poor economy, high-temperature steam leakage, and safety hazards. It has the advantages of small steam leakage, good economy and high reliability.

[0027] like Figure 1 As shown, the high and medium pressure cylinder 1 includes a first stage steam extraction port 11, a second stage steam extraction port 12, a third stage steam extraction port 13, a fourth stage steam extraction port 14 and a fifth stage steam extraction port 15; the first, second, third, fourth and fifth stage steam extraction ports 15 are respectively connected to the first steam extraction pipeline, the second steam extraction pipeline, the third steam extraction pipeline 131, the fourth steam extraction pipeline 141 and the fifth steam extraction pipeline. The high pressure section 21 and the medium pressure section 22 of the high and medium pressure rotor are respectively on the left and right sides of the high and medium pressure cylinder 1. The high pressure section 21 includes a high pressure first section 211, a high pressure second section 212 and a high pressure third section 213 of different diameters from right to left; wherein, the diameter of the high pressure first section 211>the diameter of the high pressure second section 212>the diameter of the high pressure third section 213.

[0028] The outer sides of the high-pressure first section 211 and the high-pressure second section 212 are respectively provided with a high-pressure first section leakage steam seal ring 31 and a high-pressure second section leakage steam seal ring; wherein, the side wall of the high-pressure second section leakage steam seal ring 32 close to the high-pressure first section 211, the outer side of the high-pressure second section 212 and the side wall of the high-pressure first section 211 facing the high-pressure second section leakage steam seal ring 32 together constitute a balance step 4; one end of the high-pressure first section leakage steam pipeline 5 is arranged at the balance step 4, and the other end of the high-pressure first section leakage steam pipeline 5 leads the high-pressure first section leakage steam to the third steam extraction pipeline 131 or the fourth steam extraction pipeline 141 of the high and medium pressure cylinder 1. By setting the balance step 4, the axial thrust under different working conditions can be effectively balanced, and the stability and reliability of the steam turbine operation can be improved. By reasonably guiding and utilizing the leakage steam, the energy waste caused by the direct discharge of the leakage steam into the atmosphere can be reduced, and the economy of the entire thermal system can be improved. The system design enables the steam turbine to adapt to a variety of operating conditions, including pure condensing, heating and full cut-off of high-pressure heaters, which enhances the flexibility and adaptability of the unit. By optimizing the utilization of leakage steam and thrust balance, additional energy losses are reduced, thereby improving the operating efficiency of the steam turbine. The adoption of this technical measure helps to balance the axial thrust under different operating conditions, and flexibly allows the most suitable extraction pipeline to be selected according to actual operating conditions and needs, thereby optimizing thermal efficiency and system performance. This design not only improves the operating stability and reliability of the steam turbine, but also enhances its ability to adapt to different operating conditions and improves the overall thermal efficiency and economy.

[0029] The high pressure exhaust first section steam leakage pipeline 5 includes a first branch pipe 51 and a second branch pipe 52 respectively connected to the third steam extraction pipeline 131 and the fourth steam extraction pipeline 141 of the high and medium pressure cylinders 1, and a shut-off valve is respectively provided on the first branch pipe 51 and the second branch pipe 52. In actual use, the high pressure exhaust first section steam leakage pipeline 5 can also be connected to the fifth steam extraction pipeline through a branch pipe.

[0030] The steam leakage from the second section 212 of the high row and the first section of the middle row is led to the shaft seal main pipe (SSR) through a pipeline; the steam leakage from the third section 213 of the high row and the second section of the middle row is led to the steam seal heater (CF) through a pipeline.

[0031] A design method for a large-scale heating steam turbine thrust balance system, based on the above-mentioned large-scale heating steam turbine thrust balance system, comprises the following steps:

[0032] A balancing step 4 is provided at the steam leakage point of the first section of the high-pressure exhaust of S1 and the high-pressure section 21, and a balancing plate is provided at the balancing step 4; the balancing plate area A is optimized and designed based on the thrust requirements when the steam leakage goes to the fourth steam extraction pipeline 141 under pure condensing and full-cut conditions of the high-pressure heater and goes to the third steam extraction pipeline 131 under heating conditions.

[0033] The design method can improve the axial thrust balance performance; by optimizing the balance disc area A, it is ensured that the axial thrust can meet the design requirements under the pure condensing and high-pressure full cut conditions (the first stage of the high-pressure exhaust steam leakage goes to the fourth steam extraction pipeline 141) and the heating condition (the first stage of the high-pressure exhaust steam leakage goes to the third steam extraction pipeline 131). This design can effectively reduce the imbalance of the axial thrust and reduce the load of the thrust bearing, thereby extending the service life of the equipment. Enhance the operational flexibility and adaptability. The optimized design of the balance disc area enables the steam turbine to maintain good balance performance under different operating conditions (such as pure condensing, heating, etc.). This design is not only suitable for conventional operating conditions, but also can maintain stable operation under complex conditions such as high-load steam extraction. Reduce thermal stress and mechanical stress; by reasonably setting the balance step 4 and optimizing the balance disc area, the thermal stress and mechanical stress of the high-pressure cylinder last stage blade can be effectively reduced. Especially under high-load steam extraction conditions, this design can significantly reduce the increase in axial thrust, thereby protecting the safety of the blades and rotor. Improve the economic efficiency of the unit; the optimized design not only improves the operating efficiency of the equipment, but also reduces the operating cost of the unit by reducing steam leakage losses and reducing system complexity. For example, the optimized steam seal system and balance plate design can reduce steam leakage and improve the overall economic efficiency of the unit. Simplify the system design; the use of the balance plate and balance step 4 design can simplify the system structure and reduce the need for additional balancing devices. This design makes the system more compact and reduces the initial investment and maintenance costs of the equipment. Improve the peak-shaving capacity of the unit;

[0034] The optimized balance plate design can quickly adapt to load changes, reduce start-up and shutdown time, and improve the peak load regulation capacity of the unit. This is especially important for units that need to adjust the load frequently. Reduce the temperature of the hot end; through the reasonable design of the balance step 4 and the balance plate, the temperature of the high-pressure cylinder exhaust area can be effectively reduced, the damage to the equipment caused by high temperature can be reduced, and the service life of the equipment can be extended. In summary, this design not only improves the operating efficiency and safety of the equipment, but also reduces the operating cost and enhances the adaptability and economy of the unit.

[0035] Specifically, A is the area of ​​the balancing disk;

[0036] F 纯凝 is the axial thrust under pure condensing conditions;

[0037] F 供热 is the axial thrust under heating conditions;

[0038] P 高压缸 is the pressure of the high pressure cylinder;

[0039] P 4抽 is the pressure of the fourth steam extraction pipeline 141;

[0040] P 3抽 is the pressure of the third steam extraction pipeline 131

[0041] ΔP 纯凝 is the pressure difference before and after the balance plate under pure condensing conditions;

[0042] ΔP 供热 is the pressure difference before and after the balancing plate under heating conditions;

[0043] The goal of the optimization design is to make the balancing disc area A meet the following conditions:

[0044] 1) Under pure condensing conditions, when the steam leakage from the first stage of the high-pressure exhaust goes to the fourth steam extraction pipeline 141, the balance disk can balance the axial thrust:

[0045] A·ΔP 纯凝 ≥F 纯凝

[0046] Among them, ΔP 纯凝 =P 高压缸 -P 4抽 ;

[0047] 2) Under heating conditions, when the steam leakage from the first stage of the high-pressure exhaust goes to the third steam extraction pipeline 131, the balance disk can balance the axial thrust:

[0048] A·ΔP 供热 ≥F 供热

[0049] Among them, ΔP 供热 =P 高压缸 -P 3抽 Combining the above two conditions, the balancing disk area A should meet the following requirements:

[0050] A≥max(F 纯凝 / ΔP 纯凝 ,F 供热 / ΔP 供热 )

[0051] The above formula indicates that the balancing disc area A should be at least equal to the maximum value of the required area calculated under the pure condensing and heating conditions to ensure that the axial thrust balance requirements can be met under both conditions.

[0052] S2. The first section steam leakage seal ring 31 and the second section steam leakage seal ring 32 outside the first section 211 and the second section 212 of the high pressure section 21 are designed according to a certain total number of teeth and a maximum pressure difference under a limited length.

[0053] This method can improve the sealing performance and reduce the amount of steam leakage: by optimizing the number of steam seal teeth and the layout, the sealing effect can be maximized within a limited length, the amount of steam leakage can be reduced, and thus the overall efficiency of the unit can be improved. Adapt to different working conditions: the maximum pressure difference design ensures that the steam seal ring can maintain good sealing performance under different operating conditions (such as pure condensation, heating, high-load steam extraction, etc.). Improve system stability; reduce axial thrust: optimizing the number of steam seal teeth can reduce the axial thrust caused by steam leakage and reduce the load of the thrust bearing, thereby improving the operating stability of the unit. Reduce thermal stress: by reasonably designing the number of steam seal teeth and the pressure difference, the thermal stress in the steam seal area can be reduced, and the thermal deformation caused by temperature changes can be reduced. Extend equipment life; reduce wear: the optimized number of steam seal teeth and the pressure difference design can reduce the wear between the steam seal ring and the rotor, and extend the service life of the steam seal ring and the rotor. Reduce fatigue damage: reasonable steam seal design can reduce vibration and fatigue damage caused by steam leakage and improve equipment reliability. Improve economy; reduce operating costs: reducing the amount of steam leakage can improve the thermal efficiency of the unit, reduce fuel consumption, and thus reduce operating costs. Reduce maintenance costs: The optimized design reduces the wear and damage of the steam seal ring, reduces the maintenance frequency and repair costs. Enhance flexibility and adaptability; adapt to a variety of working conditions: The maximum pressure difference design ensures that the steam seal ring can work normally under different working conditions, enhancing the operating flexibility of the unit. Quick response to load changes: The optimized steam seal design can quickly adapt to load changes, reduce start-up and shutdown time, and improve the peak-shaving capacity of the unit. Simplify system design; compact structure: Optimizing the number of steam seal teeth under a limited length can reduce the space requirements of the steam seal system and make the entire system more compact. Reduce additional devices: Through the optimized design, the need for additional sealing devices is reduced, and the system structure is simplified. Reduce the temperature of the hot end; reduce high temperature damage: The optimized steam seal design can reduce the amount of steam leakage, reduce the temperature of the high-pressure cylinder exhaust area, and reduce the damage to the equipment caused by high temperature.

[0054] The adoption of the above technical measures can not only significantly improve the sealing performance and operating stability of the steam seal system, but also reduce operating costs, extend equipment life, and enhance the flexibility and adaptability of the unit. These improvements are of great significance to improving the overall performance and economy of the unit.

[0055] Specifically,

[0056] ΔP1: The maximum pressure difference designed for the steam seal ring 31 of the first stage of high exhaust;

[0057] ΔP2: The maximum pressure difference designed for the steam seal ring 32 of the second stage of high exhaust;

[0058] n1: number of teeth of the steam seal ring 31 of the first stage of high exhaust;

[0059] n2: number of teeth of the second stage steam leakage seal ring 32 of the high exhaust;

[0060] N: Total number of teeth of the steam seal ring (constant value)

[0061] L: Axial length of the steam seal ring (limited length)

[0062] According to the design requirements, the following formula is obtained:

[0063] 1) The total number of teeth is certain:

[0064] n1+n2=N;

[0065] 2) The steam seal ring 31 of the first stage of high exhaust is designed according to the maximum pressure difference:

[0066] ΔP1≤ΔP max；

[0067] 3) The second stage steam leakage seal ring 32 of the high exhaust is designed according to the maximum pressure difference:

[0068] ΔP2≤ΔP max；

[0069] 4) Optimal distribution of teeth number:

[0070] n1=f(ΔP1); n2=f(ΔP2);

[0071] Where f is a function that represents the relationship between the number of teeth and the pressure difference.

[0072] 4) Arrangement under limited length:

[0073] l1+l2≤L

[0074] Where l1 and l2 represent the axial lengths of the high-pressure first-stage steam seal ring 31 and the high-pressure second-stage steam seal ring 32, respectively. Under the premise of a certain limited length L and a certain total number of teeth N, the number of teeth n1 and n2 are optimized so that both steam seal rings can be within the maximum pressure difference ΔP max； It can work normally and meet the axial length limit L.

[0075] S3, combining S1 and S2, on the basis of satisfying the design requirements of optimizing the steps of each shaft section and optimizing the number of steam seal teeth of each section, taking the reasonable arrangement of the steam seal teeth of the high-row first-section steam leakage steam seal ring 31 and the high-row second-section steam leakage steam seal ring 32 and the excellent economy of the whole machine as the criteria, the steps of each shaft section and the number of steam seal teeth of each section are preferably determined;

[0076] Adopting this method; Improve economic efficiency; By reducing steam leakage loss and optimizing the steam seal system, the thermal efficiency of the unit can be improved, fuel consumption can be reduced, and thus the operating cost can be significantly reduced. In addition, the optimized design reduces the maintenance frequency and repair cost, further improving the economic efficiency of the unit. Improve the overall efficiency of the unit; By optimizing the number and layout of steam seal teeth, reduce steam leakage loss, improve the internal efficiency of the unit, and thus improve the overall performance of the unit. For example, a power plant has significantly reduced steam leakage and improved the operating efficiency of the unit by adopting new steam seal technology. Reduce maintenance workload; The optimized design reduces the wear and damage of the steam seal ring, and reduces the maintenance frequency and repair cost. For example, due to its soft material, the honeycomb steam seal will not cause damage to the shaft neck even if dynamic and static friction occurs, thereby reducing the maintenance workload.

[0077] The adoption of the above technical measures can not only significantly improve the sealing performance and operating stability of the steam seal system, but also reduce operating costs, extend equipment life, and enhance the flexibility and adaptability of the unit. These improvements are of great significance to improving the overall performance and economy of the unit.

[0078] Specifically,

[0079] S1: Optimize the design requirements of each shaft segment step

[0080] S2: Optimize the design requirements for the number of teeth of each steam seal

[0081] C(n1,n2): The economic cost function of the whole machine, which depends on the number of teeth n1 and n 2；

[0082] According to the above requirements, the following optimization problem is obtained:

[0083] Objective function: minC(n1,n2) is to minimize the economic cost of the whole machine.

[0084] Constraints:

[0085] 1) Meet the design requirements S1 for optimizing the steps of each shaft segment:

[0086] l1+l2≤L;

[0087] Wherein l1 and l2 represent the axial lengths of the high row first section steam leakage seal ring 31 and the high row second section steam leakage seal ring 32 respectively.

[0088] 2) Meet the design requirement S2 of optimizing the number of teeth of each steam seal: n1+n2=N;

[0089] Where N is the total number of teeth on the steam seal ring (a constant value).

[0090] 3) The steam seal teeth of the first stage steam leakage seal ring 31 of the high exhaust and the second stage steam leakage seal ring 32 of the high exhaust are arranged reasonably: n1≥n1,min ; n2≥n 2，min Where n 1,min and n 2,min They respectively represent the minimum number of teeth of the high-row first-stage steam leakage seal ring 31 and the high-row second-stage steam leakage seal ring 32.

[0091] 4) Excellent economic efficiency of the whole machine: C(n1,n2)≤C max ; where C max It is the maximum allowable value of the economic cost of the whole machine. The specific optimization method depends on the cost function C(n1,n2) and the actual design requirements.

[0092] S4. According to the thrust balance of the unit under pure condensing and heating conditions, the destination of the steam leakage in the first stage of high exhaust is selected optimally.

[0093] S5. Calculate the thrust under each operating condition, the step size of each shaft section, and the steam leakage parameters according to the final optimal solution, and select and design the first high exhaust steam leakage pipeline and the shut-off valve installed on the branch line.

[0094] Preferably, in S2, the number of teeth of the high-pressure exhaust first-stage steam leakage sealing ring 31 is designed according to the pressure difference between the high-pressure exhaust first-stage steam leakage and the fourth-stage steam extraction port 14 under the condition of fully open pure condensing valve; the number of teeth of the high-pressure exhaust second-stage steam leakage sealing ring 32 is designed according to the pressure difference between the third-stage steam extraction port 13 and the steam seal mother pipe under heating conditions; the number of teeth of the high-pressure exhaust first-stage steam leakage sealing ring 31 and the high-pressure exhaust second-stage steam leakage sealing ring 32 are optimized and allocated according to a certain principle of the total number of teeth.

[0095] in,

[0096] ΔP3: The pressure difference between the first stage steam leakage of the high-pressure exhaust and the fourth stage steam extraction port 14 under pure condensing conditions ΔP4: The pressure difference between the third stage steam extraction port 13 and the steam seal mother pipe under heating conditions According to the design requirements, the following formula can be obtained:

[0097] 1) Design of the number of teeth of the steam seal ring 31 of the first stage of high exhaust:

[0098] n1=f1(ΔP3)

[0099] Wherein, f1 is a function representing the relationship between the number of teeth n1 and the pressure difference ΔP3.

[0100] 2) Design of the number of teeth of the second stage steam leakage seal ring 32 of the high exhaust:

[0101] n2=f2(ΔP4)

[0102] Wherein, f2 is a function representing the relationship between the number of teeth n2 and the pressure difference ΔP4.

[0103] 3) Optimal allocation under a certain principle of total number of teeth:

[0104] n1+n2=N;

[0105] 4) The goal of optimizing the number of teeth is to optimize the performance of the steam seal ring, which can be achieved by minimizing a performance loss function V(n1,n2):

[0106] minV(n1,n2);

[0107] Where V is a performance loss function that depends on the number of teeth n1 and n2.

[0108] The specific optimization method depends on the performance loss function V(n1,n2) and the specific forms of functions f1 and f2.

[0109] Preferably, in S3, optimizing the steps of each shaft section includes reasonably determining the size and position of the balancing step 4 on the first-stage high-row steam leakage rotor according to the design requirements of the balancing step 4, so as to ensure that the axial thrust balance requirements are met under different working conditions; optimizing the number of teeth of each section of the steam seal includes optimizing the distribution of the number of teeth of the two sections of the steam seal rings according to the design requirements of the first-stage high-row steam leakage steam seal ring 31 and the second-stage high-row steam leakage steam seal ring 32 under limited length and in accordance with the principle of a constant total number of teeth and maximum pressure difference.

[0110] Specifically,

[0111] P in : Pressure at the entrance of the steam seal ring

[0112] P out : Pressure at the steam seal ring outlet

[0113] ΔP max :The maximum pressure difference of the steam seal ring is designed according to the design requirements, and the following formula is obtained:

[0114] 1) Optimize the number of teeth of each steam seal:

[0115] n1+n2=N;

[0116] ΔP1=P in -P out1 ≤ΔP max ;

[0117] ΔP2=P in -P out2 ≤ΔP max；

[0118] Among them, ΔP1 and ΔP2 are the pressure differences between the high-pressure exhaust first-stage steam leakage steam seal ring 31 and the high-pressure exhaust second-stage steam leakage steam seal ring 32, and neither of them exceeds the designed maximum pressure difference ΔP max .

[0119] 2) Arrangement under limited length:

[0120] l1+l2≤L

[0121] Wherein, l1 and l2 represent the axial lengths of the high-pressure first-stage steam seal ring 31 and the high-pressure second-stage steam seal ring 32, respectively. The goal is to optimize the number of teeth n1 and n2 under the premise of a certain limited length L and a total number of teeth N, so that both steam seal rings can be within the maximum pressure difference ΔP max It can work normally under the condition of axial length limit L and axial thrust balance requirement.

[0122] In S4, the destination of the first-stage steam leakage from the high-pressure exhaust is preferably selected to include leading the first-stage steam leakage from the high-pressure exhaust to the third steam extraction pipeline 131 or the fourth steam extraction pipeline 141, leading the first-stage steam leakage from the high-pressure exhaust to the third steam extraction pipeline 131 and the fourth steam extraction pipeline 141 or the third steam extraction pipeline 131 and the fifth steam extraction pipeline respectively, and the first-stage steam leakage from the high-pressure exhaust is connected to the third steam extraction pipeline 131, the fourth steam extraction pipeline 141 and the fifth steam extraction pipeline and is provided with a switching device for switching according to actual operating conditions.

[0123] Specifically, suppose:

[0124] x1: decision variable for directing the leaked steam from the first stage of the high-pressure exhaust to the third steam extraction pipeline 131 (1 means directing, 0 means not directing)

[0125] x2: decision variable for directing the leaked steam from the first stage of the high-pressure exhaust to the fourth steam extraction pipeline 141 (1 means directing, 0 means not directing)

[0126] x3: Decision variable for directing the leaked steam from the first stage of the high-pressure exhaust to the fifth steam extraction pipeline (1 means directing, 0 means not directing)

[0127] S: A collection of actual operating conditions

[0128] N i : The cost or performance index of the i-th destination plan

[0129] T: The total cost or performance loss of the switching device is obtained according to the design requirements:

[0130] 1) The destination of the first stage of high exhaust steam leakage:

[0131] x1+x2≥1 or x1+x3≥1 or x2+x3≥1

[0132] This means that the steam leakage from the first stage of the high exhaust is led to at least one of the third steam extraction pipeline 131 , the fourth steam extraction pipeline 141 or the fifth steam extraction pipeline.

[0133] 1) The steam leakage from the first stage of the high-pressure exhaust is led to the third steam extraction pipeline 131 and the fourth steam extraction pipeline 141 respectively:

[0134] x1=1,x2=1

[0135] 2) The steam leakage from the first stage of the high-pressure exhaust is led to the third steam extraction pipeline 131 and the fifth steam extraction pipeline respectively:

[0136] x1=1,x3=1

[0137] 3) The first stage steam leakage of the high exhaust is connected to the third steam extraction pipeline 131, the fourth steam extraction pipeline 141 and the fifth stage steam extraction pipeline:

[0138] x1=1,x2=1,x3=1

[0139] 4) Switching device for switching according to actual operating conditions:

[0140]

[0141] Among them, t s is the cost or performance loss of switching the device under condition s, x s is the decision variable under working condition s.

[0142] 5) Select the best destination for the first stage of high exhaust steam leakage:

[0143] minN(x1,x2,x3)+T

[0144] Wherein, N is the cost or performance index function of the first stage steam leakage destination plan of the high exhaust.

[0145] Based on the above, we can get the following optimization formula:

[0146] minN(x1,x2,x3)+T;

[0147] x1+x2≥1 or x1+x3≥1 or x2+x3≥1;

[0148] x1,x2,x3∈{0,1}

[0149] The specific optimization method depends on the specific form of the cost or performance index function N and the cost or performance loss function T of the switching device.

[0150] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A large-scale heating steam turbine thrust balance system, characterized in that: It comprises a high- and medium-pressure cylinder provided with a high- and medium-pressure rotor, the high-pressure section comprises a high-pressure first section, a high-pressure second section and a high-pressure third section, and the diameter of the high-pressure first section is greater than the diameter of the high-pressure second section> the diameter of the high-pressure third section; a high-pressure first section steam leakage seal ring and a high-pressure second section steam leakage seal ring are respectively provided on the outer sides of the high-pressure first section and the high-pressure second section; the side wall of the high-pressure second section steam leakage seal ring close to the high-pressure first section, the outer side of the high-pressure second section and the side wall of the high-pressure first section facing the high-pressure second section steam leakage seal ring together form a balance step; one end of the high-pressure first section steam leakage pipeline is arranged at the balance step, and the other end of the high-pressure first section steam leakage pipeline leads the high-pressure first section steam leakage to the third steam extraction pipeline or the fourth steam extraction pipeline of the high- and medium-pressure cylinder.

2. The large-scale heating steam turbine thrust balance system according to claim 1, characterized in that: The high pressure exhaust first section steam leakage pipeline comprises a first branch pipe and a second branch pipe respectively connected to the third steam extraction pipeline and the fourth steam extraction pipeline of the high and medium pressure cylinders, and the first branch pipe and the second branch pipe are respectively provided with shut-off valves.

3. The large-scale heating steam turbine thrust balance system according to claim 1, characterized in that: The leaking steam from the second section of the high row and the first section of the middle row is led to the shaft seal main pipe through a pipeline; the leaking steam from the third section of the high row and the second section of the middle row is led to the steam seal heater through a pipeline.

4. A design method for a large-scale heating steam turbine thrust balance system, based on the large-scale heating steam turbine thrust balance system according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. A balancing step is provided at the steam leakage of the first section of the high-pressure exhaust of the high-pressure section, and a balancing plate is provided at the balancing step; the balancing plate area A is optimized and designed according to the thrust requirements when the steam leakage goes to the fourth steam extraction pipeline under pure condensing and full cut-off conditions of the high-pressure heater and goes to the third steam extraction pipeline under heating conditions; S2, the steam seal rings of the first section of the high-pressure section and the second section of the high-pressure section are designed according to the total number of teeth and the maximum pressure difference under the limited length; S3. Combine S1 and S2, and on the basis of meeting the design requirements of optimizing the steps of each shaft section and optimizing the number of steam seal teeth of each section, the steam seal teeth of the first section of the high-row steam leakage seal ring and the second section of the high-row steam leakage seal ring are arranged reasonably and the economy of the whole machine is excellent, and the steps of each shaft section and the number of steam seal teeth of each section are preferably determined; S4. According to the thrust balance of the unit under pure condensing and heating conditions, the destination of the first stage steam leakage of the high exhaust is selected optimally; S5. Calculate the thrust under each operating condition, the step size of each shaft section, and the steam leakage parameters according to the final optimal solution, and select and design the first high exhaust steam leakage pipeline and the shut-off valve installed on the branch line.

5. The design method of the thrust balance system of a large-scale heating steam turbine according to claim 4 is characterized in that: In S2, the number of teeth of the steam seal ring of the first stage of high-pressure exhaust is designed according to the pressure difference between the first stage of high-pressure exhaust steam leakage and the fourth stage steam extraction port under the condition of full opening of the pure condensing valve; The number of teeth of the second stage steam leakage seal ring of the high-pressure exhaust is designed according to the pressure difference between the third stage steam extraction port and the steam seal mother pipe under heating conditions; The number of teeth of the high-pressure exhaust first-stage steam leakage steam sealing ring and the high-pressure exhaust second-stage steam leakage steam sealing ring are optimally allocated based on a certain principle of the total number of teeth.

6. The design method of the thrust balance system of a large-scale heating steam turbine according to claim 4 is characterized in that: In S3, the optimization of each shaft section step includes reasonably determining the size and position of the balance step on the first section of the high row steam leakage rotor according to the design requirements of the balance step, so as to ensure that the axial thrust balance requirements are met under different working conditions; The optimization of the number of teeth of each steam seal section includes optimizing the distribution of the number of teeth of the two steam seal rings according to the design requirements of the first steam leakage seal ring of the high row and the second steam leakage seal ring of the high row, under limited length, according to the principle of a certain total number of teeth and maximum pressure difference.

7. The design method of the thrust balance system of a large-scale heating steam turbine according to claim 4 is characterized in that: In S4, the preferred destination of the first-stage steam leakage from the high-pressure exhaust is selected to include leading the first-stage steam leakage from the high-pressure exhaust to the third steam extraction pipeline or the fourth steam extraction pipeline, leading the first-stage steam leakage from the high-pressure exhaust to the third steam extraction pipeline and the fourth steam extraction pipeline or the third steam extraction pipeline and the fifth steam extraction pipeline respectively, and the first-stage steam leakage from the high-pressure exhaust is connected to the third steam extraction pipeline, the fourth steam extraction pipeline and the fifth steam extraction pipeline and is provided with a switching device for switching according to actual operating conditions.

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