Positive pressure shaft sealing system for steam turbine
By combining a positive pressure shaft seal system with new sealing technology and utilizing positive pressure steam leakage cooling, the high cost and high consumption problems caused by the negative pressure design of the turbine shaft seal cooler have been solved, achieving energy saving, consumption reduction, cost reduction and efficiency improvement.
Patent Information
- Application Number
- CN202520554468.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-27
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2035-03-27
AI Technical Summary
Existing turbine shaft seal coolers require the formation of negative pressure, which increases the water seal height, thereby increasing civil engineering costs and energy consumption. Furthermore, traditional designs are complex and costly.
A positive pressure shaft seal system is adopted, which combines a low-pressure section seal and a high-pressure section seal in the heat exchanger. The positive pressure leakage steam enters the heat exchanger for cooling, eliminating the water seal structure. New sealing technologies such as carbon ring seals and labyrinth seals are used to create a micro-positive pressure environment and reduce steam leakage.
It effectively reduces steam consumption, lowers civil engineering costs and energy consumption, simplifies design, and improves system efficiency.
Smart Images
Figure CN223767569U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of turbine shaft seal cooling technology, and in particular, a positive pressure shaft seal system for turbines. Background Technology
[0002] During turbine operation, there is a certain gap between the front and rear shaft seals. To prevent steam from leaking from the shaft end into the bearing lubrication system, contaminating the lubricating oil, and causing poor unit operation, shaft seal extraction devices are installed at the front and rear bearings to remove the leaking steam. In existing technology, steam leaking from the high and medium pressure shaft seals can be connected to the turbine interstage to continue doing work, or introduced into heaters and deaerators to achieve system energy utilization. Generally, the outermost low-pressure section steam seal is connected to a steam seal cooler. The steam seal cooler adopts a slight negative pressure design, and its principle is a counter-flow small heat exchanger. Cooling water flows in the heat exchange tubes, while steam condenses in the steam chamber.
[0003] As the steam ejector draws air from the steam seal, the pressure inside the cooler is slightly lower than atmospheric pressure. This causes the steam in the front and rear steam seal leakage chambers to enter the cooler through the steam seal leakage inlet under the pressure difference, condensing into water and exiting through the condensate outlet. A small portion of the uncondensed steam mixed with air is discharged into the atmosphere through the exhaust port. Because the steam seal cooler chamber needs to generate sufficient negative pressure to function, a certain water seal height is required at the condensate outlet. The water seal height directly determines the maximum negative pressure that the steam seal cooler can generate. To ensure smooth condensate discharge, the steam seal cooler also needs to be installed at a certain height, increasing civil engineering costs. Utility Model Content
[0004] To reduce steam consumption during turbine operation and lower the civil engineering costs of turbines, this utility model proposes a positive pressure shaft seal system for turbines.
[0005] The technical solution of this utility model is as follows:
[0006] A positive pressure shaft sealing system for a steam turbine includes a steam turbine, a heat exchanger, a low-pressure section seal, and a high-pressure section seal. The steam turbine is a back-pressure steam turbine, comprising a cylinder and a rotor. The cylinder is connected to an inlet pipe and an outlet pipe. The rotor is installed inside the cylinder, and both ends of the rotor are connected to the main shaft. The main shaft is equipped with a low-pressure section seal and a high-pressure section seal. Both sides of the low-pressure section seal are connected to leakage pipes, and both sides of the leakage pipes are connected to the heat exchanger. The heat exchanger is also equipped with a circulating water pipe, a condensate pipe, and an exhaust pipe.
[0007] Preferably, the low-pressure section seal is a carbon ring seal, which includes a carbon ring base, a carbon ring, and a tension spring. The carbon ring base is provided with several sealing grooves, and the tension spring and carbon ring are installed in the sealing grooves. The carbon ring is tightly bound to the rotor by the tension spring. The carbon ring seal is also provided with a retaining groove, in which an anti-rotation pressure plate is installed.
[0008] Furthermore, the high-pressure section steam seal uses a labyrinth seal, a brush seal, or a brush-type carbon ring combination seal. The labyrinth seal includes a steam seal body and steam seal rings. Several steam seal rings are installed inside the steam seal body. The sealing teeth of the steam seal rings and the steam seal plates embedded on the rotor or the comb-shaped teeth machined on the rotor form a sealing structure. The brush seal includes a brush body and brush filaments. The brush body is fixedly installed, and brush filaments are provided on the brush body. The brush filaments are composed of multiple metal wires and are in active contact with the rotor. The contact surface between the brush filaments and the rotor forms an inclined angle and forms an adaptive seal. The brush-type carbon ring combination seal adopts a combination of an inner brush seal and an outer carbon ring seal. The carbon ring of the outer carbon ring seal is tightly clamped to the brush body by a tension spring. The brush filaments of the inner brush seal are inclined and contact the rotor to form an adaptive seal.
[0009] Preferably, the steam turbine includes a base, bearing seats are provided at both ends of the base, a main shaft and a cylinder are movably installed in the bearing seats, a rotor is provided in the cylinder, two impellers are provided on the rotor, blades are installed on the impellers, and the two impellers are respectively located in two working chambers of the cylinder.
[0010] Furthermore, the cylinder is equipped with a partition that divides the cylinder into two working chambers. A steam chamber is located inside the cylinder on one side of the primary working chamber. A primary nozzle is located between the primary working chamber and the steam chamber. The steam in the primary nozzle drives the primary impeller. Secondary nozzles are evenly arranged on the partition, and the steam in the secondary nozzle drives the secondary impeller.
[0011] Furthermore, the rotor is equipped with a fly hammer, which can strike the safety device at a certain speed to protect the rotor from overspeed. The rotor is also equipped with an interrogator, which is used in conjunction with the probe to monitor the turbine speed, displacement, and key phase data.
[0012] Preferably, the heat exchanger includes a rear water chamber, a steam outlet tube bundle, a middle water chamber, a steam inlet tube bundle, and a front water chamber installed inside the heat exchanger shell. The heat exchanger shell is provided with a steam inlet pipe, a steam outlet pipe, a water inlet, and a water outlet. The steam inlet tube bundle and the steam outlet tube bundle are installed through the front water chamber, the middle water chamber, and the rear water chamber. The steam inlet tube bundle is connected to the steam inlet pipe, and the steam outlet tube bundle is connected to the steam outlet pipe.
[0013] Furthermore, the rear water chamber is divided into upper and lower water chambers by a partition plate, and the front water chamber is divided into upper and lower water chambers by a partition plate. Baffles are installed in the rear and front water chambers. The middle water chamber is a short section. The middle water chamber is integrally installed with the rear and front water chambers by a flange. The water passage in the middle water chamber is divided into three chambers by a partition rib. The water passage of each water chamber is separated from the steam passage of the steam inlet pipe bundle and the steam outlet pipe bundle.
[0014] Furthermore, the steam inlet pipe bundle and the steam outlet pipe bundle are installed inside the heat exchanger cylinder via a tube sheet, and a baffle is installed on the tube sheet.
[0015] As a further embodiment of this utility model, a steam leakage pipe is provided between the low-pressure section seal and the high-pressure section seal on both sides, and the steam leakage pipe is directly connected to the low-pressure pipeline network.
[0016] This utility model has the following beneficial effects:
[0017] 1. By adopting a positive pressure shaft seal system, the steam consumption of traditional steam seal coolers is eliminated, water seals are not required, the heat exchanger area is effectively reduced, costs are reduced and efficiency is increased, and energy consumption is reduced;
[0018] 2. This design incorporates new turbine sealing technology, overcoming the shortcomings of traditional steam seal coolers, such as high civil engineering costs and high energy consumption. As a result, the designed new positive pressure shaft seal system has broad application prospects in certain turbine fields. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the structure of a positive pressure shaft seal system for a steam turbine according to Embodiment 1 of this utility model;
[0020] Figure 2 This is a schematic diagram of the structure of a positive pressure shaft seal system for a steam turbine according to Embodiment 2 of this utility model;
[0021] In the diagram, 1-steam turbine, 2-heat exchanger, 3-low-pressure pipeline, 4-low-pressure section seal, 5-high-pressure section seal. Detailed Implementation
[0022] The present invention will be further described below with reference to embodiments and accompanying drawings:
[0023] Example 1:
[0024] like Figure 1 As shown, this utility model provides a positive pressure shaft seal system for steam turbines, mainly applied to low-power back-pressure steam turbines 1. These turbines 1 require control over auxiliary system consumption, cost, and civil engineering space. The heat exchanger 2 of this utility model differs from traditional designs; it operates under a slight positive pressure during steam stroke. Steam can enter the heat exchanger 2 through positive pressure leakage, thus eliminating the need for nozzles to consume working steam to establish negative pressure, reducing utility consumption, and eliminating the need for water seals, thereby reducing civil engineering costs.
[0025] Specifically, the positive pressure shaft sealing system for the steam turbine 1 includes the steam turbine 1, heat exchanger 2, low-pressure section seal 4, and high-pressure section seal 5. The steam turbine 1 is a back-pressure steam turbine 1, which includes a stationary part and a rotating part. There is steam leakage at the shaft end in both the stationary and rotating parts. If the steam leakage at the shaft end enters the bearing lubrication system, it will contaminate the lubricating oil and cause poor unit operation. The steam sealing system effectively prevents a large amount of leaked steam from entering the bearing housing lubrication oil system.
[0026] Specifically, the steam turbine 1 includes a cylinder and a rotor. The cylinder is connected to an inlet pipe and an outlet pipe. The rotor is installed inside the cylinder, and both ends of the rotor are connected to the main shaft. The main shaft is equipped with a low-pressure section seal 4 and a high-pressure section seal 5. Both sides of the low-pressure section seal 4 are provided with shaft seal leakage ports and connected to leakage pipes. Both sides of the leakage pipes are connected to the heat exchanger 2. The heat exchanger 2 is also equipped with a circulating water pipe, a condensate pipe, and an atmospheric exhaust pipe. The heat exchanger 2 is cooled by circulating water. Most of the leakage is cooled and discharged as condensate, and a small portion of non-condensable gases and water vapor are discharged into the atmosphere.
[0027] In this embodiment, the low-pressure section seal 4 uses a carbon ring seal. The carbon ring seal includes a carbon ring base, a carbon ring, and a tension spring. Several sealing grooves are provided within the carbon ring base, and the tension spring and carbon ring are installed within the sealing grooves. The carbon ring is tightly bound to the rotor by the tension spring, forming multiple coils. The carbon ring seal also has a retaining groove, and an anti-rotation pressure plate is installed to prevent the carbon ring seal from rotating. By using a carbon ring steam seal, the carbon ring and rotor are tightly fitted with a very small gap, effectively reducing steam leakage. Simultaneously, positive pressure steam leakage is achieved, with a small amount of steam escaping to the atmosphere after passing through heat exchanger 2. This is acceptable as it does not affect the lubrication system and the normal operation of the unit.
[0028] Furthermore, the high-pressure section steam seal uses a labyrinth seal, brush seal, or brush-carbon ring combination seal. The labyrinth seal includes a seal body and seal rings. Several seal rings are installed inside the seal body. The sealing teeth of the seal rings form a sealing structure with the seal plates embedded on the rotor or the comb-shaped teeth machined on the rotor. The brush seal includes a brush body and brush filaments. The brush body is fixedly installed, and brush filaments are provided on the brush body. The brush filaments are composed of multiple metal wires and are in moving contact with the rotor. The contact surface between the brush filaments and the rotor forms an inclined angle and forms an adaptive seal. The brush-carbon ring combination seal adopts a combination of inner brush seal and outer carbon ring seal. The carbon ring of the outer carbon ring seal is tightly clamped to the brush body by a tension spring. The brush filaments of the inner brush seal are inclined and contact the rotor to form an adaptive seal. A suitable high-pressure section steam seal type is selected according to the turbine's operating parameters to withstand a large pressure difference and control the amount of steam leakage in the high-pressure section.
[0029] In this embodiment, the steam turbine 1 includes a base, bearing seats are provided at both ends of the base, a main shaft and a cylinder are movably installed in the bearing seats, a rotor is provided in the cylinder, two impellers are provided on the rotor, blades are installed on the impellers, and the two impellers are respectively located in the two working chambers of the cylinder.
[0030] Furthermore, the cylinder is equipped with a partition that divides the cylinder into two working chambers. A steam chamber is located inside the cylinder on one side of the primary working chamber. A primary nozzle is located between the primary working chamber and the steam chamber. The steam in the primary nozzle drives the primary impeller. Secondary nozzles are evenly arranged on the partition, and the steam in the secondary nozzle drives the secondary impeller.
[0031] Furthermore, the rotor is equipped with a fly hammer, which can strike the safety device at a certain speed to protect the rotor from overspeed. The rotor is also equipped with an interrogator, which is used in conjunction with the probe to monitor the turbine speed, displacement, and key phase data.
[0032] In this embodiment, the heat exchanger 2 includes a rear water chamber, a steam outlet tube bundle, a middle water chamber, a steam inlet tube bundle, and a front water chamber installed inside the heat exchanger 2 cylinder. The heat exchanger 2 cylinder is provided with a steam inlet pipe, a steam outlet pipe, a water inlet, and a water outlet. The steam inlet tube bundle and the steam outlet tube bundle are installed through the front water chamber, the middle water chamber, and the rear water chamber. The steam inlet tube bundle is connected to the steam inlet pipe, and the steam outlet tube bundle is connected to the steam outlet pipe.
[0033] Furthermore, the rear water chamber is divided into upper and lower water chambers by a partition plate, and the front water chamber is divided into upper and lower water chambers by a partition plate. Baffles are installed in the rear and front water chambers. The middle water chamber is a short section. The middle water chamber is integrally installed with the rear and front water chambers by a flange. The water passage in the middle water chamber is divided into three chambers by a partition rib. The water passage of each water chamber is separated from the steam passage of the steam inlet pipe bundle and the steam outlet pipe bundle.
[0034] Furthermore, the steam inlet pipe bundle and the steam outlet pipe bundle are installed inside the heat exchanger 2 cylinder through a tube sheet, and a baffle is installed on the tube sheet.
[0035] Example 2:
[0036] like Figure 2 As shown, the main structure of Embodiment 2 is the same as that of Embodiment 1, except that a section of leaked steam is introduced into the user's low-pressure pipeline 3. Embodiment 2 is suitable for energy recovery and utilization through a section of leaked steam when the exhaust pressure of turbine 1 is high, while reducing the load on heat exchanger 2. Depending on the back pressure of turbine 1, when the back pressure is high, a section of leaked steam is connected to the low-pressure pipeline 3 to improve energy utilization, while reducing the amount of second-stage leaked steam, reducing the circulating water volume, reducing the area of heat exchanger 2, reducing costs, and achieving overall cost reduction and efficiency improvement.
[0037] In specific implementation, the heat exchanger 2 steam chamber of this utility model is designed to be slightly positive pressure, and the pressure of the steam seal leakage port is slightly higher than the pressure of heat exchanger 2. Due to the pressure difference, the steam seal leakage will enter the cooler, the cooling water flows in the heat exchange tube, the leakage steam will be cooled and condensed into water and discharged from the condensate outlet, and a small part of the uncondensed steam and air mixture will be discharged into the atmosphere from the exhaust port.
[0038] Meanwhile, the combined use of heat exchanger 2, low-pressure section seal 4, and high-pressure section seal 5 reduces shaft end leakage and meets the requirements for positive pressure shaft seal operation. A carbon ring seal is installed between the low-pressure steam seal leakage and the atmosphere. Under slightly positive pressure conditions, the amount of water vapor leaking into the atmosphere is small, which meets the requirements for stable unit operation.
[0039] In summary, this utility model, by allowing low steam leakage into the heat exchanger 2, helps to reduce the size of the heat exchanger 2, lower costs and footprint, reduce circulating water consumption, save energy and reduce costs and increase efficiency, and also helps to reduce energy consumption, costs, and civil engineering space.
[0040] This utility model may have other various embodiments. Without departing from the spirit and essence of this utility model, those skilled in the art can make various corresponding changes and modifications based on this utility model, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.
Claims
1. A positive pressure shaft seal system for a steam turbine, characterized by: The application relates to a back pressure turbine, a heat exchanger, a low-pressure section seal and a high-pressure section seal, wherein the turbine comprises a cylinder and a rotor, the cylinder is connected with an inlet pipe and an exhaust pipe, the rotor is arranged in the cylinder, the two ends of the rotor are connected with a main shaft, the main shaft is provided with the low-pressure section seal and the high-pressure section seal, the low-pressure section seals on the two sides are connected with steam leakage connecting pipes, the steam leakage connecting pipes on the two sides are connected with the heat exchanger, and the heat exchanger is provided with a circulating water pipeline, a condensate water pipeline and an air exhaust pipe.
2. A positive pressure shaft sealing system for a steam turbine as claimed in claim 1, characterized in that: The low-pressure section seal adopts a carbon ring seal, the carbon ring seal comprises a carbon ring base, a carbon ring and a tension spring, a plurality of sealing grooves are arranged in the carbon ring base, the tension spring and the carbon ring are arranged in the sealing grooves, the carbon ring is tightly clamped on the rotor through the tension spring, and the carbon ring seal is further provided with a clamping groove, and an anti-rotation pressing plate is arranged in the clamping groove.
3. A positive seal system for a steam turbine as set forth in claim 2, characterized in that: The high-pressure section seal adopts a labyrinth seal, a brush seal or a brush type carbon ring combined seal, the labyrinth seal comprises a steam seal body and a steam seal ring, a plurality of steam seal rings are arranged in the steam seal body, the sealing teeth of the steam seal ring and steam seal pieces embedded on the rotor or comb-shaped teeth processed on the rotor form a sealing structure, the brush seal comprises a brush body and brush wires, the brush body is fixedly arranged, the brush wires are arranged on the brush body, the brush wires are composed of a plurality of metal wires and are in movable contact with the rotor, the contact surface of the brush wires and the rotor forms an inclined angle and forms a self-adapting seal, and the brush type carbon ring combined seal adopts a combined mode of an inner brush seal and an outer carbon ring seal, the carbon ring of the outer carbon ring seal is tightly clamped on the brush body through the tension spring, and the brush wires of the inner brush seal are arranged in an inclined mode and are in contact with the rotor to form a self-adapting seal.
4. A positive pressure shaft sealing system for a steam turbine as claimed in claim 1, wherein: The turbine comprises a base, bearing seats are arranged at the two ends of the base, a main shaft and a cylinder are movably arranged in the bearing seats, a rotor is arranged in the cylinder, two impellers are arranged on the rotor, blades are arranged on the impellers, and the two impellers are arranged in two working chambers of the cylinder respectively.
5. A positive pressure shaft sealing system for a steam turbine as claimed in claim 4, wherein: The cylinder is provided with a partition plate, the partition plate divides the cylinder into two working chambers, a steam chamber is arranged in the cylinder on the side of the first working chamber, a first nozzle is arranged between the first working chamber and the steam chamber, steam in the first nozzle drives the first impeller, and second nozzles are uniformly arranged on the partition plate, steam in the second nozzles drives the second impeller.
6. A positive pressure shaft sealing system for a steam turbine as claimed in claim 5, wherein: A fly hammer for rotor overspeed protection and an inquiry disc cooperating with a probe for monitoring are arranged on the rotor.
7. A positive seal system for a steam turbine as set forth in claim 1, characterized by: The heat exchanger comprises a rear water chamber, an exhaust chamber tube bundle, a middle water chamber, an inlet pipe bundle, a front water chamber and a heat exchanger cylinder body, the heat exchanger cylinder body is provided with an inlet pipe, an outlet pipe, an inlet and an outlet, the inlet pipe bundle and the outlet pipe bundle are arranged in the front water chamber, the middle water chamber and the rear water chamber, the inlet pipe bundle is connected with the inlet pipe, and the outlet pipe bundle is connected with the outlet pipe.
8. A positive pressure shaft sealing system for a steam turbine as claimed in claim 7, wherein: The rear water chamber is divided into upper and lower water chambers through a partition plate, the front water chamber is divided into upper and lower water chambers through a partition plate, baffles are arranged in the rear water chamber and the front water chamber, the middle water chamber is a short section, the middle water chamber is integrally arranged with the rear water chamber and the front water chamber through flanges, the water path in the middle water chamber is divided into three chambers through a partition rib plate, and the water path of each chamber is separated from the steam path of the inlet pipe bundle and the outlet pipe bundle.
9. A positive pressure shaft sealing system for a steam turbine as claimed in claim 8, wherein: The steam inlet pipe bundle and the steam outlet pipe bundle are installed in the heat exchanger cylinder through pipe plates, and baffles are installed on the pipe plates.
10. A positive pressure shaft sealing system for a steam turbine as claimed in any one of claims 1 to 9, characterized in that: The steam leakage connecting pipes are directly connected with the low-pressure pipe network.